Aerobic exercise capacity in long-term survivors of critical illness: secondary analysis of the post-EPaNIC follow-up study

Abstract

Purpose: To evaluate aerobic exercise capacity in 5-year intensive care unit (ICU) survivors and to assess the association between severity of organ failure in ICU and exercise capacity up to 5-year follow-up.

Methods: Secondary analysis of the EPaNIC follow-up cohort (NCT00512122) including 433 patients screened with cardiopulmonary exercise testing (CPET) between 1 and 5 years following ICU admission. Exercise capacity in 5-year ICU survivors (N = 361) was referenced to a historic sedentary population and further compared to demographically matched controls (N = 49). In 5-year ICU survivors performing a maximal CPET (respiratory exchange ratio > 1.05, N = 313), abnormal exercise capacity was defined as peak oxygen consumption (VO₂peak) < 85% of predicted peak oxygen consumption (%predVO₂peak), based on the historic sedentary population. Exercise liming factors were identified. To study the association between severity of organ failure, quantified as the maximal Sequential Organ Failure Assessment score during ICU-stay (SOFA-max), and exercise capacity as assessed with VO₂peak, a linear mixed model was built, adjusting for predefined confounders and including all follow-up CPET studies.

Results: Exercise capacity was abnormal in 118/313 (37.7%) 5-year survivors versus 1/48 (2.1%) controls with a maximal CPET, p < 0.001. Aerobic exercise capacity was lower in 5-year survivors than in controls (VO₂peak: 24.0 ± 9.7 ml/min/kg versus 31.7 ± 8.4 ml/min/kg, p < 0.001; %predVO₂peak: 94% ± 31% versus 123% ± 25%, p < 0.001). Muscular limitation frequently contributed to impaired exercise capacity at 5-year [71/118 (60.2%)]. SOFA-max independently associated with VO₂peak throughout follow-up.

Conclusions: Critical illness survivors often display abnormal aerobic exercise capacity, frequently involving muscular limitation. Severity of organ failure throughout the ICU stay independently associates with these impairments.

Keywords: Critical illness; Exercise testing; Exercise tolerance; Organ failure.

Fig. 1

Patient flow chart and reasons for not performing CPET during the 5-year follow-up period. EPaNIC: Early Parenteral Nutrition in Intensive Care, CPET cardiopulmonary exercise testing, FU, follow-up

Fig. 2

Key outcomes of cardiopulmonary exercise testing in the post-EPaNIC 5-year follow-up cohort and controls, depicted as mean and standard deviation. A VO₂peak in ml/kg/min and as percentage predicted of VO₂peak; B VO₂AT in ml/kg/min and as percentage predicted of VO₂peak. Comparisons were performed with t test. VO₂peak: peak oxygen consumption rate; VO₂AT: oxygen consumption rate at the anaerobic threshold