WORLD SLEEP DAY
WORLD SLEEP DAY- 2017 -MARCH 17TH 2017- IS BEING ORGANISED ACROSS THE WORLD WITH THW SLOGAN, “SLEEP SOUNDLY & NURTURE LIFE”
SLEEP DISORDERED RESPIRATION – A POTENTIALLY DANGEROUS MEDICAL DISORDER “SLEEP SOUNDLY TO NURTURE YOUR PRECIOUS LIFE”
The term ‘sleep disordered breathing’(SDB) encompasses a range of conditions characterised by abnormal breathing during sleep; in many cases this is associated with narrowing or obstruction of the upper airway (pharynx). The disordered breathing ranges from intermittent, partial obstruction of the airway without sleep disturbance (snoring) to, at the other end of the spectrum, frequent apnoeas associated with repetitive hypoxaemia (decrease in oxygen content of blood) and arousals leading to sleep disruption. This frequent sleep disruption is called Sleep Fragmentation, which leads to a non-restorative sleep & hence daytime sleepiness. The sleep disruption results in daytime sleepiness and, in the long term, it can lead to cognitive impairment and cardiovascular morbidity. The prevalence of OSAS is higher in certain groups, particularly in the obese, diabetics, hypertensives requiring many drugs to control blood pressure or difficult to control blood pressure, heart disease, kidney patients & those receiving treatment for epilepsy & psychiatric conditions. The term ‘obstructive sleep apnoea’ (OSA) refers to intermittent obstruction of the airway, irrespective of the presence of daytime symptoms. If symptoms result, the condition is called obstructive sleep apnoea syndrome (OSAS).
Sleep disordered breathing is very common in India but no statistics are collected routinely on the associated morbidity or mortality. In my clinical practice, at least 10 to 15 new cases are seen & diagnosed per month. OSAS is a major public health problem in our nation. In one North Indian database, the prevalence of SDB among general population is close to 14%. OSAS is common, underdiagnosed and eminently treatable. In developed countries, it is reported to affect between 3–7% of middle-aged men and 2–5% of women.
WHY & HOW of Sleep Disordered Breathing: Any change that narrows the upper airway when awake will predispose the individual to obstructive apnoea or hypopnoea when asleep. Obesity is the single most common predisposing factor, but patients with OSAS may have other contributory factors that narrow the upper airway, such as a large tongue, enlarged tonsils, increased total soft tissue in the pharynx or a retropositioned mandible (receding jaw).
OSAS is characterised by episodes of upper airway occlusion: these are termed apnoeas if the airway is completely occluded and hypopnoeas if the occlusion is partial. An obstructive apnoea is defined pragmatically as the cessation of airflow despite continued breathing efforts for at least 10 s. At their termination, apnoeas/hypopnoeas are often, but not always, associated with a change in the electroencephalographic (EEG) signal indicative of arousal and with a drop in blood oxygen saturation. In most instances, such brief arousals are not accompanied by complete awakening and the patient is usually unaware of them.
OSAS is more common in men than women and is attributed to differences in anatomical and functional properties of the upper airway, differences in craniofacial morphology and fat deposition, and different ventilatory responses to arousal from sleep. The disease prevalence is higher in post-menopausal women and hormone replacement therapy is associated with a lower prevalence; the prevalence of OSAS increases during pregnancy, particularly in the third trimester.
Congenital conditions affecting craniofacial development, such as Marfan syndrome, Down syndrome and the Pierre Robin sequence, predispose to OSAS, as do acromegaly and hypothyroidism.
Smoking is associated with a higher prevalence of snoring and OSAS, and alcohol can increase upper airway collapsibility leading to apnoeas.
Muscle-relaxant medication (sedative hypnotic drugs, opiates), sleep deprivation and supine posture can all exacerbate OSAS, although the degree to which sleep disordered breathing is worsened in the individual may depend on the predominant pathological mechanism in the individual patient and his or her intrinsic physiological responses.
Reduced nasal patency, due to congestion or anatomical defects, as well as respiratory allergy are also potential contributors.
CLINICAL MANIFESTATIONS :
The most common complaint is excessive daytime sleepiness (EDS). However, absence of EDS doesnt rule out OSAS. However, other causes of diurnal sleepiness, such as shift work, medication (sedatives) and alternative diagnoses – like periodic limb movement disorder and narcolepsy have to be ruled out by clinicians before labelling as OSAS. Nocturnal symptoms of OSAS are generally reported by a bed partner. The most common are snoring (which is almost always a feature), snorting, choking attacks terminating a snore, and witnessed apnoeas. Apnoeic episodes are reported by about 75% of bed partners.
How to arrive at diagnosis ?
Polysomnography(PSG), which simultaneously monitors, nasal and/or oral airflow, thoraco-abdominal movement, snoring , electroencephalogram (EEG), electro-oculogram (EOG) , electromyogram (EMG) & oxygen saturation is the gold standard in diagnosis. In some complex sleep disorder evaluation, we will recommend Video monitoring of sleep in addition to PSG called as Video-PSG.
Simpler diagnostic investigations are increasingly being used and these often take place in the patient’s home rather than in hospital, called as home sleep testing (HST). All home testings are of not uniform standard. At least Level 2 testing is recommended.
OSAS is an independent risk factor for hypertension and is associated with an increased risk of cardiovascular disease, abnormal glucose metabolism, depression and sleepiness-related accidents. OSAS results in higher medical costs than those incurred by age-and sex-matched healthy individuals. Even a single road accident due to sleepiness caused by OSAS can incur considerable health costs & the risk of having a accident is 4 fold more than a normal population.
Once OSAS is diagnosed, its treatment is relatively straightforward.
- Lifestyle measures, such as weight loss, alcohol consumption and smoking are the more important ones to address. Pranayam, Practicing YOGA & some exercises of tongue muscles& neck muscles can play an important role in prevention of upper airway collapse.
- Continuous positive airway pressure (CPAP) is the commonest and most rapidly effective treatment for moderate-to-severe OSAS. This is usually delivered through the upper airway using a mask over the nose, attached by a hose to an air compressor that generates a flow of air at positive pressure throughout the breathing cycle, of sufficient magnitude to keep the upper airway open and prevent it from collapsing. CPAP thereby acts as a pneumatic splint for the upper airway. Unfortunately, CPAP does not permanently restore or correct the problems leading to upper airway obstruction; it therefore needs to be applied throughout each night for maximum effect. If well tolerated and used consistently, CPAP has been shown to reverse or ameliorate the somnolence, cognitive deficit, reduced health status, hypertension and metabolic disturbances associated with OSAS.
- In snoring or mild OSAS, an alternative therapy like the mandibular repositioning device, constructed by a trained professional can be used.
- Sugeries like tonsillectomy, adenoidectomy, upper airway surgery and bariatric surgery are recommended in special cases only.
- Hypoglossal nerve pacing is increasingly being trialled in patients with OSAS who fail to respond to more conventional modes of therapy. This modality is yet to get USFDA approval for clinical application.
- No effective pharmacological therapies are currently available.
The prognosis for OSAS is very good and reverts to that of the non-OSAS population, particularly in terms of cardiovascular mortality and morbidity. Adherence to recommended modality of treatment (especially CPAP) is very crucial for overall favourable outcome.