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ANATOMY OF RESPIRATORY
SYSTEM
ZISHAN AKHTAR
Organs of the Respiratory system
 Nose
 Pharynx
 Larynx
 Trachea
 Bronchi
 Lungs –
alveoli
 Gas exchange: Oxygen enters blood and carbon
dioxide leaves
 Regulation of blood pH: Altered by changing
blood carbon dioxide levels
 Voice production: Movement of air past vocal
folds makes sound and speech
 Olfaction: Smell occurs when airborne
molecules drawn into nasal cavity
 Protection: Against microorganisms by
preventing entry and removing them
 Upper tract
 Nose, pharynx
and associated
structures
 Lower tract
 Larynx, trachea,
bronchi, lungs
 Nose
 External nose
 Nasal cavity
 Functions
 Passageway for air
 Cleans the air
 Humidifies, warms air
 Smell
 Along with paranasal
sinuses are resonating
chambers for speech
 Pharynx
 Common opening for
digestive and
respiratory systems
 Three regions
 Nasopharynx
 Oropharynx
 Laryngopharynx
 Functions
 Maintain an open passageway for air movement
 Epiglottis and vestibular folds prevent swallowed material
from moving into larynx
 Vocal folds are primary source of sound production
 Windpipe
 Divides to form
 Primary bronchi
 Carina: Cough reflex
 Conducting zone
 Trachea to terminal bronchioles which is ciliated for
removal of debris
 Passageway for air movement
 Cartilage holds tube system open and smooth muscle
controls tube diameter
 Respiratory zone
 Respiratory bronchioles to alveoli
 Site for gas exchange
Respiratory system, physiology of respiratory system and neural control
Trachea (Windpipe)
Slide
 Connects larynx with bronchi
 Lined with ciliated mucosa
Beat continuously in the opposite direction of
incoming air
Expel mucus loaded with dust and other
debris away from lungs
 Walls are reinforced with C-shaped
hyaline cartilage
Primary Bronchi
Slide
 Formed by division of the trachea
 Enters the lung at the hilus
(medial depression)
 Right bronchus is wider, shorter,
and straighter than left
 Bronchi subdivide into smaller
and smaller branches
Lungs
Slide
 Occupy most of the thoracic cavity
Apex is near the clavicle (superior portion)
Base rests on the diaphragm (inferior
portion)
Each lung is divided into lobes by fissures
Left lung – two lobes
Right lung – three lobes
Lungs
Slide
Coverings of the Lungs
Slide
 Pulmonary (visceral)
pleura covers the
lung surface
 Parietal pleura lines
the walls of the
thoracic cavity
 Pleural fluid fills the
area between layers
of pleura to allow
gliding
Respiratory Tree Divisions
Slide
 Primary bronchi
 Secondary bronchi
 Tertiary bronchi
 Bronchioli
 Terminal bronchioli
Bronchioles
Slide
 Smallest
branches of
the bronchi
 All but the smallest
branches have
reinforcing cartilage
Bronchioles
Slide
 Terminal
bronchioles
end in alveoli
Alveoli
Slide
 Structure of alveoli
Alveolar duct
Alveolar sac
Alveolus
Gas exchange occurs here.
Respiratory Membrane
(Air-Blood Barrier)
Slide
 Thin squamous epithelial layer lining
alveolar walls
 Pulmonary capillaries cover external
surfaces of alveoli
 The blood–air barrier (alveolar–
capillary barrier or membrane) exists in
the gas exchanging region of the lungs.
It exists to prevent air bubbles from
forming in the blood, and from blood
entering the alveoli.
Respiratory Membrane
(Air-Blood Barrier)
Slide
Events of Respiration
Slide
Pulmonary ventilation: O2 into lungs from inspired
air; CO2 out of lungs from expired air.
External respiration: Gas exchange between
alveoli and the capillaries.
Respiratory gas transport: Gasses are transported
in blood (via vessels) to tissues.
Internal respiration: Gas exchange between blood
and tissue cells in systemic capillaries
Cellular respiration.
Mechanics of Breathing
(Pulmonary Ventilation)
Slide
 Two phases
Inspiration – flow of air into lung
Expiration – air leaving lung
ZISHAN
AKHTAR
MPT
 Trachea lies in midline of neck
 Extends from vertebral level C6 in the lower
neck to vertebral level T4 in the mediastium
where it bifurcates into a right and left main
bronchus.
Respiratory system, physiology of respiratory system and neural control
 Each lung is conical in shape
 It has:-
 APEX
 BASE
 THREE BORDERS
 TWO SURFACES
 APEX- it lies above the level of first rib. It
reaches 2-5 cm above the medial one third of
clavicle, just medial to supraclavicular fossa.
 BASE- rest on the diaphgram which seperates
the right lung from the right lobe of the liver
and the left lung from the left lobe of the liver,
fundus of stomach and the spleen.
RIGHT
LEF
T
Respiratory system, physiology of respiratory system and neural control
 BORDERS
 ANTERIOR BORDER- right lung continues
running downwards till the 6th costochondral
junction.
 ANTERIOR BORDER- left lung continues
running downwards till the 4th costal cartilage
then curves laterally ½ inch forming the cardiac
notch then descends downwards till the 6th
costochondral junction.
 INFERIOR BORDER- Is sharp and seperates
the base from costal surface.
 POSTERIOR BORDER-Is rounded, thick and
lies beside the vertebral column.
Respiratory system, physiology of respiratory system and neural control
SURFACES
 COASTAL SURFACE- lies immediately adjacent to the
ribs and intercostal spaces of the thoracic wall
 MEDIAL SURFACE- It is divided into two parts:
a) Anterior(mediastinal part): Contains a HILUM in the
middle(depression in which bronchi,vessels and nerves
forming the root of lungs.
b) Posterior(vertebral part): It is related to:
-bodies of thoracic vertebrae, IV discs, posterior
intercostal vessels.
 DIAPHRAGMATIC SURFACE
Respiratory system, physiology of respiratory system and neural control
RIGHT
LEFT
 LOBES
 The right lung have 3 lobes-
Upper, Middle and lower lobes
 The left lung have 2 lobes-
Upper and Lower lobes
 FISSURES
 OBLIQUE FISSURE: (right and left lung)
It starts at the 3rd thoracic spine while the arms
are elevated, decends downwards, laterally
and anteriorly along the medial border of the
scapula touching the inferior angle of scapula
cutting the midaxillary line in the 5th rib and
ending the 6th costal cartilage 3 inches from the
midline.
 HORIZONTAL FISSURES( right lung)
It follows the 4th intercostal space from the
sternum until it meets the oblique fissure as it
crosses the 5th rib.
Respiratory system, physiology of respiratory system and neural control
by
Sunil
MPT – 1 SEM
Mechanics of Breathing
(Pulmonary Ventilation)
 Completely mechanical process
 Depends on volume changes in the
thoracic cavity
 Volume changes lead to pressure
changes, which lead to the flow of
gases to equalize pressure
Mechanics of Breathing
(Pulmonary Ventilation)
 Two phases
Inspiration – flow of air into lung
Expiration – air leaving lung
Inspiration
 Diaphragm and intercostals muscles
contract
 The size of the thoracic cavity increases
 External air is pulled into the lungs due to
an increase in intrapulmonary volume
Inspiration
Figure 13.7a
1.
Sternocleidomast
oid muscles,
which lift upward
on the sternum
2. Anterior serrati,
which lift many of
the ribs
3. Scaleni, which lift
the first two ribs.
Exhalation
 Largely a passive process which depends
on natural lung elasticity
 As muscles relax, air is pushed out of the
lungs
 Forced expiration can occur mostly by
abdominal recti, which have the powerful
effect of pulling downward on the lower
ribs and internal intercostal muscles
depress the rib cage
Exhalation
Figure 13.7b
Lung recoil It is due to Elastic recoil and surface tension.
Elastic recoil:
Elastic forces of the lung tissue it is determined mainly by
elastin and collagen fibers.
Surface tension:
It is the elastic tendency of a fluid surface which makes it
acquire the least surface area possible.
As the air inside the lungs is moist, there is considerable
surface tension within the tissue of the lungs. Because
the alveoli are highly elastic, they do not resist surface
tension on their own, which allows the force of that
deflate the alveoli as air is forced out during exhalation
by the contraction of the pleural cavity.
.
Surfactant: Reduces tendency of lungs to collapse
It is secreted by special surfactant-secreting
epithelial cells called type II alveolar epithelial
cells
Respiratory system, physiology of respiratory system and neural control
Pleural fluid produced by pleural membranes
Acts as lubricant
Helps hold parietal and visceral pleural membranes together
The difference between the alveolar pressure and
the pleural pressure, this is called the
transpulmonary pressure.
 TPP can be measured by performing
oesophageal manometry
# Pneumothorax : In this an abnormal collection
of air in the pleural space between the lung and
the chest wall. https://www.hamilton-
medical.com/en_IN/Solutions/Transpulmona
ry-pressure-measurement.html
https://www.hamilton-medical.com/en_IN/Solutions/Transpulmonary-pressure-measurement.html
Respiratory system, physiology of respiratory system and neural control
Measure of the ease with which lungs and
thorax expand
A lower-than-normal compliance means the lungs and
thorax are harder to expand
 Tidal volume : Volume of air inspired or expired
during a normal inspiration or expiration , Usually
500 millilitres in the adult male
 Inspiratory reserve volume: Amount of air
inspired forcefully after inspiration of normal tidal
volume , It is usually equal to about 3000 millilitres
• Expiratory reserve volume: Amount of air forcefully
expired after expiration of normal tidal volume It is
usually 1100 milliliters
• Residual volume: Volume of air remaining in
respiratory passages and lungs after the most
forceful expiration. It is usually 1200 milliliters.
All pulmonary volumes and capacities are about 20 to 25
percent less in women than in men, and they are greater in
large and athletic people than in small and asthenic
people.
