By Brandon Peters, MD. Medically reviewed by Sanja Jelic, MD
People with obstructive sleep apnea (OSA) typically have low oxygen levels when they sleep because of gaps in their breathing. Blood oxygen during sleep is considered low if levels are below 95%. Medical intervention may be advised if it drops below 92%.
Low blood oxygen places you at risk of hypoxemia in which tissues are deprived of the oxygen they need to function, causing fatigue, lightheadedness, and shortness of breath. Over time, OSA associated hypoxia can increase the risk of stroke and brain aneurysm and even affect your cognitive function.
What Is Obstructive Sleep Apnea (OSA)?
Obstructive sleep apnea is one of two main forms of sleep apnea in which your throat muscles relax, blocking the passage of air into your trachea (windpipe) while sleeping. When this happens, breathing can stop for anywhere from a few seconds to over a minute in some people.
People with OSA have frequent, repeated gaps in breathing, with some experiencing more than a hundred per night. While the person with OSA may be unaware of these gaps, their sleep partner often is.
According to the National Council on Aging, around 39 million adults in the United States have sleep apnea, of whom 33 million
use CPAP machines to help normalize their breathing at night.
Sleep Apnea and Normal Blood Oxygen Levels
Obstructive sleep apnea can affect your blood oxygen levels due to the inadequate intake of air while sleeping. During the day, blood oxygen levels—also known as oxygen saturation levels—generally fall between 95% and 100% in healthy people, whether asleep or awake. This is considered normal.
However, prolonged or repeated gaps in breathing while asleep can cause oxygen levels to drop to where tissues and organs are adversely affected. This is referred to as sleep-related hypoxemia. Oxygen saturation levels of 92% or below generally require medical intervention. This is the level often seen in someone with COPD who is on oxygen therapy.
The interpretation of oxygen saturation levels can be described as
follows:
Oxygen Saturation Interpretation
95% to 100% - Normal
93% to 94% - Borderline low
89% to 92% - Low; monitor and contact your healthcare provider
88% or below - Dangerously low; seek immediate medical care
Symptoms of Sleep Apnea
Although sleep apnea is often recognized by a person’s sleep partner, there are signs and symptoms of OSA to be aware of if you live or sleep alone, including:
- • Snoring, snorting, gasping, or choking during sleep
- • Dry mouth when awakening
- • Night sweats
- • Nighttime urination
- • Nighttime acid reflux
- • Insomnia
- • Headaches
- • Irritability
- • Memory problems
- • Depression
- • Low sex drive
- • Weight gain
If sleep-related hypoxemia occurs, you may also experience more profound and problematic symptoms like:
- • Anxiety upon waking
- • Breathlessness
- • Cyanosis (bluish skin discoloration due to the lack of oxygen)
- • Dizziness or lightheadedness
- • Heart palpitations
- • Tinnitus (ringing in the ears)
Even more concerning, sleep-related hypoxemia can cause peripheral vein dilation (meaning the swelling of veins usually caused by spikes in blood pressure). With OSA, this can lead to cerebrovascular diseases like ischemic stroke, brain aneurysm, brain bleeds, and carotid artery disease.
Risk Factors for Obstructive Sleep Apnea
People of any age, sex, or weight can have obstructive sleep apnea, but it is much more common in males, people over the age of 50, and those diagnosed with obesity.
Other risk factors for OSA include:
- • Smoking cigarettes
- • Sleeping on your back
- • Regular use of alcohol or sedatives
- • Hypothyroidism (underactive thyroid)
- • Having had a stroke
- • Having enlarged tonsils or adenoids
- • Anatomical abnormalities in your nasal or sinus passages,
- throat, tongue, or epiglottis
Diagnosis
Obstructive sleep apnea is diagnosed with an overnight sleep study, also known as a polysomnogram. This is a test conducted in a specialized facility that records multiple body symptoms while you sleep. This includes checking your blood oxygen levels.
Components of an overnight sleep study include:
- • Audiovisual monitoring: This allows sleep lab staff to see and record what is happening while you sleep.
- • Breathing sensors: This measures air movement through your mouth and nose, including any gaps in your breathing.
- • Electrocardiography (EKG): This measures the electrical activity of your heart to see if there is any problem that may either be a cause or consequence of OSA.
- • Electroencephalography (EEG): This measures brain waves during different stages of sleep to identify sleep disorders.
- • Electromyography (EMG): This tracks the movements of your leg muscles to check for a condition associated to OSA called periodic limb movement disorder (PLMD).
- • Electrooculography (EOG): This tracks your eye activity to see how often you enter rapid eye movement (REM) sleep.
- • Pulse oximetry: This is a clamp-like device worn on the tip of your index finger to measure and monitor your blood oxygen saturation.
- • Respiratory inductive plethysmography (RIP): This is a belt worn around the torso that measures the expansion of your chest and belly while breathing.
Other Causes of Low Blood Oxygen During Sleep
Obstructive sleep apnea is the most common—but not only— explanation of low oxygen saturation levels during sleep. Some other possible causes fall under three broad categories:
- • Sleep-related hypoventilation: Involving conditions like obesity, neuromuscular disorders, lung diseases, or neurological disorders that cause hypoventilation (rapid, shallow breathing)
- • Drug-induced bradypnea: Involving medications like opioids and benzodiazepine that cause bradypnea (abnormally slow breathing)
- • Other causes of sleep-related hypoxemia: Including chronic obstructive pulmonary disease (COPD), heart failure, asthma, pneumonia, or nighttime respiratory allergy.
Treating Sleep Apnea
In general, the first-line treatment is continuous positive air pressure (CPAP) therapy. This involves wearing a device that delivers pressurized room air through a mask to keep your airways open at night.
In addition to CPAP, your healthcare provider may recommend:
- • Sleep positioning devices: Including holsters or belts that keep you from sleeping on your back
- • Nasal steroids: Like fluticasone that reduces tissue swelling to help keep nasal passages open
- • Adhesive nose strips: Like BreatheRight that mechanically widen your nostrils while sleeping
- • Losing weight: Which cannot cure OSA but may improve symptoms
If these conservative options fail, there are surgeries that can reduce airway obstruction or better direct airflow from the nose and mouth to the trachea. including:
- 1. Tonsillectomy or adenoidectomy: A surgery to remove the tonsils or adenoids
- 2. Uvulopalatopharyngoplasty: The surgical removal of the fleshy part of the soft palate
- 3. Maxillomandibular advancement: A surgery that moves the upper jaws forward
Treating OSA will increase blood oxygen levels while sleeping. Left
untreated, OSA can increase the risk of high blood pressure, coronary artery disease (CAD), atrial fibrillation, and type 2 diabetes. This is why treating OSA is so important, especially when it is moderate to severe.
Summary
Obstructive sleep apnea (OSA) is a sleep disorder caused when throat muscles relax and interfere with breathing. Frequent and prolonged gaps can reduce the level of oxygen in the bloodstream.
Untreated OSA can lead to serious health problems, including an
increased risk of high blood pressure, heart disease, and diabetes.
This is why it is important to get diagnosed if you have symptoms
and risk factors of OSA.
OSA is typically diagnosed with an overnight sleep study that, among other things, measures your blood oxygen with a pulse oximeter. Depending on the results of these and other tests, a doctor can decide which treatment options are best for you.
source: verywellhealth.com
