Respiratory muscle dysfunction in long-COVID patients
Jan K. Hennigs, Marie Huwe, Annette Hennigs, Tim Oqueka, Marcel Simon, Lars Harbaum, Jakob Körbelin, Stefan Schmiedel, Julian Schulze zur Wiesch, Marylyn M. Addo, Stefan Kluge, Hans Klose
Abstract
Abstract Purpose Symptoms often persistent for more than 4 weeks after COVID-19—now commonly referred to as ‘Long COVID’. Independent of initial disease severity or pathological pulmonary functions tests, fatigue, exertional intolerance and dyspnea are among the most common COVID-19 sequelae. We hypothesized that respiratory muscle dysfunction might be prevalent in persistently symptomatic patients after COVID-19 with self-reported exercise intolerance. Methods In a small cross-sectional pilot study ( n = 67) of mild-to-moderate (nonhospitalized) and moderate-to-critical convalescent (formerly hospitalized) patients presenting to our outpatient clinic approx. 5 months after acute infection, we measured neuroventilatory activity P 0.1 , inspiratory muscle strength ( P I max ) and total respiratory muscle strain ( P 0.1 / P I max ) in addition to standard pulmonary functions tests, capillary blood gas analysis, 6 min walking tests and functional questionnaires. Results Pathological P 0.1 / P I max was found in 88% of symptomatic patients. Mean P I max was reduced in hospitalized patients, but reduced P I max was also found in 65% of nonhospitalized patients. Mean P 0.1 was pathologically increased in both groups. Increased P 0.1 was associated with exercise-induced deoxygenation, impaired exercise tolerance, decreased activity and productivity and worse Post-COVID-19 functional status scale. Pathological changes in P 0.1 , P I max or P 0.1 / P I max were not associated with pre-existing conditions. Conclusions Our findings point towards respiratory muscle dysfunction as a novel aspect of COVID-19 sequelae. Thus, we strongly advocate for systematic respiratory muscle testing during the diagnostic workup of persistently symptomatic, convalescent COVID-19 patients.