Pressure-volume curve: methods and meaning

The pressure-volume curve of the respiratory system is a physiological method used for diagnotic purposes to describe the static mechanical properties of the respiratory system. A renewal of interest in the pressure-volume curve has recently appeared because of experimental evidence regarding the information conveyed by the curve, a better understanding of the pathophysiologic factors influencing its interpretation and the beneficial results of clinical trials based on the use of the pressure-volume curve for ventilatory management of acute respiratory distress syndrome. Thus, adapting ventilatory settings to individual characteristics of the patients in terms of respiratory mechanics may be an extremely important aspect for a better management of the most difficult to ventilate patients with acute lung injury. There is considerable experimental evidence that both the opening-collapse phenomena and the excessive lung stretch may cause damage to the lungs. Therefore tools allowing an individual titration of ventilatory settings taking into account the constraints of the respiratory system seem highly desirable. The pressure-volume curve might be easily achievable at the bedside as a monitoring tool. The low-flow technique using ventilator technology has several potential advantages. It is hopeful to think that in the future the measurement of the P-V curve and the quantification of alveolar recruitment may be easily provided at the bedside and may help for the titration of the ventilatory settings in clinical practice. This review will focus briefly on the physiologic background, technique description, and recent advances concerning the interpretation of the P-V curve in the critically ill patient