Cardiopulmonary Exercise Testing in Critically Ill Coronavirus Disease 2019 Survivors: Evidence of a Sustained Exercise Intolerance and Hypermetabolism

OBJECTIVES: To investigate exercise capacity at 3 and 6 months after a prolonged ICU stay. DESIGN: Observational monocentric study. SETTING: A post-ICU follow-up clinic in a tertiary university hospital in Liège, Belgium. PATIENTS: Patients surviving an ICU stay greater than or equal to 7 days for a severe coronavirus disease 2019 pneumonia and attending our post-ICU follow-up clinic. MEASUREMENTS AND MAIN RESULTS: Cardiopulmonary and metabolic variables provided by a cardiopulmonary exercise testing on a cycle ergometer were collected at rest, at peak exercise, and during recovery. Fourteen patients (10 males, 59 yr [52–62 yr], all obese with body mass index > 27 kg/m(2)) were included after a hospital stay of 40 days (35–53 d). At rest, respiratory quotient was abnormally high at both 3 and 6 months (0.9 [0.83–0.96] and 0.94 [0.86–0.97], respectively). Oxygen uptake was also abnormally increased at 3 months (8.24 mL/min/kg [5.38–10.54 mL/min/kg]) but significantly decreased at 6 months (p = 0.013). At 3 months, at the maximum workload (67% [55–89%] of predicted workload), oxygen uptake peaked at 81% (64–104%) of predicted maximum oxygen uptake, with oxygen pulse and heart rate reaching respectively 110% (76–140%) and 71% (64–81%) of predicted maximum values. Ventilatory equivalent for carbon dioxide remains within normal ranges. The 50% decrease in oxygen uptake after maximum effort was delayed, at 130 seconds (115–142 s). Recovery was incomplete with a persistent anaerobic metabolism. At 6 months, no significant improvement was observed, excepting an increase in heart rate reaching 79% (72–95%) (p = 0.008). CONCLUSIONS: Prolonged reduced exercise capacity was observed up to 6 months in critically ill coronavirus disease 2019 survivors. This disability did not result from residual pulmonary or cardiac dysfunction but rather from a metabolic disorder characterized by a sustained hypermetabolism and an impaired oxygen utilization.