The recent article by Dr. Ayache and Dr. Strohl adds valuable insight in to standardizing the interpretation of overnight oximetries.1 With the increase in home sleep testing and auto titration, overnight oximetries are frequently used to verify adequate oxygenation in patients who have concerning oxygen saturation findings during their home sleep tests. One common pattern that is seen in such patients is an overnight oximetry which shows an acceptable baseline oxygen saturation, an elevated oxygen desaturation index (ODI), but a continuous positive airway pressure (CPAP) download that shows the apnea-hypopnea index (AHI) in the normal range. Take for example, the overnight oximetry of a 66-year-old male with CPAP at 12 cmH2O that showed a basal oxygen saturation of 92% and an ODI (3%) of 28 events/h. The duration of this test was 7 hours 39 minutes. Time during this test with oxygen saturation ≤ 89% was 23 minutes and time with oxygen saturation ≤ 88% was 13 minutes. Significant sustained desaturations were not seen. Interestingly enough, the AHI and leak on the CPAP download for this patient on the night of the above overnight oximetry and the days preceding and following this test were at the desired levels. The reason for such a discrepancy between the ODI and AHI is perplexing and unclear. As a provider in such situations, one is left with the questions of which reading do you trust and what do you do with these patients? Erring on the side of caution, it would be worthwhile to consider titrating these patients in the sleep laboratory. However, one is then left with another question: what should be the cutoff for the ODI at which a titration in the sleep laboratory should be pursued? Further research is needed in this area to provide adequate guidance to clinical providers.
Dr. Kapoor reports no conflicts of interest.
Kapoor M. Discrepancy between oxygen desaturation index and apnea-hypopnea index: what do you do with the results? J Clin Sleep Med. 2018;14(8):1437.
Ayache M, Strohl KP. High interrater reliability of overnight pulse oximetry interpretation among inexperienced physicians using a structured template. J Clin Sleep Med. 2018;14(4):541–548. [PubMed]