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Practical guides on sleep, blood oxygen and pulse oximetry, and how to read your overnight data.
Top stories
Brain Oxygen vs Finger SpO2 at Altitude
A 2026 study recorded brain and finger oxygen overnight at 2,500 m in 16 people with pulmonary vascular disease. Finger SpO2 fell by 6.7 points, while brain oxygen stayed about the same.
Back vs Side Sleeping and Your Oxygen Levels
What sleep lab studies found about sleeping position, and how to compare back and side nights with an overnight oximeter that doesn't record position.
Checkme O2 Max Tips: Using the Long Battery
Practical tips for wearing a Wellue Checkme O2 Max, recording several nights between syncs, and keeping those nights clean and comparable.
Pulse Oximeters and Skin Tone: The Research
What published studies and the FDA say about pulse oximeter readings on darker skin, and what that means for your own overnight tracking.
Breathing Rate From Heart Rhythm: A Pilot
A 2026 pilot study estimated breathing rate from beat-to-beat heart rhythm, the method behind many wearables. It was within 2 breaths a minute in 4 of 10 older adults and off by 6 to 17 in the other 6.
Does a Blocked Nose Lower Overnight Oxygen?
How to tag blocked-nose and allergy nights and compare them with clear ones in your overnight oxygen data from an oximeter.
Do Cheap Pulse Oximeters Work Overnight?
Why a cheap fingertip pulse oximeter is fine for a quick reading but usually can't record a night's sleep, and what to check on the listing.
New research
275 articles
Breathlessness at Simulated Altitude: A Study
22 healthy young adults cycled for 30 minutes in a low-oxygen gym set to about 9,000 ft. How breathless they felt varied widely, had no significant link with resting HRV, and went with how much oxygen their thigh muscle lost. Men felt more breathless than women.
CPAP, Heart Events and Time Below 90%
A 2026 study of 350 adults aged 60 and over with sleep apnea linked regular CPAP use to fewer heart events in those with a T90 of 1.5% or more, with no statistically significant link below that. It's observational and the CPAP group was 70 people.
Does ODI Track Breathing Events? A 2026 Study
A 2026 study of 52 people with sleep apnea found the oxygen desaturation index moved closely with breathing events per hour (r = 0.89). Time below 90% and average SpO2 tracked less closely, and lowest SpO2 least.
Home Sleep Tests and CPAP Use: Iceland Study
A 2026 Icelandic study offered home sleep tests to 334 adults aged 54 to 91. 4 in 10 had 15 or more breathing events per hour, and 53 of the 99 referred for a PAP machine were still using it two years later.
Long COVID Fatigue, Sleep and HRV
A 2026 study tracked 14 adults with long COVID fatigue on a Fitbit for a median of 28 days. Nights with more sleep than usual were linked to less fatigue the next day, but night-to-night HRV wasn't.
Oxygen Sessions and Sleep at High Altitude
A 2026 survey of 1,316 military personnel at high-altitude posts in China found more frequent and longer oxygen sessions went with fewer sleep difficulties. The links were small, and the study cannot show cause.
Sleep Efficiency and HRV in Footballers
A 2026 study of 53 male football players in Brazil found professionals had higher resting HRV and higher self-reported sleep efficiency than under-15 and under-17 players, and the two went up together.
More in new research
- Sleep Habits and Thyroid Disease: A Study
- Sleep Hours and Osteoporosis After Menopause
- Two Kinds of Oxygen Burden in Sleep Apnea
- TyG Index and Lowest Overnight SpO2
- Who Stops CPAP in the First Year? A Study
- WHOOP Strain vs Perceived Effort in Athletes
- 34 Pulse Oximeters Tested for Skin Tone Bias
- Best Time to Exercise for Sleep: 13 Trials
- Does Beer Affect HRV? The BEER-HIIT Trial
- Insomnia and Altitude Sickness: A Small Study
Show 256 more
- Irregular Sleep Timing, Training and HRV
- Low-Altitude Bedrooms in Lhasa: 12-Week Trial
- Morning vs Evening Exercise and Night BP
- Mouthpiece vs CPAP for Blood Pressure
- Oxygen Burden: Why the Method Matters
- Progressive Muscle Relaxation for Sleep
- Sense of Coherence and CPAP Use: A Study
- Sleep at High Altitude: A Firefighter Study
- Sleep Deprivation and How You Walk
- Snore Recording App vs a Home Sleep Test
- Warm Footbath and Sleep in Heart Failure
- A Probiotic and SpO2 at 5,050 m: A Trial
- Almonds and Sleep Quality: A 5-Month Trial
- Cold Fingers and False Low Oximeter Readings
- Does Lack of Sleep Make You Thirsty?
