The level of partial pressure of carbon dioxide affects respiratory effort in COVID-19 patients undergoing pressure support ventilation with extracorporeal membrane oxygenation

Patients with COVID-19 undergoing pressure support ventilation (PSV) with extracorporeal membrane oxygenation (ECMO) commonly had high respiratory drive, which could cause self-inflicted lung injury. The aim of this study was to evaluate the influence of different levels of partial pressure of carbon dioxide(PaCO₂) on respiratory effort in COVID-19 patients undergoing PSV with ECMO.

ECMO gas flow was downregulated from baseline (respiratory rate < 25 bpm, peak airway pressure < 25 cm H₂O, tidal volume < 6 mL/kg, PaCO₂ < 40 mmHg) until PaCO₂ increased by 5 − 10 mmHg. The pressure muscle index (PMI) and airway pressure swing during occlusion (ΔPOCC) were used to monitor respiratory effort, and they were measured before and after enforcement of the regulations.

Ten patients with COVID-19 who had undergone ECMO were enrolled in this prospective study. When the PaCO₂ increased from 36 (36 − 37) to 42 (41–43) mmHg (p = 0.0020), there was a significant increase in ΔPOCC [from 5.6 (4.7–8.0) to 11.1 (8.5–13.1) cm H₂O, p = 0.0020] and PMI [from 3.0 ± 1.4 to 6.5 ± 2.1 cm H₂O, p < 0.0001]. Meanwhile, increased inspiratory effort determined by elevated PaCO₂ levels led to enhancement of tidal volume from 4.1 ± 1.2 mL/kg to 5.3 ± 1.5 mL/kg (p = 0.0003) and respiratory rate from 13 ± 2 to 15 ± 2 bpm (p = 0.0266). In addition, the increase in PaCO₂ was linearly correlated with changes in ΔPOCC and PMI (R2 = 0.7293, p = 0.0003 and R2 = 0.4105, p = 0.0460, respectively).

In patients with COVID-19 undergoing PSV with ECMO, an increase of PaCO₂ could increase the inspiratory effort.