Mild Intermittent Hypoxia Significantly Reduces the Critical Closing Pressure and Continuous Positive Airway Pressure

Purpose Adherence to continuous positive airway pressure (CPAP) therapy is low in part because of patient discomfort initiated by high therapeutic pressures (TP). Improved adherence could ultimately lead to more effective treatment of co‐morbidities linked to sleep apnea. Acute and repeated daily exposure to mild intermittent hypoxia (MIH) initiates long‐term facilitation of upper airway muscle activity. Initiation of this form of plasticity could increase upper airway patency and as a result decrease the therapeutic pressure required to treat obstructive sleep apnea (OSA). Therefore, we investigated if repeated daily exposure to MIH reduces the upper airway critical closing pressure (P CRIT ) and therapeutic CPAP pressure. Likewise, we examined if reductions in the therapeutic pressure were linked to improved adherence Methods Five hypertensive male participants newly diagnosed with OSA were treated with twelve 2‐minute episodes of hypoxia (P ET O 2 ≈ 50 mmHg) separated by 2‐minute intervals of normoxia each day for a period of 15 days over 3 weeks (i.e. 5 days/week). P ET CO 2 levels were sustained at 3 mmHg above baseline during MIH administration. Prior to exposure to MIH the critical closing pressure and therapeutic CPAP was determined. Thereafter, participants were treated with CPAP at home each night throughout the 15 day protocol. Mid‐way and at the end of the protocol measures of the critical closing pressure and therapeutic pressure were repeated. Results Mid way through the MIH protocol the therapeutic pressure was reduced from 12.6 ± 0.93 to 11.2 ± 0.97 cmH 2 O (P ≤ 0.05) accompanied by a reduction in passive P CRIT from 4.2 ± 0.92 to 2.5 ± 0.95 cmH 2 O (P ≤ 0.03). Similar modifications were also evident at the end of the protocol. The frequency of breathing events recorded remotely from participants treated with CPAP at home was not altered following reductions in TP (AHI: 1.48 ± 0.4 vs 2.30 ± 1.6, P ≥ 0.2) indicating that the participants were effectively treated despite a decrease in TP. Adherence to CPAP increased in 4 of 5 participants. An increase in adherence to CPAP was not evident in one individual because treatment throughout a given sleep period was uninterrupted from the onset to the end of the protocol (7.7 vs. 7.4 hours/night). In the remaining participants adherence increased from 4.9 ± 0.87 to 6.1 ± 0.37 hours per night. In addition, the number of days participants used CPAP for less than 6 hours significantly decreased before compared to after the TP was reduced (5 to 2.4 days, P ≤ 0.02). A correlation between the change in TP and number of hours of use trended toward significance (R 2 = 0.89, P ≤ 0.06). Conclusion MIH improves upper airway patency as suggested by the decrease in P CRIT and the reduction in TP. The reduced TP was coupled to improvements in CPAP adherence. Improved CPAP adherence might ultimately lead to improved treatment of co‐morbidities linked to sleep apnea. Support or Funding Information This material is based upon work 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 .