The relationship among 6-minute walk test performance, respiratory muscles, ventilatory parameters and dyspnoea severity in long COVID patients: Preliminary results

Abstract

Background: Long COVID is associated with shortness of breath and limited lung functions. Shortness of breath can lead to decreased exercise tolerance, which often correlates with pulmonary functions and dyspnoea severity. Nevertheless, relation between exercise tolerance and respiratory muscles functions has not been well investigated so far, neither in patients with long COVID, which pathophysiology is still unclear.

Objective: To determine the association between 6-minute walk test (6MWT), Modified Medical Research Council dyspnoea scale (mMRC), ventilatory parameters (vital capacity: VC, forced expiratory volume in 1 second: FEV1, peak expiratory flow: PEF), tension time index of inspiratory muscles (TTmus) and inspiratory muscles strength (PImax) in patients with long COVID.

Methods: Respiratory muscles and lung functions (TTmus, PImax, VC, FEV1, PEF), dyspnoea (mMRC) and exercise tolerance (6MWT) were assessed in 33 patients with long COVID (mean age 48.2 years, 51.5 % men).

Results: The study revealed a positive significant correlation between 6MWT and VC (r=0,54), 6MWT and FEV1 (r=0,68), 6MWT and PEF (r=0,61), and a negative significant correlation between 6MWT and TTmus (r=-0.55), and 6MWT and mMRC (r=-0.58) as well. There was no significant correlation between PImax and 6MWT.

Conclusions: Decreased exercise tolerance is possibly significantly more related to pulmonary functions and respiratory muscle fatigue, and less to the inspiratory muscle strength. This relation should be considered during pulmonary rehabilitation. Nevertheless, further research is needed in this area.