Cardiopulmonary Exercise Testing to Assess Persistent Symptoms at 6 Months in People With COVID-19 Who Survived Hospitalization: A Pilot Study

Objective. The aim of this pilot study was to assess physical fitness and its relationship with functional dyspnea in survivors of COVID-19 6 months after their discharge from the hospital. Methods. Data collected routinely from people referred for cardiopulmonary exercise testing (CPET) following hospitalization for COVID-19 were retrospectively analyzed. Persistent dyspnea was assessed using the modified Medical Research Council dyspnea scale. Results. Twenty-three people with persistent symptoms were referred for CPET. Mean modified Medical Research Council dyspnea score was 1 (SD = 1) and was significantly associated with peak oxygen uptake (VO(2)peak; %) (rho = -0.49). At 6 months, those hospitalized in the general ward had a relatively preserved VO(2)peak (87% [SD = 20]), whereas those who had been in the intensive care unit had a moderately reduced VO(2)peak (77% [SD = 15]). Of note, the results of the CPET revealed that, in all individuals, respiratory equivalents were high, power-to-weight ratios were low, and those who had been in the intensive care unit had a relatively low ventilatory efficiency (mean VE/VCO2 slope = 34 [SD = 5]). Analysis of each individual showed that none had a breathing reserve <15% or 11 L/min, all had a normal exercise electrocardiogram, and 4 had a heart rate >90%. Conclusion. At 6 months, persistent dyspnea was associated with reduced physical fitness. This study offers initial insights into the mid-term physical fitness of people who required hospitalization for COVID-19. It also provides novel pathophysiological clues about the underlaying mechanism of the physical limitations associated with persistent dyspnea. Those with persistent dyspnea should be offered a tailored rehabilitation intervention, which should probably include muscle reconditioning, breathing retraining, and perhaps respiratory muscle training. Impact. This study is the first, to our knowledge, to show that a persistent breathing disorder (in addition to muscle deconditioning) can explain persistent symptoms 6 months after hospitalization for COVID-19 infection and suggests that a specific rehabilitation intervention is warranted.