Can Obstructive Sleep Apnea Impair Cardiorespiratory Responses to Aerobic Exercise in Hypertensive Elderly?

The sample was randomly recruited from the Lauro Wanderley University Hospital and older people living together centers located in João Pessoa/PB (Brazil). All subjects were submitted to anthropometric assessments (body mass index, neck circumference, hip circumference and waist circumference), polysomnography, echocardiography, cardiopulmonary exercise test (CPET). Moreover, they were submitted to a sleep quality questionnaire (Pittsburgh Sleep Quality Index).

Cardiopulmonary Exercise Test Protocol All subjects performed an incremental cardiopulmonary exercise test (CPET) of maximum exercise tolerance. All procedures were performed in agreement with the guidelines of the American Thoracic Society/American College of Chest Physicians for cycle ergometer tests. The CPET was performed on an Inbrasport CG-04 cycle ergometer (Inbrasport, Porto Alegre, Rio Grande do Sul, Brazil) with electromagnetic braking. Subjects performed a 5-min warm-up with no resistance (0 W), then the activity rate was increased using a ramp protocol (5-10 W.min-1) until maximum exercise tolerance. Verbal encouragements were given during the CPET to ensure maximal effort.

Pulmonary gas exchange variables (VO2, VCO2, minute ventilation [VE], oxygen pulse (O2Pu), respiratory quotient (R), ventilatory efficiency index (VE/VCO2slope), cardiovascular function index (ΔHR/ΔVO2), deviation from oxygen consumption efficiency (OUES), metabolic efficiency index (VO2/ΔWR), blood pressure (BP), heart rate (HR) recovery at first (HRR1) and second (HRR2) minutes were measured breath-by-breath with an on-line gas expiration analysis system (VO2000, MedGraphics, St. Paul, Minnesota, USA). Peak values were established by the highest values achieved during effort.

Polysomnography Assessment All hypertensive subjects were submitted to a polysomnography exam to diagnose OSA. OSA diagnosis was confirmed by the apnea/hypopnea index (AHI) and classified as follows: AHI < 5 events/h, absence of OSA; 5 ≤ AHI ≤ 15 events/h, low OSA; 15 ≤ AHI ≤ 30 events/h, moderate OSA; AHI > 30 events/h, severe OSA.

The assessment was carried out during an entire night of sleep in the participant's residence without the use of sedatives. The variables were monitored by an Embletta portable respiratory monitor (Embla, Embletta® Gold, EUA), previously validated and in agreement with manufacturer's instructions. The Embletta monitor is capable to continuously monitor pulse oximetry, to detect respiratory efforts, to measure the airflow, and to record snoring episodes. Additionally, HR was continually measured by the analysis of pulse waves by oximetry. Finally, brain and muscle activities were monitored by electrodes, and oxygen desaturation (O2D) was defined as the amount of reduction in O2S at 4%/h.