2. Guyton & Hall Textbook of Physiology - 13th ed. P. 465-467.
3. Pulmonary Ventilation
Defn: Mechanical process of air flow in or out of the lungs to the
atmp due to pr gradients & vol changes.
Cause: Contraction of skeletal muscles.
Two processes: Inspiration & Expiration.
Significance : pulmonary ventilation is to continually renew the
air in the gas exchange areas of the lungs.
Amount :6-7 litres /min
4. Pulmonary ventilation
● Flow of air b/w the atmp.
& the lung alveoli.
● Mechanical process
● Inspiration & Expiration
● Due to Pr gradient of air
b/w lungs & Atmp
Alveolar ventilation
● Exchange of air b/w Alveoli
& atmp.
● Chemical Process
● Internal & External respn.
● Based on partial pr of gases
b/w blood & atmp /tissues
● Amt air utilized for gaseous
exchange/min
7. Respiratory Cycle & Respiratory Rate
Respiratory cycle : Sequence of inspiration & expiration
description of the changes in pressure, lung volumes
& airflow in one cycle.
Inspiration Rest Expiration Rest Inspiration
Respiratory Rate(RR): Number of breaths taken within a specific
amount of time (one minute).
In healthy adult:12-15 breaths/minutes
9. ➢Eupnea: Normal quiet respiration
➢Bradypnea: Slow rate of respiration
➢Tachypnea: Increased rate of respiration
➢Apnea: Cessation of respiration
➢Hypoventilation: Decrease in Rate & Depth of ventilation.
➢Hyperventilation: Increase in Rate & Depth of ventilation
➢Hypoapnea: Shallow breathing
➢Dyspnea: Difficulty in breathing.
10. Mechanics of normal & forced respiration.
Lung mechanics: It is study of forces & factors responsible for
ventilation.
Mechanics of ventilation depends on
1. Muscles & bones of thoracic cage.
2. Pleura & pleural cavity.
3. Dead space & value & types.
4. Different pressure & derived pressures.
5. Elastic property of lungs and thorax
6. Surface tension of the alveoli.
11.
12. Muscles of Respiration
Quiet Inspiration: Diaphragm,External intercostal muscles
Quiet Expiration: Passive relaxation of inspiratory muscles
Forced Inspiration:Ala nostrils, scalene of neck
Sternocleidomastoids, pectoris minor,lavator scapulae,
Forced Expiration: Internal intercostal, Rectus abdominis, External
oblique muscles.
Muscles of inspiration:Elevate the chest cage
Muscles of expiration: Depress the chest cage
Thoracic cage bones: Ribs, Sternum, Vertebral column.
13. Diaphragm(75%)
Dome shaped- Attached to lower ribs, sternum & vertebral column.
Nerve supply: Phrenic nerve- C3,4,5.
Action :>75% of quiet inspiration . vertical dimension of thorax.
Contraction dome/pulls the dome of muscle down.
Causes flow of air into lungs.
Relaxation: dome thus decrease vertical diameter.
Causes expulsion of gases.
Moves down 1.5 cm normal (7.5cms - forced ) inspiration
Abdominal contents forced downward & forward causing ↑ in vertically
Rib margins are lifted & moved outward causing ↑ transverse diameter
14. Applied :Reduced movement:Obesity(moderate to severe),Pregnancy,
Tight Clothing.
Paradoxical movement of diaphragm when paralyzed
Upward movement with inspiratory drop of intrathoracic pr.
Inspiration Expiration
15. External intercostals (25%)
Location: Obliquely b/w ribs in forward & downward direction.
Nerve supply: Intercostal nerves (T1-11).
Action and effects:T.S+ A.P ↑by 2 mechanisms:
1: 6–10 ribs rotates upwards and outwards by a “bucket-handle
movement” → ↑ T.S.
2: upper 4 ribs rotate the sternum in upward & outward (pump-
handle movement) → ↑ in vertically .
Applied: Paralysis does not seriously alter inspiration diaphragm is
so effective but sensation of inhalation is decreases.
