What is Sleep Disordered Breathing and Why is it Important to be Assessed and Treated?
By Dr David Lee | BSc PhD CertEd AFBPsS CPsychol CSci | Clinical Director at Sleep Unlimited Ltd.
The cessation of breathing in sleep is referred to as sleep apnoea, from the Greek for “no-gas.” There is also a variation of this where there is reduced ventilation, referred to as “hypopnoea,” or “reduced-gas,” where the individual still breathes, but not enough to maintain blood oxygen (O2) Saturation levels (or to rid the blood of carbon dioxide (CO2)). This increase of CO2 in the blood causes the blood to become slightly acidic, a condition referred to as hypercapnia. During sleep, hypercapnia is recognised by the brainstem, which triggers an awakening to enable the individual to start breathing again and so excrete the troublesome CO2 and replenish the blood with the required O2.
The experience of the sleeper with apnoea is that (in extreme cases) individuals may stop breathing for up to, or even over, a minute and this can occur perhaps thirty to forty times per-hour during through the night. The hypercapnia-induced awakenings often result in a large gasp for air. This gasping is a key diagnostic feature of apnoea and is often noticed by spouses or partners of people with the condition. The characteristic gasping of people with apnoea re-balances the gas levels of the blood, but the individual may be completely unaware that they are waking for these brief periods to gasp for air. Such “micro-arousals” are often out-with the awareness of the individual experiencing them if the arousal lasts for less than a minute. There are two very important considerations for the person with apnoea here:
- The continual awakening to re-balance the gas-levels in the blood persistently knock the sleeper out of their all-important deep, slow wave sleep stages, leaving them with mostly light sleep through the night, so depriving them of much of their restorative deep sleep.
- As these awakenings are often very transient (microarousals are usually less than one minute in duration), they may often (or even always) occur without the awareness of the person with apnoea. So, even though they may have awoken up to thirty times per-hour during through the night, they may feel like they have slept continually.
The result is that in the morning the person with apnoea awakens feeling terrible (as they have had very little restorative, deep sleep and have had multiple awakenings and very disturbed sleep through the night). They are also often confused as they feel like that have had fairly undisturbed sleep. Further to this, they also experience Excessive Daytime Sleepiness (EDS) to the point where they may be unable to function effectively during the daytime even to the point where they can no longer work. The prolonged experience of apnoea precipitates significant loading to the pulmonary side of the heart (the part of the heart that cycles blood to and back from the lungs), eventually leading to chronic pulmonary heart disease. These can collaborate to significantly reduce the lifespan, and quality of life, of the person with apnoea. As the experience often occurs out-with the conscious awareness of the individual themselves. Apnoea is often reported by partners or spouses, and, as there are a large number of people who sleep alone, exact numbers of people with apnoea in the community is unknown, but are likely to be much larger than are known to healthcare professionals treating these conditions due to ignorance of the presence of the condition. Current (2014) estimates suggest that there may be around 1.5 million people with sleep disordered breathing in the UK at the present time, but only 330,000 currently have a confirmed diagnosis (Office of Health Economics, 2014)
Risk factors for apnoea include:
- Being male (although women are also affected).
- Being over-weight.
- Snoring (the more extreme, the more likely to have apnoea).
- Having hypertension.
- Being over fifty years of age.
- Being excessively tired during the daytime, despite feeling as if enough sleep has been taken (Phillips et al., 1989).
There are subdivisions of apnoea (obstructive and central), these will be discussed below.
Obstructive sleep apnoea
Obstructive sleep apnoea (OSA) is caused by a physical reduction in the aperture of the airway, this is often exacerbated when lying down to sleep. OSA affects 4% of men and 2% of women in the UK (Gibson, 2005). There can be various causes, for example, excessive weight around the neck, swollen tonsils, an enlarged epiglottis, etc. OSA is usually readily treatable. In the case of excess weight around the neck, then dieting and exercise to lose weight (both generally and in the neck region) can be very effective at reducing OSA symptoms. Antibiotic treatment of infected adenoid glands (or their removal) can also be very effective in the management of OSA, as can mandibular advancement devices (Lindeman & Bondemark, 2001) and rhinoplasty surgical procedures for epiglottal, or, nose, mouth, throat and jaw-related obstructions (McDonald, 2003). Often these approaches can prove very effective in the successful management of OSA.
