Arousal plays an important role in the termination of each apnoea, but may also contribute to the development of further apnoea, because of a reduction in respiratory drive related to the hypocapnia which results from postapnoeic hyperventilation. A cyclical pattern of repetitive obstructive apnoeas may result.A better understanding of the integrated pathophysiology of OSA should help in the development of new therapeutic techniques.

The Robin sequence is a congenital disorder characterized by micrognathia and cleft palate [1] and has been associated with a predisposition to obstructive sleep apnoea (OSA) [2][3][4]. The associated posterior displacement of the tongue (glossoptosis) results in a narrowed upper airway (UA), which favours UA collapse during inspiration [5,6]. We report a case of severe OSA in a teenage female with the Robin sequence, which was successfully treated with nasal continuous positive airway pressure (nCPAP) and in whom the OSA resolved spontaneously over a three-year period associated with changes in UA bony and soft tissue dimensions. Case reportThe patient details and initial response to nCPAP have previously been reported elsewhere [7], and are summarized as follows. A 12 yr old female with Robin sequence presented with a history of habitual snoring since infancy and witnessed apnoeas during sleep over the previous 12 months. A cleft palate repair had been performed at the age of 11 months, a tonsillectomy/adenoidectomy at the age of 5 yrs, and palatoplasty 2 yrs later to correct a speech disturbance. The patient complained of chronic fatigue and sleepiness, frequent nocturia and occasional nocturnal enuresis. Her weight was 29 kg (3rd centile) and height 150 cm (50th centile). Apart from prominent micrognathia and a resting tachycardia, physical examination was normal. A 12-lead electrocardiogram (ECG) showed sinus tachycardia (110-115 beats·min -1 ) and p-pulmonale, suggesting right-heart strain.Full overnight sleep studies using standard polysomnographic techniques [8] demonstrated severe OSA with 49 obstructive apnoeas (no airflow despite inspiratory effort) or hypopnoeas (tidal volume <50% baseline, with associated O 2 desaturation Š4%) per hour of sleep and associated oxygen desaturations to levels below 50% ( fig. 1). She had poor quality sleep with no slow wave sleep (SWS) or rapid-eye movement (REM) sleep. The OSA was effectively controlled with nCPAP (REMstar™; Respironics, Murrayville, PA, USA) at a pressure level of 14 cmH 2 O and this therapy was associated with an immediate improvement in energy and daytime sleepiness. Follow-up sleep studies and assessment on nCPAP after 6 and 18 months of continuous therapy at home showed abolition of apnoeas and hypopnoeas, normal oxygen saturation (Sa,O 2 ), and normal amounts of SWS and REM sleep with no further daytime sleepiness, nocturia or nocturnal enuresis. Her ECG had reverted to normal and nCPAP pressure was reduced to 10 cmH 2 O, without the reappearance of apnoea or hypopnoeas.After 3.5 yrs of continuous nCPAP therapy, aged 16 yrs, she had grown to 162 cm (50th centile) and weighed 50.5 kg (25th centile). She wished to try sleeping without nCPAP and, therefore, full polysomnography (PSG) was repeated after 1 week without the device. This study showed that her OSA had resolved and oxygen saturation remained >90% throughout sleep. Nasal CPAP was discontinued and a further follow-up PSG after 6 months confirmed