Sleep-related respiratory disorders: Sleep apnoea syndrome

The most frequent and probably best known sleep disorders are sleep-related respiratory disorders. A distinctive feature of sleep-related respiratory disorders is the nocturnal cessation of airflow during sleep and with some forms, hereinafter described more precisely, a combination with nocturnal snoring. This disease is also called sleep apnoea, obstructive sleep apnoea or Pickwickian syndrome.

Incidence

About 1 – 2 % of the population suffer from sleep apnoea with men clearly outnumbering women. Most frequently, people between the age of 45 to 60 develop this disease. Depending on the study you rely on, the incidence in this age group is 5 – 9 % of the population.

Causes

Obstructive forms of sleep-related respiratory disorders are characterized by repeated episodes of constriction of the upper airways during sleep which are usually accompanied by a temporary cessation of breathing, reduction in the blood oxygen saturation and respiration-stimulating arousal reactions. Episodes of apnoea can occur quite often at an incidence of up to 60 times per hour of sleep. Due to the respiration-stimulating arousal reactions nocturnal sleep is fragmented, the recovery function of sleep is annulled and day-time sleepiness may be caused. Noticeably often, sleep apnoea exists in obese persons. Episodes of apnoea during sleep are caused by an occlusion of the upper airway in the area of the abyss which occurs with a reduction in muscle tone and is provoked by negative airway pressure. Factors encouraging a narrowing of the upper airways may be an enlarged palate, enlarged tonsils, fatty deposits in the area of the abyss or the uvula. Occasionally, a recessed lower jaw (retrognathy) can be identified as the cause. During apnoea the heart is stressed more. As a consequence the risk of cardiovascular diseases increases. In this context, an increased risk for cardiac insufficiency, hypertension and apoplexy is seen.

Symptoms

Cardinal symptoms are loud and intermittent snoring during the night as well as episodes of apnoea reported by the bed partner. During sleep, people with this disorder are not aware of the episodes of apnoea and the frequently explosion-like restarting of the respiration associated with a short period of awakening and they cannot remember them upon waking up. Very often day-time sleepiness with disposition to fall asleep, intolerance of monotony, morning sleepiness, morning headaches, impairment of daytime function as well as depressive mood are observed. Sleep apnoea patients sometimes complain of nocturnal sweating, disturbed sleep, loss of libido and erectile dysfunction.

Important are secondary diseases affecting the vitals organs which may reduce life expectancy by up to 10 years if serious sleep apnoea syndromes are not treated. Up to 90 % of the patients with obstructive sleep apnoea syndrome suffer from overweight.

Examination

Besides taking down the medical history (anamnesis) it is essential to question the bed partner about nocturnal apnoea and loud, intermittent snoring. The drug and addictive drug anamneses have to be collated exactly because muscle-relaxing substances such as alcohol or hypnotics of the class of benzodiazepine-receptor agonists may cause nocturnal episodes of apnoea and can considerably increase their incidence and duration. A differentiated sleepiness-related anamnesis serves among other things to evaluate the risk of endangerment to others as well as the risk of self-endangerment. Especially for patients at risk, e.g. professional drivers or people working at monitoring machines, a detailed sleepiness-related diagnostic investigation in a specialized sleep laboratory is – if evidence suggests – inevitable. A detailed internal examination with regard to possible secondary diseases is unavoidable. Before the patient is admitted to the sleep laboratory and in order to avoid wrong occupancy, a practice-based specialized physician shall carry out a preliminary examination with sophisticated methods to find out if a sleep-related respiratory disorder exists. If the result is positive, a polysomnographic examination in an inpatient sleep laboratory cannot be avoided. Before an inpatient treatment is started, an ear, nose and throat specialist should examine whether the upper airways are obstructed. 

Sleep diagnostics

Nothing but an inpatient polysomnography can provide information on the type and degree of severity as well as on an appropriate therapy. It can also be very helpful for a convincing evaluation of the therapy. Depending on the degree of severity, the inpatient sleep examination reveals a changed sleep pattern with suppression of deep and dream sleep due to the increased number of apnoea-caused arousal reactions. The nocturnal sleep cycle may be completely disrupted. The blood oxygen saturation may have considerably changed because of the nocturnal episodes of apnoea and can be a sign of a shortage of oxygen in the body.

Therapy

Since overweight is probably an important cause in the development of the disease, weight reduction plays a crucial role in therapy. For a mild degree of severity (less than 10-15 episodes of apnoea per hour of nocturnal sleep), conservative methods such as sleep hygiene, avoiding alcoholic beverages in the evening, avoiding nicotine, maintaining a stable sleep-wake cycle, avoiding late meals and maybe taking sleep position training are given priority. Sleep position training proves beneficial, especially with apnoea, if the patient sleeps on his/her back. Therefore it may be helpful to simply sew in a tennis ball in the back part of the pyjama jacket, to wear a small backpack or to wear specially developed belts or waistcoats to avoid lying on one’s back. In particular cases, such devices as for example mandibular advancement splints can occasionally be useful, too. Drug therapy refers first and foremost to theophylline drugs. In patients reacting positive to this drug, a dose of up to 500 mg serves to relieve nocturnal episodes of apnoea and the resulting daytime symptoms – at least for a short time. In case of a long-time treatment that is to be expected, tolerance developments as well as side effects affecting the heart put a limit on therapy.

Surgical measures to correct the upper airways are used to eliminate changes in the abyss or in the nose. Occasionally, enlarged tonsils or a deviated nasal septum can favour nocturnal episodes of apnoea and, in this case, a surgical intervention represents an efficient therapy. Specialized surgical procedures are aimed at enlarging the upper part of the throat. Due to the dimension of these interventions and possible complications they should be carried out - after a risk-benefit analysis - by an experienced specialist.

Nocturnal positive airway pressure therapy is considered a first choice. There exist different ventilation methods:

Nasal continuous positive airway pressure (nCPAP) is suitable for a maximum pressure of up to 12 mbar. Bi-level positive airway pressure with different pressure levels for breathing-in and breathing-out is advisable for pressures of 10 mbar and more. Due to different technological solutions, auto-nCPAP devices are in a position to identify narrowed passages in the upper airways and flexibly regulate the pressure required to keep the airways open at night. Auto-nCPAP devices are used for abnormal snoring or position-related sleep apnoea syndromes. By means of different types of nocturnal positive airway pressure therapy, a pneumatic splinting of the upper airways is caused which keeps the airways open and actually keeps the number of nocturnal episodes of apnoea down at a normal level. For all therapeutic measures, sufficient efficiency has to be proved by polysomnography.