Oxygen desaturation during the 6-min walk test as a risk for osteoporosis in non-cystic fibrosis bronchiectasis

BACKGROUND: Osteoporosis is a common comorbidity in non-cystic fibrosis (non-CF) bronchiectasis patients. We determined whether desaturation during 6-min walk test (6MWT) can be a predictor for osteoporosis risk. METHODS: This was a retrospective cross-sectional study. Sixty-six non-CF bronchiectasis patients were enrolled. Lung function, walking distance, the lowest oxygen saturation (SpO(2)), the fall in SpO(2) (ΔSpO(2)), and the distance–saturation product (DSP) were determined during the 6MWT. Desaturators (n = 45) were defined as those with ΔSpO(2) > 10% or the lowest SpO(2) < 88%. Bone mineral density (BMD) was determined through dual-energy X-ray absorptiometry. The severity of non-CF bronchiectasis was evaluated using high-resolution computed tomography. RESULTS: Osteoporosis was evident in more desaturators (82%) than non-desaturators (43%, p < 0.01). BMD at the level of the femoral neck was significantly lower in desaturators than in non-desaturators (− 3.6 ± 1.1 vs. − 2.4 ± 0.9, p < 0.01). BMD was correlated positively with the lowest SpO(2) and negatively with ΔSpO(2) and severe exacerbations. In multivariate linear regression analysis, desaturation during 6MWT was the most significant predictive factor for osteoporosis (95% confidence interval − 1.60 to − 0.26, p = 0.01). Other risk factors included old age, low body mass index and severe exacerbation. CONCLUSIONS: Exertional desaturation during the 6MWT was a significant predictive factor for osteoporosis in Asian non-CF bronchiectasis patients. The 6MWT may be useful in identifying the osteoporotic phenotype of non-CF bronchiectasis and increasing clinician awareness to promote early intervention.