The document provides information on the respiratory system. It discusses: 1. The respiratory system functions to exchange oxygen and carbon dioxide between the atmosphere and tissues through breathing and gas diffusion. It is divided into an upper and lower system. 2. The lower respiratory system includes the lungs, which are made up of conducting and respiratory zones. Gas exchange occurs in the alveoli via diffusion driven by partial pressures. 3. Respiration includes pulmonary ventilation, external respiration in the lungs, and internal respiration in tissues. Various tests like spirometry and diffusion testing evaluate lung function and gas exchange ability.

1. Respiratory System
Applied Physiology
Dr.Dony John, PT
Principal
Nanjappa College Of Physiotherapy.

2. Introduction: Function
• Respiratory System plays an Inevitable role in
Maintaining Homeostasis by exchange of
Oxygen(O2) and Carbon dioxide(CO2 ) between
atmospheric air, blood and tissue cells.
• Maintain PH of Body fluids.
• Olfaction
• Voice production.
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3. Introduction: Components of Respiratory System
• Structurally;
1. Upper Respiratory System: Nose, nasal cavity,
and Pharynx
2. Lower Respiratory System: Larynx, trachea,
bronchi and lungs.
Functionally;
I. Conducting Zone; cavities and tubes which
interconnect both outside and within lungs.
II. Respiratory Zone: tubes and tissues within
lungs where exchange of gas occur.
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4. Structural & functional parts of LRS
Structural Functional
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5. Respiration
• The process of exchange of gases as,
i. Pulmonary Ventilation/Breathing: The exchange of
gas between atmosphere and alveoli of the lungs;
ie, inhalation and exhalation.
ii. External/pulmonary Respiration: The exchange of
gases between alveoli and blood in pulmonary
capillaries across respiratory membrane; O2 diffuses
to pulmonary capillaries and co2 back to alveoli.
iii. Internal/Tissue Respiration: Gas exchange occur
across blood in systemic capillaries and tissue cells;
o2 diffuses to cells and co2 back to blood capillaries.
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6. Respiration
Ventilation: the movement
of air in and out of lung.
Perfusion: the flow of
blood in pulmonary
capillaries
Diffusion:
movement/exchange of
molecules (gas molecule as
o2 and co2) from their
region of higher
concentration to lower
concentration region.
Many factors such as
regional gravity/altitude,
surface tension of alveolar
fluid, airway resistance and
compliance of lungs
influence ventilation and
perfusion.
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7. Lung volumes and Capacities
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8. Oxygen and Carbon Dioxide exchange
• The passive diffusion across pulmonary blood
and alveolar air is determined by two gas Laws
as, Dalton’s & Henry’s Laws.
• Gas molecule exert a pressure on the surface
where they are occupied; this force is called
Pressure.
• In natural system gases are a mixture of
different gases and each molecule in the
mixture exert a certain pressure called; Partial
pressure (Px).
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9. Dalton’s Law
• Describes the behavior of nonreactive gases in a
gaseous mixture.
“A specific gas in a mixture exert its on pressure ;
thus, the total pressure exerted by a mixture of
gas is the partial pressures of each gases in the
mixture”.
• Eg: atmospheric air :- Nitrogen, oxygen, argon,
carbon dioxide, water vapor and other gases in
trace amounts.
• Atmospheric air (760mmHg) =
PN2+PO2+PAr+PH2O+PCo2+Pother gases
These partial pressures determine movement of O2 and CO2
between atmosphere and lungs, Lungs and Blood and across
blood and tissues.
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10. Hyperbaric Chamber
• Here the behavior of gas with partial pressure
concentration is used.
• In hyperbaric chamber patient is exposed to
100% oxygen with increased pressure or a
mixture of gas where concentration of oxygen
is above atmospheric air and above normal
level partial pressure too than atmosphere.
• Two types: Monoplace- single patient
Multiplace- multiple clients.
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11. Indication-Hyperbaric chamber Rx
• Decompression sickness
• Acute Carbon monoxide poisoning
• Gas embolism/Gas gangrene
• Preservation of compromised skin graft
• Cyanide poisoning
• Anaerobic bacterial infections etc…
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12. Hyperbaric Chambers
• Monoplace • Multiplace
Multiple patient receive oxygen via mask or light
weight clear hood placed over head
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13. Henry’s Law
• Describes the behavior of gases in contact
with a liquid. Eg: blood
“The concentration of gas in a liquid is directly
proportional to the solubility and partial
pressure of that gas”.
The relative concentration of air in the
atmosphere; N2>O2>H2O>CO2. However,
nitrogen solubility in blood at sea level is very
low.
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14. Nitrogen Narcotics/Rupture of the deep
‘As the total pressure increases, the partial pressure of
all its gases increase.’
In SCUBA diving; the composition of the compressed air
that divers breathe causes nitrogen to have higher Px
than at sea level leading to more dissolution into
plasma and interstitial fluid cause giddiness, fatigue,
lack of coordination etc.
On the other hand, if the diver come to the
surface/ascend too quickly, nitrogen come out of
solution very rapidly and forms gas bubbles in
tissues:- Decompression sickness.
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15. Oxygen & Carbon Dioxide
Exchange
External Respiration/Pulmonary gas
Exchange: This process takes place in Lungs
only. At rest PO2 in pulmonary capillaries is
about 40mmHg causes O2 to diffuse into blood
from alveolar air where the PO2 is 100-
105mmHg. Diffusion continues until the PO2 of
alveolar air and pulmonary capillaries reach
equilibrium.
On the other hand CO2 is diffusing in the
opposite direction, at rest Pco2 in blood is
45mmHg and Pco2 in alveolar air is 40mmHg .
Internal Respiration/Systemic gas
Exchange: It occurs in tissues throughout the
body. The cells constantly use O2 to produce
ATP, thereby the drop in Po2 inside the cells
compare to systemic blood capillaries results
in the diffusion and CO2 back.
A person at rest , tissue cells need is about
25% of the available O2 in oxygenated blood ,
despite the name deoxygenated blood retains
75% of its O2 content.4/25/2020 Don john 15

