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Title: Daytime function after continuous positive airway pressure (CPAP) therapy for the sleep apnoea/hypopnoea syndrome (SAHS
Author: Engleman, Heather M.
ISNI:       0000 0004 2704 429X
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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The sleep apnoea/hypopnoea syndrome (SAHS) is characterised by obstruction of the airway during sleep, resulting in repetitive nocturnal breathing pauses, which provoke both oxygen desaturations and arousals from sleep. SAHS is associated with daytime deficits of excessive daytime sleepiness, cognitive impairment and psychological distress, probably as a result of these nocturnal events. The treatment of choice for SAHS is continuous positive airway pressure (CPAP) therapy, a mechanical treatment in which positive airstream pressure is administered to the upper airway through a nasal mask, splinting the airway open and preventing the nocturnal events of SAHS. A limited number of small clinical studies have indicated improvements in daytime function following CPAP therapy, but these have not been well-controlled, particularly in the area of cognitive performance. This thesis contributes controlled studies to the knowledge-base describing CPAP's effects on daytime function. A pilot study employing a parallel-group design in 37 patients showed improvements in objective daytime sleepiness and psychological distress with CPAP, but not cognitive function. This null finding however might have resulted from inter-individual variability. To rectify this, a randomised placebo-controlled crossover study of daytime function on CPAP and on an oral placebo was conducted in 64 patients with a wide range of severity of SAHS. This study showed CPAP-related improvement in symptoms, objective and subjective daytime sleepiness, cognitive performance and well-being. The use of balanced treatment order within a subgroup of 16 patients with mild SAHS (apnoea+hypopnoea index 5 to 14.9) allowed investigation of the minimum illness severity at which daytime benefits from CPAP are observed. Such mild patients demonstrated improvements in symptom score, cognitive performance and psychological distress on CPAP. Although the minimum illness severity meriting CPAP treatment has not been well defined, these data support the efficacy of CPAP at the lowest severity range of SAHS. A randomised study of auditory evoked potentials in 18 patients showed trends only towards improved neurophysiological function after CPAP, and a randomised crossover study of ambulatory blood pressure in 13 patients showed reduced blood pressure on CPAP only in a subgroup of patients who lacked significant dipping of nocturnal blood pressure. The nocturnal determinants of daytime dysfunction in SAHS were explored by correlating factors extracted from polysomnographic and daytime function variables. The principal component extracted from the polysomnographic variables was found to correlate significantly with daytime sleepiness and with intellectual function, corroborating weak or moderate associations between the severity of nocturnal events and daytime deficits. Patients' perceptions of benefit from CPAP, and their self-reported driving competence, were examined in a survey of 215 CPAP users. Patients reported wide-ranging improvements in nocturnal and daytime symptoms of SAHS, and showed a significant improvement in mileage adjusted rates of road traffic incidents following CPAP. Although side-effects of CPAP were common, these were minor in nature. Thus patients' reports corroborated the daytime benefits from CPAP documented in the project's controlled studies. The studies of this thesis demonstrated objective and subjective improvements in symptoms, daytime sleepiness, cognitive performance and well-being in SAHS patients treated with CPAP.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available