Heart rate recovery post 6-minute walking test in obstructive sleep apnea: cycle ergometry versus 6-minute walking test in OSA patients.

PURPOSE: To examine the clinical usefulness of heart rate recovery (HRR) post 6-minute walking test (6MWT) as a simple marker of cardiovascular risk in obstructive sleep apnea (OSA) patients in comparison to HRR post cycle ergometry, the validated and more sophisticated protocol. METHODS: Seventy-four participants underwent full overnight polysomnography, cycle ergometry and 6MWT. The HRR at 1, 2 and 3 min (HRR-1, HRR-2 and HRR-3) 6MWT was compared to HRR at 1, 2, and 3 min post cycle ergometry in normal subjects and in moderate and severe OSA patients before and after 6-month CPAP treatment. RESULTS: The HRR-1, HRR-2 and HRR-3 in 6MWT were significantly different between normal, moderate and severe OSA patients with higher rates achieved in normal. The higher the severity of OSA the lower the HRR was. There were also no differences found between work rate and distance walked during cycle ergometry or 6MWT, respectively, concerning normal, moderate and severe OSA patients. Heart rate recovery was further associated with minimum saturation of oxygen during sleep independently of the duration of apnea episodes of BMI and ESS. The treatment with CPAP had a beneficial effect on HRR both post-6MWT and post cycle ergometry. CONCLUSIONS: Autonomic nervous system dysfunction in OSA can be found even with submaximal exertion. Heart rate recovery post-6MWT, such as HRR post cycle ergometry, was significantly impaired in OSA patients in comparison to normals and was favorably influenced from CPAP treatment. Furthermore, it was found to be more sensitive compared with distance walked in 6MWT in discriminating severity of OSA. The HRR post-6MWT was found to be an easily measured and reliable marker of OSA severity both before and after CPAP treatment.

Asleep home blood pressure monitoring in obstructive sleep apnea: a pilot study.

BACKGROUND: Obstructive sleep apnea (OSA) is known to be related to nocturnal blood pressure (BP) and nondipping hypertension. This pilot study evaluated night-time BP assessed using a home monitor in patients with OSA. PARTICIPANTS AND METHODS: Patients referred to a sleep clinic were subjected to polysomnography, clinic BP measurements, and home BP monitoring using a device that allows daytime (3 days, two duplicate readings per day) and automated night-time BP measurement (3 nights, three readings per night). RESULTS: Thirty-nine patients were included [72% men, mean age 48.7±10.8 years, clinic BP 131.2±19.6/84.1±11.9 mmHg, apnea-hypopnea index (AHI): 35.2±25.7]. All BP measurements were significantly correlated with the polysomnography indices. There was a consistent trend toward stronger correlations of the night-time diastolic home BP with the AHI (r=0.56), the duration of desaturation (0.53), and the maximum (-0.57) and minimum (-0.48) arterial oxygen saturation (all P<0.001). In stepwise multivariate analysis (independent variables age, sex, body weight, smoking status, and BP parameters), the AHI was associated independently with weight and night-time diastolic home BP (R=0.53). CONCLUSION: In patients with OSA, the assessment of night-time BP using a home monitor appears to be feasible and related to the severity of OSA. Given the wide availability of home BP monitoring in clinical practice, this method appears to be useful in the evaluation of BP in patients with OSA.