Effect of a home-based inspiratory muscle training programme on functional capacity in postdischarged patients with long COVID: the InsCOVID trial

Background: Fatigue and exercise intolerance are the most common symptoms in patients with long COVID.
Aims: This study aimed to evaluate whether a home-based inspiratory muscle training (IMT) programme 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 IMT or usual care alone ( NCT05279430 ). 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 the change 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-CI_{x}- formula). We used linear mixed regression analysis for evaluating changes in primary and secondary endpoints.
Results: The mean age of the sample and time to first visit after discharge were 50.4±12.2 years and 362±105 days, respectively. A total of 11 (42.3%) were female. At baseline, the mean of peakVO_{2}, ventilatory efficiency and CIx were 18.9±5 mL/kg/min, 29.4±5.2 and 0.64±0.19, respectively. The IMT arm improved their peakVO_{2} significantly compared with 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 CI_{x} 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.
Trial registration number: NCT05279430 .