Effect of a home-based inspiratory muscle training program on functional capacity in post-discharged patients with long COVID: The InsCOVID trial

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Sociedad Española de Cardiología. Background Fatigue and exercise intolerance are the most common symptoms in patients with long COVID. Purpose This study aimed to evaluate whether a home-based inspiratory muscle training (IMT) program improves maximal functional capacity in patients long COVID after a previous admission due to SARS-CoV-2 pneumonia. Methods This study was a single-centre, blinded assessor, randomised controlled trial. Twenty-six patients with long COVID and a previous admission due to SARS-CoV-2 pneumonia were randomly assigned to receive either a 12-week program of IMT or usual care alone. The physiotherapist and participants were not blinded. Patients allocated to the IMT arm were instructed to train at home twice daily using a threshold inspiratory muscle trainer and to maintain diaphragmatic breathing during the training session. The usual care arm received no intervention. The primary endpoint was changes in peak oxygen consumption (peakVO2). Secondary endpoints were changes in quality of life (QoL), ventilatory efficiency and chronotropic response during exercise (evaluated by chronotropic index-CIx- formula). We used linear mixed regression analysis for evaluating changes in primary and secondary endpoints. Results The median (interquartile range) age of the sample and time to first visit after discharge were 52 (42-59) years and 405 (301-435) days, respectively. A total of 11 (42.3%) were female. At baseline, the median of peakVO2, ventilatory efficiency and CIx were 17.4 (15.6-21.1) mL/kg/min, 29 (24.5-33.3), and 0.64 (0.54-0.87), respectively. The IMT arm improved their peakVO2 significantly compared to usual care (+Δ 4.46 mL/kg/min, 95% CI 3.10 to 5.81; p<0.001). Similar positive findings were found when evaluating changes for CIx and some QoL dimensions. We did not find significant changes in ventilatory efficiency. Conclusion In long COVID patients with a previous admission due to SARS-CoV-2 pneumonia, IMT was associated with marked improvement in exercise capacity and QoL.