BACKGROUND: High respiratory drive in mechanically ventilated patients with spontaneous breathing effort may cause excessive lung stress and strain and muscle loading . Therefore, it is important to have a reliable estimate of respiratory effort to guarantee lung and diaphragm protective mechanical ventilation . Recently, a novel non-invasive method was found to detect excessive dynamic transpulmonary driving pressure (∆PL) and respiratory muscle pressure (Pmus) with reasonable accuracy . During the Coronavirus disease 2019 (COVID-19) pandemic, it was impossible to obtain the gold standard for respiratory effort, esophageal manometry, in every patient . Therefore, we investigated whether this novel non-invasive method could also be applied in COVID-19 patients .
METHODS: ∆PL and Pmus were derived from esophageal manometry in COVID-19 patients . In addition, ∆PL and Pmus were computed from the occlusion pressure (∆Pocc) obtained during an expiratory occlusion maneuver . Measured and computed ∆PL and Pmus were compared and discriminative performance for excessive ∆PL and Pmus was assessed . The relation between occlusion pressure and respiratory effort was also assessed .
RESULTS: Thirteen patients were included . Patients had a low dynamic lung compliance [24 (20-31) mL/cmH2O], high ∆PL (25 ± 6 cmH2O) and high Pmus (16 ± 7 cmH2O). Low agreement was found between measured and computed ∆PL and Pmus . Excessive ∆PL> 20 cmH2O and Pmus> 15 cmH2O were accurately detected (area under the receiver operating curve (AUROC) 1.00 [95% confidence interval (CI), 1.00-1.00], sensitivity 100% (95% CI , 72-100 %) and specificity 100% (95% CI , 16-100 %) and AUROC 0.98 (95% CI , 0.90-1.00), sensitivity 100% (95% CI , 54-100 %) and specificity 86% (95% CI , 42-100 %), respectively). Respiratory effort calculated per minute was highly correlated with ∆Pocc (for esophageal pressure time product per minute (PTPes/min) r2 = 0.73; P = 0.0002 and work of breathing (WOB) r2 = 0.85; P <0.0001).
CONCLUSIONS: ∆PL and Pmus can be computed from an expiratory occlusion maneuver and can predict excessive ∆PL and Pmus in patients with COVID-19 with high accuracy.