Oxygen uptake kinetics and chronotropic responses to exercise are impaired in survivors of severe COVID-19, 2022, Longobardi et al

Abstract

The post-acute phase of COVID-19 is often marked by several persistent symptoms and exertional intolerance, which compromise survivors' exercise capacity. This was a cross-sectional study aiming to investigate the impact of COVID-19 on oxygen uptake (VO2) kinetics and cardiopulmonary function in survivors of severe COVID-19 three to six months after intensive care unit (ICU) hospitalization.

Thirty-five COVID-19 survivors previously admitted to ICU (5±1 months after hospital discharge) and 18 controls matched for sex, age, comorbidities, and physical activity level with no prior history of SARS-CoV-2 infection were recruited. Subjects were submitted to a maximal graded cardiopulmonary exercise test (CPX) with an initial 3-minute period of a constant, moderate-intensity walk (i.e., below ventilatory threshold, VT). VO2 kinetics was remarkably impaired in COVID-19 survivors as evidenced at the on-transient by an 85% (P=0.008) and 28% (P=0.001) greater oxygen deficit and mean response time (MRT), respectively. Furthermore, COVID-19 survivors showed a 11% longer (P=0.046) half-time of recovery of VO2 (T1/2VO2) at the off-transient. CPX also revealed cardiopulmonary impairments following COVID-19. VO2peak, percent-predicted VO2peak and VO2VT were reduced by 17%, 17% and 12% in COVID-19 survivors, respectively (all P<0.05). None of the ventilatory parameters differed between groups (all P>0.05). Additionally, COVID-19 survivors also presented with blunted chronotropic responses (i.e., chronotropic index, maximum heart rate, and heart rate recovery; all P<0.05).

These findings suggest that COVID-19 negatively affects central (chronotropic) and peripheral (metabolic) factors that impair the rate at which VO2 is adjusted to changes in energy demands.

Open access, https://journals.physiology.org/doi/abs/10.1152/ajpheart.00291.2022