The introduction of positive endexpiratory pressure into mechanical ventilation: a retrospective

Continuous positive pressure breathing consisting of a pressure in the airways above the atmospheric level during spontaneous inspiration and expiration was used in the treatment of pulmonary edema and severe pneumonia even before World War II [1]. Positive endexpiratory airway pressure was also very commonly used in the experimental laboratory in any open chest preparation in order to prevent expiratory lung collapse. An important precondition for the introduction of positive endexpiratory pressure (PEEP) in conjunction with mechanical ventilation was established by the experiments of Cournand et al. in 1948 [2]. They found, however, that, compared to mechanical ventilation with ambient endexpiratory pressure, mechanical ventilation with PEEP was associated with a marked decrease in cardiac output due to reduced venous return of blood to the heart. Possible negative circulatory effects were the major concern in the early phase of clinical application of positive endexpiratory pressure.