 Inspiratory capacity: Tidal volume plus
inspiratory reserve volume (about 3500
milliliters)
 Functional residual capacity: Expiratory reserve
volume plus the residual volume (about 2300
milliliters)
 Vital capacity: Sum of inspiratory reserve
volume, tidal volume, and expiratory reserve
volume (about 4600 milliliters)
 Total lung capacity: Sum of all volume (about
5800 milliliters)
 Minute ventilation:Total amount of air moved into
and out of respiratory system per minute
 Respiratory rate or frequency: Number of breaths
taken per minute. It is about 12 breaths per
minute.
 Anatomic dead space: It is the total volume of
the conducting airways from the nose or mouth
down to the level of the terminal bronchioles,
and is about 150 ml on the average in humans.
 Alveolar ventilation: How much air per minute
enters the parts of the respiratory system in which
gas exchange takes place
One of the most important
problems in all the respiratory
passageways is to keep them
open and allow easy
passage of air to and from the
alveoli.
multiple cartilage rings
less extensive curved cartilage
plates
The bronchioles are not prevented
from collapsing by the rigidity of
their walls. Instead, they are kept
expanded mainly by the same
transpulmonary pressures that
expand the alveoli
In addition to keeping the surfaces
moist, the mucus traps small
particles out of the inspired air and
keeps most of these from ever
reaching the alveoli. These particles
are either swallowed or coughed to
the exterior.
200 cilia on each epithelial cell
Cilia beat continually at a rate of 10 to 20 times per
secondcilia in the lungs beat upward, whereas those in the nose beat
downward.
 The bronchi and trachea are so sensitive to light touch
that very slight amounts of foreign matter or other
causes of irritation initiate the cough reflex
Sneeze Reflex
The sneeze reflex is like the cough reflex, except that
it applies to the nasal passageways instead of the
lower respiratory passages. The initiating stimulus of
the sneeze reflex is irritation in the nasal
passageways.
 In respiratory physiology, one deals with
mixtures of gases, mainly of oxygen, nitrogen,
and carbon dioxide.
 The rate of diffusion of each of these gases is
directly proportional to the pressure caused by
that gas alone, which is called the partial
pressure of that gas.
Respiratory system, physiology of respiratory system and neural control
 Diffusion of gases through the respiratory membrane
 Depends on membrane’s thickness,
 the diffusion coefficient of gas,
 surface areas of membrane,
 partial pressure of gases in alveoli and blood
 Relationship between ventilation and pulmonary capillary
flow
 Increased ventilation or increased pulmonary capillary
blood flow increases gas exchange
 Physiologic shunt is deoxygenated blood returning from
lungs
Respiratory system, physiology of respiratory system and neural control
Oxygen is transported by hemoglobin (98.5%)
and is dissolved in plasma (1.5%)
Oxygen-hemoglobin dissociation curve shows
that hemoglobin is almost completely saturated
when P02 is 80 mm Hg or above. At lower
partial pressures, the hemoglobin releases
oxygen.
A shift of the curve to the left because of an
increase in pH, a decrease in carbon dioxide, or
a decrease in temperature results in an increase
in the ability of hemoglobin to hold oxygen
The substance 2.3-bisphosphoglycerate
increases the ability of hemoglobin to
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
In lung capillaries, bicarbonate ions and
hydrogen ions move into RBCs and
chloride ions move out. Bicarbonate ions
combine with hydrogen ions to form
carbonic acid. The carbonic acid is
converted to carbon dioxide and water.
The carbon dioxide diffuses out of the
RBCs.
Increased plasma carbon dioxide lowers
blood pH. The respiratory system
regulates blood pH by regulating plasma
carbon dioxide levels
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
By :- PREKSHA SHARMA
 Normal rate of respiration in adults is 12-16/min
,with tidal volume of 500ml.This rate and depth
of respiration i.e total pulmonary ventilation can
be adjusted to the requirements of the body.
 The size of thorax is altered by the action of the
respiratory muscles ,which contract as a result of
nerve impulses transmitted to them from centers
in the brain and relax in absence of nerve
impulses.
 These nerve impulses are sent from clusters of
neurons located bilaterally in the medulla
oblongata and pons of the brain stem .This
widely dispersed group of neurons collectively
called the respiratory center .
 This rhythmic discharge from the brain that
produces spontaneous respiration is regulated
by 2 mechanisms:-
1) NERVOUS REGULATORY MECHANISM
2) CHEMICAL REGULATORY MECHANISM
 TWO SYSTEM:-
 AUTOMATIC CONTROL :Medullary
rhythmicity area in the medulla oblongata.
 Pneumotaxic area in pons.
 Apneustic area in pons .
 VOLUNTARY CONTROL : via cerebral cortex .
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
 Composed of neurons in medullary rhythmic
area(MRA)in medulla oblongata, pneumatoxic
& apneustic area in pons.
 MRA (Medullary rhythmic area) located in
ventrolateral medulla overlying olivary
nucleus .There are two types of respiratory
neuron I and E neuron.
Respiratory system, physiology of respiratory system and neural control
Function of MRA to control basic rhythm of
respiration .
Inspiratory & expiratory area within MRA
During quiet breathing inhalation lasts for about 2sec
and exhalation for about 3 sec .
Nerve impluse generated in inspiratory area
Establish basic rhythm of breathing
Active insp. area generate nerve impluse for about 2
sec .
Impluse propogated to ext IC muscles via IC nerve
and diagram via phrenic nerve
 When nerve impluse reach diaphragm and ext
IC muscles muscle contract and inhalation
occur .
 At the end of 2sec insp. area become inactive
nerve impulse ceases with no impulse
arriving daiphragm and ext.IC muscles relax for
about 3 sec ,allowing passive elastic recoil of lung
,thoracic wall and the cycle repeats .
 Neurons in exp. Area remain inactive during
quiet breathing .However during forceful
breathing nerve impulse from insp.area
activate the exp.area.
 Impulses from the exp. area cause contarction
of int.IC muscle and abdominal muscle which
decrease size of thoracic cavity and causes
forceful exhalation .
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
 Help to coordinate transition between inhalaton
and exhalation ( in upper pons ) .Transmit
inhibitory impulses to inspiratory area.These
impulses shorten the duration of inhalation .When
the pneumotaxic area is more active ,breathing rate
is more rapid.
APNEUSTIC AREA
 This is in lower pons. This sends stimulatory
impulses to the inspiratory area that activate and
prolong inhalation .The result is long deep
inhalation.
 When pneumotaxic area is active ,it overrides
signal from the apneustic area.
 Cerebral cortex has connections with respiratory
center, we can voluntarily alter our pattern of
breathing .We can refuse to breathe for short
period of time.
 Voluntary control is protective as it enables us to
prevent water or irritating gases entering from
lungs.This ability to not to breathe is limited by the
build up of CO₂ and H⁺ in the body.
 When Pco₂ and H⁺ conc. Increase to a certain level ,the
inspiratory area is strongly stimulated , nerve impluses
are sent along phrenic and IC nerves to respiratory
muscles ,and breathing resumes.
 Some chemical stimuli modulate how quickly
and deeply we breathe.The respiratory system
functions to maintain proper levels of CO₂ and
O₂ and is very responsive to changes in the levels of
these gases in body fluids .
 There are some sensory neurons that are
responsive to chemicals called chemoreceptors
.Chemoreceptors in 2 locations monitor levels of
CO₂,H⁺,O₂ and provide input to respiratory center .
 2 types of chemoreceptors :-
 CENTRAL CHEMORECEPTORS :-Are located
near medulla oblongata in CNS.They respond
to changes in H⁺ conc. Or pCO₂ or both in CSF .
 PERIPHERAL CHEMORECEPTORS :-Are located in the
aortic bodies( clusters of chemoreceptors located in
the wall of the arch of aorta ) and cartoid bodies
(oval nodules in the wall of the left and right
common carotid arteries .These are part of PNS and
are sensitive to changes in Po₂,H⁺,Pco₂ in blood .
 Axons of sensory neurons from the aortic bodies
are part of the vagus nerve and those of carotid
bodies are part of right and left glosdopharyngeal
nerves.
Respiratory system, physiology of respiratory system and neural control
 Normally ,Pco₂ in arterial blood is 40 mmHg .Slight
increase in it cause condition called hypercarbia or
hypercapina. Central chemoreceptors are
stimulated by both high Pco₂ and the rise in H ⁺.
 When Po₂ in arterial blood falls from normal level of
100mmHg but is still above 50mmHg ,peripheral
chemoreceptors are stimulated .Deficiency of O₂
depresses activity of central chemoreceptors and
inspiratory area which then don’t respond to any input
and send fewer impulses to muscles of inhalation .As a
result breathing rate decreases.
 Chemoreceptors participate in a negative feedback
that regulates level of CO₂,O₂ and H⁺in blood ,as a
result of increased H⁺ ,Pco₂ input from the central and
peripheral chemoreceptor causes inspiratory area to
become highly active .Rate and depth of breathing
increases called hyperventilation, allows the inhalation
of more O₂ and exhalation of more CO₂ until level of
Pco₂ and H⁺ are lowered to normal.
 If arterial Pco₂ is lower than 40mmHg – hypocapnia
and hypocarbia, both the chemoreceptor are not
stimulated therefore impulses are not sent to
inspiratory area.As a result the area sets to it own pace
until CO₂ accumulates and rises above 40 mmHg .The
inspiratory area is stimulated more strongly when Pco₂
level rises above normal and Po₂ fall below normal.
Respiratory system, physiology of respiratory system and neural control
 EXERCISE rate and depth of breathing ,even
before changes in Po₂,Pco₂,H⁺level occur.
 Main stimulus for these changes is input from
propiroceptors which mointor movement of joint
and musles nerve impulse from propiroceptors
stimulate inspiratory area of the medulla oblongata.
 At same time axon collateral of UMN that originate
in primary motor cortex also feed exctitatory
response to inspiratory area.
 Recent advances have clarified how the brain
detects CO₂to regulate breathing (central respiratory
chemoreception ).These mechanism are reviewed and
their significance is presented in the general context of
CO₂/pH homeostasis via breathing .
 At rest resp. chemoreflexes initiated at peripheral and
central sites mediate rapid stabilization of arterial
PCO₂and PH .
 Specific brainstem neurons ( retrotrapezoid
nucleus,serotonergic ) are activated by PCO₂ and
stimulate breathing .