- Early Infection Signs in Wearable Data
- Flying With Lung Disease: Oxygen Formulas
- High Altitude to Sea Level: Overnight Oxygen
- Oximeter vs Blood Gas at a Black Lung Clinic
- Oxygen Burden and Night-Time Blood Pressure
- Oxygen Overshoot After a Dip: 2026 Commentary
- Shallow Oxygen Dips and Memory: 2026 Study
- Sleep After an Ultra-Trail Race
- Sleep Apnea and Atrial Fibrillation Risk
- Social Jetlag in 5 Million Fitbit Nights
- Wrist-Tracked Sleep Stages and Disease Risk
- Bed Sensor Sleep Data and Next-Day Thinking
- Breathing Pause Length and Oxygen Levels
- Compression Tights in Bed: A Sleep Lab Study
- CPAP Cheyne-Stokes Data Before Heart Events
- CPAP Comfort Settings and Hours of Use
- Exercise Plus Sleep Coaching for Poor Sleep
- Insomnia Plus Sleep Apnea: Heart Risk Study
- Nurses Are Sleeping Less: A 2026 Analysis
- Philips CPAP Recall: What Users Went Through
- Physical Activity and Insomnia: 19 Studies
- Sleep Apnea in Women vs Men: Overnight Oxygen
- Sleep Apnea Traits From Oximeter Data
- Sleep Apnea Waiting Times in England
- Sleep Habits and Pneumonia Risk: A Study
- Smart Ring Data, Anxiety and Depression
- Asleep or Awake on CPAP? A 2026 Study
- Bilevel vs CPAP: Does It Add Hours of Use?
- CPAP Mouth Leaks: What Comes Before Them
- CPAP Use in Over-70s: A Spanish Study
- EmbracePlus Wristband SpO2 Accuracy Tested
- Exercise, HRV and Sleep Apnea: A Study
- Heart Failure: 6 Nights of Overnight Oxygen
- Making Smartwatch Oxygen Data Make Sense
- Sitting Time and Sleep: A UK Biobank Study
- Sleep Apnea, Thinking Tests and CPAP Hours
- Sleep Habits and Neck Disc Problems: A Study
- Sleep Habits and Weight After Menopause
- Sleep Quality and Walking Steadiness
- Slightly Low Oxygen and Memory in Smokers
- Smoking and REM Sleep: A 2026 Study
- Acid Reflux, CPAP and Time Below 90%
- Broken Sleep and Next-Morning Brain Scans
- Daridorexant and Sleep Apnea: A 2026 Trial
- Does Daytime HRV Reflect Night Breathing?
- ICU Pulse Oximeter Accuracy: Age vs Skin Tone
- Laser vs LED Oximeters and Skin Pigment
- Oxygen Dips and the Inner-Ear Balance Organ
- Oxygen Signal Entropy and Sleep Apnea
- Pulmonary Hypertension: A Night at 2,500 m
- Shoulder Pulse Oximeter vs Finger: A Pilot
- Sleep Apnea Oxygen Profiles: An Italian Study
- The Menstrual Cycle in Wearable Data: A Study
- Time Below 90% and Triglyceride Particles
- Time Below 90% in Sleep Apnea: Who Has More?
- Tirzepatide and Sleep Apnea: Who Responded?
- Acetazolamide in REM Sleep Apnea: A Trial
- Apple Watch Blood Oxygen Accuracy: A Review
- BMI and Overnight Oxygen Dips at Altitude
- Early Bedtime, Blood Pressure and Sleep Apnea
- Garmin Fenix SpO2 at 4,559 m vs Blood Samples
- Home Oximeter Readings in Phone Triage
- Is SpO2 Higher on a Second Altitude Trip?
- Night Oxygen Dips: Asleep or Moving?
