Evaluation of primary and accessory respiratory muscles and their influence on exercise capacity and dyspnea in pulmonary arterial hypertension

Published:October 08, 2022DOI:


      • SCM muscle strength is preserved, while SA and PM muscle strength are reduced in PAH.
      • The SA is the most affected muscle among respiratory muscles in patients with PAH.
      • The SA muscle has the highest correlation with exercise capacity among other peripheral and respiratory muscles in PAH patients.
      • The model consisting of primary and accessory respiratory muscle, explains 37% of variation in exercise capacity of PAH patients.



      Skeletal and respiratory muscle disfunction has been described in pulmonary arterial hypertension (PAH), however, involvement of accessory respiratory muscles and their association with symptomatology in PAH is unclear.


      To assess the primary and accessory respiratory muscles and their influence on exercise tolerance and dyspnea.


      27 patients and 27 healthy controls were included. Serratus anterior (SA), pectoralis muscles (PM) and sternocleidomastoid (SCM) muscle strength were evaluated as accessory respiratory muscles, maximal inspiratory (MIP) and expiratory pressures (MEP) as primary respiratory muscles, and quadriceps as peripheral muscle. Exercise capacity was evaluated with 6-min walk test (6MWT), dyspnea with modified Medical Council Research (MMRC) and London Chest Activity of Daily Living (LCADL) scales.


      All evaluated muscles, except SCM, and 6MWT were decreased in patient group (p < 0.01). SA was the most affected muscle among primary and accessory respiratory muscles (Cohen's-d = 1.35). All evaluated muscles significantly correlated to 6MWT (r = 0.428–0.525). A multivariate model including SA, SCM and MIP was the best model for predicting 6MWT (R = 0.606; R2 = 0.368; p = 0.013) and SA strength had the most impact on the 6MWT (B = 1.242; β = 0.340). None of the models including respiratory muscles were able to predict dyspnea, however PM and SA strength correlated to LCADL total (r = -0.493) and MMRC (r = -0.523), respectively.


      SCM may be excessively used in PAH since it retains its strength. Considering the relationship of accessory respiratory muscles with exercise tolerance and dyspnea, monitoring the strength of these muscles in the clinical practice may help providing better management for PAH.



      PAH (pulmonary arterial hypertension), SA (serratus anterior), PM (pectoralis muscles), SCM (sternocleidomastoid), MIP (maximal inspiratory pressure), MEP (maximal expiratory pressures), 6MWT (6-min walk test), MMRC (modified medical council research), LCADL (London chest activity of daily living), RV (right ventricular), WHO FC (World Health Organization functional class), 6MWD (six-minute walk distance), COPD (chronic obstructive pulmonary disease), CHF (chronic heart failure), EMG (electromyography)
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