Obstructive Sleep Apnoea – what is it and how can it be identified?

April 17, 2014

Obstructive Sleep Apnoea (OSA) affects a large percentage of the population – around:

  • 1 in 4 men and
  • 1 in 10 women

are estimated to have OSA, however the majority of these people are undiagnosed1.

OSA is the repetitive cessation or marked reduction of breathing during sleep.  If an obstruction lasts for 10 seconds or more, oxygen levels will drop and carbon dioxide levels will rise to a point that the individuals’ sleep becomes disturbed. The individual may be completely unaware of this.

Symptoms of OSA can be loosely divided into:

  • Night time symptoms – these can include heavy snoring, limb movement, sudden awakening with noisy breathing, sweating and dry mouth; and
  • Daytime symptoms – these can include sleepiness, difficulty concentration, sexual dysfunction, reflux and irritability1.

OSA and Anaesthetists

It is important for anaesthetist to screen all patients for OSA, as many patient are undiagnosed and the administration of an anaesthetic, sedative or analgesic can exacerbate OSA and hamper the body’s ability to respond. The result can be respiratory failure requiring re-intubation or mechanical ventilation. In addition to pulmonary complications, post-operative cardiac complications (in particular atrial fibrillation) are more common in patients with OSA2.

The STOPBang Questionnaire is a validated screening tool for OSA.  It considers some of the most common symptoms of OSA, as well as other factors that have been associated with having OSA – high blood pressure, obesity, age, large neck circumference and gender.

The STOPBang Questionare3

1. Snoring. Do you snore loudly (louder than talking or loud enough to be heard through closed doors)?

2. Tired. Do you often feel tired, fatigued, or sleepy during daytime?

3. Observed. Has anyone observed you stop breathing during your sleep?

4. Blood Pressure. Do you have or are you being treated for high blood pressure?

5. BMI. BMI more than 35 kg/m2?

6. Age. Age over 50 yr old?

7. Neck circumference. Neck circumference greater than 40 cm?

8. Gender. Gender male?

High risk of OSA: answering yes to three or more items; Low risk of OSA: answering yes to less than three items.

While studies have shown increased rates of post-operative complications in OSA patients, it has not been demonstrated consistently that mortality rates or length of stay are adversely affected2. Possible reasons include;

  • If OSA if reported prior to surgery then the anaesthetist will be closely monitoring for any signs of respiratory failure, and hence interventions are provided earlier.
  • Many patients are not recognised as having OSA and hence their statistics around mortality and length of stay incorrectly fall into the comparator group.
  • The obesity paradox – obese patients with chronic conditions are more likely to survive some complications than their normal weight counterparts. 2

None-the-less it is preferable that patients do not experience post-operative complications, for their comfort and safety and because complications are resource intensive.

Possible ways to reduce the risk of post-operative complications in OSA patients include;

  • Screen for OSA and treat high risk patients in the same manner as those diagnosed with OSA
  • Consider a regional anaesthetic instead of a general anaesthetic
  • Consider using CPAP pre and post operatively (although patient compliance may be an issue)
  • Do not give any benzodiazepine pre-medication, OR use oral clonidine instead
  • Have equipment for managing airway issues on hand
  • Use anaesthetic agents with short half lives4

Further details on the evidence for these risk reducing strategies can be found in “Obstructive sleep apnea and anaesthesia: perioperative issues” by Corso R &  Gregoretti C.

References

1.  University of Toronto (2012) General Information, http://www.stopbang.ca/osa.php, accessed 28/2/14

2.  Cheung F (2014) Postoperative Complications Associated with Obstructive Sleep Apnea:Time to Wake Up! in Anesthesia and Analgesia, vil 118, no. 2 pp.251-252

3.  Chung F et.al (2008) STOP Questionnaire A Tool to Screen Patients for Obstructive Sleep Apnea in American Society of Anaesthesiologist, volume 108 pp812-21

4.  Corso R, Gregoretti C (2013), Obstructive sleep apnea and anaesthesia: perioperative issues in  Shortness of Breath, vol 2, no.2 p.p72-79

Disclaimer: this information is of a general nature only. Please consult your health professional before acting on information contained herein.
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Posted in Blog by Douglas Fahlbusch