Understanding obstructive sleep apnea
OSA is a reduction of airflow during sleep. You may not feel it happening, but your body registers every interruption, night after night.
Two adults in their fifties, both asleep inside an MRI scanner. Look closely:
- Whom would you rather be when you are in your fifties?
- How many differences do you see between the two individuals?
Why it matters
Disrupted sleep causes excessive daytime sleepiness, which becomes dangerous when driving or operating machinery.
Repeated drops in oxygen worsen arrhythmia, hypertension, and diabetes over the years untreated OSA is allowed to continue.
OSA is closely associated with depression and anxiety, and treating the airway often improves both.
Where the airway collapses
There are anatomic and non-anatomic causes of OSA. The anatomic ones come down to obstruction or collapse somewhere along the upper airway, and obstruction can occur anywhere from the nose to the epiglottis. In most adults, it is more than one site at once.
Airflow begins here, and so can obstruction. Nasal allergy plays a role, alongside structural causes: a deviated septum, enlarged inferior turbinates, and collapsible upper lateral cartilage at the nasal valve.
In children, the adenoids and palatine tonsils are a frequent site of obstruction. In adults, the problem is more often redundancy of the soft palate.
A complex contributor. The tongue can carry excess fat or enlarged lingual tonsils. It can also simply feel "too large for the mouth," which usually means the upper and lower jaws are too small to house it. Muscles such as the genioglossus normally hold the tongue forward during sleep; when they underperform, the tongue falls back and obstructs.
Two under-recognized contributors are the size and position of the upper and lower jaws. Jaws too small to accommodate the soft palate and tongue, or oriented too far back or at an unfavorable angle, narrow the airway. Once the jaws stop growing, surgery is the only way to change their size or position.
Two further sites round out the picture: the lateral pharyngeal walls, the floppy side walls of the airway that are a major driver of adult OSA severity, and the epiglottis, the flap that protects the airway during swallowing and can itself become a site of obstruction.
The non-anatomic side
Not all of OSA is structural. Non-anatomic causes are neurologic: terms like arousal threshold, loop gain, and muscle tone describe the interactions between the brain and the airway muscles that decide how readily the airway collapses and how violently the body wakes to reopen it. A complete plan accounts for both the anatomy and these traits, which is why evaluation matters before any surgery is chosen.
See how the airway is evaluated (DISE) →Common questions
What is obstructive sleep apnea?
OSA is characterized by reduced airflow during sleep. Even a slight reduction, though unnoticeable to the sleeper, significantly disrupts sleep quality and causes daytime sleepiness. Persistent reduction leads to loss of oxygenation, which in the short term causes disruptive waking, and over the long term worsens arrhythmia, hypertension, and diabetes, with significant implications for mental health as well.
How is OSA diagnosed?
Diagnosis begins with an assessment of symptoms, best captured by patient-reported outcome measures such as the Epworth Sleepiness Scale. That is followed by a sleep study (polysomnography), done either in a lab (attended) or at home. Your doctor helps determine which is appropriate; often a home study is performed first, with an in-lab study to follow if needed.
What are common risk factors?
In children: nasal allergies, enlarged adenoids and tonsils, and under-development of the jaws. Notably, younger children with OSA can be underweight rather than obese.
In adults: obesity becomes a larger factor, with fat accumulating in the airway and in the tongue, and can also cause hypoventilation. With age the airway lengthens, adding redundancy and collapsibility of the soft palate and side walls, while the dilator muscles function less well during sleep.
Every airway is different
If OSA can begin almost anywhere along the airway, treatment has to start with where yours collapses. Dr. Liu's treatment map shows how each site is addressed, and how procedures combine.