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 ≥ 15 cmH2O 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 ≥ 3 cmH2O. 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.

► To assess esophageal pressure (Pes) reliability in the presence of lung distortion.
► Lung distortion was produced by saline lavage (BAL) or chest deformation (CD).
► With BAL, lung P–V curve was depressed, but chest P–V curve was unchanged.
► With CD, both P–V curves shifted rightwards, in line with greater work due to distortion.
► Pes reliably reflects average pleural pressure with marked lung mechanical heterogeneity.