Inspiratory muscle capacity in Long Covid

ABSTRACT

Persistent symptoms beyond three months are common following acute infection with Covid 19 and termed Long Covid. There are a broad range of symptoms including breathlessness, fatigue, reduced exercise tolerance, chest pains, sleep disturbance and palpitations. The pathophysiology of Long Covid is poorly understood limiting treatment options. We hypothesised that diaphragm muscle weakness would be common in Long Covid and may in part be responsible for a number of the reported symptoms thereby providing a therapeutic option via inspiratory muscle training. We examined lung function, hand grip strength, Chester step test and symptom scores;mMRC (modified Medical Research Council), HADS (Hospital Anxiety And Depression), SF36 quality of life, Chalder Fatigue, in patients attending the Beacon Hospital Long Covid Clinic. Ethical approval was granted by our institutional review board. 101 patients were aged 40 +/- 14 years (Mean +/- SD). 63% were female. 75% had their acute illness managed at home. mMRC was 0 (16%), 1 (39%), 2 (34%), 3 (9%), 4 (2%). Predicted spirometry was normal however DLCO (diffusing capacity for carbon monoxide) was reduced at 86 +/- 14 % predicted as was MIP (Mean Inspiratory Pressure) at 70 +/- 25 % predicted. DLCO was significantly different when analysed by mMRC scores (ANOVA p<0.005). DLCO was correlated with MIP (R2= 0.22, p<0.0005). We propose implementing inspiratory muscle training as part of the therapeutic response to Long Covid to ascertain the role of diaphragm weakness in the pathophysiology of this syndrome and evaluate its effect on a range of presenting symptoms.