A Closer Look: The Pathophysiology of Obstructive Sleep Apnea
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The?pathophysiology of obstructive sleep apnea ?has anatomical and neuromuscular elements. The combination of these elements can be quite complex.?Obstructive sleep apnea ?is caused by an obstruction to the upper airways. The breathing pauses this causes can result in frequent if somewhat brief mini-arousals. Without an obstructive sleep apnea diagnosis and subsequent treatment, this can lead to sleep deprivation and chronic daytime fatigue.
Understanding the underlying pathophysiology of obstructive sleep apnea helps diagnose the cause of the disorder and the most appropriate treatment for an individual.
The pharynx is a key element of the upper airways, linking the mouth and nasal cavity to the esophagus. It plays a major role in our ability to speak and swallow.
The pharynx consists of soft tissue and muscles, and it is the collapse of these soft tissues during sleep that causes obstructive sleep apnea.?
There are three constituent parts of the pharynx:
Neuromuscular Elements
An obstruction in the upper airways prompts a neuromuscular response. This involves communication from the central nervous system to stimulate the throat muscles and open the airways.
An inability of the dilating muscles in the pharynx to overcome negative pressures such as a narrowing of the airways can place someone at more risk of obstructive sleep apnea.?
The largest of the dilating muscles, the genioglossus muscle, has been seen to be more active in sleep apnea patients. This stems from it trying to maintain airways that are free of obstruction. However, chronic obstructive sleep apnea can result in muscle and nerve damage in the pharynx.
Anatomical Factors Behind the Pathophysiology of Obstructive Sleep Apnea
1. Obesity
Weight is a major contributing risk factor for obstructive sleep apnea. Over 50% of obstructive sleep apnea patients are obese. This can result in a large neck size, and the accumulation of additional soft tissues in the neck places you at an increased risk of their collapsing into the throat when the muscles relax during sleep.
Lifestyle changes that help with weight loss can form part of a treatment plan for sleep apnea. This will include increased exercise and eating a more balanced, nutritious diet. You will be advised to quit smoking if applicable and also to reduce alcohol consumption.
2. Craniofacial Abnormalities
Another factor underlying the pathophysiology of obstructive sleep apnea is craniofacial abnormalities. This includes an undersized or receding lower jaw, which can reposition the tongue in a way that increases the risk of an obstruction to the upper airways.
A high-arched palate can also increase the risk of obstructive sleep apnea by reducing the size of the upper airways. Those with Down syndrome can also be more at risk of this sleep disorder.
3. Nasal Congestion
Chronic nasal congestion can result in negative pressure on the airways. Blocked nasal passages and inflamed sinuses from rhinitis make breathing more difficult and can worsen sleep apnea.
Rhinitis can result from allergens. Therefore, people prone to allergies?can be at increased risk and should take precautions to limit their exposure to allergens that cause their allergic reactions.
4. Enlarged Tonsils, Adenoids and Tongue
Those with obstructive sleep apnea are more likely to experience enlarged soft tissues. This can include enlarged tonsils, adenoids, or tongue.
Enlarged tonsils and adenoids are common causes of sleep apnea among children, and removal may be recommended to reduce their breathing problems.?
If the tongue is causing breathing issues, an oral appliance may be recommended to reposition it forward to prevent the tongue from falling back to block the airways. Sleeping on your side rather than your back may also offset the gravitational pull on the tongue down into the throat.
The Importance of Genetics in the Pathophysiology of Obstructive Sleep Apnea
Your family history will be one of the first points of reference for a healthcare provider when exploring obstructive sleep apnea complications. Genetics is increasingly seen as a significant influence on a person’s predisposition to the disorder.
Genetics can increase the likelihood of someone having a narrower upper airway, instantly increasing their susceptibility to obstructive sleep apnea. Indeed, a study indicated that people with obstructive sleep apnea had a smaller upper airway area compared to those who did not have the sleep disorder.
Genetics can also cause the craniofacial abnormalities discussed earlier as one of the underlying factors of the pathophysiology of obstructive sleep apnea. Research also points to a genetic influence on obesity for some people.
This link between genetics and the anatomical factors behind sleep apnea indicates a complex pattern in the pathophysiology of obstructive sleep apnea. It can also make it difficult to pinpoint the root causes during an obstructive sleep apnea diagnosis.
The Prospect of Further Personalized Sleep Apnea Treatment
A better understanding of the pathophysiology of obstructive sleep apnea holds out the prospect for more personalized treatment plans.
This is aided by an increased appreciation of the neuromuscular factors in relation to the anatomical factors. Diminished genioglossus muscle responsiveness while asleep and a low arousal threshold are examples of non-anatomical influences seen in sleep apnea patients.
The leading treatment for obstructive sleep apnea is APAP , BiPAP ?and CPAP therapy, but not everyone can tolerate the pressurized air. An improved understanding of the underlying pathophysiology of the disorder could help personalize treatments that are more appropriate for the patient.
Anatomical structures and genetics play a significant role, combined with a neuromuscular response, in the narrowing of the upper airways that causes sleep apnea. Obstructive sleep apnea diagnosis and subsequent treatment are aided by an increasing understanding of the complex nature of the pathophysiology of obstructive sleep apnea.