6-Min walk-test data in severe obstructive-sleep-apnea-hypopnea-syndrome (OSAHS) under continuous-positive-airway-pressure (CPAP) treatment

Introduction Few studies have evaluated the functional capacity of severe OSAHS. Aims To assess their functional capacity, identify their 6-min walking-distance (6MWD) influencing factors and compare their data with those of two control-groups. Methods Sixty (42 males) clinically consecutive stable patients with severe OSAHS under CPAP were included. Clinical, Epworth questionnaire, anthropometric, polysomnographic, plethysmographic and 6-min walk-test (6MWT) data were collected. Univariate and multivariate analyses were used to identify the 6MWD influencing factors. Data of a subgroup of severe OSAHS aged ≥40 Yrs (n = 49) were compared with those of non-obese (n = 174) and obese (n = 55) groups. Results The means ± SD of age and apnea-hypopnea-index were, respectively, 49 ± 10 Yr and 62 ± 18/h. The profile of OSAHS patients carrying the 6MWT, was as follows: at the end of the 6MWT, 31% and 25% had, respectively, a high dyspnea (>5/10, visual analogue scale) and a low heart-rate (<60% of-maximal-predicted), 13% had an abnormal 6MWD ( 5 points and 3% stopped the walk. The factors that significantly influenced the 6MWD, explaining 80% of its variability, are included in the following equation: 6MWD (m) = 29.66 × first-second-forced-expiratory-volume (L) - 4.19 × Body-mass-index (kg/m2) - 51.89 × arterial-hypertension (0. No; 1. Yes) + 263.53 × Height (m) + 2.63 × average oxy-sat during sleep (%) - 51.06 × Diuretic-use (0. No; 1. Yes) - 20.68 × Dyspnea (NYHA) (0. No; 1. Yes) - 38.09 × Anemia (0. No; 1. Yes) + 5.79 × Resting oxy-sat (%) - 586.25. Compared with non-obese and obese groups, the subgroup of OSAHS has a significantly lower 6MWD [100 ± 9%, 100 ± 8% and 83 ± 12%, respectively). Conclusion Severe OSAHS may play a role in reducing the functional capacity.