Lung Recruitability in Early ARDS Lung Recruitment in ARDS

The symptoms of acute respiratory distress syndrome (ARDS) include cyanosis refractory to oxygen therapy, lower lung compliance, radiographic evidence of diffuse bilateral infiltrates, and PaO2/FiO2 ? 200 mmHg (reviewed by LaFollette, Norton, DiRocco, Carney, and Nieman, 2006). Problems arise when normal tidal volumes are used to ventilate ARDS lungs, because much of the lung tissue is refractory to recruitment. As a result, ventilator-induced lung injury (VILI) occurs due to lung distention. Mechanical ventilation of patients with ARDS therefore is associated with a high rate of mortality.

Awareness of the association between a poor prognosis and mechanical ventilation in ARDS is several decades old, yet considerable controversy remains concerning the optimal treatment approach (reviewed by de Matos et al., 2012). There is some consensus that positive end-expiratory pressure (PEEP) should be titrated during recruitment maneuvers, to minimize lung distention. Some clinicians have even argued for the efficacy of the so-called 'open-lung hypothesis', which states that collapsed lung tissue in early ARDS can be reclaimed with acceptable clinical costs. To date this hypothesis has received no empirical support, primarily...

The mean age of the study group was 50.7 years, with a range from 14 to 80 years of age. Most were suffering from primary ARDS (84%) and sepsis (71%).
MRS maneuvers were conducted while patients were being monitored live by computed tomography (CT) (de Matos et al., 2012, Figure 1). The recruitment phase involved pressure controlled ventilation that increased PEEP from 10 to 45 cmH2O in four steps, with each lasting two minutes. This was followed by a PEEP titration phase that decreased cmH2O from 25 to 10 in four steps. At the end of each end-expiratory pause, the lungs were imaged by CT. The only complications observed were transient decreases in blood pressure in two patients, which were not severe enough to interrupt MRS maneuvers.

The results of this study revealed that the median recruitable lung tissue was 45%, far higher than that revealed by previous studies (de Matos et al., 2012). Surprisingly, no evidence of barotrauma…