 RTN neurons detect CO₂via intrinsic proton
receptors ,synaptic input from peripheral
chemoreceptors and signals from astrocytes .
 Respiratory chemoreflexes are arousal state
dependent whereas chemoreceptor stimulation
produces arousal .
 When abnormal these interactions lead to sleep
disorderd breathing .During exercise ,” central
command “ and reflexes from exercising muscles
produce the breathing stimulation required to
maintain arterial PCO₂ and ph despite elevated
metabolic activity .
 New advances in the neural control of
breathing.
 This issue contain 3 review articles based on
talks given as part of a symposium entitled
“New Advances in the neural control of
breathing “ took place during the 1st pan
American congress of Physiological sciences
on 3 aug 2014 by Brazilian society of
physiology and sponsored by “The Journal of
Physiology “.
 AIM: To discuss cellular and molecular
mechanism by which the brain control
breathing .
 TOPIC: Includes:-
 Network basis of respiratory rhythmogenesis
by pre botzinger complex.
 Role of purinergic signalling in central and
peripheral chemoreception .
 Role of serotonergic raphe neurons in control
of breathing .
 The next caudal segment of the VRC, the B¨otzinger
complex, contains GABAergic expiratory neurons which
modulate respiratory rhythm . The next most rostral region
is the pre-B¨otC; neurons in this region form the core
respiratory rhythm-generating circuit and relay this
inspiratory drive to more rostral premotor populations that
control breathing. Finally, the rostral and caudal segments
of the VRG contain premotor neurons dedicated to the
control of inspiratory and expiratory activities, respectively.
 The authors propose that respiratory rhythm generation by
the pre-B¨otC is not dependent on intrinsic pacemaker
.Specifically, they suggest that pre-inspiratory ‘burstlets’
produced by the convergent activity of a few neurons can
produce a subthreshold rhythm that is translated into an
inspiratory burst by a recurrently connected network of
excitatory preB¨otC neurons. These exciting new insights
will enhance our understanding of mechanisms underlying
respiratory rhythmogenesis, and in a broader context, may
provide useful insight into the complex underpinnings of
other rhythmic microcircuits.
 The review by Moreira and colleagues entitled
‘Independent purinergic mechanisms of central and
peripheral chemoreception in the rostral ventrolateral
medulla.’ describes the role of purinergic signalling at
the level of the ventrolateral medulla in coordinating
cardiorespiratory responses to hypoxia and
hypercapnia by activating RTN chemoreceptors and
presympathetic neurons. In the context of central
chemoreception, evidence suggests that RTN astrocytes
respond to high CO₂ by releasing ATP via 26
hemichannels . This purinergic signal up-regulates the
activity of local RTN chemoreceptors and contributes
to the ventilatory response to CO₂. The authors also
describe the contribution of purinergic signalling to
peripheral chemoreceptor modulation of breathing and
blood pressure by a P2Y1-receptor-dependent
mechanism.
The review by Mulk and colleagues entitled
‘Molecular underpinnings of ventral surface
chemoreceptor function: focus on KCNQ channels’
describes key regulators of intrinsic excitability of
RTN chemoreceptors .They summarize evidence
suggesting that KCNQ channels regulate the activity
of RTN chemoreceptors. They also put forth a model
where KCNQ and TASK-2 channels work together to
limit activity under control conditions and during
activation by high CO2/H+. Considering that
respiratory failure is thought to be an underlying
cause of sudden unexplained death in epilepsy
(SUDEP), and since KCNQ channels regulate the
activity of neurons that control breathing and loss of
function mutations in certain KCNQ channels can
cause certain types of epilepsy, the authors propose
that KCNQ channels represent a common substrate
for epilepsy and respiratory problems.
BY :- ZAINAB KHAN
•Pulmonary function tests are a
group of tests that measure how
well the lung works i.e., how well
your lungs take in and release air
and how well they move oxygen
into the blood.
 Compare your lung function with known standards
that show how well your lungs should be working.
 Measure the effect of chronic diseases like asthma,
chronic obstructive pulmonary disease (COPD), or
cystic fibrosis on lung function.
 Identify early changes in lung function that might show
a need for a change in treatment.
 Detect narrowing in the airways.
 Decide if a medicine (such as a bronchodilator) could be
helpful to use.
 Show whether exposure to substances in your home or
workplace have harmed your lungs.
 Determine your ability to tolerate surgery and medical
procedures.
 Pediatric neuromuscular disorder such
as Duchenne muscular Dystrophy.
 Musculoskeletal deformities such as
kyphoscoliosis (contribute to restrictive lung
disease)
 Chronic dyspnoea
 Asthma
 Chronic obstructive pulmonary disease (COPD)
 Restrictive lung disease
 Preoperative testing
 Recent eye surgery
 Thoracic , abdominal and cerebral aneurysms
 Active hemoptysis
 Pneumothorax
 Unstable angina/ recent MI within 1 month
Standard PFTs include:
 Spirometry
 Lung volumes
 Diffusion capacity
 Spirometry (meaning the measuring of breath) is the most
common of the pulmonary function tests (PFTs),
measuring lung function, specifically the amount
(volume) and/or speed (flow) of air that can be inhaled
and exhaled.
 The most common parameters measured in spirometry
are
1. Vital capacity (VC),
2. Forced vital capacity (FVC),
3. Forced expiratory volume (FEV) at timed intervals of 0.5,
1.0 (FEV1), 2.0, and 3.0 seconds,
4. Forced expiratory flow 25–75% (FEF 25–75) and
5. Maximal voluntary ventilation (MVV)
• In a spirometry test, you breathe into a mouthpiece
that is connected to an instrument called a spirometer.
The spirometer records the amount and the rate of air
that you breathe in and out over a period of time. The
primary signal measured in spirometry may be volume
or flow.
• The test effort can be presented as a ‘flow-volume
loop’ or as a ‘volume-time curve’.
 Normal values vary and depend on:
 height – directly proportional
 age – inversely proportional
 gender
 ethnicity
1. No coughing: especially during first second of FVC
2. Good start of test: <5% of FVC exhaled prior to a
max expiratory effort. (<5% extrapolation)
3. No early termination of expiration: exhalation time
of six seconds or a plateau of 2 seconds
4. No variable flows: flow rate should be consistent
and as fast as possible throughout exhaled VC
5. Good reproducibility or consistency of efforts: 2
best FVC's and 2 best FEV1's should agree within
5% or 100 ml (whichever is greatest)
Respiratory system, physiology of respiratory system and neural control
 Place the nose clip.
 Have patient seated comfortably
 Have patient take a deep breath (inspiration) as
fast as possible.
 Place the spirometer on mouth (should be
sealed within the lips),blow out as hard as they
can until you tell them to stop.(expiration)
 Flow volume loops provide a graphical
illustration of a patient's spirometric efforts.
Flow is plotted against volume to display a
continuous loop from inspiration to expiration.
The overall shape of the flow volume loop is
important in interpreting spirometric results
Respiratory system, physiology of respiratory system and neural control
(A) Normal. Inspiratory limb
of loop is symmetric and
convex. Expiratory limb is
linear. Flow rates at the
midpoint of the inspiratory
and expiratory capacity are
often measured. Maximal
inspiratory flow at 50% of
forced vital capacity (MIF
50%FVC) is greater than
maximal expiratory flow at
50% FVC (MEF 50%FVC)
because dynamic compression
of the airways occurs during
exhalation.
(B) Obstructive disease
(e.g, emphysema,
asthma). Although all
flow rates are diminished,
expiratory prolongation
predominates, and MEF <
MIF. Peak expiratory flow
is sometimes used to
estimate degree of
airway obstruction but is
dependent on patient
effort.
(C) Restrictive disease (eg,
interstitial lung disease,
kyphoscoliosis). The loop is
narrowed because of
diminished lung volumes, but
the shape is generally the
same as in normal volume.
Flow rates are greater than
normal at comparable lung
volumes because the
increased elastic recoil of
lungs holds the airways open.
(D) Fixed obstruction of
the upper airway (eg,
tracheal stenosis). The
top and bottom of the
loops are flattened so
that the configuration
approaches that of a
rectangle. Fixed
obstruction limits flow
equally during
inspiration and
expiration, and MEF =
MIF.
(E) Variable extrathoracic
obstruction (eg, unilateral
vocal cord paralysis, vocal
cord dysfunction).
When a single vocal cord is
paralyzed, it moves
passively with pressure
gradients across the glottis.
During forced inspiration, it
is drawn inward, resulting in
a plateau of decreased
inspiratory flow. During
forced
expiration, it is passively
blown aside, and expiratory
flow is unimpaired.
Therefore, MIF 50%FVC <
MEF 50%FVC.
Expiratory
flow
unimpaire
d
 Asthma and COPD have many similarities and can
occur together in the same patient.
 The major difference between asthma and COPD is
that airflow obstruction is largely reversible in
asthma, but in COPD it is largely irreversible.
 When spirometry shows an obstructive pattern, it
is important to establish whether the obstruction is
reversible.
 In order to establish the diagnosis, reversibility
should be tested with both short- acting
bronchodilators and corticosteroids (when FEV1 is
less than 60% of the predicted value).
 The reversibility test is as follows:
 Spirometry test ( with at least two reproducible
flow-volume loops)
 Intake of a fast acting bronchodilator (often
salbutamol) thorough inhalation.
 15 minutes pause.
 A second spirometry test (with at least two
reproducible flow-volume loops)
 A positive response is demonstrated by:
 FVC increase >10%
 FEV1 increase of 200ml or 15% over baseline
FEV1 FVC FEV1/ FVC
NORMAL > 80% of predicted > 80% of predicted >70% of predicted
OBSTRUCTUVE Decreased:
•Close to 80
Borderline
•65-79 Mild
•50-64 Moderate
•< 50 severe
Normal Decreased (<70%)
RESTRICTIVE Normal or
decreased
Decreased:
•Close to 80
Borderline
•65-79 Mild
•50-64 Moderate
•< 50 severe
Normal or increased
 The diffusing capacity of the lungs (DL)
estimates the transfer of oxygen from alveolar
gas to red blood cells.
