Esophageal pressure as an estimate of average pleural pressure with lung or chest distortion in rats.

Pressure-volume curves of the lungs and chest wall require knowledge of an effective 'average' pleural pressure (Pplav), and are usually estimated using esophageal pressure as Ples-V and Pwes-V curves. Such estimates could be misleading when Ppl becomes spatially non-uniform with lung lavage or shape distortion of the chest. We therefore measured Ples-V and Pwes-V curves in conditions causing spatial non-uniformity of Ppl in rats. Ples-V curves of normal lungs were unchanged by chest removal. Lung lavage depressed PLes-V but not Pwes-V curves to lower volumes, and chest removal after lavage increased volumes at PL≥15cmH2O by relieving distortion of the mechanically heterogeneous lungs. Chest wall distortion by ribcage compression or abdominal distension depressed Pwes-V curves and Ples-V curves of normal lungs only at Pl≥3cmH2O. In conclusion, Pes reflects Pplav with normal and mechanically heterogeneous lungs. With chest wall distortion and dependent deformation of the normal lung, changes of Ples-V curves are qualitatively consistent with greater work of inflation.