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  • Writer's pictureDr. Koralla Raja Meghanadh

Obstructive Sleep Apnea Syndrome (OSAS)

Updated: Mar 12

Although we do not have exact data on India, in the United States, roughly 20% of the population suffers from heroic snoring(loud snoring) or sleep apnea. The parameters vary from study to study and area to area. Still, approximately one-fourth of the 20% have heroic snoring (loud snoring that might not affect the patient's health but his family or his roommates), and the rest have obstructive sleep apnea syndrome or OSAS. Although this is a rough estimate, the takeaway is that this is a widespread problem. We do not have proper metrics like diabetes or blood pressure because the diagnosis process of OSAS is complicated and will burden the pocket of an average individual. People ignore it most of the time, as snoring is considered normal.

obstructive sleep apnea syndrome symptoms, causes, diagnosis

To understand obstructive sleep apnea let's first understand apnea and hypopnea.

What is apnea?

Apnea means a halt in breathing for more than ten seconds.

What is hypopnea?

Hypopnea is a syndrome where the breathing is reduced by more than 50%.

What is sleep apnea?

If apnea happens during sleep, it is called sleep apnea.

Types of sleep apnea

There are two types of sleep apnea.

  1. Central sleep apnea or non-obstructive sleep apnea

  2. Obstructive sleep apnea syndrome (OSAS)

What is central sleep apnea or non-obstructive sleep apnea?

Central sleep apnea or non-obstructive sleep apnea can occur in certain brain diseases. Central sleep apnea means no physical obstruction in the breathing path, but the brain has missed or delayed sending signals to breathe for ten or more seconds. This type of sleep apnea needs a consultation with a neurologist.

Obstructive sleep apnea syndrome or OSAS

Obstructive sleep apnea syndrome, or OSAS, is a condition where breathing stops during sleep due to a physical obstruction at various places in the breathing pathway. It is the most common type among two types of sleep apnea, typically treated by an ENT doctor and sometimes by a pulmonologist. We can see a complete stop in breathing for more than 10 seconds, i.e., apnea or reduction in air inflow in obstructive sleep apnea. If the reduction in airflow during breathing is more than 50%, it is called a hypopnea.


As mentioned above, the name indicates that obstructive sleep apnea stops breathing for more than 10 seconds due to physical obstruction in the breathing pathway. This obstruction could be due to one or more reasons, i.e., an abnormality in single or multiple structures that blocks the breathing pathway. This abnormality can be at any of the five places of the breathing pathway mentioned below.

  1. Nose

  2. Velopharynx – uvula and soft palate. Uvula’s function is to clean the back of the throat, and the soft palate separates the nasopharynx and oropharynx, i.e., the soft palate separates the back of the nose and back of the mouth to prevent the food from entering the nose and nasopharynx.

  3. Tonsil and tonsil region

  4. Back of the tongue or base of the tongue

  5. Epiglottis

These structures are usually larger than they are supposed to cause the blockage.

what is the cause of obstructive sleep apnea

Aside from abnormally large structures, obstructive sleep apnea can occur due to obesity. If an obese person has fat around the neck that narrows down the breathing pathway, it could lead to sleep apnea.

Obstructive Sleep Apnea due to obesity

One of the significant reasons for sleep apnea is obesity or overweight and excessive fat in the neck that narrows the breathing path in the neck. During sleep, the muscles in the breathing path relax and become a soft tube during suction due to negative pressure, halting the breath.


OSAS can be easily confused with loud snoring called heroic snoring. It has clear differentiating symptoms. Sleepiness or feeling drowsy after even adequate hours of sleep is a trademark symptom of sleep apnea.

The symptoms are

  1. Pain in the throat in the morning

  2. Headache

  3. Sleepiness

  4. Psychological issues

Sleep deprivement in sleep apnea

We can divide the sleep of a person into four categories or stages.

Sleep stages

Sleep name






deep sleep or N3


REM - Rapid Eye Movement

Generally, when we go to bed, we spend some time in stage one, followed by two, three, and four. Later, we go back to stages 3, 2, and 1 and wake up. In approximately 7 hours of sleep, we spend about 50 minutes in stage 3, i.e., deep sleep, and 30 minutes in REM. Fulfilling this minimum requirement of deep sleep and REM will refresh our minds.

