Pulmonary Ventilation. Week 2 Dr. Walid Daoud A. Professor. Pulmonary Ventilation. Pulmonary ventilation is mass movement of air in and out of the lungs. Forces for Pulmonary Ventilation: Pressure gradient between alveoli and atmosphere.
Dr. Walid Daoud
Pulmonary ventilation is mass movement of air in and out of the lungs.
Forces for Pulmonary Ventilation:
Pressure gradient between alveoli and atmosphere.
Inspiration occurs when pressure in atmosphere exceeds pressure in alveoli.
At sea level, atm. pressure is 760 mmHg and all pressures in the respiratory system are expressed relative to atmospheric pressure.
-During inspiration Palv. = - 1 mmHg
-During expiration Palv. = + 1 mmHg
-At ends of inspiration & expiration= 0 mmHg
Changes in intra-alveolar pressure are caused by changes in volumes of lungs.
It is the pressure inside pleural space.
It is always negative under normal conditions.
. At end of normal expiration= - 4 mmHg
. At end of normal inspiration= -6 to -8 mmHg
. During forced inpiration with glottis closed
= - 30 to - 40 mmHg (Muller experiment).
. During forced expiration with glottis closed
= + 50 mmHg (Valsalva experiment).
- It helps lung expansion.
- It helps venous and lymphatic return to the
- It is a measure of lung elasticity (recoil
It is difference between intralveolar and intrapleural pressures.
= Palv. – Ppl
= 0 – (-4 ) = 4 mmHg
Transpulmonary pressure is called distending pressure which is the force acting to expand the lung against elastic recoil of the stretched lung.
The negativity is due to continuous tendency
of lungs to recoil inward against continuous tendency of chest wall to expand outward to reach their relaxation volume.
Causes of recoil tendency of lungs:
1- Elastic tissues of lungs
2- Surface tension of fluid lining the alveoli.
A detergent -like substance secreted by
type II alveolar cells.
Complex mixture of phospholipid dipalmitoyl lecithin, apoproteins and calcium ions.
- Facilitation of lung expansion.
- Prevention of alveolar collapse during exp.
- Prevention of pulmonary edema.
1- Respiratory distress syndrome (RDS).
2- Long-term inhalation of 100% oxygen.
3- Occlusion of one pulmonary artery.
4- Cigarette smoking.
Resting expiration is a passive process
while forced expiration is an active one.
Itis a device to measure lung volumes and capacities.
Itis the used technique .
Itis the recording.
1- Tidal volume (VT).
2- Inspiratory reserve volume (IRV).
3- Expiratory reserve volume (ERV).
4- Residual volume (RV).
RV can not be measured by spirometry
but can be calculated by helium-dilution method.
1- Inspiratory capacity (IC).
2- Vital capacity (VC).
3- Functional residual capacity (FRC).
4- Total lung capacity (TLC).
FRC and TLC can not be measured by spirometry.
1- VC increases in:
Males, athletes and standing position.
2- VC decreases in:
Females, pregnancy and recumbent
Clinical significance of VC:
VC is an index of lung function and strength
of respiratory muscles:
1- Paralysis or myositis of resp. muscles.
2- Bone deformities e.g, kyphosis or scoliosis.
3- Loss of lung elasticity e.g, emphysema.
4- Restrictive lung diseases e.g, lung fibrosis.
5- Obstructive lung diseases e.g, asthma.
6- Abdominal tumors.
- Forced expiratory volume in first second (FEV1).
- Forced vital capacity (FVC).
Normally FEV1 = 80% of FVC
-Restrictive lung diseases: lung fibrosis:
. Both FEV1 & FVC are reduced.
. FEV1/FVC % is normal.
-Obstructive lung diseases: brochial asthma.
. FEV1 is reduced more than FVC
. FEV1/FVC % is low.