Abstract
The preferred form of treatment for the sleep apnoea/hypopnoea syndrome (SAHS)
is continuous positive airway pressure (CPAP). This thesis investigates the usage,
benefits to patients and partners, and method of initiation of CPAP therapy.
A database of all 1,211 patients booked for CPAP between 1986-1997 was
constructed, with 95.4% follow-up at a median of 22 months. Fifty-two (4.5%)
patients refused CPAP treatment; these were more often female and current
smokers. The methods of survival analysis found 68% of patients continued
treatment at 5 years and the independent baseline predictors of continued CPAP use
were snoring history, apnoea/hypopnoea index (AHI), and Epworth sleepiness score
(ESS). CPAP use at 3 years was > 92% in sleepy patients with severe disease
(ESS>10, AHI>60) but only 40% in non-sleepy mild severity patients (ESS<10,
AHI<15). Average nightly use within 3 months was strongly predictive of longterm
use.
Using the above database the independent predictors of long-term use were used to
match (AHI+/-15%, ESS +/-3) 46 patients prescribed split-night (diagnostic +
CPAP titration studies in 1 night) studies with 92 full night patients. Classical
symptoms of SAHS were the main reason for split-night studies (n=27). There was
no difference between these split and full night studies in long-term CPAP use,
median (IQR) nightly CPAP use [split 6.0 (3.8-7.4)hr/night, full 6.2 (3.7-
7.0)hr/night, p=0.9], post-treatment ESS, or frequency of nursing
interventions/clinic visits required. Split-night patients received treatment quicker
[median (IQR) time from referral to treatment 13 (11-20) versus 22 (12-34) months,
p=0.003].
In a randomised crossover study 22 unselected SAHS patients [median (IQR) AHI
= 40(25-65)] events/hr had 1 month limbs on CPAP and placebo capsules, and
home polysomnography was performed at the end of each month. During CPAP
patients had a lower arousal index, less stage 1 and more stage 3+4 sleep (all;
p<0.03), but no increase in stage REM sleep. In the above study the partners' sleep
quality was also monitored while the patient received CPAP and placebo. There
was no difference in the partners' objective sleep quality between CPAP and
placebo. However partners reported improved subjective sleep quality (p=0.05) and
less disturbance to sleep (p=0.03) during the patients' use of CPAP compared to
placebo.
Thus long-term CPAP use is related to disease severity and subjective sleepiness
and can be predicted within 3 months. Low usage in mild patients with few
symptoms suggests alternative treatments are needed. These studies also show that
treatment waiting time and cost can be reduced, with no loss of effectiveness, by
performing split-night studies in selected patients. Patients with SAHS have better
objective sleep quality and their partners have improved subjective sleep quality
when the patient is treated with CPAP.
