Clinical implications of maximal respiratory pressure determinations for individuals with duchenne muscular dystrophy

Abstract Objective: To analyze the relationship between disease progression, pulmonary volumes, respiratory muscle strength (maximum inspiratory [MIP] and expiratory [MEP] pressures), and arterial blood gases for patients with Duchenne muscular dystrophy (DMD). Design: An inception cohort study of pulmonary volumes, MIPs, and MEPs, correlated with age and Paco 2 levels and with each other using linear and nonlinear regression analyses. Setting: Outpatient clinic. Patients: Fifty-two consecutive DMD patients who presented for regular evaluations at a regional DMD center. Results: Maximum expiratory pressures were 47.7% ± 10.9% of normal in the 16 7- to 14-year-old patients and decreased linearly thereafter (MEP% = −2.7 X age +73.8; p p p p p p 2 O. Conclusions: Lung volume changes in DMD patients correlate with respiratory muscle weakness, and although inspiratory muscle dysfunction plays a key role in the development of chronic ventilatory insufficiency, reductions in expiratory muscle strength are the first signs of dysfunction and lead to the first episodes of respiratory failure.