1. (a) Describe briefly the mechanics of breathing in terms of the three pressur

Question

1. (a) Describe briefly the mechanics of breathing in terms of the three pressures and their inter-relationship during equilibrium, inspiration, and expiration.

(b) What are the values of the transpulmonary pressure PL during equilibrium, inspiration, and expiration? Express the values in mm Hg and Pa.

(c) What is the change in transpulmonary pressure ?PL during inspiration and expiration as measured from the value during equilibrium?

(d) Suppose that the change in volume as measured from the equilibrium value for a normal adult lung during inspiration or expiration is 0.5 litres. Calculate the compliance of the lung and express the value both in m3/Pa and litres/kPa.

Explanation / Answer

MECHANISM OF BREATHING : There are three different pressures those directly involve in the mechanism of breathing.

1. Atmospheric pressure ( pressure created by gases present in air)

2. Intra-pleural pressure ( pressure in pleural cavity)

3. Intra-alveolar pressure (pressure of air in alveoli of lungs)

Inhalation and exhalation (inspiration and expiration respectively) dependent onpressure difference between lungs and atmosphere according to Boyle's law (P =1/V)

Hence, Air would move from low volume(high pressure ) to high volume(low pressure)

INTER RELATIONSHIP BETWEEN PRESSURES :-

Atmospheric pressure is 760mmHg that is non variable and alveoli of lungs are related to trachea (wind pipe) so it equalize the intra alveolar pressure to atmospheric pressure(0 mmHg) at different breathing cycle.

Intra pleural pressure is always negative (-4mm Hg ) with atm. pressure but flactuates at different phases of breathing.

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