The relationship between peak inspiratory pressure and positive end expiratory pressure on the volume of air lost through a bronchopleural fistula.

A bronchopleural fistula (BPF) may complicate the management of patients with major pulmonary disease or thoracic surgery. Neonates with idiopathic respiratory distress syndrome and requiring ventilation are especially susceptible to pulmonary barotrauma, which may result in a BPF. Morbidity and mortality are consistently high. In ventilating patients with BPF, the effects of peak inspiratory pressure (PIP) and positive and expiratory pressure (PEEP) on air leak have not been documented. These relationships were studied in rabbits prepared by thoracotomy and creation of a standardized BPF. Randomized trials of various levels of PIP and PEEP were applied, and the percent of inspired tidal volume lost through the BPF calculated. The percent of inspired volume lost does not increase significantly from 10 to 30 cm H2O PIP (p greater than 0.05). Percent leak does increase significantly when increasing PEEP frm 0 to 16 cm H2O (p less than 0.001). Any PEEP greater than 6 cm H2O results in more air loss through the BPF than any level of PIP (p less than 0.01). Linear regressions through a common origin were calculated to illustrate the relationship of PIP versus leak and PEEP versus leak. The slopes of these lines (0.572 and 3.97, respectively) are significantly different (p less than 0.001). When using equal increments of PIP and PEEP, PEEP will have over a sixfold greater effect on air leak than doses PIP. These data suggests that PIP should be increased preferentially when ventilating patients with BPF in order to minimize air leak. PEEP less than 6 cm H2O can be used without any significant increase in the volume of air lost.