Obstructive sleep apnoea

This blog provides free general information for anyone who is seeking to understand more about obstructive sleep apnoea, not intended as a medical consult. Please seek proper medical advice for individual assessment and management.



The crucial learning points are:

  • Obstructive sleep apnoea (OSA) is common the obese patient cohort and is often undiagnosed.
  • Untreated OSA is associated with poor sleep patterns and difficulties in losing weight.
  • Severe OSA increases the risk of surgery.



This section won’t discuss cigarette smoking and its respiratory issues.

  • Obviously all patients need to stop cigarette smoking (also no vaping) for at least several months before bariatric surgery and should never recommence smoking after.





Obstructive sleep apnoea (OSA)


OSA is a chronic disorder characterized by repetitive obstruction of the upper airways during sleep. This leads to fragmented sleep and low oxygen levels in the blood (hypoxemic episodes).


Apnoea hypopnoea index (AHI) is the number of apnoea or hypopneoea events (>10 seconds in duration) recorded during sleep in one hour. In a simplistic term:

  • AHI < 5 is normal
  • AHI 5-14 is mild OSA
  • AHI 15-29 is moderate OSA
  • AHI > 30 is severe OSA


A continuous positive airway pressure (CPAP) machine at home is usually recommended for moderate and severe OSA.



70-80% of patients with morbid obesity is estimated to have OSA.

Surgery increases the risk of hypoxemia and the post op complications are increased in patients with OSA.

After surgery patients will need continuous positive airway pressure (CPAP) therapy starting straight away from post op day 1.


Successful weight loss after bariatric surgery reports significant improvements in AHI, hence improvements in OSA.




Subjective screening tools: STOP-BANG and ESS questionnaire

Many different surveys are available, these are the more common ones


Patients can be screened using the STOP-BANG questionnaire, which is a simple yes or no answer to the following criteria:

  • Snoring loudly
  • Tired or falling asleep during the daytime, during driving or when talking to other people
  • Observed to have stop breathing during sleep
  • Pressure – high blood pressure
  • Body Mass Index
  • Age over 50 years
  • Neck circumference (male > 43cm, females > 41cm)
  • Gender (Male)


If the response is yes to 4 criteria or more, it is likely that the patients have OSA.




The Epworth Sleepiness Scale (ESS) for adults (1997) is a questionnaire asking the patient to score between 0 to 3 for the following scenarios

0 = would never doze

1 = slight chance of dozing

2 = moderate chance of dozing

3 = high chance of dozing


In situations such as:

  • Sitting and reading
  • Watching tv
  • Sitting inactive in a public space (theatre, meeting)
  • As a passenger in a car (for an hour without a break)
  • Lying down to rest in the afternoon
  • Sitting or talking to someone
  • Sitting quietly after lunch (without alcohol)
  • In a car (stopped for a few minutes in the traffic)


ESS scores:

  • 0-5 is normal daytime sleepiness
  • 6-10 is upper limit of daytime sleepiness
  • 11-12 is mild excessive daytime sleepiness
  • 13-15 is moderate excessive daytime sleepiness
  • 16-24 is severe excessive daytime sleepiness


Narcolepsy patients often has an ESS >13




OSA and bariatric surgery patients


However it is also noted that a lot of younger morbidly obese patients who come for weight loss surgery do have OSA but don’t have the symptoms above.


Obesity is a significant risk factor for OSA.

  • Untreated OSA may be associated with increased cardiovascular morbidity and mortality.
  • For now there is no mandatory routine pre-op sleep studies for patient coming for bariatric surgery.


However the high risk patients (criteria above) are recommended to have a sleep study and a respiratory physician review as well as having a pre-op Echocardiogram (to look for cardiomyopathy and pulmonary hypertension).



Patients with severe cardiomyopathy, pulmonary hypertension or right heart failure may be rejected fir elective weight loss surgery because of the prohibitive risk.