- Oximeter Accuracy: Motion and Cold Fingers
- Positional Sleep Apnea and Daytime Sleepiness
- Sleeping on a Flight: Oxygen Below 90%
- Temperature Swings and Sleep Apnea Study
- Time Below 90% and Cholesterol: A CPAP Study
- Time Below 90% and Kidney Risk in Diabetes
- Time Below 90% and Preserved-EF Heart Failure
- Fingertip Oximeter vs Arterial Blood Test
- Home Oximetry ODI vs a Lab Sleep Study
- Lung Function and Overnight Oxygen: A Study
- Night-Time Heart Attacks and Sleep Apnea
- Oxygen Dips in the First Nights at Altitude
- Periodic Breathing at Simulated Altitude
- REM Sleep Oxygen Dips and Memory: 2024 Study
- Skin Pigment and Oximeter Error: Lab Data
- Sleep Apnea After 70: Women's Oxygen vs Men's
- Sleep Apnea, Fitness and Mortality: A Study
- Smartphone SpO2 Accuracy: A Lab Test
- Three Smartwatches Tested in Low Oxygen
- Warming the Arm and Pulse Oximeter Accuracy
- Wearable Ring Oximeter Tested in Low Oxygen
- Weight Loss Videos for Sleep Apnea, Rated
- 3% vs 4% Oxygen Dip Rule: Does Sex Matter?
- Alcohol, Heart Rate and Sleep: A WHOOP Study
- Aroma Oil and CPAP Use: A Small Pilot Study
- Bedroom Temperature and HRV in Older Adults
- Caffeine Naps for Drivers With Sleep Apnea
- CPAP and Heart Events: A 2026 Cohort Study
- CPAP Hours and Atrial Fibrillation Returning
- CPAP, BiPAP or Oxygen: 5-Year Survival
- Do Oximeters Miss Low Oxygen on Dark Skin?
- Does a Vibrating Device Stop Back Sleeping?
- Getting Used to CPAP as a Couple: A Study
- Home Sleep Test in Primary Care: A 2026 Study
- How Common Is Sleep Apnea? A São Paulo Study
- Is Fitbit Versa 4 Overnight HRV Accurate?
- ODI and Coronary Artery Disease: 2026 Study
- Opioids and Sleep Apnea Symptoms: 2026 Study
- Oximeter-Only Home Sleep Test: How Accurate?
- Pulse Oximeter Accuracy: Bench vs Human Tests
- Sleep Apnea and Attention: Oxygen or Sleep?
- Sleep Apnea and CPAP in Taxi Drivers: A Study
- Sleep of High-Altitude Workers: A 2025 Study
- Smartwatch SpO2 Accuracy at High Altitude
- Snoring and Jaw Muscle Pain: A 2026 Study
- Snoring Sound AI vs a Wearable: 2026 Study
- Still Sleepy on CPAP? A 2026 Clinic Review
- Time Below 90% and the Heart Transplant Wait
- Tongue Nerve Implant vs CPAP: A Records Study
- Untreated Sleep Apnea: Does It Get Worse?
- What Predicts CPAP Hours? 136 Trials Pooled
- Which Early CPAP Problems Predict Less Use?
- 3 Nights of Oximetry in Motor Neuron Disease
- Broken Sleep and Next-Day Thinking Speed
- COPD, Sleep Apnea and Overnight Oxygen
- Do Wearable Oxygen Reports Change CPAP Use?
- EEG Headband vs Actigraphy in Older Adults
- Forest Bathing and SpO2: A Small Trial
- Is Overnight Oxygen Lower With Long COVID?
- Liraglutide, COPD and Overnight Oxygen Dips
- Night Oxygen for Central Sleep Apnea: A Trial
- Overnight Pulse Rate and Cognitive Decline
- Oxygen Dips and Reading Faces: A Small Study
- Oxygen Saturation by Age: Women vs Men
- Smartwatch Breathing Alert and AFib: One Case
- Testosterone Therapy and Sleep Apnea: A Study
- Time Below 90% and a Brainstem MRI Study
- WatchPAT Home Sleep Test With Insomnia
- What Goes With Sleepiness in Sleep Apnea?
- What Your CPAP Log Misses on Part-Use Nights
- A Pill for Sleep Apnea? The AD109 Trial
- Acetazolamide and SpO2 at Altitude: A Trial
- AI and Overnight Oximetry: How Accurate?
- Apple Watch Accuracy in Heart Patients
- Apple Watch Sleep Tracking in Shift Nurses
- Apple Watch vs Finger Oximeter in Low Oxygen
- Back Sleeping vs REM Sleep in Sleep Apnea
- Bed Sensor vs CPAP Data: A 2026 Study
- Belun Ring vs Lab Sleep Study: What Matched?
- Breathing Technique and SpO2 in Thin Air
- Brief Awakenings and Oxygen Dips: 2026 Study
- Carbon Monoxide and a 98% Oximeter Reading
- Chronic Hives and Sleep: A 2026 Study
- CPAP and Heart Health: A 2026 Review
- CPAP and Long-Term Survival: Up to 20 Years
- CPAP and Night-Time Urination: A 2026 Study
- CPAP Break and Sex Hormones: A 2026 Study
- CPAP Follow-Up: Yearly Visit or On Request?
