Evaluation of respiratory status in patients with myopathy

Myopathic diseases can lead to significant respiratory disorders due to the involvement of skeletal muscles, including respiratory muscles. These disorders not only affect the quality of life of patients, but are also one of the main causes of mortality in this group. This study aimed to evaluate pulmonary function and its associated factors in patients with myopathy. This is a prospective cross-sectional study that was performed in 2020-2021 on 44 patients with myopathy. The participant's demographic information and features of disease, including age, sex, type of disease, age of onset and duration of disease, and mobility status of the patient (using Walker or wheelchair) were collected by a checklist. The slow inspiratory vital capacity (VC) and FEV1 were obtained. Data analysis was performed with SPSS version 24 software using t-test, Mann-Whitney, Pearson, and Spearman correlation tests. The sitting and lying FVC were significantly higher in patients who had no drug usage (P = 0.007 and P = 0.005, respectively), no sputum (0.003 and 0.002, respectively), no dysphagia (P = 0.002 and P = 0.001, respectively), and no coughs while eating (P = 0.022 and P = 0.006). There were significant inverse relationships between age and sitting FVC (r = -0.638) and lying FVC (r = -0.497), and age had a significant direct relationship with changes in the FVC (r = 0.652) (P < 0.001 for all). Furthermore, we observed a significantly inverse relationship between age of disease onset and sitting FVC (r = -0.491, P = 0.001) and significantly direct relationship between age of disease onset and lying FVC (r = 0.447, P = 0.002) and FVC changes (r = 0.371, P = 0.013). Assessments of respiratory functions, especially through spirometry in both sitting and supine positions, and attention to clinical symptoms such as dysphagia and cough, are of great clinical importance in the management of myopathy patients. These assessments can help in the early diagnosis of respiratory failure and timely interventions.