mark wrote:
Quote:
a. Lung compliance is less than total compliance
b. Dynamic compliance can only be measured in a ventilated patient
c. Total compliance is less in a paralysed patient
d. In IPPU tidal volume depends only on compliance
e. Compliance is directly proportioned to V/Q ratio
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1/total compliance=1/chest wall+1/lung. Normal lung compliance is 200ml/cmH20. Normal total thoracic compliance is 85ml/cmH20.(A-Z pg130) Dynamic compliance can be measured by body plethysmography or an oesophageal ballon during normal breathing.(West, pg 162) In a paralysed patient FRC is reduced, reducing compliance. In constant-flow generators the TV is fixed but the rise in airway pressure and peak pressure is determined by lung compliance.
There is low compliance at extremes of lung volume, V/Q relationship alters with lung volume (high at apex where alveoli are more expanded, in collapsed lung V/Q relationship would be low, compliance reduced in both situations), therefore the relationship is not directly proportional.
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