The effect of the minimal deflation pressure on lung mechanics in isolated rabbit lungs.

Abstract

Alterations in the PV relationships of isolated rabbit lungs which are dependent on the minimal deflation pressure (Pmin) have been studied. When Pmin remains positive both inflation and deflation limbs of the PV loop are shifted toward lower transpulmonary (P1) pressures throughout most of the cycle. In addition, Pmin(+) conditions eliminate the deflation inflection and increase deflation compliance at low and mid-lung volumes. Results from indicator washout and spontaneous deflation reveal that Pmin(+) conditions produce a more even inflation of the lung parenchyma and dilate airways at low lung volumes. These effects cause a stabilization of the parenchyma and a delay in airway closure resulting in the increased deflation compliance and a decrease in the trapped gas volume during Pmin(+) conditions. The relevance of Pmin(+) and (−) conditions are discussed for several clinical conditions.