Assessment of Pulmonary Function in Children with Duchenne Muscular Dystrophy

Background: Duchenne Muscular Dystrophy (DMD) is the most common neuromuscular disorder of childhood. Restrictive lung disease contributes significantly to morbidity and mortality. Although spirometry is widely used, it may be inappropriate for assessing restrictive disease. Additional techniques, such as plethysmography, might be challenging for children with DMD. Peak cough flow (PCF) is advocated for treatment adjustment in international guidelines, however, there is a lack of standardization for children.

Aims: To establish the best method for pulmonary function testing as a predictor for respiratory disease severity and for follow-up.

Methods: Analysis of spirometry (Forced Vital Capacity

[FVC] and PCF), lung volumes (Total Lung Capacity [TLC], Residual Volume [RV]), respiratory pressures tests from DMD patients enrolled in a natural history cohort study. Data was analyzed for change with age, mutation type, ambulation status, and glucocorticoid use.

Results: 116 DMD patients, (median age 11.6 years, range 5–26 years) were enrolled in the study. Successful rates performing different tests were as follow: spirometry 68% (79), plethysmograph 21% (25), inspiratory and expiratory pressures 23% (27), and 36 (31%) patients completed the PCF test. The %FVC and %TLC predicted for age, as well as maximum expiratory pressure showed a decrease with age of 4% a year. Surprisingly, no significant change with age was observed in PCF, even when correcting for ambulation or steroid treatment.

Conclusion: Restrictive lung disease can be followed by plethysmography and expiratory pressure measurements, but not by PCF. The decreased lung volumes can be predicted according to age, ambulation and steroid treatment.