What are oxygen drops? A simple guide to what they mean
What are O2 drops?
Oxygen drops (or O2 drops) are decreases in blood oxygen levels during sleep.
Your O2 ring estimates this by using SpO2, which is the percentage of oxygen in your blood (or Saturation of Peripheral Oxygen).
In obstructive sleep apnoea (OSA), the airway can partly or fully narrow during obstructive events, and blood oxygen may drop as a result until the airway opens back up again, when blood oxygen then returns to baseline1.
Why do they happen?
O2 drops can occur when airflow is reduced during sleep2.
That is why they are commonly linked with OSA3.
They can also be influenced by :
- sleep stage4,
- sleep position5,
- alcohol consumption6,
- nasal congestion7.
Because of these multiple factors, it is important to look at patterns over time rather than a single night.
How is the number counted?
An O₂ drop is identified when your SpO₂ decreases by a certain amount compared to your usual level. These individual drops are then counted over the night.
Oxygen desaturation index, or ODI represents the average number of these drops per hour of sleep.
A common clinical threshold is a drop of 3% or more from baseline, although exact rules can vary by system8.
How to think about the metric in myNarval
To calculate O₂ drops per hour, myNarval divides the total number of qualifying oxygen drops (≥3%) by the number of hours tracked.
For example :
What does a higher number mean?
- A higher number means drops are happening more often.
- A lower number generally suggests steadier oxygen through sleep.
The most useful question is not “what was my number last night?” but “what direction is my pattern moving in over several nights?”8.
What to remember
O2 drops are a clue about how stable your breathing and oxygen were overnight.
The per-hour average helps you spot patterns, especially when you compare similar time periods.
Looking at trends over time can help you better understand your sleep patterns.
References:
1. Li P, Ning XH, Lin H, Zhang N, Gao YF, Ping F. Continuous positive airway pressure versus mandibular advancement device in the treatment of obstructive sleep apnea: a systematic review and meta-analysis. Sleep Med. 2020;72:5-11. doi:10.1016/j.sleep.2020.03.015
2. Danny J. Eckert, Atul Malhotra. Pathophysiology of Adult Obstructive Sleep Apnea | Annals of the American Thoracic Society | Oxford Academic. Proc Am Thorac Soc. 2008;Volume 5(Issue 2):Pages 144-153. doi:https://doi.org/10.1513/pats.200707-114MG
3. Jordan A, McSharry D, Malhotra A. Adult obstructive sleep apnoea. The Lancet,. 2013;383:736-747. doi:10.1016/S0140-6736(13)60734-5
4. Findley LJ, Wilhoit SC, Suratt PM. Apnea Duration and Hypoxemia During REM Sleep in Patients with Obstructive Sleep Apnea. Chest. 1985;87(4):432-436. doi:10.1378/chest.87.4.432
5. Oksenberg A, Khamaysi I, Silverberg DS, Tarasiuk A. Association of Body Position With Severity of Apneic Events in Patients With Severe Nonpositional Obstructive Sleep Apnea. CHEST. 2000;118(4):1018-1024. doi:10.1378/chest.118.4.1018
6. Kolla BP, Foroughi M, Saeidifard F, Chakravorty S, Wang Z, Mansukhani MP. The impact of alcohol on breathing parameters during sleep: A systematic review and meta-analysis. Sleep Med Rev. 2018;42:59-67. doi:10.1016/j.smrv.2018.05.007
7. Alotaibi S, Bin Saddiq BW, Alfarhoud RS, et al. Clinical Effectiveness of Nasal Dilators in Sleep-Disordered Breathing: A Systematic Review and Meta-Analysis. Cureus. 18(1):e100663. doi:10.7759/cureus.100663
8. Fabius, T.M., Benistant, J.R., Bekkedam, L., van der Palen, J., de Jongh, F.H., & Eijsvogel, M.M. (. Validation of the oxygen desaturation index in the diagnostic workup of obstructive sleep apnea. Sleep Breath. 2019;23,:57-63.
This article contains general information about medical conditions and potential treatments. It is not medical advice. If you have any medical questions, please consult your doctor.
myNarval is not a medical device.
PROMOTIONAL MATERIAL – Narval CC is compliant with applicable regulations. Manufacturer: Resmed.
Pulse Oxymeter O2 ring is a CE-marked medical device (CE NB0197). Manufacturer: Shenzhen Viatom Technology