Question

1) Patient “A” has a change in pressure of 5 resulting in a tidal volume return of 600. Patient “B” has a change is pressure of 5 resulting in a tidal volume of 250cc. Calculate the total compliance of the lungs and thorax for each patient.

a. Once compliance has been figured; explain what is happening to patient “B”.

Answer 1

For patient "A",

Change in plueral pressure=5cm H2O

Tidal volume=600ml=0.6L

Therefore,lung compliance=0.6L/5cmH20

=0.1L/cm H2O

For patient "B"

Change in plueral pressure=5cmH2O

Tidal volume=250cc=0.25 L

Therefore,Lung compliance=0.25L/5cm H2O

=0.05L/cm H2O

Normal adult lung compliance ranges from 0.1 to 0.4 L/cm H20.In the case of patient "B" thelung compliance is 0.05L/cmH2O which indicates a low lung compliance.Low compliance indicates a stiff lung and means extra work is required to bring in a normal volume of air. This occurs as the lungsin this case become fibrotic, lose their distensibility and become stiffer.