Non-invasive assessment of intrinsic positive end-expiratory pressure

Assessment of intrinsic positive end-expiratory pressure (PEEPi) in spontaneously breathing subjects requires an esophageal balloon (ES) to estimate the end-expiratory sudden drop of alveolar pressure (Palv) corresponding to PEEPi. With the advent of electronic compensation, Palv can be estimated also plethysmographically, opening the possibility to assess PEEPi non-invasively. The aim of this study is to develop a procedure to identify PEEPi on plethysmographic Palv tracings and to compare the result of its application with ES-derived data (PEEPies) from the literature. 60 COPD patients underwent plethysmography before and after bronchodilation (BD). 35 patients exhibited tidal expiratory flow-limitation (FL), a condition likely to induce PEEPi. Plethysmographic PEEPi (PEEPipl) was identified as the sudden drop of Palv immediately before end-expiration by an automated algorithm. Before BD, 34 COPD patients with FL and 11 without FL presented PEEPipl. In patients with PEEPipl, PEEPipl was greater in the presence than in the absence of FL (3.8 (1.8) versus 2.0 (1.4) cmH2O, P=0.007). On average, after BD PEEPipl decreased by ~30%. PEEPipl was inversely correlated with IC%p and FEV1%p, and positively correlated with dyspnea at rest (p<0.001). PEEPipl values were similar to PEEPies previously measured (Haluszka 1990; Dal Vecchio 1990). In conclusion, although a direct PEEPipl-PEEPies comparison is needed to validate the technique, non invasive assessment of PEEPi seems feasible.