O056 The effect of acetazolamide and oxygen (ACZ+O2) combination therapy on loop gain and OSA severity Open Access

One third of patients with OSA have high loop gain. Acetazolamide (ACZ) and supplemental oxygen (O2) individually reduce loop gain (via different mechanisms) and the apnoea-hypopnoea-index (AHI). The current study aimed to explore the efficacy of combining both ACZ and O2 to maximally lower loop gain.

Randomised single-blind cross-over trial. Participants took ACZ (500mg orally) or placebo for 7 days. Within each arm, participants completed two polysomnograms (PSGs) during which they slept with supplemental oxygen (3L/min) or sham-air. Sleep and respiratory events were scored by a (blinded) technologist. In addition to standard scoring, respiratory events were scored without SpO2 or arousal information to calculate a ‘flow-based AHI’ (fAHI). PSG data were then imported into Matlab for loop gain analysis.

Nine participants (5 males, Age=52.4±9.1, BMI=32.0±4.9, AHI=39.9±22.0) have so far completed the trial. Loop gain was significantly reduced by ACZ (-22%, -0.15 CI95:-0.03 to -0.26, p=0.011), O2 (-25%, -0.19 CI95:-0.08 to -0.29, p=0.001) and combination ACZ+O2 (-33%, -0.23 CI95:-0.12 to -0.34, p<0.001) relative to placebo-sham-air condition. Similarly, fAHI was significantly reduced by ACZ (-34%, -15.7/hr CI95:-8.6 to -22.7, p<0.001), O2 (-21%, -10.2/hr CI95:-3.1 to -17.3, p<0.001) and ACZ+O2 (-45.2%, -21.3/hr CI95:-14.6 to -28.4, p<0.001). While fAHI was significantly lower on ACZ+O2 compared with O2 (p=0.003), the difference between ACZ+O2 and ACZ was not significant (-5.6/hr, p=0.12). ACZ+O2 induced a >50% reduction in fAHI in 4/9 participants.

Our preliminary data demonstrate that ACZ+O2 may be an efficacious combination therapy for some OSA patients.