Correlation Between PaCO2 and Respiratory Effort in Patients With COVID-19 With Extracorporeal Membrane Oxygenation

A stable environment was maintained during the study to avoid stress and abrupt stimulation. Before the start of the study, sedative drugs were titrated to Richmond agitation sedation scale values of -3 to -2, an assisted breathing mode trial was conducted, and support pressure level were adjusted to achieve tidal volume \< 6 mL/kg. The ECMO GF was adjusted to achieve stable baseline conditions, defined as PaCO2 \< 40 mmHg, respiratory rate \< 25 bpm, and peak airway pressure \< 25 cm H2O. PEEP, fraction of inspired oxygen, pressure support ventilation (PSV), ECMO blood flow, and dose of vasoconstrictors, sedatives, and analgesics remained unchanged throughout the study. The study protocol was initiated when the baseline parameters s were stable. The baseline parameters, including ventilation settings, arterial and arterial blood gas analysis, hemodynamics, and indicators of respiratory effort were measured in the baseline group. Then, the ECMO GF was modified to 50% of the baseline, and etCO2 values were monitored. ECMO GF was adjusted at 5-min intervals (increasing or decreasing by 0.5 L/min each time) until etCO2 stabilized at a level 5-10 mmHg higher than the baseline. After 20 min, the parameters were measured for the second time in the high-CO2 group (Figure 1). The study was stopped if the heart rate (HR) was \> 140 beats/min and/or respiratory rate was \> 40 bpm and/or systolic blood pressure \> 180 mmHg and/or patients experienced anxiety or diaphoresis.