16.
17. Inspiration Expiration
Muscles ➢ Contraction:Diaphragm
& External internal
intercostal muscles
➢ Daiphragm dome flattens
➢ Relaxation:Diaphragm &
External internal
intercostal muscles
➢ Daiphragm dome flattens
Ribs
Move
➢ up & out wards ➢ down & in wards
Thorax
Vol &Pr
➢ Vol increases &
➢ Air pr decreases
➢ Vol decreases &
➢ Air pr increases
Air flows ➔ Into lungs from atmp ➔ From lungs to atmp
Normal quiet respiration
18.
19.
20.
21. Pleura & pleural cavity
Two layers :
1. Visceral :Attached to the lung parenchyma ,get
the same nerve supply not painful
(no pain receptors).
2. Parietal :Attached to inner aspect of thoracic
cavity, get the nerve supply from the
same,painful(contain pain receptors)
1. Intrapleural space:Space is closed space with
negative pressure , filled with pleural
fluid.
Intrapleural
space
22. Intrapleural Space: Has thin layer of mucoid transudate
(interstitial fluid + protein)
10-20 ml Secreted by Parietal layer.
Drained by lymphatics constant suction on pleura (-5cmH2O) of
(Mediastinum, superior - diaphragm, lateral)of parietal pleura
★ Helps create Negative pressure.
Functions:
➢ Lubricant for lungs to slide against chest wall facilitates change
in size & shape of lungs. Protects lungs from external damage.
➢ Prevents frictional irritation so membranes slide against each
other & are difficult to separate apart .
23. Pleural pressure
Defn:The pr of the fluid in the thin space b/w Visceral &Parital pleurae
Negative pr as compared to the atmp pr. < 760mmHg.
Beginning of the respiration is -5 cms of H2O
Function: This amount hold the lungs open to their resting position.
Negativity leads to sucking of air in lungs from the atmosphere.
During Normal quiet :the lungs and chest wall are stretched in
equal & opposite direction.
Intrapleural space increases but it being closed cavity ,negativity in it
increases more (-5 to 7.5cms of H2o)
24. Significance: If positive /equal to atmp pr
Leads to lungs collapse(recoil inwards)
Pneumothorax, Hemothorax, Chylothorax .
28. Alveolar pressure
● Defn: The pr of air inside the lung alveoli
● When glottis is open:
● No air moves into the & out of the lungs
● Pr in alveoli = atmp pr =760mmHg /Zero cms of H2O
● Quiet inspiration: Alveoli opens pr = -ve /-1cm of H2o
This pulls air into alveoli in 2 seconds
● Quiet expiration: Alveolar pr =+ve/ + 1cm of H2o
This forces the inspired air out of lungs during 2-3 seconds.
29.
30. TRANSMURAL PRESSURE
Thoracic cavity larger than lungs
Transmural pr:Pr across Lung Wall
Pr gradient holds thoracic wall & lungs
in close apposition
Pr gradient is balanced by the elastic forces
in the alveoli producing equilibrium
Under static conditions,
Transmural pr = the elastic recoil pr
of the compartment.
31. Transpulmonary pressure
● Defn:Alveolar pr- Pr on
outer space of lungs
● Measure of the elastic
forces in the lungs
● Tends to collapse the lungs
at each instant of
respiration
32. 32
Physiological factors that affect:
Valsalva manoeuvre
Pathological factors:
Emphysema
Injury to thoracic wall will produce collapse of lungs
33. Dead spaces
Defn: A fraction of tidal volume of air that does not take part in
exchange of gases.
Types:
Anatomical :Vol. of air that does not reach the alveoli
Physiological: 1) Inspired air in alveoli that has no/less
blood supply.
2) Inspired air in alveoli that has normal blood flow
but less air reaches.
Normal Value:150 ml
Significance: regulation of temperature and humidification of air.
Increasing the depth of breathing is more effective in increasing
alveolar ventilation.
VT