- CPAP Headgear and Neck Nerve Pain: A Case
- CPAP Shows Cheyne-Stokes? A Blocked-Nose Case
- CPAP vs Mouthpiece: What 14 Reviews Found
- Daylight, Evening Light and Sleep: A Study
- Diabetes, Insomnia and Sleep Apnea Together
- Do Throat Exercises Help Sleep Apnea? A Trial
- Do Wearable Sleep Devices Help Insomnia?
- Does a Back-Sleeping Alarm Cut Snoring?
- Does CPAP Mask Leak Predict CPAP Use?
- Fingertip Pulse Oximeter Accuracy: 11 Tested
- Galaxy Watch 6 SpO2 in Older Adults: A Study
- Garmin fenix 6 Blood Oxygen Accuracy: A Study
- GLP-1 vs SGLT2 vs Exercise for Sleep Apnea
- Heart Rate and SpO2 at Altitude: A Review
- Home Oximeters in COVID: A Manchester Study
- Home Oximeters in COVID: A Randomised Trial
- Hospital Lighting and Snoring After a Stroke
- How Accurate Are Smart Rings for Sleep?
- How Accurate Is AI at Spotting Sleep Apnea?
- How Close Is Wearable HRV to an ECG?
- How Common Is Altitude Sickness?
- How Do Partners of CPAP Users Sleep?
- How Many Hours Does a Home Sleep Test Need?
- How Sleep Apnea Changes Over Time: A Review
- How Valid Are Smartwatch Health Numbers?
- Is Sleep Apnea More Common After COVID?
- Left vs Right Side Sleeping and Sleep Apnea
- Long Breathing Pauses and Hypoxic Burden
- Lowest Overnight Heart Rate and Brain Vessels
- Melatonin and Children's Sleep: A Lab Study
- Migraine, Insomnia and Sleep Apnea: A Study
- Mood and Thinking at 4,500 m: First 4 Hours
- Mouth Taping and a Blocked Nose: 2026 Review
- Neck Collar for Sleep Apnea: A 2025 Trial
- New Oxygen Dip Measures vs ODI: A 2026 Study
- NHS Home Oximeters and Skin Tone: BMJ Study
- Obesity and Sleep Apnea: A 2026 Cohort Study
- One Sleep Study vs 3 Months of Tracking
- Overnight Oxygen and Altitude Sickness
- Overnight Oxygen at Lower Altitude: A Trial
- Oxygen Burden and Blood Pressure on CPAP
- Oxygen Burden and Heart Rhythm After Stroke
- Oxygen Dips and Blood Pressure: 2026 Review
- PCOS and Sleep: What a 2026 Review Found
- Portable Oxygen vs Air on a Walking Test
- Positional Sleep Apnea in 12,036 Patients
- Positional Therapy vs Mouthpiece vs CPAP
- Pre-Acclimatising for Altitude: How Long?
- Predicting Altitude Sickness From Oximetry
- Pressurised Rooms and Sleep at Altitude
- Ring Oximeter vs Sleep Study: How Close?
- Short Sleep, Heart Rate and Overnight Oxygen
- Skin Tone, Oximeters and Wearable Pulse Rate
- Sleep Apnea and Acid Reflux: Is There a Link?
- Sleep Apnea and Alzheimer's Biomarkers Study
- Sleep Apnea and Children's Height: 2026 Study
- Sleep Apnea and Erectile Problems Under 40
- Sleep Apnea and Fatty Liver: A 2026 Review
- Sleep Apnea and Gum Disease: Is There a Link?
