DIAPHRAGM THICKNESS AND INSPIRATORY STRENGTH IN PATIENTS WITH DUCHENNE MUSCULAR-DYSTROPHY

Background - There is little information on the morphometric character istics of the diaphragm in patients with Duchenne muscular dystrophy. Methods - The thickness of the diaphragm was measured at the zone of a pposition using B mode ultrasonography in 10 boys with Duchenne muscul ar dystrophy of mean (SD) age 10.3 (1.3) years and 12 normal controls of mean (SD) age 11.3 (2.0) years during relaxation (DiTrelax) and dur ing maximum effort inspiratory manoeuvres (DiTPImax) at functional res idual capacity. Results - DiTrelax was greater in the patients with Du chenne muscular dystrophy (1.74 (0.21) mm) than in controls (1.48 (0.2 0) mm), mean difference (95% CI) 0.26 (0.08 to 0.44), despite consider able impairment of maximum effort inspiratory mouth pressure (PImax) ( patients with Duchenne muscular dystrophy -37 (8) cm H2O, controls -80 (33) cm H2O), mean difference (95% CI) 43 (65 to 20). During a PImax manoeuvre, compared with measurements taken during relaxation, the dia phragm thickened 1.6 times in patients with Duchenne muscular dystroph y and 2.3 times in controls (DiTPImax 2.62 (0.7) mm and 3.5 (0.85) mm, respectively), mean difference (95%, CI) -0.88 (-1.58 to -0.18). Conc lusions - Resting diaphragm thickness is increased in young patients w ith Duchenne muscular dystrophy with impaired respiratory muscle force . This finding could be analogous to the pseudohypertrophy that is obs erved in some limb muscle groups.