C Guillou

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

OBJECTIVE To analyze the relationship between disease progression, pulmonary volumes, respiratory muscle strength (maximum inspiratory [MIP] and expiratory [MEP] pressure), 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 PaCO2 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 167- to 14-year-old patients and decreased linearly thereafter (MEP% = -2.7 x age +73.8; p < .001). Declines in MEP also correlated linearly with expiratory reserve volume (p < .001) and inversely with residual volume (p < .001). By contrast, MIP was 66.3% +/- 19.0% in the 357- to 14-year-old patients and then declined to 30.2% +/- 19.5% after age 14. No linear relationships were found with age but declines did correlate linearly with inspiratory reserve volume (p < .001) and total lung capacity (p < .001). PaCO2 elevations correlated best with decreases in MIP (p < .0001) and appeared when MIP was below 30cmH2O. 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.

Apical left ventricular myocardial dysfunction is an early feature of cardiac involvement in myotonic dystrophy type 1.

Left ventricular (LV) dysfunction is a major prognostic determinant in myotonic dystrophy type 1 (DM1). Therefore, markers of early‐stage LV impairment may be useful. The aim of this study was to evaluate 2D echocardiographic LV strain in a cohort of DM1 patients with preserved left ventricular ejection fraction (LVEF) and to compare the results with matched controls.