Respiratory muscle function and inspiratory muscle strength in patients with long COVID, ILD or COPD in comparison to healthy controls: Preliminary results

Abstract

<b>Background:</b> Most of the patients with long COVID report respiratory symptoms which could be associated with reduced respiratory muscle strength and their functions. The symptoms are also present in patients with interstitial lung disease (ILD) or chronic obstructive pulmonary disease (COPD). Such comparison of these variables has not been performed yet. <b>Objective:</b> To compare inspiratory muscles strength (PImax), tension time index of inspiratory muscles (TTmus) and airway occlusion pressure (P0.1) among long COVID, ILD or COPD patients and healthy controls. <b>Methods:</b> Respiratory muscles functions (P0.1, TTmus) and strength (PImax) were assessed in 60 patients who were equally divided into 4 groups (15 per group: 7 women, 8 men; mean age 60.92 years) according to the health status. The long COVID, ILD and COPD groups were compared to healthy controls. <b>Results:</b> No significant differences were observed in PImax, TTmus and P0.1 between long COVID and healthy controls, nor in the PImax between COPD, ILD and controls. However, a statistically significant difference was found in the P0.1 and TTmus within ILD (both p=0.01), COPD (p=0.1; p=0.3) and controls. Eight of long COVID patients had P0.1 values &gt; 0.2 kPa in comparison to ILD (n=15) and COPD (n=14) and controls (n=4). Also, eight long COVID patients had &lt; 80% predicted values of PImax compared to ILD (n=5) and COPD (n=4) and controls (n=2). <b>Conclusion:</b> Despite no significant differences being observed, results indicate that long COVID patients’ respiratory muscles strength and functions are more limited compared to healthy controls. But not as much as in patients with ILD or COPD.