737 adults who snored and had a lab sleep study at one hospital between 2018 and 2025. 587 had sleep apnea on the sleep study and 150 did not.

Medians without and with sleep apnea: ODI: 0.8 against 21.6 dips an hour. pRED_3p: 0.003 against 0.126. SBII: 0.326 against 21.018. For telling the two groups apart: pRED_3p flagged 92.3% of people with sleep apnea and cleared 92.1% of those without. SBII flagged 89.2% and cleared 91.4%. Both moved almost in step with ODI. The correlation was 0.957 for pRED_3p and 0.955 for SBII, where 1 is a perfect match. The authors rank ODI, pRED_3p and SBII as the three strongest measures. BMI and the longest breathing event had limited value.

It looked back at records from one hospital, where most people tested had sleep apnea. The authors say the results may not carry over to the general public. People with sleep apnea were older (median 43 against 32) and had a higher BMI (28.5 against 25.1). Nothing was tested on a home oximeter.

New Oxygen Dip Measures vs ODI: A 2026 Study

Q: What are the two measures?

pRED_3p. The share of sleep time taken up by breathing events that came with an oxygen drop of 3% or more. SBII. Each breathing event's length is multiplied by the size (depth and duration) of the oxygen dip that followed, and the total is divided by sleep time. Both need the start and length of each breathing event. In this study those came from a lab sleep study, not from the oxygen trace alone.

A 2026 study of 737 adults compared two newer oxygen-dip measures, SBII and pRED_3p, with ODI. Both tracked ODI closely, and both were worked out from lab sleep study data.

PulseOxTracker Team9 October 2026

Infographic. Two newer oxygen-dip measures compared with ODI, for telling people with sleep apnea from people without. pRED_3p, time spent in events: 92.3% of people with it flagged, 92.1% without it cleared. SBII, length times size of dips: 89.2% of people with it flagged, 91.4% without it cleared. Who was studied: 737 adults who snored, one hospital in Tianjin, China. All had a lab sleep study. 587 had sleep apnea, 150 did not. What the study found: pRED_3p median 0.003 without sleep apnea, 0.126 with. SBII median 0.326 without sleep apnea, 21.018 with. ODI median 0.8 dips an hour without, 21.6 with. Correlation with ODI: pRED_3p 0.957, SBII 0.955. Against ODI, the authors say both did better in lower grade groups, with the figures in the supplement. BMI and the longest event had limited value for telling the groups apart. What it cannot show: one hospital, looking back at past records. Both measures used breathing-event timing from the sleep study. People with sleep apnea were older, with a higher BMI. Not tested on a home oximeter or in the general public. The ODI comparison figures are not in the main paper. Source: Zhang et al. 2026, Sleep and Breathing. — What the study found: in 737 adults who had a lab sleep study, two newer oxygen-dip measures separated people with and without sleep apnea about nine times in ten.

ODI counts how many times an hour your oxygen dips. It says nothing about how long or how deep each dip was.

Researchers have proposed measures that fold those in. A 2026 study from Tianjin, China compared two of them with ODI.

What are the two measures?

pRED_3p. The share of sleep time taken up by breathing events that came with an oxygen drop of 3% or more.
SBII. Each breathing event's length is multiplied by the size (depth and duration) of the oxygen dip that followed, and the total is divided by sleep time.

Both need the start and length of each breathing event. In this study those came from a lab sleep study, not from the oxygen trace alone.

Who was studied?

737 adults who snored and had a lab sleep study at one hospital between 2018 and 2025.
587 had sleep apnea on the sleep study and 150 did not.

What did it find?

Medians without and with sleep apnea:

ODI: 0.8 against 21.6 dips an hour.
pRED_3p: 0.003 against 0.126.
SBII: 0.326 against 21.018.

For telling the two groups apart:

pRED_3p flagged 92.3% of people with sleep apnea and cleared 92.1% of those without.
SBII flagged 89.2% and cleared 91.4%.

Both moved almost in step with ODI. The correlation was 0.957 for pRED_3p and 0.955 for SBII, where 1 is a perfect match.

The authors rank ODI, pRED_3p and SBII as the three strongest measures. BMI and the longest breathing event had limited value.

Did they beat ODI?

The authors say so for people with fewer breathing events per hour, especially those who weren't obese and had smaller oxygen drops. The main paper doesn't print the ODI figures behind that. They're in a supplement.

What can't it show?

It looked back at records from one hospital, where most people tested had sleep apnea.
The authors say the results may not carry over to the general public.
People with sleep apnea were older (median 43 against 32) and had a higher BMI (28.5 against 25.1).
Nothing was tested on a home oximeter.

What does that mean for your own recordings?

As this paper defines them, SBII and pRED_3p need the length of each breathing event, which a ring or fingertip oximeter doesn't record. It does report ODI, which this study put in the top three. T90 and your lowest reading add the depth and duration that ODI leaves out. Home oximetry is not a sleep study.

Not a medical device. Does not diagnose, treat or prevent any condition. Discuss results and changes with a clinician.

References

Zhang Y, Cai J, Liu M, Wang Y, Zhao H, Zhang J. Analysis of the predictive ability of novel hypoxia-related indicators for disease severity in obstructive sleep apnea syndrome. Sleep and Breathing. 2026;30(3):175. doi:10.1007/s11325-026-03721-z