Effect of CPAP or oxygen on high loop gain sleep apnea and associated blood pressure change- an analysis using respiratory self-similarity.

BACKGROUND

Respiratory high loop gain (HLG) is an important driver of obstructive apnea and may be modified by continuous positive airway pressure (CPAP) or supplemental oxygen. Respiratory self-similarity is a marker of expressed HLG.

METHODS

The baseline and on-therapy (CPAP, oxygen, healthy lifestyle and sleep education, HLSE) follow-up home sleep apnea tests (HSAT) from the Heart Biomarker Evaluation in Apnea Treatment (HeartBEAT) study were analyzed using self-similarity based on the respiratory effort signal. Linear regression analysis assessed the role of treatment efficacy in improving HLG obstructive sleep apnea (HLGSA). The association of HLGSA change and impact on 24-h blood pressure after treatment was estimated.

RESULTS

A total of 272 subjects, 92 HLSE, 94 oxygen and 86 CPAP were analyzed. No significant differences in self-similarity % (SS%) or a central respiratory event index were noted after treatment in the HLSE and oxygen groups. CPAP lowered both self-similarity % (3.1[0-6.9] vs. 1.2[0-3.93]%, p < 0.001) and CREI (6.79[0-13.96] vs. 2.78[0.25-7.84] hour, p: <0.001). The baseline apnea hypopnea index (AHI) (β:0.261, p:< 0.001) and 24-h diastolic blood pressure (β:0.177, p: 0.015) were associated with the efficacy of CPAP in reducing SS%. An improvement in SS% was associated with sleep systolic blood pressure decrease (OR 1.739, 95%CI 1.031-2.934, p: 0.038) induced by treatment. Similar results was found with the CREI.

CONCLUSIONS

CPAP but not oxygen improved expressed HLG in sleep apnea, which in turn was associated with systolic blood pressure reductions.