A comparison between auto-scored apnea-hypopnea index and oxygen desaturation index in the characterization of positional obstructive sleep apnea

OBJECTIVE: Evaluate the concordance between overall and positional oxygen desaturation indices (ODI) and apnea-hypopnea indices (AHI) according to two different definitions for positional obstructive sleep apnea (POSA). METHODS: A total of 184 in-home polysomnograms were edited to simulate Level III home sleep apnea tests (HSAT) with the auto-scored AHI and ODI based on recording time. POSA was determined using 132 records with an AHI≥5 and at least 20 mins of recording time in both supine and non-supine positions. POSA was defined independently for the AHI and ODI based on ratios of overall/non-supine event/h ≥1.4 (O/NS) and supine/non-supine event/h≥2.0 (S/NS). RESULTS: Correlation between the AHI and ODI was 0.97 overall, 0.94 for supine, and 0.96 for non-supine recording times (all p<0.001). For most records, differences between the AHI and ODI were small, with only 14% of the records having a AHI-ODI difference exceeding >5/hr, and 6% exceeding >10 events/hr. The positive and negative percent agreements were uniformly good to excellent across varying clinical POSA cutoffs; percent agreements (positive, negative) were: AHI≥5=0.99, 0.78; AHI≥10=0.96, 0.89; and AHI≥15=0.96, 0.89. Cohen’s Kappa scores also showed substantial agreement for overall as well as supine and non-supine positions across varying clinical cutoffs of the AHI. Frequency of POSA was reproducibly uniform between 59% and 61% for both POSA criteria. When the O/NS and S/NS definitions conflicted in POSA characterization, O/NS was superior for identifying patients who might exhibit a greater response to supine restriction positional therapy. CONCLUSIONS: Auto-scored positional oximetry is a clinically viable alternative to an auto-scored Level III HSAT AHI in the characterization of POSA based on a 3% desaturation.