Static pressure-volume curves of the respiratory system: were they just a passing fad?

PURPOSE OF REVIEW The aim of this article is to describe the physiologic utility, correlation with lung morphology, difficulties in interpretation and current clinical applications of static respiratory system pressure-volume curves at the bedside in patients with acute lung injury or acute respiratory distress syndrome. RECENT FINDINGS Complex interpretation of pressure-volume curves indicates that alveolar reopening continues past the lower inflection point on the linear part of the curve and suggests the presence of homogeneous lung disease in which recruitment is still possible by positive end-expiratory pressure application. Setting positive end-expiratory pressure above the lower inflection point and tidal ventilation (approximately 6 ml/kg) in the linear portion of the respiratory system pressure-volume curve improved mortality and ameliorated lung and plasma inflammatory mediators compared with ventilation with the lowest positive end-expiratory pressure at traditional tidal volumes. Recent studies have found that regular use of pressure-volume curves provides useful physiological data that help to optimize mechanical ventilation at the bedside. SUMMARY The physiologic data obtained by measuring the static pressure-volume curves have helped clinicians to better understand the behavior of the respiratory system when positive-pressure ventilation is applied. The advanced technology incorporated into modern ventilators allows routine measurement of pressure-volume curves under sedation without paralysis, with acceptable variability and no serious adverse effects.