C100-09 Improvements In Obstructive Sleep Apnea Disease Severity Are Not Needed For Blood Pressure Reductions Following Repeated Daily Exposure To Mild Intermittent Hypoxia

Abstract Rationale Obstructive sleep apnea (OSA) is known to result in comorbid hypertension. Treatment with continuous positive airway pressure (CPAP) is difficult to adhere to and reported blood pressure reductions following treatment are often modest. Our lab has previously shown that 15 days of exposure to mild intermittent hypoxia (MIH) with concomitant CPAP use elicits reductions in blood pressure and associated measurements of OSA disease severity. However, it was not determined if concomitant CPAP usage is required for OSA improvements to manifest and if disease severity improvements mediate resting blood pressure reductions. We hypothesize that those treated with MIH+CPAP will experience reductions in OSA disease severity not seen when treated with MIH alone. Additionally, we postulate that resting blood pressure will be reduced independent of changes in OSA disease severity. 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, a polysomnogram (PSG) and CPAP titration were performed to assess OSA disease severity. P 0.05 was considered statistically significant. Results Baseline anthropometric characteristics were similar between groups. Group 1 experienced a 4-week reduction in non-REM apnea-hypopnea index (AHI) compared to baseline and sham groups (Δ from baseline 4 days: -14.68 ± 16.25; 4 weeks: -17.83 ± 16.51 events/hour). The AHI reduction was significantly greater than Group 3 immediately after treatment (Δ from baseline 4 days: + 2.48 ± 16.25 events/hour). AHI improvements were mediated by a 4-week reduction in the therapeutic pressure required to maintain airway patency compared to baseline and sham groups (Δ from baseline 4 days: -1.22 ± 1.09; 4 weeks: -2.58 ± 2.50 cmH2O). Despite AHI reductions only in Group 1, resting blood pressure was reduced in Groups 1 and 3 for 4 weeks compared to both baseline and sham groups (Δ from baseline Group 1: -10.50 ± 7.25 mmHg; Group 3: -12.93 ± 9.51 mmHg). Conclusions Treatment with MIH + CPAP effectively reduces AHI and upper airway collapsibility. However, OSA disease severity improvements are not needed to elicit reductions in resting blood pressure. This abstract is funded by: United States Department of Veterans Affairs (I01CX000125; IK6CX002287); National Institute of Heart, Lung and Blood (R01HL085537)