16. Mechanism of Breathing
• The act of breathing depends on pressure
relationship of,
1. Atmospheric pressure (Patm)
2. Alveolar Pressure (Patv)
3. Intrapleural pressure (Pip)
Boyle’s Law- the inverse relationship of volume and
pressure
Diaphragm and External intercostals action change
volume of thoracic cavity in which lungs
occupied and thus pressure changes resulting in
inhalation and exhalation.
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17. Muscle action & pressure change
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18. Control of Breathing
• The action of respiratory muscle action is controlled
by nerve impulses from neurons located bilaterally in
the brain stem- Respiratory Center.
Respiratory Center
Medullary Respiratory
Center in the Medulla
DRG/ Inspiratory area
VRG/expiratory area
Pontine Respiratory
Group/Pneumotaxic
area in Pons
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19. Normal Quiet Breathing/Eupnea
Dorsal Respiratory Group
Active Inactive
Diaphragm & external intercostals
contracts during active phase
Normal quiet inhalation
Diaphragm and external intercostals
relax, elastic recoil of thorax and lungs
Normal quiet exhalation
2 seconds 3 seconds
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20. Forceful Breathing
DRG VRG (forceful
inhalation neurons)
VRG (forceful exhalation
neurons)
Diaphragm & external
intercostals contract during
most active stage
Accessory muscles of
inhalation contract (SCM,PM
and scalene)
Accessory muscles of
exhalation contract (internal
intercostals, external and
internal oblique,
transeversus and rectus
abdominus)
Forceful inhalation Forceful exhalation
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21. Nervous Control of Breathing
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22. 1.Respiratory System:- Exercise
• Pulmonary perfusion O2 & CO2 diffusion
capacity rate increases.
• At onset of Vigorous exercise , an abrupt
increase of in breathing followed by more
gradual hike .
• In moderate exercise the increase is in depth
than rate of breathing.
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23. Vigorous Exercise
Rate
DRG
Excitation of Limbic system, sensory
impulse from joint, muscle and
tendon propioceptors, motor
impulse from primary motor cortex
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24. Moderate Exercise
• The depth and gradual increase of breathing;
i. Slightly decreased Po2 by greater oxygen
consumption
ii. Slight increase in Pco2 by contracting muscle
fibers
iii. Increase in temperature.
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25. 2.Spirometry
• A standard measure/test to know how well
the lungs function by measuring airflow.
• Vital role in the diagnosis of COPD, asthma,
interstitial pulmonary fibrosis etc…
• To differentiate obstructive and restrictive
pattern
• Different variables are checked chiefly, FVC
FEV1 and FEV1/FVC Ratio.
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26. FVC,FEV1,FEV1/FVC
• Forced vital capacity (FVC)– The volume of air that
can be forcefully exhaled after a maximal inhalation.
The majority of FVC can be exhaled in less than three
seconds of exhalation in normal people, however it
may be prolonged in people with obstructive lung
diseases.
• Forced expiratory volume in 1 second (FEV1) – The
volume of air exhaled in the first second of FVC,
Normal subjects can exhale 75- 80% of their FVC in
the first second, hence the FEV1/FVC ratio is an
important determinant in assessing lung disease.
FEV1/FVC Ratio represents the capacity to exhale in
one second. The low the ratio suggestive of a block in
airways.
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27. Spirometry Graph
FVC and FEV1 plotted on a flow to time
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28. 3.Diffusion Test
• A lung diffusion test is used to examine how
your lungs are processing air, ie how well your
lungs allow oxygen and carbon dioxide to pass
in and out of your blood.
• It may also be known as a diffusing capacity of
the lung for carbon monoxide (DLCO) test.
• A quick comfortable procedure which cause
zero discomfort.
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29. Procedure & interpretation
• The test look into the difference in the
quantity of gas inhaled and exhaled.
• It uses CO as it has higher affinity to get
dissolve in blood.
• If the exhaled air contain,
75-140% of predicted Value – Normal
60-79% of predicted Value - Mildly Reduced
Below 40% - Reduced Lung function.
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30. 4.Lung Plethysmography
• Pulmonary/Body Plethysmography
• It works by the principle of Boyle’s law
• Measures the lung size/volume and capacity
• Primarily measures/assess functional residual
capacity(FRC Pleth) and airway resistance
(Raw)
• With deep inspiration & expiration TLC & RV
also be measured.
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