Pressure Control Ventilation in Acute Lung Injury

Abstract

High peak inspiratory pressures during mechanical ventilation result in lung injury with hyaline membranes in many animal studies. Recent prospective, randomized studies demonstrated that lower tidal volumes and low plateau pressures decreased mortality rate and increased the number of days without ventilator use in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). As a reduction in peak airway pressures has gained more attention in the critical care literature, a closer look at pressure control ventilation (PCV) is indeed warranted. PCV is a mode of mechanical ventilation that provides a constant pressure for a preset inspiratory time (I-time).Although inspiratory flow varies to maintain the preset inspiratory pressure, it is generally delivered as a decelerating flow waveform. I-time is lengthened as necessary to improve oxygenation and gas distribution. If I-time is longer than expiratory time (E-time), the term, inverse ratio ventilation (IRV) is used to describe this method of ventilation. PCV with and without IRV has been used to treat patients with refractory hypoxemia and reduced lung compliance. PCV also may be beneficial in oxygenating and ventilating patients with air leak syndrome (bronchopleural fistula or cuff leak) and unilateral lung disease. PCV with minimal air trapping (occult positive end-expiratory pressure [PEEP]) can be used to maintain oxygen delivery, ventilation, and clinically acceptable peak airway pressures while lowering FIO 2 and improving compliance in ARDS. The intent of this review is to compare theoretical benefits of PCV to other modes of ventilation, describe a method of instituting PCV that will allow for longer I-times in spontaneously breathing patients without inducing a large amount of air trapping, and discuss recent advances in PCV.