- Sleep Apnea and Hippocampus Blood Vessels
- Sleep Apnea and Sudden Cardiac Death: Review
- Sleep Apnea at Altitude: One Man's Case
- Sleep Apnea by Age and Sex: 556,474 Records
- Sleep Apnea Deaths in the US: 1999 to 2023
- Sleep Apnea in Older Adults: A 2026 Review
- Sleep Apnea Risk and Memory: A 2026 Study
- Sleep Apnea Risk and Mental Health in Canada
- Sleep Apnea Without Sleepiness: A 2026 Study
- Sleep Apnea: Misjudging How Long You Slept
- Sleep Apnea: What Event Counts Miss
- Sleep Trackers for Athletes: A 2026 Review
- Sleepiness After Menopause With Sleep Apnea
- Snoring and Quality of Life: A 2026 Survey
- SpO2 Cut-offs for Opioid Breathing Problems
- Steroid Cycles and Sleep Apnea: A 2026 Study
- Teeth Grinding and Overnight Oxygen: A Study
- Time Below 90% and Heart Failure Outcomes
- Tirzepatide and Sleep Apnea: Early Weight Loss
- Tirzepatide and Sleep Apnea: Patient Views
- Tongue Nerve Implant for Sleep Apnea: A Trial
- Wearable Sensor Fit and Pressure: A Review
- Wearables, Sleep Apnea and Blood Pressure
- Weight Gain After Tonsillectomy in Children
- What Tobacco Days Look Like in Wearable Data
- Which Finger Is Best for a Pulse Oximeter?
- Who Sticks With CPAP? A 2026 Review
- Who Wearable Accuracy Studies Leave Out
- Why Events Still Show Up on CPAP
- Zolpidem and Sleep Apnea: A 2026 Review
Habits and self-experiments
11 articles
How Many Nights of Oximeter Data Do You Need?
Why one night of oximeter data isn't enough, and how many baseline and experiment nights to record before you compare them.
Does a Late Dinner Change Overnight Oxygen?
Why a late meal might show up in your overnight oximeter data, and how to compare early-dinner and late-dinner nights.
Does Alcohol Change Your Overnight Oxygen?
What studies found about evening drinks and breathing during sleep, and how to compare drinking and dry nights with your own oximeter.
Does Bedroom Temperature Affect Your Oxygen?
How to check whether a cooler, better-aired bedroom changes anything in your overnight oxygen and pulse numbers from an oximeter.
Is an Overnight Pulse Oximeter Worth It?
What an overnight pulse oximeter records, what it costs, what it can't tell you, and how to decide whether to buy one.
Should You Use the O2Ring Vibration Alert?
What the O2Ring vibration alert does, why you shouldn't rely on it, and how to decide whether to leave it on or off.
Snoring Apps vs Oximeters: What Each Records
A snoring app records sound and an overnight oximeter records blood oxygen, so here's what you get from each and when to use both.
More in habits and self-experiments
Devices and apps
16 articles
Moving From ViHealth Without Losing Your Data
How to get your past nights out of ViHealth as CSV files, import them somewhere else, and keep them safe before you switch phones or apps.
First Night With an O2Ring: What to Expect
How to set up an O2Ring for its first night, what the morning report will look like, and why you shouldn't read much into one recording.
How to Share Oximeter Data With Your Doctor
What to bring from your overnight oximeter to an appointment, how to get it out of the app, and what to leave at home.
Ring vs Fingertip vs Wrist Pulse Oximeter
How ring, fingertip clip and wrist pulse oximeters compare for recording a full night's sleep, and which one suits how you sleep.
Smartwatch SpO2 vs Pulse Oximeter for Sleep
What an Apple Watch, Oura ring or Garmin records for blood oxygen while you sleep, and how that differs from an overnight pulse oximeter.
Tracking Your Oxygen Alongside CPAP
What an overnight pulse oximeter adds to your CPAP machine's own data, what it can't tell you, and how to log it for your clinic.
Wellue SleepU Tips for a Clean Recording
Practical tips for wearing, charging and syncing a Wellue SleepU so your overnight recordings are complete and comparable.
Understanding your data
9 articles
What Counts as an Oxygen Dip?
The three rules that decide whether a drop in your overnight SpO2 gets counted as a dip, and why two apps can disagree.
What Does SpO2 Mean?
What the SpO2 number on a pulse oximeter measures, how the device works it out, and how to read your overnight readings.
What Is T90? Time Below 90% SpO2 Explained
T90 is the share of the night your blood oxygen spent below 90%, and here's how to read it next to your other numbers.
What Is ODI? Oxygen Desaturation Index
ODI is how many times an hour your blood oxygen dipped and recovered. Here's what it counts, 3% versus 4%, and how to compare your nights.
Overnight Heart Rate and CVHR Explained
What your pulse usually does while you sleep, what the CVHR number counts, and how to compare your overnight heart rate across nights.
Why a Pulse Oximeter Reading Might Be Wrong
Cold hands, movement, nail polish and a poor fit can all throw off a pulse oximeter reading, so here's how to spot one and record a clean night.
Snoring vs Sleep Apnea and Overnight Oxygen
How snoring and sleep apnea differ, what an overnight oxygen recording can and can't show you about either, and when to see a doctor.