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.
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 DMDpatients 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 DMDpatients 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.
Authors: A F Mead; M Petrov; A S Malik; M A Mitchell; M K Childers; J R Bogan; G Seidner; J N Kornegay; H H Stedman Journal: J Appl Physiol (1985) Date: 2014-01-09
Authors: Alison M Barnard; Donovan J Lott; Abhinandan Batra; William T Triplett; Sean C Forbes; Samuel L Riehl; Rebecca J Willcocks; Barbara K Smith; Krista Vandenborne; Glenn A Walter Journal: J Neurol Date: 2019-07-26 Impact factor: 4.849