 The amount of oxygen transferred is largely
determined by three factors:
 One factor is the area (A) of the alveolar–capillary
membrane, which consists of the alveolar and capillary
walls. The greater the area, the greater the rate of
transfer and the higher the DL. Area is influenced by
the number of blood-containing capillaries in the
alveolar wall.
 The second factor is the thickness (T) of the membrane.
The thicker the membrane, the lower the DL.
 The third factor is the driving pressure, that is, the
difference in oxygen tension between the alveolar gas
and the venous blood (∆PO2). Alveolar oxygen tension
is higher than that in the deoxygenated venous blood
of the pulmonary artery. The greater this difference
(∆PO2), the more oxygen transferred.
 Measuring the diffusing capacity of carbon
monoxide (DLCO) provides a valid reflection of
the diffusion of oxygen.
 The subject exhales to residual volume and then
inhales a gas mixture containing a very low
concentration of carbon monoxide (CO) plus an
inert gas, usually helium. After a maximal
inhalation, the patient holds his or her breath for
10 seconds and then exhales completely. During
the breath hold, CO is absorbed while helium is
equilibrating with alveolar gas. A sample of
exhaled alveolar gas is collected and analyzed.
Respiratory system, physiology of respiratory system and neural control
 LOW DLCO (<80% predicted)
Causes:
EMPHYSEMA ,
INTERSTITIAL LUNG DISEASE ,
PULMONARY HYPERTENSION ,
PULMONARY EMBOLISM ,
PULMONARY EDEMA ,
RIGHT TO LEFT SHUNT TOF,
ANAEMIA .
 HIGH DLCO( >120-140%
predicted)
Causes:
ASTHMA,
POLYCYTHEMIA ,
LEFT TO RIGHT SHUNT:
Ventricular septal defect (VSD)
Patent ductus arteriosus (PDA)
Atrial septal defect (ASD),
OBESITY,
PULMONARY HEMORRHAGE .
Respiratory system, physiology of respiratory system and neural control
 Lung volumes can be measured by:
 Helium dilution method
 Nitrogen washout method
 Body plethysmography
 Nitrogen washout (or
Fowler’s method) is a test
to measure the anatomic
dead space in the lung
during a respiratory
cycle, as well as some
other parameters related
to closure of airways.
 A nitrogen washout can
be performed with a
single nitrogen breath, or
multiple ones. Both tests
can estimated the
functional residual
capacity (FRC)
 The subject breathes 100% oxygen, and all the
nitrogen in the lungs is washed out.
 The exhaled volume and the nitrogen concentration
in that volume are measured by analyzer.
 The difference in nitrogen volume at the initial
concentration and at the final exhaled concentration
allows a calculation of intrathoracic volume, usually
FRC.
 Most people with normal distribution of airway
resistances will reduce their expired end-tidal
nitrogen concentrations to less than 2.5% within
seven minutes.
• The helium dilution technique is a way to measure
the functional residual capacity (FRC) of the lungs.
• This technique is a closed circuit system where a
spirometer is filled with a mixture of helium and
oxygen. The amount of helium in the spirometer is
known at the beginning of the test.
(concentration x volume = amount)
• The subject is asked to breathe (normal breaths) in
the mixture starting from FRC, which is the gas
volume in the lung after a normal breath out.
 The spirometer measures the helium concentration.
 Because there is no leak of substances in the system,
the amount of helium remains constant during the
test, and the FRC is calculated using the following
equation:
C1 x V1 = C2 x V2
C1 x V1 = C2 x (V1+FRC)
FRC= ((C1 x V1)/C2) – V1
Where, V2= total gas volume (FRC+ volume of
spirometer)
V1= volume of gas in spirometer
C1= initial (unknown) concentration of helium
C2= final concentration of helium (measured by spirometer).
 Body plethysmography is a test to find out how much air is
in your lungs after you take in a deep breath, and how much
air is left in your lungs after breathing out as much as you
can.
 Based on principle of BOYLE’S LAW(P*V=k)
 Principle advantage over other two method is it quantifies
non‐ communicating gas volumes.
 The subject is placed inside a sealed chamber with a
single mouthpiece.
 At the end of normal expiration, the mouthpiece is
closed. The subject is then asked to make an inspiratory
effort.
 As the subject tries to inhale, the lungs expand,
decreasing pressure within the lungs and increasing lung
volume.
 This, in turn, increases the pressure within the box since
it is a closed system and the volume of the box
compartment has decreased to accommodate the new
volume.
 Boyles law is used to calculate the unknown volume
within the lungs.
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
It is a diagnostic procedure in which a blood is obtained from an
artery directly by an arterial puncture or accessed by a way of
indwelling arterial catheter.
 ABG analysis is one of the first tests ordered to assess
respiratory status because it helps evaluate gas
exchange in the lungs.
 An ABG test can measure how well the person's lungs and
kidneys are working and how well the body is using
energy.
 It measures the acidity (pH) and the levels of oxygen
and carbon dioxide in the blood from an artery. This test
is used to check how well your lungs are able to move
oxygen into the blood and remove carbon dioxide from
the blood.
 Respiratory failure - in acute and chronic states.
 Any severe illness which may lead to a metabolic acidosis
- for example:
 Cardiac failure.
 Liver failure.
 Renal failure.
 Hyperglycaemic states associated with diabetes
mellitus.
 Multiorgan failure.
 Sepsis.
 Burns.
 Poisons/toxins.
 Ventilated patients.
 Sleep studies.
 An arterial blood gas (ABG) test is done to:
 Check for severe breathing problems and lung
diseases, such as asthma, cystic fibrosis, or chronic
obstructive pulmonary disease (COPD).
 See how well treatment for lung diseases is working.
 Find out if you need extra oxygen or help with
breathing (mechanical ventilation).
 Find out if you are receiving the right amount of
oxygen when you are using oxygen in the hospital.
 Measure the acid-base level in the blood of people
who have heart failure, kidney failure,
uncontrolled diabetes, sleep disorders, severe
infections, or after a drug overdose.
 Overlying infection or burn at insertion site.
 Absence of collateral circulation.
 Synthetic graft.
SITES
 Preferred site-Radial and femoral artery.
 Less common-Dorsalis pedis and post tibial artery.
 Avoid – artery without collateral supply.
Arterial blood can be obtained by direct arterial puncture most usually at
the wrist (radial artery) as it is easy to palpate and has a good collateral
presentation. Alternatives to the radial artery include the femoral and
brachial artery. It is important to ensure good collateral circulation as
there is a theoretical risk of thrombus occlusion.
 If the radial artery is to be used, perform Allen's test to confirm
collateral blood flow to the hand.
 Allen's test
 Elevate the hand and make a fist for approximately 30 seconds.
 Apply pressure over the ulnar and the radial arteries occluding both
(keep the hand elevated).
 Open the hand which will be blanched.
 Release pressure on the ulnar artery and look for perfusion of the
hand (this takes under eight seconds).
 If there is any delay then it may not be safe to perform radial artery
puncture.
 The patient's arm is placed palm-up on a flat
surface, with the wrist dorsiflexed at 45°. A towel
may be placed under the wrist for support. The
puncture site should be cleaned with alcohol or
iodine, and a local anaesthetic should be infiltrated.
 Local anaesthetic makes arterial puncture less
painful for the patient. The radial artery should be
palpated for a pulse, and a pre-heparinised syringe
with a 23 or 25 gauge needle should be inserted at
an angle just distal to the palpated pulse.A small
quantity of blood is sufficient. If repeated arterial
blood gas analysis is required, it is advisable to use a
different site (such as the other radial artery) or
insert an arterial line.
 Bleeding at the puncture site.
 Blood flow problems at puncture site (rare).
 Bruising at the puncture site.
 Delayed bleeding at the puncture site.
 Fainting or feeling light-headed.
 Hematoma (blood accumulating under the skin).
 Infection (a slight risk any time the skin is broken).
 PH:
measures hydrogen ion concentration in the blood, it shows
blood’ acidity or alkalinity
 PCO2 :
It is the partial pressure of CO2 that is carried by the blood
for excretion by the lungs, known as respiratory parameter
 PO2:
It is the partial pressure of O2 that is dissolved in the blood ,
it reflects the body ability to pick up oxygen from the lungs
 HCO3 :
known as the metabolic parameter, it reflects the kidney’s
ability to retain and excrete bicarbonate
 PH = 7.35 – 7.45
 PCO2 = 35 – 45 mmhg
 PO2 = 80 – 100 mmhg
 HCO3 = 22 – 26 meq/L
 The following indices should be looked at in the following
order :
 Blood pH - high indicates alkalosis, low indicates acidosis
and normal indicates either normal, mixed defect or a
compensated defect.
 PaCO2 level - is it a respiratory problem? If not, look at
the bicarbonate level. High PaCO2 with an acidosis
indicates a respiratory problem. If the PaCO2 is normal
or low it indicates compensation.
 Bicarbonate - if the bicarbonate fits with the pH it
suggests a primary metabolic problem. If not, it
indicates compensatory changes.
 Look for any compensation - eg, low PaCO2 in severe
metabolic acidosis.
 Anion gap in metabolic acidosis
 O2 level - is hypoxaemia present?
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
 It is possible to have a mixed respiratory and
metabolic disorder that makes interpretation of an
arterial blood gas result difficult. As a general rule,
when a normal pH is accompanied by an abnormal
PaCO2 or HCO3ˉ then a mixed metabolic-
respiratory disorder exists. (Table) provides some
common clinical examples of mixed respiratory and
metabolic disturbances.
Disorder Characteristics Selected situations
Respiratory acidosis with
metabolic acidosis
↓in pH
↓ in HCO3
↑ in PaCO2
•Cardiac arrest
•Intoxications
•Multi-organ failure
Respiratory alkalosis with
metabolic alkalosis
↑in pH
↑ in HCO3-
↓ in PaCO2
•Cirrhosis with diuretics
•Pregnancy with vomiting
•Over ventilation of COPD
Respiratory acidosis with
metabolic alkalosis
pH in normal range
↑ in PaCO2,
↑ in HCO3-
•COPD with diuretics, vomiting, NG suction
•Severe hypokalemia
Respiratory alkalosis with
metabolic acidosis
pH in normal range
↓ in PaCO2
↓ in HCO3
•Sepsis
•Salicylate toxicity
•Renal failure with CHF or pneumonia
•Advanced liver disease
Metabolic acidosis with
metabolic alkalosis
pH in normal range
HCO3- normal
•Uremia or ketoacidosis with vomiting, NG
suction, diuretics, etc.
