Comparison of activity and fatigue of the respiratory muscles and pulmonary characteristics between post-polio patients and controls: A pilot study

OBJECTIVES To compare pulmonary function measures, maximal respiratory pressure and fatigue of respiratory muscles between patients with Post-Polio Syndrome (PPS) and controls. DESIGN Cross-sectional study. PATIENTS Patients with PPS (N = 12; age 62.1±11.6 years) able to walk for 6 minutes without human assistance; age-matched controls with no history of polio or pulmonary dysfunction (N = 12; age 62.2±6.5 years). MEASUREMENTS A body plethysmograph was used to quantify Residual Volume (RV), Total Lung Capacity (TLC), and Thoracic Gas Volume (TGV) etc. A manometer was used to measure Maximal Inspiratory Pressure (MIP) and Maximal Expiratory Pressure. A spirometer was used to measure Maximal Voluntary Ventilation (MVV). Surface electromyography (sEMG) recorded diaphragmatic muscle activity while performing MVV. RESULTS The control group had significantly higher TGV and showed improvement in MIP following the effort (difference of 5.5±4.0cmH2O) while the PPS group showed deterioration in MIP (difference of -2.5±5.0cmH2O). Subjects with scoliosis had significantly higher RV/TLC values compared with subjects without scoliosis. The 25th frequency percentile of the sEMG signal acquired during MVV was reduced in the PPS group. CONCLUSIONS Maximal respiratory pressure test and sEMG measurements may identify fatigue of respiratory muscles in patients with PPS. Early diagnosis of respiratory impairment may delay respiratory decline and future need of invasive respiratory aids.