To Peep or not to Peep Ards Patients?
PEEP was introduced in 1967 in the treatment of ARDS (1). Suter et al. (2) introduced the concept of “best PEEP” to describe the optimal level of PEEP at which static compliance was the highest. This level was also associated with maximum oxygen delivery and minimum dead space. In general- the beneficial effects of PEEP are thought to be achieved by reeruiting collapsed alveoli and restoring the functional residual capacity (FRC) toward normal (3,4). However, while PEEP is known to increase the endexpiratory lung volume (EELV) in ARDS patients (3,4), with the exception of the studies of Gattinoni's group (5,6) there are no systematic studies in which the recruitment of collapsed lung units due to PEEP has been quantified. Hence, the question remains whether this increase in lung volume simply reflects a displacement of EELV along a fixed static volume pressure (V-P) curve of the respiratory system with concomitant alveolar overinflation or is associated with an upward shift of the static P-V eurve caused by recruitment of previously eollapsed lung units. Assessment of stabe thoracopulmonary V-P curves with the “super-syringe” method has been proposed for diagnosis, staging and management of ARDS patients (7). However, the long time required to perform V-P curves with this method introduces significant errors due to continuing gas exchange.
KeywordsLung Volume Acute Respiratory Failure Functional Residual Capacity Adult Respiratory Distress Syndrome Alveolar Recruitment
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