Pressure volume loops with decreased compliance

Pressure volume loops are most useful as an indication of compliance. This figure shows the change in the pressure volume loop that might occur with decreased compliance during pressure controlled ventilation (panel a) and volume controlled ventilation (panel b). If compliance decreases, a line drawn from the zero point through the point of end inspiration becomes more horizontal, and the curve rotated to the right. The normal pressure volume loop is shown by the solid lines, and the dashed lines show the curve with decreased compliance.

During pressure controlled ventilation, with a decrease in compliance the tidal volume is reduced. During volume controlled ventilation, with a decrease in compliance peak inspiratory pressure increases.