Pulmonary function abnormalities in Prader-Willi syndrome.

OBJECTIVE: To determine whether individuals with Prader-Willi syndrome (PWS) have abnormalities in pulmonary function as a result of thoracic muscle weakness.

DESIGN: Testing of spirometry, flow-volume curves, lung volumes, and static respiratory pressures was performed in patients with PWS who are followed at the University of Connecticut. All tests were performed in triplicate on two or more occasions. Only reproducible tests were accepted. Established normative data were applied for all test results.

RESULTS: A total of 18 male subjects (age, 17.9 +/- 10.2 years (mean +/- SD); range, 5-39 years) and 17 female subjects (age, 23.5 +/- 13.0 years; range, 5-54 years) completed the tests. Forced vital capacity and forced expiratory volume in 1 second were reduced; the forced expiratory volume in 1 second/forced vital capacity ratio was normal, total lung capacity was in the low normal range, and residual volume was elevated. Maximum inspiratory (PImax) and expiratory (PEmax) pressures were markedly reduced in 32 subjects tested. Fifteen subjects had PEmax values and 20 subjects had PImax values < 60 cm H2O, respectively. There was a linear correlation between forced expiratory volume in 1 second and both PImax and PEmax (r = 0.71; r = 0.62, respectively), and between forced vital capacity and both PEmax and PImax (r = 0.62 and r = 0.74, respectively). There was an inverse relationship between both PImax and PEmax, and residual volume (r = 0.47 and r = 0.72, respectively).

CONCLUSION: Children and adults with PWS have restrictive ventilatory impairment primarily as a result of respiratory muscle weakness. Efforts to improve thoracic muscle strength may be useful in improving pulmonary function in individuals with PWS.