Cardiopulmonary fitness and muscle strength in patients with osteogenesis imperfecta type I

OBJECTIVE: To evaluate cardiopulmonary function, muscle strength, and cardiopulmonary fitness (VO 2 peak) in patients with osteogenesis imperfecta (OI).

STUDY DESIGN: In 17 patients with OI type I (mean age 13.3 +/- 3.9 years) cardiopulmonary function was assessed at rest using spirometry, plethysmography, electrocardiography, and echocardiography. Exercise capacity was measured using a maximal exercise test on a bicycle ergometer and an expired gas analysis system. Muscle strength in shoulder abductors, hip flexors, ankle dorsal flexor, and grip strength were measured. All results were compared with reference values.

RESULTS: Cardiopulmonary function at rest was within normal ranges, but when it was compared with normal height for age and sex, vital capacities were reduced. Mean absolute and relative VO 2 peak were respectively -1.17 (+/- 0.67) and -1.41 (+/- 1.52) standard deviations lower compared with reference values ( P < .01). Muscle strength also was significantly reduced in patients with OI, ranging from -1.24 +/- 1.40 to -2.88 +/- 2.67 standard deviations lower compared with reference values.

CONCLUSIONS: In patients with OI type I, no pulmonary or cardiac abnormalities at rest were found. The exercise tolerance and muscle strength were significantly reduced in patients with OI, which might account for their increased levels of fatigue during activities of daily living.