The immediate effect of a Boston brace on lung volumes and pulmonary compliance in mild adolescent idiopathic scoliosis

Idiopathic scoliosis (IS) is known to result in lung volume and pulmonary compliance reduction. Boston brace treatment of IS is an additional factor causing restrictive respiratory syndrome due to external chest wall compression. Nevertheless, the immediate effect of Boston bracing on the pulmonary compliance of scoliotic patients has not been studied systematically. Spirometric and plethysmographic lung volumes, static lung compliance (C(ST)(L)) and specific lung compliance (C(ST)(L)/functional residual capacity) of 15 scoliotic adolescents (14 females and 1 male, of mean age 14.1+/-1.67 years, with mean Cobb angle 24.1 degrees+/-7.88 degrees) were recorded twice, in a random sequence: once without the Boston brace (nBB) and once immediately after wearing the brace (BB). Our findings showed that bracing reduced vital capacity, residual volume, functional residual capacity (FRC), total lung capacity, and forced expiratory volume in 1s in a proportional and significant way (P < 0.001). C(ST)(L) was also significantly reduced (P < 0.001), but C(ST)(L)/FRC remained unaltered. All BB and nBB indices were highly correlated. We concluded that Boston bracing in IS patients results in an immediate, predictable, and uniform reduction of lung volumes and pulmonary compliance. The reduction of C(ST)(L) under bracing conditions was related to the decrease of lung volume; the C(ST)(L)/FRC remained unaltered.