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Sleep and ventilation 

Sleep and ventilation
Chapter:
Sleep and ventilation
Author(s):

Stephen Chapman

, Grace Robinson

, John Stradling

, Sophie West

, and John Wrightson

DOI:
10.1093/med/9780198703860.003.0014
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date: 27 January 2022

History

The problem

Sleep apnoea and related problems are now a common reason for referral to many respiratory units. This is due to much better recognition of the syndromes and the increasing prevalence of obesity in the general population. Respiratory units with sleep services are seeing increasing numbers of patients, primarily for possible OSA, and, therefore, most patients tend to be sleepy, and referrals for insomnia are not usually encouraged.

Patients arrive at a respiratory sleep unit for several different reasons. They are commonly:

  • Concerns that the patient may have sleep apnoea, with or without a full house of symptoms

  • Concerns that an obese individual may have obesity hypoventilation

  • Loud snoring, with the patient or spouse seeking advice about noise reduction

  • Referrals from the ENT department who may be considering offering surgery for snoring and wish to exclude OSA first

  • Excessive daytime sleepiness, diagnosis unclear, might just be OSA, might be narcolepsy, etc.

  • Assessment pre-bariatric surgery, as prevalence of OSA very high

  • Other nocturnal symptoms such as sleepwalking, panic arousals, etc.

Thus, in sleep outpatients, the issues revolve around making the correct diagnosis of the excessive daytime sleepiness or nocturnal symptoms (and referring on, if appropriate), offering simple advice for snoring, or putting the patient through the CPAP induction programme.

Some units perform a sleep study first, on the basis of an appropriate referral letter, as it is more efficient; others see the patient first and then book a sleep study if indicated (usually >95% are studied). For the purposes of this account, it is assumed that the patient is seen first.

History

A clear history of the exact presenting complaint is obviously necessary, concentrating on the following points when OSA is suspected (a full discussion is available in the section on OSA; see Sleep and ventilation p. [link]).

  • Sleepiness: how severe, what does it interfere with, over how long has it been coming on, and does it reduce QoL? The Epworth sleepiness scale (ESS) is useful as part of the assessment of this (see Fig. 14.1); scored out of 24: 0–9 is considered normal, and >9 excessively sleepy. It is only a guide and should be interpreted with the overall history

  • Important to differentiate sleepiness (tendency to nod off, due to inadequate sleep) from tiredness (feelings of exhaustion due to many causes, often without a tendency to nod off). OSA usually causes sleepiness more than tiredness, although this is not always so clear-cut, especially in women

  • Snoring and apnoeas. Best assessed from a witness: how loud, continuous, intermittent, and are there recognized ‘stopping breathing’ or choking episodes during sleep?

  • Other OSA symptoms such as nocturia and restless sleep

  • History of weight and neck size increases over the last 5–10y (recent weight gains common)

  • History of nasal or other ENT surgery (previous palate surgery increases discomfort of CPAP)

  • Previous medical history (certain risk factors such as mandibular surgery, hypothyroidism, acromegaly, Down’s, Prader–Willi, etc.)

  • Previous cardiovascular/cerebrovascular history (especially atrial fibrillation (AF)) and hypertension history (may influence decision to treat)

  • Alcohol and smoking history (both worsen OSA, especially alcohol)

  • Occupation (is it vigilance-critical?)

  • Shift working (may exacerbate the sleepiness from OSA)

  • Driving issues: such as sleepiness while driving and ‘near misses’ or actual sleep-related accidents (sensitive issue requiring careful handling)

  • Does the patient drive for a living and what kind of vehicle or licence?

Fig. 14.1 Epworth Sleepiness Scale questionnaire. Reproduced from Murray W. Johns - A New Method For Measuring Daytime Sleepiness: The Epworth Sleepiness Scale - Sleep 1991;14:540–5, with permission from Associated Professional Sleep Societies, LLC.

Fig. 14.1 Epworth Sleepiness Scale questionnaire. Reproduced from Murray W. Johns - A New Method For Measuring Daytime Sleepiness: The Epworth Sleepiness Scale - Sleep 1991;14:540–5, with permission from Associated Professional Sleep Societies, LLC.

If OSA seems unlikely, then other causes of sleepiness need to be considered more carefully, concentrating on the commonest (see Box 14.1).

Examination and investigations

Examination of these patients is often relatively unhelpful.

In OSA, the main features to look for are:

  • Neck circumference (best measure of the obesity contribution to the cause of OSA, >17in) and body mass index (BMI)

  • Oropharynx, often crowded with boggy mucosa, enlarged tonsils (Mallampati score can be used; see Sleep and ventilation p. [link])

  • Teeth, crowding suggests retrognathia/micrognathia (and mandibular advancement devices require sound teeth)

  • Nasal patency (how easy will CPAP be?).

Also (see Box 14.2)

  • Assessment of respiratory function, signs of cor pulmonale, FEV1/VC ratio, and SaO2 (associated COPD increases likelihood of being in type II ventilatory failure, so-called ‘overlap syndrome’)

  • BP (may influence decision to treat OSA)

  • Endocrinology: hypothyroidism, acromegaly, Cushing’s, diabetes.

It may also be appropriate to look for:

  • Evidence of a neuromuscular disorder including a previous stroke

  • Evidence of heart failure (central sleep apnoea (CSA), or Cheyne–Stokes respiration, which can produce overnight oximetry tracings similar to those of OSA).

Other scenarios

If it is known already that the patient has OSA, then a joint decision between the doctor and the patient needs to be made as to whether to undergo a trial of treatment (usually CPAP). This will depend mainly on the symptom severity vs the perceived inconvenience of the treatment. Recent evidence suggests that even relatively asymptomatic patients with OSA, presenting to a sleep clinic, may benefit from a trial of CPAP, thus to quote, ‘if in doubt, blow up the snout’. However, an abnormal sleep study is rarely a reason in its own right for CPAP. Weight loss works but is rarely achievable. Other causes must not be missed (e.g. hypothyroidism, tonsillar hypertrophy) simply because CPAP is available.

If the patient has come via ENT and is being considered for pharyngeal surgery, then the respiratory physician’s role is to dissuade the patient from this route, as the objective success rate is poor and the hazards significant. The presence of significant OSA is a contraindication to surgery. All other approaches to snoring, such as the use of mandibular advancement devices, should be considered first and pharyngeal surgery regarded as the last resort of the totally desperate.