COMPLIANCE - according to the lung size Obviously the...

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COMPLIANCE: The slope of the pressure-volume curve, the volume change per unit pressure is known as compliance . In normal expanding range (2-10 mm water) the lung is very dispensable, in other words it is very compliant. The compliance of the human lung is 0.15 L/cm H 2 O. However, it gets stiffer (compliance smaller) as it is expanded above the normal range. Compliance is reduced when (1) The pulmonary venous pressure is increased and the lung becomes engorged with blood (2) There is alveolar oedema due to insufficiency of alveolar inflation (3) The lung remains unventilated for a while e.g. atelectasis and (4) Because of diseases causing fibrosis of the lung e.g. chronic restrictive lung disease. On the contrary in chronic obstructive pulmonary disease (COPD, e.g. emphysema) the alveolar walls progressively degenerate, which increases the compliance. The lung compliance is changed
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Unformatted text preview: according to the lung size: Obviously the compliance of a mouse lung is much smaller than a human lung. At the birth the lung compliance is the smallest and increased with age (until adulthood) due to increase in the size of the lungs. Specific compliance (compliance per unit of lung volume) could be calculated in order to correct this value for lung size. In asthma (hyperactive airway smooth muscle) the lung compliance is usually normal. 5 The standard procedure for measuring compliance in humans is to determine the pressure-volume relationship during a passive expiration from total lung capacity. If the lung deflates slowly, alveolar pressure is equal to atmospheric pressure, and pleural pressure is nearly same as the pressure in the oesophagus, which is usually measured with a thin-walled balloon attached via a plastic tube to a pressure-sensor....
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COMPLIANCE - according to the lung size Obviously the...

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