Causes & Diagnosis of Obstructive Sleep Apnoea (OSA) In-Depth Sleep Assessment to Determine Cause & Severity of OSA
What is OSA and Why is it Dangerous?

OSA is a type of breathing disorder that occurs while the patient is asleep, causing them to momentarily stop breathing in their sleep.

This is as a result of the throat muscles relaxing too much, thus partially or entirely blocking the airways. This is dangerous because it can cause the patient’s oxygen levels to fall, and carbon dioxide to build up.

The main risk that arises from this is increased stress on the heart, which now has to pump much harder and faster to supply oxygen-rich blood around the body; which increases the risk of high blood pressure, abnormal heart rhythms, heart failure and other cardiovascular conditions.

Typically, the brain senses the difficulty breathing and briefly wakes the patient in order to reopen his airways, but this is so brief that patients often don’t remember it happening. Nonetheless, as this pattern repeats itself throughout the night, it makes getting deep restful sleep impossible.

What are the Common Symptoms of OSA?
  • Loud snoring that disrupts sleep
  • Severe daytime fatigue
  • Morning headaches
  • Waking up gasping or choking
  • Pauses in breathing while asleep
  • Waking up with a very dry mouth
  • High blood pressure

A telling difference between OSA and simple snoring is – loud snoring that’s occasionally followed by periods of silence, where the patient essentially stops breathing, or breathes very low and little.

Who’s at Risk of OSA?
  • People who are overweight
  • People with high blood pressure
  • Middle aged men
  • People who smoke
  • People with chronic nasal congestion
  • People with a family history of OSA
  • People with narrow airways or enlarged tonsils
How is OSA Diagnosed?

If you suspect that you might have OSA, the most definitive way to diagnose OSA and its severity is through a detailed, overnight sleep study at the lab. However, in some cases, a home sleep apnoea test may also suffice.

Nonetheless, preliminary investigations will involve a physical exam whereby the doctor will examine your mouth, throat and nose for any extra or enlarged tissues; advise you on any current medications that might affect sleep quality; as well as take basic measurements such as weight and blood pressure.

Overnight Sleep Study (Polysomnography)

There are 2 main types of in-lab sleep studies: the full-night and split-night one.

You will be required to sleep overnight at a sleep clinic while you are hooked up to various sensors on multiple parts of the body. The purpose is to record vital information such as brain waves, heart rate, blood oxygen levels, breathing patterns, air movement through the nose and arm and leg movement.

You will only be monitored for the first half of the night. If diagnosed with clinically significant OSA then, the medical team may request that you try on the Continuous Positive Airway Pressure (CPAP) device for the second half of the night. In a CPAP titration study, the air compressor increases the pressure of the air inhaled until the optimum pressure is reached—the pressure that resolves the disordered breathing and snoring.

The in-lab option may be recommended if the patient does not have a high risk of OSA, or if the patient has some major medical issues such as heart and lung conditions, in which case an in-lab study will be the safest and most comprehensive examination of one’s sleep.

Home Sleep Apnoea Testing

As the name suggests, this form of testing can be conducted at home. You will be required to attach a variety of sensors and equipment to your body as instructed. These sensors will collect information on your breathing patterns, blood oxygen level, heart rate and so on.

The home testing option may be recommended if it is very likely that the patient has moderate to severe OSA, and has no major medical issue besides the suspected OSA.

However, if the home test did not record enough data or hints at a different sleep disorder, you may be redirected to an in-lab study instead for a more accurate diagnosis.

Preparing for an OSA Sleep Study

On the day of the study:

  • Adhere to your typical schedule as far as possible
  • Avoid taking an afternoon nap
  • Avoid drinking caffeinated drinks
Study Outcomes and Tailoring a Treatment

If you are diagnosed with OSA, your doctor will determine its severity and from there, tailor a treatment plan for you which may include lifestyle changes, therapy and surgery (if conservative methods haven’t been effective or appropriate).

With the right treatment plan, your breathing disorder, snoring, sleep quality and overall health will surely make good progress.

Our Specialists
Dr Paul Mok
Consultant ENT Head & Neck Specialist,
MBBS, FRCS (Glasgow), FAMS (ORL)

For more than 20 years, Dr Paul Mok is a Ministry of Health-accredited ENT specialist in Singapore with a sub-specialty in Obstructive Sleep Apnoea (OSA), Voice and Swallowing. To that end, Dr Mok was responsible for setting up the Voice, Swallowing & Obstructive Sleep Apnoea Service at Tan Tock Seng Hospital and headed the Sleep Clinic at Khoo Teck Puat Hospital. Apart from his clinical contributions, Dr Mok is also regularly invited to present at local and international ENT conferences, perform live surgery and remains actively involved in medical missions.

Dr Lau Hung Tuan
Consultant ENT Surgeon,
MBBS (London), MRCS (Edinburgh), MMed (ORL), FAMS (ORL)

Dr Lau Hung Tuan is an accredited, international fellowship-trained Ear, Nose and Throat (ENT) specialist in Singapore. Dr Lau is experienced in treating a wide array of ENT conditions, such as sinus infection, nasal allergy, ear and hearing problems, as well as swellings in the head and neck region. Besides these common ENT conditions, Dr Lau has special interest in the sub-specialty field of Snoring and Obstructive Sleep Apnoea (OSA). He is highly passionate about treating these conditions with holistic, tailored and individualised solutions for his patients.