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
Respiratory system, physiology of respiratory system and neural control
 Alveolar-arterial oxygen gradient - (A-a)pO2;
difference in oxygen partial pressures between the
alveolar and arterial side.It provides a measure of
oxygen diffusion across the alveoli into the blood.
Thus, will be impaired in lung disease such as
COPD. Raised (A-a)pO2 may also represent the
presence of an intrapulmonary shunt, ie a lung that
is perfused but not ventilated - for example,
pneumonia.
 The anion gap is the difference in the
measured cations (positively charged ions) and the
measured anions (negatively charged ions)
in serum, plasma, or urine.
 Anion gap can be classified as either high, normal or, in
rare cases, low.
 A high anion gap indicates acidosis.
 A low anion gap is frequently caused by hypoalbuminemia.
 Usually done when primary metabolic acidosis is
suspected. Anion gap helps determine the etiology of
the metabolic acidosis.
 Normal=10-18mmol/L
Respiratory system, physiology of respiratory system and neural control

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Respiratory system, physiology of respiratory system and neural control

  • 2. Organs of the Respiratory system  Nose  Pharynx  Larynx  Trachea  Bronchi  Lungs – alveoli
  • 3.  Gas exchange: Oxygen enters blood and carbon dioxide leaves  Regulation of blood pH: Altered by changing blood carbon dioxide levels  Voice production: Movement of air past vocal folds makes sound and speech  Olfaction: Smell occurs when airborne molecules drawn into nasal cavity  Protection: Against microorganisms by preventing entry and removing them
  • 4.  Upper tract  Nose, pharynx and associated structures  Lower tract  Larynx, trachea, bronchi, lungs
  • 5.  Nose  External nose  Nasal cavity  Functions  Passageway for air  Cleans the air  Humidifies, warms air  Smell  Along with paranasal sinuses are resonating chambers for speech  Pharynx  Common opening for digestive and respiratory systems  Three regions  Nasopharynx  Oropharynx  Laryngopharynx
  • 6.  Functions  Maintain an open passageway for air movement  Epiglottis and vestibular folds prevent swallowed material from moving into larynx  Vocal folds are primary source of sound production
  • 7.  Windpipe  Divides to form  Primary bronchi  Carina: Cough reflex
  • 8.  Conducting zone  Trachea to terminal bronchioles which is ciliated for removal of debris  Passageway for air movement  Cartilage holds tube system open and smooth muscle controls tube diameter  Respiratory zone  Respiratory bronchioles to alveoli  Site for gas exchange
  • 10. Trachea (Windpipe) Slide  Connects larynx with bronchi  Lined with ciliated mucosa Beat continuously in the opposite direction of incoming air Expel mucus loaded with dust and other debris away from lungs  Walls are reinforced with C-shaped hyaline cartilage
  • 11. Primary Bronchi Slide  Formed by division of the trachea  Enters the lung at the hilus (medial depression)  Right bronchus is wider, shorter, and straighter than left  Bronchi subdivide into smaller and smaller branches
  • 12. Lungs Slide  Occupy most of the thoracic cavity Apex is near the clavicle (superior portion) Base rests on the diaphragm (inferior portion) Each lung is divided into lobes by fissures Left lung – two lobes Right lung – three lobes
  • 14. Coverings of the Lungs Slide  Pulmonary (visceral) pleura covers the lung surface  Parietal pleura lines the walls of the thoracic cavity  Pleural fluid fills the area between layers of pleura to allow gliding
  • 15. Respiratory Tree Divisions Slide  Primary bronchi  Secondary bronchi  Tertiary bronchi  Bronchioli  Terminal bronchioli
  • 16. Bronchioles Slide  Smallest branches of the bronchi  All but the smallest branches have reinforcing cartilage
  • 18. Alveoli Slide  Structure of alveoli Alveolar duct Alveolar sac Alveolus Gas exchange occurs here.
  • 19. Respiratory Membrane (Air-Blood Barrier) Slide  Thin squamous epithelial layer lining alveolar walls  Pulmonary capillaries cover external surfaces of alveoli  The blood–air barrier (alveolar– capillary barrier or membrane) exists in the gas exchanging region of the lungs. It exists to prevent air bubbles from forming in the blood, and from blood entering the alveoli.
  • 21. Events of Respiration Slide Pulmonary ventilation: O2 into lungs from inspired air; CO2 out of lungs from expired air. External respiration: Gas exchange between alveoli and the capillaries. Respiratory gas transport: Gasses are transported in blood (via vessels) to tissues. Internal respiration: Gas exchange between blood and tissue cells in systemic capillaries Cellular respiration.
  • 22. Mechanics of Breathing (Pulmonary Ventilation) Slide  Two phases Inspiration – flow of air into lung Expiration – air leaving lung
  • 24.  Trachea lies in midline of neck  Extends from vertebral level C6 in the lower neck to vertebral level T4 in the mediastium where it bifurcates into a right and left main bronchus.
  • 26.  Each lung is conical in shape  It has:-  APEX  BASE  THREE BORDERS  TWO SURFACES
  • 27.  APEX- it lies above the level of first rib. It reaches 2-5 cm above the medial one third of clavicle, just medial to supraclavicular fossa.  BASE- rest on the diaphgram which seperates the right lung from the right lobe of the liver and the left lung from the left lobe of the liver, fundus of stomach and the spleen.
  • 30.  BORDERS  ANTERIOR BORDER- right lung continues running downwards till the 6th costochondral junction.  ANTERIOR BORDER- left lung continues running downwards till the 4th costal cartilage then curves laterally ½ inch forming the cardiac notch then descends downwards till the 6th costochondral junction.
  • 31.  INFERIOR BORDER- Is sharp and seperates the base from costal surface.  POSTERIOR BORDER-Is rounded, thick and lies beside the vertebral column.
  • 33. SURFACES  COASTAL SURFACE- lies immediately adjacent to the ribs and intercostal spaces of the thoracic wall  MEDIAL SURFACE- It is divided into two parts: a) Anterior(mediastinal part): Contains a HILUM in the middle(depression in which bronchi,vessels and nerves forming the root of lungs. b) Posterior(vertebral part): It is related to: -bodies of thoracic vertebrae, IV discs, posterior intercostal vessels.  DIAPHRAGMATIC SURFACE
  • 36.  LOBES  The right lung have 3 lobes- Upper, Middle and lower lobes  The left lung have 2 lobes- Upper and Lower lobes
  • 37.  FISSURES  OBLIQUE FISSURE: (right and left lung) It starts at the 3rd thoracic spine while the arms are elevated, decends downwards, laterally and anteriorly along the medial border of the scapula touching the inferior angle of scapula cutting the midaxillary line in the 5th rib and ending the 6th costal cartilage 3 inches from the midline.
  • 38.  HORIZONTAL FISSURES( right lung) It follows the 4th intercostal space from the sternum until it meets the oblique fissure as it crosses the 5th rib.
  • 41. Mechanics of Breathing (Pulmonary Ventilation)  Completely mechanical process  Depends on volume changes in the thoracic cavity  Volume changes lead to pressure changes, which lead to the flow of gases to equalize pressure
  • 42. Mechanics of Breathing (Pulmonary Ventilation)  Two phases Inspiration – flow of air into lung Expiration – air leaving lung
  • 43. Inspiration  Diaphragm and intercostals muscles contract  The size of the thoracic cavity increases  External air is pulled into the lungs due to an increase in intrapulmonary volume
  • 45. 1. Sternocleidomast oid muscles, which lift upward on the sternum 2. Anterior serrati, which lift many of the ribs 3. Scaleni, which lift the first two ribs.
  • 46. Exhalation  Largely a passive process which depends on natural lung elasticity  As muscles relax, air is pushed out of the lungs  Forced expiration can occur mostly by abdominal recti, which have the powerful effect of pulling downward on the lower ribs and internal intercostal muscles depress the rib cage
  • 48. Lung recoil It is due to Elastic recoil and surface tension. Elastic recoil: Elastic forces of the lung tissue it is determined mainly by elastin and collagen fibers. Surface tension: It is the elastic tendency of a fluid surface which makes it acquire the least surface area possible. As the air inside the lungs is moist, there is considerable surface tension within the tissue of the lungs. Because the alveoli are highly elastic, they do not resist surface tension on their own, which allows the force of that deflate the alveoli as air is forced out during exhalation by the contraction of the pleural cavity.
  • 49. . Surfactant: Reduces tendency of lungs to collapse It is secreted by special surfactant-secreting epithelial cells called type II alveolar epithelial cells
  • 51. Pleural fluid produced by pleural membranes Acts as lubricant Helps hold parietal and visceral pleural membranes together
  • 52. The difference between the alveolar pressure and the pleural pressure, this is called the transpulmonary pressure.  TPP can be measured by performing oesophageal manometry # Pneumothorax : In this an abnormal collection of air in the pleural space between the lung and the chest wall. https://www.hamilton- medical.com/en_IN/Solutions/Transpulmona ry-pressure-measurement.html https://www.hamilton-medical.com/en_IN/Solutions/Transpulmonary-pressure-measurement.html
  • 54. Measure of the ease with which lungs and thorax expand A lower-than-normal compliance means the lungs and thorax are harder to expand
  • 55.  Tidal volume : Volume of air inspired or expired during a normal inspiration or expiration , Usually 500 millilitres in the adult male  Inspiratory reserve volume: Amount of air inspired forcefully after inspiration of normal tidal volume , It is usually equal to about 3000 millilitres • Expiratory reserve volume: Amount of air forcefully expired after expiration of normal tidal volume It is usually 1100 milliliters • Residual volume: Volume of air remaining in respiratory passages and lungs after the most forceful expiration. It is usually 1200 milliliters.