In deep sleep and REM, the muscles of the breathing path are relaxed and can cause a collapse of the breathing path. The snoring in this normal stage is quite regular and stays for about 2 hours. The next stage is heroic snoring, i.e., snoring is audible to people outside the room you are sleeping in and creates a disturbance for the family or people living with the person. However, heroic or loud snoring need not affect the person.

When the obstruction becomes severe, and the breathing stops for more than 10 seconds brain is alerted due to lack of oxygen. The brain then moves from a higher stage of sleep, like deep sleep and REM, into lower stages, like stage 1 and stage 2, and acts upon the breathing muscles. This functioning causes loss of deep sleep and REM. A person might sleep for 12 hours, but due to a lack of deep sleep and REM, the patient does not feel relaxed and drowsy in the morning. Even when the person goes to bed, they will fall asleep within a few minutes and start snoring immediately. An average person takes 10 minutes, i.e., latent time to go into stage 1 sleep.


Apnea is a complete stop of breathing, and hypopnea is more than or equal to a 50% reduction in breathing. A polysomnography test helps diagnose obstructive sleep apnea syndrome by giving out the number of apneas and hypopneas that will help the doctor determine if the patient has OSAS.

Number of apneas and hypopnea in an hour

Obstructive Sleep Apnea Syndrome status

0 - 5


6 - 15


16 - 30

Moderate OSAS

31 - 45

Severe OSAS

If the polysomnography test confirms obstructive sleep apnea, an ENT specialist conducts several tests to understand where the blockage or blockages are. A CT scan of the nose, nasal endoscopy, checking throat with video laryngoscopy, and then the patient is subjected to DISE, i.e., Drug-Induced Sleep Endoscopy. All these tests will help the doctor understand the root cause of OSAS.

What is a polysomnography test?

A polysomnography test monitors the functioning of the human body during overnight sleep. This test checks for ECG, heart functioning, breathing pathway muscle tone, the sensation of airflow, oxygen saturation, and blood pressure.

Polysomnography test on a patient with obstructive sleep apnea
Polysomnography test on a patient

The polysomnography test does not need any sedation, and numerous electrodes are connected to the body to record the data. The data obtained is analyzed to derive an average number of apneas and hypopneas and the average time of each occurrence. Parameters are analyzed for the sleeping position of the patient also. The polysomnography test also gives data about sleep stages and analyzes data for sleep stages. The polysomnography test gives the doctor a report in numbers and graphical data. The doctor will confirm if the patient has obstructive sleep apnea with the aid of the report.

Drug-Induced Sleep Endoscopy – DISE test

In DISE, the anesthesia doctor gives drugs( not general anesthesia) to induce sleep, and the patient starts snoring and having apneas and hypopneas. An ENT specialist studies the patient with a fiber optic scope with a diameter of 2.7 millimeters inserted into the breathing path through the nose. This test helps an ENT doctor understand where the vibration and blockage are.


As mentioned earlier, there are six possible blockage sites, and when the blockage is in the nose or epiglottis, a patient will require surgery. As per the blockage sites diagnosed, an ENT doctor suggests the treatment. We can use CPAP or BiPAP daily to rectify the remaining other sites of blockage, i.e., the Velopharynx, tonsil, tonsil region, the base of the tongue, and breathing pathway blocked due to fat in the neck.

obstructive sleep apnea on CPAP
A person with Obstructive Sleep Apnea Syndrome on CPAP - Continuous Positive Airway Pressure

CPAP is a continuous positive airway pressure therapy unit connected to a motor and pump that takes the air from the atmosphere and pumps the air with a well-sealed mask. With air pumping and positive pressure created, the breathing pathway opens, preventing apneas and hypopneas.

How does obstructive sleep apnea cause heart failure?

As the obstruction increases, the oxygen levels in the body get depleted, decreasing the oxygen saturation during sleep. The depletion of oxygen can put the brain and heart at risk, unlike other muscles in our body that will need less oxygen during sleep or rest. The brain and heart need a constant supply of oxygen and cannot adjust to lesser oxygen, and one exception is that the heart will need more oxygen during exercise, for which the heart beats fast.

As the lung is trying to pull air from the blocked path, negative pressure inside it increases, disturbing the heart’s function, which causes a problem in the right side of the heart. After some time, the problem can also start affecting the left side of the heart.

During the low oxygen supply to the heart, if there is a small problem in blood supply to the heart, i.e., during sleep, heart muscles can get into trouble and cause a sudden heart attack. This is how many people pass during sleep without any history.

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