P.1.3 Postural changes in forced vital capacity characterize congenital muscular dystrophy subtypes

Abstract

Congenital muscular dystrophy (CMD) is a group of heterogeneous disorders with progressive respiratory insufficiency. Recommendations include screening for respiratory insufficiency by spirometry and obtaining a polysomnogram if the vital capacity (VC) is 20% decline between sitting and supine VC measures. Reports of pulmonary function, especially change in sitting to supine forced VC (FVC) % predicted, and its association with CMD subtypes and ambulatory status are limited. Therefore, in 49 individuals with CMD [Collagen VI-related myopathy (CVI-RM; n = 30) and LAMA2-related muscular dystrophy (LAMA2-MD; n = 19], we compared sitting with supine FVC % predicted, ambulatory and non-invasive mechanical ventilation (NIV) status. The CVI-RM cohort comprised ages 4–61 years with 18 (60%) males and 22 (73%) children (⩽18 years). The LAMA2-MD cohort comprised ages 5–54 years with 7 (37%) males and 18 (95%) children. We found a significant decrease in FVC % predicted from sitting to supine in subjects with CVI-RM only ( p p = 0.002) and inversely with NIV status (−0.539, p = 0.002) in CVI-RM, but only showed a trend with ambulatory status in LAMA2-MD (0.443, p = 0.058). In conclusion, this is the first report of change in sitting to supine % FVC predicted in subjects with CMD to our knowledge. This study highlights the physiologic differences between CMD subtypes and suggests a need for a more tailored approach to screening. Additional studies are needed to evaluate the predictive power of postural changes in FVC for nocturnal hypoventilation and the need to initiate ventilator support.