Airway Occlusions to Measure Inspiratory Effort, Respiratory Drive, and Lung Mechanics During Noninvasive Ventilation.

Abstract

In intubated patients, occlusion maneuvers allow non-invasive assessment of inspiratory effort, respiratory drive and lung mechanics. To assess the feasibility of occlusion maneuvers during noninvasive ventilation (NIV). In this multicenter study, 60 hypoxemic patients underwent two randomized 1-hour NIV sessions with oro-nasal and full-face masks after extubation. End-expiratory and end-inspiratory occlusions measured expiratory occlusion pressure (Pocc), 100-ms airway-pressure drop (P0.1), and plateau pressure. Esophageal manometry, calibrated before extubation, provided reference values for inspiratory effort, assessed as esophageal pressure swing (ΔPes), and dynamic transpulmonary driving pressure (ΔPL,dyn = pressure support - ΔPes). Interface-specific conversion factors (K) translating Pocc into predicted ΔPes (K × Pocc) and predicted ΔPL,dyn (pressure support - predicted ΔPes) were derived through 100-interaction cross-validation (20-patient derivation set, 40-patient validation set). Pocc was measurable in all patients. Mean K was 0.71 with the oro-nasal mask and 0.80 with the full-face mask. Predicted ΔPes agreed with observed ΔPes (oro-nasal bias -0.41 cm H2O, 95% limits of agreement -2.3 to 1.5; full-face 0.09, -2.9 to 3.1), and predicted ΔPL,dyn agreed with observed ΔPL,dyn (oro-nasal bias 0.03, -2.9 to 2.9; full-face -0.04, -4.3 to 4.2). Predicted ΔPes identified observed ΔPes ≤ -10 cm H2O, with areas under the receiver-operating-characteristic curve of 0.98 (oro-nasal) and 0.97 (full-face). Ventilator-derived P0.1 did not precisely quantify respiratory drive, but values >2.7 cm H2O with the oro-nasal mask and >3 cm H2O with the full-face mask identified high drive with specificity >90%. Plateau pressure was unstable in 78% (oro-nasal) and 90% (full-face) of patients. More negative predicted ΔPes, higher predicted ΔPL,dyn, and lower predicted lung compliance (expiratory tidal volume/predicted ΔPL,dyn) were associated with subsequent re-intubation. During NIV, Pocc-derived parameters provide non-invasive estimates of inspiratory effort, lung stress and mechanics, whereas ventilator P0.1 and plateau pressure are less reliable.