Physiological comparison of three spontaneous breathing trials in COVID-19 pneumoniae. Inspiratory effort, and relationship with the different phenotypes. Risk of patient self-inflicted lung injury.

Abstract

Abstract Background High drive and high effort during spontaneous breathing can generate potential patient self-inflicted lung injury (P-SILI), due to uncontrolled high transpulmonary and transvascular pressures, with relapse of respiratory failure. P-SILI has been demonstrated in experimental studies, and supported in recent computational models. Different treatment strategies have been proposed according to the phenotypes of elastance of the respiratory system (Ers) for patients with COVID-19. This study aimed to investigate the effect of different ventilatory strategies on the respiratory drive and muscle effort in the clinical practice, and its relationship with the different phenotypes, by obtaining respiratory signals and calculated muscle pressure. Design: Monocenter physiologic study of series cases. Setting: University medical-surgical ICU. Patients: Eleven mechanically ventilated patients COVID-19 pneumoniae at the initiation of spontaneous breathing were studied. Interventions: Three spontaneous ventilation modes were evaluated: Pressure support ventilation (PSV), airway pressure release ventilation (APRV), and CPAP double in each of the patients. Measurements and main results: The study is based on the calculation of muscle pressure (Pmus) through the equation of motion. For this purpose, we have acquired the respiratory signals of airway pressure (Paw), Flow (V´) and Volume (V) directly from the data transmission protocol of the ventilator (Dräger). The main physiological measurements have been calculation of the respiratory drive (P0.1), muscle effort through the ΔPmus, pressure-time product (PTP_pmus) and "power of breathing" considered as work of the patient J/min (WOBp). Our results show similar high drive and muscle effort in each of the spontaneous ventilatory modes tested, without significant differences between them. Median (IQR): P0.1 6.12 (4.43-7.21) cmH2O, ∆Pmus 13.48 (11.09-17.81) cmH2O, PTP 166,29 (124.02-253.33) cmH2O*sec/min; and WOBp 11.12 (5.91-17.51) J/min. High Drive and effort are found in patients even with low Ers. The relationship between respiratory drive and “power of breathing” versus Ers, although with a wide coefficient of variation, is significant. We have found a trend towards a worse prognosis in terms of survival and stay in the ICU, in patients with high drive and inspiratory effort. Conclusions: None of the spontaneous ventilatory methods tested succeeded in reducing the high respiratory drive or muscle effort, and thus potentially promoting P-SILI, regardless of the Ers.