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

Crit Care Explor. 2021 Jul 13;3(7):e0491. doi: 10.1097/CCE.0000000000000491. eCollection 2021 Jul.


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/m2) 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.

Keywords: cardiopulmonary exercise testing; coronavirus disease 2019; critical illness; hypermetabolism; survivors.