  • 56. All pulmonary volumes and capacities are about 20 to 25 percent less in women than in men, and they are greater in large and athletic people than in small and asthenic people.
  • 57.  Inspiratory capacity: Tidal volume plus inspiratory reserve volume (about 3500 milliliters)  Functional residual capacity: Expiratory reserve volume plus the residual volume (about 2300 milliliters)  Vital capacity: Sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume (about 4600 milliliters)  Total lung capacity: Sum of all volume (about 5800 milliliters)
  • 58.  Minute ventilation:Total amount of air moved into and out of respiratory system per minute  Respiratory rate or frequency: Number of breaths taken per minute. It is about 12 breaths per minute.  Anatomic dead space: It is the total volume of the conducting airways from the nose or mouth down to the level of the terminal bronchioles, and is about 150 ml on the average in humans.  Alveolar ventilation: How much air per minute enters the parts of the respiratory system in which gas exchange takes place
  • 59. One of the most important problems in all the respiratory passageways is to keep them open and allow easy passage of air to and from the alveoli. multiple cartilage rings less extensive curved cartilage plates The bronchioles are not prevented from collapsing by the rigidity of their walls. Instead, they are kept expanded mainly by the same transpulmonary pressures that expand the alveoli
  • 60. In addition to keeping the surfaces moist, the mucus traps small particles out of the inspired air and keeps most of these from ever reaching the alveoli. These particles are either swallowed or coughed to the exterior. 200 cilia on each epithelial cell Cilia beat continually at a rate of 10 to 20 times per secondcilia in the lungs beat upward, whereas those in the nose beat downward.
  • 61.  The bronchi and trachea are so sensitive to light touch that very slight amounts of foreign matter or other causes of irritation initiate the cough reflex Sneeze Reflex The sneeze reflex is like the cough reflex, except that it applies to the nasal passageways instead of the lower respiratory passages. The initiating stimulus of the sneeze reflex is irritation in the nasal passageways.
  • 62.  In respiratory physiology, one deals with mixtures of gases, mainly of oxygen, nitrogen, and carbon dioxide.  The rate of diffusion of each of these gases is directly proportional to the pressure caused by that gas alone, which is called the partial pressure of that gas.
  • 64.  Diffusion of gases through the respiratory membrane  Depends on membrane’s thickness,  the diffusion coefficient of gas,  surface areas of membrane,  partial pressure of gases in alveoli and blood  Relationship between ventilation and pulmonary capillary flow  Increased ventilation or increased pulmonary capillary blood flow increases gas exchange  Physiologic shunt is deoxygenated blood returning from lungs
  • 66. Oxygen is transported by hemoglobin (98.5%) and is dissolved in plasma (1.5%) Oxygen-hemoglobin dissociation curve shows that hemoglobin is almost completely saturated when P02 is 80 mm Hg or above. At lower partial pressures, the hemoglobin releases oxygen. A shift of the curve to the left because of an increase in pH, a decrease in carbon dioxide, or a decrease in temperature results in an increase in the ability of hemoglobin to hold oxygen
  • 67. The substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to
  • 73. In lung capillaries, bicarbonate ions and hydrogen ions move into RBCs and chloride ions move out. Bicarbonate ions combine with hydrogen ions to form carbonic acid. The carbonic acid is converted to carbon dioxide and water. The carbon dioxide diffuses out of the RBCs. Increased plasma carbon dioxide lowers blood pH. The respiratory system regulates blood pH by regulating plasma carbon dioxide levels
  • 78. By :- PREKSHA SHARMA
  • 79.  Normal rate of respiration in adults is 12-16/min ,with tidal volume of 500ml.This rate and depth of respiration i.e total pulmonary ventilation can be adjusted to the requirements of the body.  The size of thorax is altered by the action of the respiratory muscles ,which contract as a result of nerve impulses transmitted to them from centers in the brain and relax in absence of nerve impulses.  These nerve impulses are sent from clusters of neurons located bilaterally in the medulla oblongata and pons of the brain stem .This widely dispersed group of neurons collectively called the respiratory center .
  • 80.  This rhythmic discharge from the brain that produces spontaneous respiration is regulated by 2 mechanisms:- 1) NERVOUS REGULATORY MECHANISM 2) CHEMICAL REGULATORY MECHANISM
  • 81.  TWO SYSTEM:-  AUTOMATIC CONTROL :Medullary rhythmicity area in the medulla oblongata.  Pneumotaxic area in pons.  Apneustic area in pons .  VOLUNTARY CONTROL : via cerebral cortex .
  • 84.  Composed of neurons in medullary rhythmic area(MRA)in medulla oblongata, pneumatoxic & apneustic area in pons.  MRA (Medullary rhythmic area) located in ventrolateral medulla overlying olivary nucleus .There are two types of respiratory neuron I and E neuron.
  • 86. Function of MRA to control basic rhythm of respiration . Inspiratory & expiratory area within MRA During quiet breathing inhalation lasts for about 2sec and exhalation for about 3 sec . Nerve impluse generated in inspiratory area Establish basic rhythm of breathing Active insp. area generate nerve impluse for about 2 sec . Impluse propogated to ext IC muscles via IC nerve and diagram via phrenic nerve
  • 87.  When nerve impluse reach diaphragm and ext IC muscles muscle contract and inhalation occur .  At the end of 2sec insp. area become inactive nerve impulse ceases with no impulse arriving daiphragm and ext.IC muscles relax for about 3 sec ,allowing passive elastic recoil of lung ,thoracic wall and the cycle repeats .
  • 88.  Neurons in exp. Area remain inactive during quiet breathing .However during forceful breathing nerve impulse from insp.area activate the exp.area.  Impulses from the exp. area cause contarction of int.IC muscle and abdominal muscle which decrease size of thoracic cavity and causes forceful exhalation .
  • 92.  Help to coordinate transition between inhalaton and exhalation ( in upper pons ) .Transmit inhibitory impulses to inspiratory area.These impulses shorten the duration of inhalation .When the pneumotaxic area is more active ,breathing rate is more rapid. APNEUSTIC AREA  This is in lower pons. This sends stimulatory impulses to the inspiratory area that activate and prolong inhalation .The result is long deep inhalation.  When pneumotaxic area is active ,it overrides signal from the apneustic area.
  • 93.  Cerebral cortex has connections with respiratory center, we can voluntarily alter our pattern of breathing .We can refuse to breathe for short period of time.  Voluntary control is protective as it enables us to prevent water or irritating gases entering from lungs.This ability to not to breathe is limited by the build up of CO₂ and H⁺ in the body.  When Pco₂ and H⁺ conc. Increase to a certain level ,the inspiratory area is strongly stimulated , nerve impluses are sent along phrenic and IC nerves to respiratory muscles ,and breathing resumes.
  • 94.  Some chemical stimuli modulate how quickly and deeply we breathe.The respiratory system functions to maintain proper levels of CO₂ and O₂ and is very responsive to changes in the levels of these gases in body fluids .  There are some sensory neurons that are responsive to chemicals called chemoreceptors .Chemoreceptors in 2 locations monitor levels of CO₂,H⁺,O₂ and provide input to respiratory center .
  • 95.  2 types of chemoreceptors :-  CENTRAL CHEMORECEPTORS :-Are located near medulla oblongata in CNS.They respond to changes in H⁺ conc. Or pCO₂ or both in CSF .  PERIPHERAL CHEMORECEPTORS :-Are located in the aortic bodies( clusters of chemoreceptors located in the wall of the arch of aorta ) and cartoid bodies (oval nodules in the wall of the left and right common carotid arteries .These are part of PNS and are sensitive to changes in Po₂,H⁺,Pco₂ in blood .  Axons of sensory neurons from the aortic bodies are part of the vagus nerve and those of carotid bodies are part of right and left glosdopharyngeal nerves.
  • 97.  Normally ,Pco₂ in arterial blood is 40 mmHg .Slight increase in it cause condition called hypercarbia or hypercapina. Central chemoreceptors are stimulated by both high Pco₂ and the rise in H ⁺.  When Po₂ in arterial blood falls from normal level of 100mmHg but is still above 50mmHg ,peripheral chemoreceptors are stimulated .Deficiency of O₂ depresses activity of central chemoreceptors and inspiratory area which then don’t respond to any input and send fewer impulses to muscles of inhalation .As a result breathing rate decreases.
  • 98.  Chemoreceptors participate in a negative feedback that regulates level of CO₂,O₂ and H⁺in blood ,as a result of increased H⁺ ,Pco₂ input from the central and peripheral chemoreceptor causes inspiratory area to become highly active .Rate and depth of breathing increases called hyperventilation, allows the inhalation of more O₂ and exhalation of more CO₂ until level of Pco₂ and H⁺ are lowered to normal.  If arterial Pco₂ is lower than 40mmHg – hypocapnia and hypocarbia, both the chemoreceptor are not stimulated therefore impulses are not sent to inspiratory area.As a result the area sets to it own pace until CO₂ accumulates and rises above 40 mmHg .The inspiratory area is stimulated more strongly when Pco₂ level rises above normal and Po₂ fall below normal.
  • 100.  EXERCISE rate and depth of breathing ,even before changes in Po₂,Pco₂,H⁺level occur.  Main stimulus for these changes is input from propiroceptors which mointor movement of joint and musles nerve impulse from propiroceptors stimulate inspiratory area of the medulla oblongata.  At same time axon collateral of UMN that originate in primary motor cortex also feed exctitatory response to inspiratory area.
  • 101.  Recent advances have clarified how the brain detects CO₂to regulate breathing (central respiratory chemoreception ).These mechanism are reviewed and their significance is presented in the general context of CO₂/pH homeostasis via breathing .  At rest resp. chemoreflexes initiated at peripheral and central sites mediate rapid stabilization of arterial PCO₂and PH .  Specific brainstem neurons ( retrotrapezoid nucleus,serotonergic ) are activated by PCO₂ and stimulate breathing .
