C100-08 Repeated Daily Exposure To Mild Intermittent Hypoxia Improves Blood Pressure, Microvascular Function, And Exercise Capacity In OSA Patients Independent Of CPAP Usage

Abstract Rationale Exposure to fifteen days of mild intermittent hypoxia (MIH), combined with continuous positive airway pressure (CPAP) treatment, results in a significant reduction in resting blood pressure in individuals living with obstructive sleep apnea (OSA) and untreated hypertension. The present study was designed to explore if the reduction in blood pressure is sustained for up to 8 weeks and induced independent of CPAP treatment. The present investigation also explored if the reduction in blood pressure is coupled with improvements in microvascular function and exercise capacity. Methods Participants were randomized to one of four groups: Group 1 – MIH + CPAP (8M,1F), Group 2 – sham + CPAP (8M,1F), Group 3 - MIH (7M,1F), Group 4 - sham (9M,1F). Groups 1 and 3 were exposed to twelve 2-minute episodes of MIH (PETO2 = 50 mmHg) 5 days/week over a 3-week period. 24-hour blood pressure was measured before treatment, as well as, 4 days, 4 weeks, and 8 weeks after treatment. At the same time points, microvascular function was assessed using near infrared spectroscopy (NIRS). In addition, exercise capacity and fatigue were assessed utilizing a submaximal ten-minute walk test and a maximum oxygen consumption test. P 0.05 was statistically significant. Results A reduction in blood pressure that was sustained for 4 weeks was evident in all participants exposed to MIH (Δ from baseline Group 1: -10.50 ± 7.25 mmHg; Group 3: -12.93 ± 9.51 mmHg). This reduction was not evident in Groups 2 and 4. Likewise, an increase in the maximal hyperemic response was sustained for 4 weeks in Groups 1 and 3 (Δ from baseline Group1: 580.31 ± 593.21 a.u.; Group 3: 692.93 ± 519.76 a.u.) but was not evident in Groups 2 and 4. Treatment with MIH led to an increased ability to walk further compared to baseline for 4 weeks during submaximal exercise (Group 1: 109.07 ± 138.60 m; Group 3: 119.49 ± 131.99 m). An increase in oxygen consumption at the anaerobic threshold was sustained for eight weeks compared to both sham and baseline following MIH (Group 1: 1.48±0.99 mL/kg/min; Group 3: 2.38±1.86 mL/kg/min). The reduction in blood pressure was correlated with an increased ability to walk further during submaximal exercise (R2 = 0.647). Conclusions MIH treatment effectively improves blood pressure, microvascular function, and exercise capacity that is sustained for at least 4 weeks. The response to treatment occurs independent of treatment with CPAP. This abstract is funded by: United States Department of Veterans Affairs (I01CX000125; IK6CX002287); National Institute of Heart, Lung and Blood (R01HL085537)