Abstract Rationale Individuals with spinal cord injury or disease (SCI/D) often experience impaired ventilation and sleep disordered breathing (SDB). Studies have indicated that chemical stimulation induced by acute intermittent hypoxia can enhance ventilatory and motor recovery. However, the effects of intermittent hypercapnia, independent of hypoxia, have not been investigated in individuals with SCI/D. This study aimed to assess the feasibility and impact of daily acute intermittent hypercapnia (dAIHc) in individuals both with and without SCI/D. Methods We conducted a research study involving Veterans with SDB, defined as an apnea-hypopnea index of 5 events per hour, both with and without chronic SCI/D. The intervention involved daily acute intermittent hypercapnia (dAIHc), administered as 10 cycles of 3-minute iso-oxic hypercapnia (21% O2, 5% CO2) alternating with room air, 5 days a week for two weeks. The primary outcomes focused on the feasibility and tolerability of dAIHc, while secondary outcomes assessed changes in ventilatory responses to intermittent CO2 administration. Measurements were taken during steady-state wakefulness before, during, and after 40 minutes of room-air recovery. The hypercapnic ventilatory response (HCVR) is defined as the change in minute ventilation (VE) per change in end-tidal CO2 at the end of exhalation (Δ VE/ΔPetCO2). Results A total of 16 Veterans with SDB completed the protocol. Table 1 depicts the demographics and summary results of the participants. dAIHc was associated acutely with increased VE from 8.9 ± 2.6 to 16.9 ± 3.7 L/min (p 0.01) in response to increase of end-tidal CO2 from 38.5 ± 4.8 to 61.8 ± 18.1 mmHg (p 0.01). After completion of 10 days dAIHc, VE did not significantly change during the recovery period at 40 minutes (8.59 ± 2.74 and 8.43 ± 3.20, p = 0.966). Conclusion Daily acute intermittent hypercapnia (dAIHc) was both feasible and well tolerated among Veterans, regardless of whether they had SCI/D. While the dAIHc enhanced short-term ventilatory drive, it did not result in long-term ventilatory facilitation in either group, with or without SCI/D. Therefore, further exploration is needed to determine its effectiveness in addressing ventilatory and sleep disorders following SCI/D. This abstract is funded by: VA Rehabilitation R&D Service, Award # RX004114
Sunbulli et al. (Fri,) studied this question.