  • 102.  RTN neurons detect CO₂via intrinsic proton receptors ,synaptic input from peripheral chemoreceptors and signals from astrocytes .  Respiratory chemoreflexes are arousal state dependent whereas chemoreceptor stimulation produces arousal .  When abnormal these interactions lead to sleep disorderd breathing .During exercise ,” central command “ and reflexes from exercising muscles produce the breathing stimulation required to maintain arterial PCO₂ and ph despite elevated metabolic activity .
  • 103.  New advances in the neural control of breathing.  This issue contain 3 review articles based on talks given as part of a symposium entitled “New Advances in the neural control of breathing “ took place during the 1st pan American congress of Physiological sciences on 3 aug 2014 by Brazilian society of physiology and sponsored by “The Journal of Physiology “.
  • 104.  AIM: To discuss cellular and molecular mechanism by which the brain control breathing .  TOPIC: Includes:-  Network basis of respiratory rhythmogenesis by pre botzinger complex.  Role of purinergic signalling in central and peripheral chemoreception .  Role of serotonergic raphe neurons in control of breathing .
  • 105.  The next caudal segment of the VRC, the B¨otzinger complex, contains GABAergic expiratory neurons which modulate respiratory rhythm . The next most rostral region is the pre-B¨otC; neurons in this region form the core respiratory rhythm-generating circuit and relay this inspiratory drive to more rostral premotor populations that control breathing. Finally, the rostral and caudal segments of the VRG contain premotor neurons dedicated to the control of inspiratory and expiratory activities, respectively.  The authors propose that respiratory rhythm generation by the pre-B¨otC is not dependent on intrinsic pacemaker .Specifically, they suggest that pre-inspiratory ‘burstlets’ produced by the convergent activity of a few neurons can produce a subthreshold rhythm that is translated into an inspiratory burst by a recurrently connected network of excitatory preB¨otC neurons. These exciting new insights will enhance our understanding of mechanisms underlying respiratory rhythmogenesis, and in a broader context, may provide useful insight into the complex underpinnings of other rhythmic microcircuits.
  • 106.  The review by Moreira and colleagues entitled ‘Independent purinergic mechanisms of central and peripheral chemoreception in the rostral ventrolateral medulla.’ describes the role of purinergic signalling at the level of the ventrolateral medulla in coordinating cardiorespiratory responses to hypoxia and hypercapnia by activating RTN chemoreceptors and presympathetic neurons. In the context of central chemoreception, evidence suggests that RTN astrocytes respond to high CO₂ by releasing ATP via 26 hemichannels . This purinergic signal up-regulates the activity of local RTN chemoreceptors and contributes to the ventilatory response to CO₂. The authors also describe the contribution of purinergic signalling to peripheral chemoreceptor modulation of breathing and blood pressure by a P2Y1-receptor-dependent mechanism.
  • 107. The review by Mulk and colleagues entitled ‘Molecular underpinnings of ventral surface chemoreceptor function: focus on KCNQ channels’ describes key regulators of intrinsic excitability of RTN chemoreceptors .They summarize evidence suggesting that KCNQ channels regulate the activity of RTN chemoreceptors. They also put forth a model where KCNQ and TASK-2 channels work together to limit activity under control conditions and during activation by high CO2/H+. Considering that respiratory failure is thought to be an underlying cause of sudden unexplained death in epilepsy (SUDEP), and since KCNQ channels regulate the activity of neurons that control breathing and loss of function mutations in certain KCNQ channels can cause certain types of epilepsy, the authors propose that KCNQ channels represent a common substrate for epilepsy and respiratory problems.
  • 108. BY :- ZAINAB KHAN
  • 109. •Pulmonary function tests are a group of tests that measure how well the lung works i.e., how well your lungs take in and release air and how well they move oxygen into the blood.
  • 110.  Compare your lung function with known standards that show how well your lungs should be working.  Measure the effect of chronic diseases like asthma, chronic obstructive pulmonary disease (COPD), or cystic fibrosis on lung function.  Identify early changes in lung function that might show a need for a change in treatment.  Detect narrowing in the airways.  Decide if a medicine (such as a bronchodilator) could be helpful to use.  Show whether exposure to substances in your home or workplace have harmed your lungs.  Determine your ability to tolerate surgery and medical procedures.
  • 111.  Pediatric neuromuscular disorder such as Duchenne muscular Dystrophy.  Musculoskeletal deformities such as kyphoscoliosis (contribute to restrictive lung disease)  Chronic dyspnoea  Asthma  Chronic obstructive pulmonary disease (COPD)  Restrictive lung disease  Preoperative testing
  • 112.  Recent eye surgery  Thoracic , abdominal and cerebral aneurysms  Active hemoptysis  Pneumothorax  Unstable angina/ recent MI within 1 month
  • 113. Standard PFTs include:  Spirometry  Lung volumes  Diffusion capacity
  • 114.  Spirometry (meaning the measuring of breath) is the most common of the pulmonary function tests (PFTs), measuring lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled.  The most common parameters measured in spirometry are 1. Vital capacity (VC), 2. Forced vital capacity (FVC), 3. Forced expiratory volume (FEV) at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds, 4. Forced expiratory flow 25–75% (FEF 25–75) and 5. Maximal voluntary ventilation (MVV)
  • 115. • In a spirometry test, you breathe into a mouthpiece that is connected to an instrument called a spirometer. The spirometer records the amount and the rate of air that you breathe in and out over a period of time. The primary signal measured in spirometry may be volume or flow. • The test effort can be presented as a ‘flow-volume loop’ or as a ‘volume-time curve’.  Normal values vary and depend on:  height – directly proportional  age – inversely proportional  gender  ethnicity
  • 116. 1. No coughing: especially during first second of FVC 2. Good start of test: <5% of FVC exhaled prior to a max expiratory effort. (<5% extrapolation) 3. No early termination of expiration: exhalation time of six seconds or a plateau of 2 seconds 4. No variable flows: flow rate should be consistent and as fast as possible throughout exhaled VC 5. Good reproducibility or consistency of efforts: 2 best FVC's and 2 best FEV1's should agree within 5% or 100 ml (whichever is greatest)
  • 118.  Place the nose clip.  Have patient seated comfortably  Have patient take a deep breath (inspiration) as fast as possible.  Place the spirometer on mouth (should be sealed within the lips),blow out as hard as they can until you tell them to stop.(expiration)
  • 119.  Flow volume loops provide a graphical illustration of a patient's spirometric efforts. Flow is plotted against volume to display a continuous loop from inspiration to expiration. The overall shape of the flow volume loop is important in interpreting spirometric results
  • 121. (A) Normal. Inspiratory limb of loop is symmetric and convex. Expiratory limb is linear. Flow rates at the midpoint of the inspiratory and expiratory capacity are often measured. Maximal inspiratory flow at 50% of forced vital capacity (MIF 50%FVC) is greater than maximal expiratory flow at 50% FVC (MEF 50%FVC) because dynamic compression of the airways occurs during exhalation.
  • 122. (B) Obstructive disease (e.g, emphysema, asthma). Although all flow rates are diminished, expiratory prolongation predominates, and MEF < MIF. Peak expiratory flow is sometimes used to estimate degree of airway obstruction but is dependent on patient effort.
  • 123. (C) Restrictive disease (eg, interstitial lung disease, kyphoscoliosis). The loop is narrowed because of diminished lung volumes, but the shape is generally the same as in normal volume. Flow rates are greater than normal at comparable lung volumes because the increased elastic recoil of lungs holds the airways open.
  • 124. (D) Fixed obstruction of the upper airway (eg, tracheal stenosis). The top and bottom of the loops are flattened so that the configuration approaches that of a rectangle. Fixed obstruction limits flow equally during inspiration and expiration, and MEF = MIF.
  • 125. (E) Variable extrathoracic obstruction (eg, unilateral vocal cord paralysis, vocal cord dysfunction). When a single vocal cord is paralyzed, it moves passively with pressure gradients across the glottis. During forced inspiration, it is drawn inward, resulting in a plateau of decreased inspiratory flow. During forced expiration, it is passively blown aside, and expiratory flow is unimpaired. Therefore, MIF 50%FVC < MEF 50%FVC. Expiratory flow unimpaire d
  • 126.  Asthma and COPD have many similarities and can occur together in the same patient.  The major difference between asthma and COPD is that airflow obstruction is largely reversible in asthma, but in COPD it is largely irreversible.  When spirometry shows an obstructive pattern, it is important to establish whether the obstruction is reversible.  In order to establish the diagnosis, reversibility should be tested with both short- acting bronchodilators and corticosteroids (when FEV1 is less than 60% of the predicted value).
  • 127.  The reversibility test is as follows:  Spirometry test ( with at least two reproducible flow-volume loops)  Intake of a fast acting bronchodilator (often salbutamol) thorough inhalation.  15 minutes pause.  A second spirometry test (with at least two reproducible flow-volume loops)  A positive response is demonstrated by:  FVC increase >10%  FEV1 increase of 200ml or 15% over baseline
  • 128. FEV1 FVC FEV1/ FVC NORMAL > 80% of predicted > 80% of predicted >70% of predicted OBSTRUCTUVE Decreased: •Close to 80 Borderline •65-79 Mild •50-64 Moderate •< 50 severe Normal Decreased (<70%) RESTRICTIVE Normal or decreased Decreased: •Close to 80 Borderline •65-79 Mild •50-64 Moderate •< 50 severe Normal or increased
  • 129.  The diffusing capacity of the lungs (DL) estimates the transfer of oxygen from alveolar gas to red blood cells.
  • 130.  The amount of oxygen transferred is largely determined by three factors:  One factor is the area (A) of the alveolar–capillary membrane, which consists of the alveolar and capillary walls. The greater the area, the greater the rate of transfer and the higher the DL. Area is influenced by the number of blood-containing capillaries in the alveolar wall.  The second factor is the thickness (T) of the membrane. The thicker the membrane, the lower the DL.  The third factor is the driving pressure, that is, the difference in oxygen tension between the alveolar gas and the venous blood (∆PO2). Alveolar oxygen tension is higher than that in the deoxygenated venous blood of the pulmonary artery. The greater this difference (∆PO2), the more oxygen transferred.
