Adult obstructive sleep apnoea

Abstract

Obstructive sleep apnoea is an increasingly common disorder of repeated upper airway collapse during sleep, leading to oxygen desaturation and disrupted sleep. Features include snoring, witnessed apnoeas, and sleepiness. Pathogenesis varies; predisposing factors include small upper airway lumen, unstable respiratory control, low arousal threshold, small lung volume, and dysfunctional upper airway dilator muscles. Risk factors include obesity, male sex, age, menopause, fluid retention, adenotonsillar hypertrophy, and smoking. Obstructive sleep apnoea causes sleepiness, road traffic accidents, and probably systemic hypertension. It has also been linked to myocardial infarction, congestive heart failure, stroke, and diabetes mellitus though not definitively. Continuous positive airway pressure is the treatment of choice, with adherence of 60-70%. Bi-level positive airway pressure or adaptive servo-ventilation can be used for patients who are intolerant to continuous positive airway pressure. Other treatments include dental devices, surgery, and weight loss.

Figure 1. An example of the signals recorded during overnight polysomnography

Shows an obstructive apnoea with cessation of airflow for more than 10 s despite persistent respiratory efforts shown on the chest and abdominal respiratory bands. The apnoea is associated with arterial oxygen desaturation and is terminated by arousal from sleep. C4-A1=electroencephalogram. LOC=left electro-oculogram. ROC=right electro-oculogram. CHIN=chin electromyogram. CHEST=respiratory inductance plethysmography bands placed around the thorax. ABDM=respiratory inductance plethysmography bands placed around the abdomen. P_Nasal=airflow monitoring by nasal air pressure. Therm=airflow monitoring by thermal air sensor. SaO₂=arterial oxygen saturation. EKG=electrocardiogram. ABDM=abdomen.

Figure 2. An example summary report from an overnight split night polysomnography

Total time in bed was 489·5 min. Half of the night was diagnostic, half therapeutic. The hypnogram shows sleep stages throughout the night. Shortly before midnight, continuous positive airway pressure was started (P_mask increases from 0), which was followed by elimination of respiratory events, normalisation of arterial oxygen saturation, and REM rebound (>2 h of REM). Sleep efficiency is the proportion of time in bed spent asleep after lights out. Sleep latency is the time from lights out until the first epoch of sleep. REM latency is the time from lights out until the first epoch of sleep. An epoch is a time window of 30 s. CnA=central apnoea. ObA=obstructive apnoea. MxA=mixed apnoea. Hyp=hypnoea. Uns=unclear events. RERA=respiratory event related arousal. PLM=periodic limb movement. TST=total sleep time. REM=rapid eye movement. W=awake. NREM=non-rapid eye movement. R=right. B=back. L=left. F=front. U=upright. On the hypnogram, 1, 2, and 3 represent NREM stages 1, 2, and 3.

Figure 3. Risk factors, pathogenic mechanisms, and possible treatments for obstructive sleep apnoea

Risk factors for obstructive sleep apnoea probably act through one or more pathogenic mechanisms. One or two of the pathogenic mechanism might predominate in each patient and give rise to the disorder. Although CPAP treats obstructive sleep apnoea irrespective of underlying cause, treatments based on tackling individual pathogenic mechanisms might prove a successful alternative approach—eg, fluid accumulation outside the airway could make the upper airway lumen smaller and might respond to diuretic treatment. CPAP=continuous positive airway pressure. MAD=mandibular advancement device. HGNS=hypoglossal nerve stimulation.

Figure 4. Suggested steps for management of patients struggling with CPAP

CPAP=continuous positive airway pressure.