Mild Intermittent Hypoxia Improves Cardiovascular and Neurocognitive Function in Obstructive Sleep Apnea Patients

Abstract

ObjectiveStudies in humans and other animals have provided compelling evidence that mild intermittent hypoxia (MIH) initiates long term facilitation of respiratory motor function and might offer cardiovascular, neurocognitive and metabolic protection. Despite this recognition, the beneficial responses to MIH in individuals with obstructive sleep apnea (OSA) have not been fully delineated. Hence, we aimed to determine if MIH coupled with continuous positive airway pressure (CPAP) therapy improves cardiovascular and neurocognitive function in OSA patients.MethodsData was collected from five hypertensive male participants who were diagnosed with OSA during overnight polysomnography at our laboratory and were subsequently treated with CPAP over a 3 week period of time. In addition, participants were treated with twelve 2‐minute episodes of hypoxia (PETO2 ≈ 50 mmHg) separated by 2‐minute intervals of normoxia for a period of 15 days over 3 weeks (i.e. 5 day/week). PETCO2 levels were sustained at 3 mmHg above baseline during MIH administration. Heart rate and beat to beat blood pressure measures obtained before exposure to MIH on the first and last day of the protocol were analyzed to determine if modifications in blood pressure and autonomic function were evident. Similarly, performance in neurocognitive tests designed to measure attention, learning and memory were also obtained pre‐ and post MIH therapy.ResultsPreliminary data suggests that daily exposure to MIH over 3 weeks led to a significant decrease in systolic blood pressure (before MIH vs. after MIH: 142.9 ± 4.4 vs. 132.7 ± 5.4 mmHg, p ≤ 0.05). Likewise, changes were observed in the high frequency (HF) component of heart rate variability (48.4 ± 5.7 vs. 60.0 ± 6.0 normalized units, p ≤ 0.01) and low frequency component of blood pressure variability (71.4 ± 5.7 vs. 63.8 ± 6.3 normalized units, p ≤ 0.06). The Buschke selective reminding test showed improvements in the number of trials required for recall (9 ± 0.9 vs. 2.2 ± 0.5, p ≤ 0.01) as well as long term recall (7.4 ± 1.4 vs. 17.8 ± 0.6, p ≤ 0.001) following MIH therapy. Daytime sleepiness did not show a significant change (7.5 ± 1.5 vs. 6.6 ± 1.6).ConclusionDespite being treated with CPAP for a short period of time (i.e. 3 weeks) significant modifications in cardiovascular, autonomic and neurocognitive modifications were evident. Typically this degree of change is not evident following treatment with CPAP for a short duration. We propose that repeated exposure to MIH was responsible for the significant modifications that were evident. Although data from control participants (i.e. CPAP alone) is required to support our results the data suggests that MIH may effectively treat cardiovascular co‐morbidities and improve memory in patients with OSA.Support or Funding InformationThis work is supported by the Department of Veterans Affairs, Veterans Health 507 Administration, Office of Research and Development (I01CX000125 & 15SRCS003 ‐ JHM).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.