  • 131.  Measuring the diffusing capacity of carbon monoxide (DLCO) provides a valid reflection of the diffusion of oxygen.  The subject exhales to residual volume and then inhales a gas mixture containing a very low concentration of carbon monoxide (CO) plus an inert gas, usually helium. After a maximal inhalation, the patient holds his or her breath for 10 seconds and then exhales completely. During the breath hold, CO is absorbed while helium is equilibrating with alveolar gas. A sample of exhaled alveolar gas is collected and analyzed.
  • 133.  LOW DLCO (<80% predicted) Causes: EMPHYSEMA , INTERSTITIAL LUNG DISEASE , PULMONARY HYPERTENSION , PULMONARY EMBOLISM , PULMONARY EDEMA , RIGHT TO LEFT SHUNT TOF, ANAEMIA .  HIGH DLCO( >120-140% predicted) Causes: ASTHMA, POLYCYTHEMIA , LEFT TO RIGHT SHUNT: Ventricular septal defect (VSD) Patent ductus arteriosus (PDA) Atrial septal defect (ASD), OBESITY, PULMONARY HEMORRHAGE .
  • 135.  Lung volumes can be measured by:  Helium dilution method  Nitrogen washout method  Body plethysmography
  • 136.  Nitrogen washout (or Fowler’s method) is a test to measure the anatomic dead space in the lung during a respiratory cycle, as well as some other parameters related to closure of airways.  A nitrogen washout can be performed with a single nitrogen breath, or multiple ones. Both tests can estimated the functional residual capacity (FRC)
  • 137.  The subject breathes 100% oxygen, and all the nitrogen in the lungs is washed out.  The exhaled volume and the nitrogen concentration in that volume are measured by analyzer.  The difference in nitrogen volume at the initial concentration and at the final exhaled concentration allows a calculation of intrathoracic volume, usually FRC.  Most people with normal distribution of airway resistances will reduce their expired end-tidal nitrogen concentrations to less than 2.5% within seven minutes.
  • 138. • The helium dilution technique is a way to measure the functional residual capacity (FRC) of the lungs. • This technique is a closed circuit system where a spirometer is filled with a mixture of helium and oxygen. The amount of helium in the spirometer is known at the beginning of the test. (concentration x volume = amount) • The subject is asked to breathe (normal breaths) in the mixture starting from FRC, which is the gas volume in the lung after a normal breath out.
  • 139.  The spirometer measures the helium concentration.  Because there is no leak of substances in the system, the amount of helium remains constant during the test, and the FRC is calculated using the following equation: C1 x V1 = C2 x V2 C1 x V1 = C2 x (V1+FRC) FRC= ((C1 x V1)/C2) – V1 Where, V2= total gas volume (FRC+ volume of spirometer) V1= volume of gas in spirometer C1= initial (unknown) concentration of helium C2= final concentration of helium (measured by spirometer).
  • 140.  Body plethysmography is a test to find out how much air is in your lungs after you take in a deep breath, and how much air is left in your lungs after breathing out as much as you can.  Based on principle of BOYLE’S LAW(P*V=k)  Principle advantage over other two method is it quantifies non‐ communicating gas volumes.
  • 141.  The subject is placed inside a sealed chamber with a single mouthpiece.  At the end of normal expiration, the mouthpiece is closed. The subject is then asked to make an inspiratory effort.  As the subject tries to inhale, the lungs expand, decreasing pressure within the lungs and increasing lung volume.  This, in turn, increases the pressure within the box since it is a closed system and the volume of the box compartment has decreased to accommodate the new volume.  Boyles law is used to calculate the unknown volume within the lungs.
  • 145. It is a diagnostic procedure in which a blood is obtained from an artery directly by an arterial puncture or accessed by a way of indwelling arterial catheter.
  • 146.  ABG analysis is one of the first tests ordered to assess respiratory status because it helps evaluate gas exchange in the lungs.  An ABG test can measure how well the person's lungs and kidneys are working and how well the body is using energy.  It measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood from an artery. This test is used to check how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.
  • 147.  Respiratory failure - in acute and chronic states.  Any severe illness which may lead to a metabolic acidosis - for example:  Cardiac failure.  Liver failure.  Renal failure.  Hyperglycaemic states associated with diabetes mellitus.  Multiorgan failure.  Sepsis.  Burns.  Poisons/toxins.  Ventilated patients.  Sleep studies.
  • 148.  An arterial blood gas (ABG) test is done to:  Check for severe breathing problems and lung diseases, such as asthma, cystic fibrosis, or chronic obstructive pulmonary disease (COPD).  See how well treatment for lung diseases is working.  Find out if you need extra oxygen or help with breathing (mechanical ventilation).  Find out if you are receiving the right amount of oxygen when you are using oxygen in the hospital.  Measure the acid-base level in the blood of people who have heart failure, kidney failure, uncontrolled diabetes, sleep disorders, severe infections, or after a drug overdose.
  • 149.  Overlying infection or burn at insertion site.  Absence of collateral circulation.  Synthetic graft. SITES  Preferred site-Radial and femoral artery.  Less common-Dorsalis pedis and post tibial artery.  Avoid – artery without collateral supply.
  • 150. Arterial blood can be obtained by direct arterial puncture most usually at the wrist (radial artery) as it is easy to palpate and has a good collateral presentation. Alternatives to the radial artery include the femoral and brachial artery. It is important to ensure good collateral circulation as there is a theoretical risk of thrombus occlusion.  If the radial artery is to be used, perform Allen's test to confirm collateral blood flow to the hand.  Allen's test  Elevate the hand and make a fist for approximately 30 seconds.  Apply pressure over the ulnar and the radial arteries occluding both (keep the hand elevated).  Open the hand which will be blanched.  Release pressure on the ulnar artery and look for perfusion of the hand (this takes under eight seconds).  If there is any delay then it may not be safe to perform radial artery puncture.
  • 151.  The patient's arm is placed palm-up on a flat surface, with the wrist dorsiflexed at 45°. A towel may be placed under the wrist for support. The puncture site should be cleaned with alcohol or iodine, and a local anaesthetic should be infiltrated.  Local anaesthetic makes arterial puncture less painful for the patient. The radial artery should be palpated for a pulse, and a pre-heparinised syringe with a 23 or 25 gauge needle should be inserted at an angle just distal to the palpated pulse.A small quantity of blood is sufficient. If repeated arterial blood gas analysis is required, it is advisable to use a different site (such as the other radial artery) or insert an arterial line.
  • 152.  Bleeding at the puncture site.  Blood flow problems at puncture site (rare).  Bruising at the puncture site.  Delayed bleeding at the puncture site.  Fainting or feeling light-headed.  Hematoma (blood accumulating under the skin).  Infection (a slight risk any time the skin is broken).
  • 153.  PH: measures hydrogen ion concentration in the blood, it shows blood’ acidity or alkalinity  PCO2 : It is the partial pressure of CO2 that is carried by the blood for excretion by the lungs, known as respiratory parameter  PO2: It is the partial pressure of O2 that is dissolved in the blood , it reflects the body ability to pick up oxygen from the lungs  HCO3 : known as the metabolic parameter, it reflects the kidney’s ability to retain and excrete bicarbonate
  • 154.  PH = 7.35 – 7.45  PCO2 = 35 – 45 mmhg  PO2 = 80 – 100 mmhg  HCO3 = 22 – 26 meq/L
  • 155.  The following indices should be looked at in the following order :  Blood pH - high indicates alkalosis, low indicates acidosis and normal indicates either normal, mixed defect or a compensated defect.  PaCO2 level - is it a respiratory problem? If not, look at the bicarbonate level. High PaCO2 with an acidosis indicates a respiratory problem. If the PaCO2 is normal or low it indicates compensation.  Bicarbonate - if the bicarbonate fits with the pH it suggests a primary metabolic problem. If not, it indicates compensatory changes.  Look for any compensation - eg, low PaCO2 in severe metabolic acidosis.  Anion gap in metabolic acidosis  O2 level - is hypoxaemia present?
  • 164.  It is possible to have a mixed respiratory and metabolic disorder that makes interpretation of an arterial blood gas result difficult. As a general rule, when a normal pH is accompanied by an abnormal PaCO2 or HCO3ˉ then a mixed metabolic- respiratory disorder exists. (Table) provides some common clinical examples of mixed respiratory and metabolic disturbances.
  • 165. Disorder Characteristics Selected situations Respiratory acidosis with metabolic acidosis ↓in pH ↓ in HCO3 ↑ in PaCO2 •Cardiac arrest •Intoxications •Multi-organ failure Respiratory alkalosis with metabolic alkalosis ↑in pH ↑ in HCO3- ↓ in PaCO2 •Cirrhosis with diuretics •Pregnancy with vomiting •Over ventilation of COPD Respiratory acidosis with metabolic alkalosis pH in normal range ↑ in PaCO2, ↑ in HCO3- •COPD with diuretics, vomiting, NG suction •Severe hypokalemia Respiratory alkalosis with metabolic acidosis pH in normal range ↓ in PaCO2 ↓ in HCO3 •Sepsis •Salicylate toxicity •Renal failure with CHF or pneumonia •Advanced liver disease Metabolic acidosis with metabolic alkalosis pH in normal range HCO3- normal •Uremia or ketoacidosis with vomiting, NG suction, diuretics, etc.
  • 169.  Alveolar-arterial oxygen gradient - (A-a)pO2; difference in oxygen partial pressures between the alveolar and arterial side.It provides a measure of oxygen diffusion across the alveoli into the blood. Thus, will be impaired in lung disease such as COPD. Raised (A-a)pO2 may also represent the presence of an intrapulmonary shunt, ie a lung that is perfused but not ventilated - for example, pneumonia.
  • 170.  The anion gap is the difference in the measured cations (positively charged ions) and the measured anions (negatively charged ions) in serum, plasma, or urine.  Anion gap can be classified as either high, normal or, in rare cases, low.  A high anion gap indicates acidosis.  A low anion gap is frequently caused by hypoalbuminemia.  Usually done when primary metabolic acidosis is suspected. Anion gap helps determine the etiology of the metabolic acidosis.  Normal=10-18mmol/L