Pressure-volume curve in ARDS

Pressure-volume curve in a patient with acute respiratory distress syndrome (ARDS). The slope of the curve is flat at low and high airway pressures (ie, below the inflection point and above the deflection point). In these areas, increases in airway pressure produce minimal increases in lung volume. Compliance is maximized on the straight part of the curve. The deflection point is defined as the level at which the curve begins to divert from a straight line. Above this threshold, the lung is likely to begin to become overdistended. Mechanical ventilation is considered optimal when it takes place on the straight part of the curve between the inflection and deflection points.