Lung clearance in children with Duchenne muscular dystrophy or spinal muscular atrophy with and without CPAP (continuous positive airway pressure)

Bronchiolar clearance was studied in 7 boys in the age range of 8 to 17 yea rs, 6 with Duchenne muscular dystrophy (DMD) and I with spinal muscular atr ophy type II (SMA-II). These boys had healthy lungs but a severely reduced muscular strength (wheelchair dependent). In 6 of the boys, clearance was s tudied twice, at one occasion as a control and at the other occasion follow ing treatment with continuous positive airway pressure (CPAP). A control gr oup of healthy adults was used. In the clearance examinations, 6-mum Teflon particles, labeled with In-111 was inhaled extremely slowly, 0.05 L/s. Thi s gives a deposition mainly in the bronchioles. Lung retention was measured after 0, 24, 48, and 72 hours. A model for deposition of particles in the adult lung was scaled down to represent the children in this study. Deposit ion in various airway generations was calculated to be similar in children and adults. Also the measured retentions were similar in the boys and the a dults. In the clearance experiments during CPAP treatment, there was a sign ificantly lower retention after 72 hours (but not after 24 and 48 hours) th an in the control experiments. The results indicate that a severe reduction of muscular strength, and thereby a reduction of mechanical Movement of th e lung, does not affect clearance from large and small airways. However, so me effect of clearance from, small airways cannot be excluded due to the sh ort measuring period. The small but significant effect of the CPAP treatmen t might have potential clinical importance and suggest that bronchiolar cle arance can be affected by some form of mechanical force.