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 P0.1, inspiratory muscle strength (PImax) and total respiratory muscle strain (P0.1/PImax) in addition to standard pulmonary functions tests, capillary blood gas analysis, 6 min walking tests and functional questionnaires.
Results: Pathological P0.1/PImax was found in 88% of symptomatic patients. Mean PImax was reduced in hospitalized patients, but reduced PImax was also found in 65% of nonhospitalized patients. Mean P0.1 was pathologically increased in both groups. Increased P0.1 was associated with exercise-induced deoxygenation, impaired exercise tolerance, decreased activity and productivity and worse Post-COVID-19 functional status scale. Pathological changes in P0.1, PImax or P0.1/PImax 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.
Source: Hennigs JK, Huwe M, Hennigs A, Oqueka T, Simon M, Harbaum L, Körbelin J, Schmiedel S, Schulze Zur Wiesch J, Addo MM, Kluge S, Klose H. Respiratory muscle dysfunction in long-COVID patients. Infection. 2022 May 16:1–7. doi: 10.1007/s15010-022-01840-9. Epub ahead of print. PMID: 35570238; PMCID: PMC9108020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9108020/ (Full text)