Central sleep apnoea
Where it is possible to treat and “cure” OSA, central sleep apnoea has no cure, rather its symptoms are managed using Continuous Positive Airway Pressure (CPAP) machines. As its name suggests central sleep apnoea is a manifestation of a dysfunction in the central nervous system. More specifically the brain-stem. Many autonomic functions are controlled in the brainstem (the cardiac, sleep and wakefulness, and the respiratory centres are all located there). In fact, the Raphe nuclei and the pedunculopontine nucleus of the brainstem, that are essential for the control and regulation of sleep and wakefulness are located very close to the respiratory centres. This goes some way to explain the pathogenesis of central sleep apnoea. Although the exact mechanisms are unknown, it is thought that the changing state of the brainstem as it phases through the different stages of sleep can, in some cases, interfere with these respiratory centres and cause periods of apnoea. As we saw above, this causes an increase in blood-borne CO2 which in turn causes the slight acidification of the blood (hypercapnia). This hypercapnia is detected by the sleep centres of the brainstem, precipitating an “emergency” reaction that wakes the person from their apnoeatic episode, so enabling them to take on more oxygen – with the characteristic gasp of the person with apnoea.
As this phenomenon is occurring centrally (in the brainstem) central sleep apnoea can be considered to be a “hard-wired” condition and so remains, at the present time, incurable. The treatment for this condition involves symptom management with the use of a CPAP machine. These machines blow a continuous stream of air into the airway via the application of a facemask which is attached to the CPAP machine via a long tube. This air, as it is blown into the mouth and airway of the person with apnoea, keeps the airway open during the night and enables the person to avoid episodes of apnoea and hypercapnia. The result is that, sometimes within a very short space of time, the person with apnoea can regain their normal quotient of deep sleep (which may have eluded them for many years). As a result, their excessive daytime sleepiness (EDS) dissipates and they can begin to regain a functional life. Unfortunately, there is no “cure” for central sleep apnoea and the individual with the condition will be required to wear a facemask at night for the rest of their lives, in order to successfully manage the symptoms of this rather enigmatic condition (Bradley & Phillipson, 1992). Compliance with the use of CPAP is essential in this regard. Older machines tended to dry the mouths and throats of users and many found this side-effect too much to bear, but more modern machines are equipped with humidifiers which help to prevent this problem and so improve compliance.
The Consequences of Untreated Apnoea
As we saw above, there are many people living with sleep apnoea but whom are currently undiagnosed. The excessive daytime sleepiness, synonymous with the condition, not only affects the quality of life of those living with apnoea, but also places than at a much-increased risk of having an accident due to their lack of vigilance that is related to this sleepiness. Accidents that may occur in the workplace, at home, or perhaps more seriously, whilst driving. They are also at an increased risk of cardiovascular events and stroke.
The Office for Health Economics (2014) estimated that treating currently undiagnosed apnoea patients would save the NHS in the order of £55 million per year and result in 40,000 fewer road traffic accidents.
Professional drivers are a particularly at-risk group for sleep apnoea as they are often male, many are overweight and the average age of professional drivers in the UK is 53 years (BRAKE, 2016), they also spend more time driving more than non-commercial drivers and often drive on boring arterial routes whereby boredom may become a factor in falling asleep whilst driving. It has been estimated that 41% of professional drivers may be at a moderate risk for having sleep disordered breathing and that 16% may be at a high risk and require immediate treatment (Respironics, 2005). The Driver Vehicle Licencing Agency (DVLA) in the UK requires drivers with apnoea to cease driving until their symptoms have been treated and point out that causing death by dangerous driving (which includes driving whilst tired) carries a maximum penalty of 14 years imprisonment. Furthermore, under the Health and Safety at Work Act employers of a driver who causes an accident whilst driving for their work, may be liable for prosecution.
Assessment for Sleep Apnoea
First-line diagnosis for sleep apnoea is made using overnight oximetry, this can be conducted at the client’s own home and involves wearing a small (pack of playing cards) sized device on the wrist with an attached finger cuff that extends from the device and is fitted over the index finger of the wearer. This finger-cuff and device detects blood oxygen desaturations during the one night of assessment to either confirm or deny the presence of apnoea. Oximetry assessments are available via a GP referral to respiratory medicine through the NHS, although waiting times for assessment can be protracted (often many months). Assessments can also be arranged privately.
If you or anyone you know or employ has suspected sleep apnoea then please do contact us for more information and guidance as required.