Neil J. Douglas

Compliance with CPAP therapy in patients with the sleep apnoea/hypopnoea syndrome.

BACKGROUND--Continuous positive airway pressure (CPAP) therapy is the treatment of choice for the sleep apnoea/hypopnoea syndrome. Compliance with this relatively obtrusive therapy has not been well studied. METHODS--Usage of CPAP was investigated in 54 patients with sleep apnoea/hypopnoea syndrome (median 36 (range 7-129) apnoeas + hypopnoeas/hour slept) over the first 1-3 months after starting CPAP therapy. In all cases CPAP usage was monitored by hidden time clocks that indicated for how long the machines were switched on--that is, the CPAP run time. In 32 patients the time at which the CPAP mask pressure was at the therapeutic level of CPAP pressure set for that patient--that is, the mask time--was also monitored. In all patients objective daytime sleepiness was assessed by multiple sleep latency before and after CPAP therapy. RESULTS--The mean (SE) nightly CPAP run time was 4.7 (0.4) hours. There was no correlation between run time and severity of the sleep apnoea/hypopnoea syndrome as assessed by apnoea + hypopnoea frequency or multiple sleep latency, and no correlation between CPAP usage and improvement in multiple sleep latency. Thirty two patients in whom mask time was recorded had therapeutic CPAP pressures for 89% (3%) of their CPAP run times. Patients who experienced side effects from CPAP used their CPAP machines significantly less than those who did not. CONCLUSIONS--Patients with sleep apnoea/hypopnoea syndrome used CPAP for less than five hours/night on average with no correlation between severity of sleep apnoea/hypopnoea syndrome and CPAP usage. Patients who complained of side effects used their CPAP therapy less. It is recommended that, as a minimum, CPAP run time should be regularly recorded in all patients receiving CPAP therapy.

Randomised placebo controlled trial of daytime function after continuous positive airway pressure (CPAP) therapy for the sleep apnoea/hypopnoea syndrome.

BACKGROUND Patients with the sleep apnoea/hypopnoea syndrome (SAHS) report improved sleepiness, cognitive function, and psychological well being after continuous positive airway pressure (CPAP) therapy, and it is for these daytime features that CPAP is usually given. However, few randomised or controlled studies exist on the effects of CPAP on daytime function. METHODS A prospective, randomised, single blind, placebo controlled, crossover trial of daytime function after CPAP was conducted in 23 patients with SAHS, all with ⩾15 apnoeas+hypopnoeas/hour and ⩾2 symptoms of SAHS. All patients spent four weeks on CPAP therapy and four weeks on oral placebo treatment, following randomisation to treatment order. With ethics committee approval, patients were told the placebo tablet might improve upper airway function. Average effective CPAP use was monitored using hidden time clocks. Assessments of objective and subjective sleepiness, symptoms, cognitive performance, and psychological well being were performed on the last day of each treatment and compared. RESULTS Objective sleepiness measured by sleep onset latency on the multiple sleep latency test improved with CPAP (mean difference from placebo +2.4 min, 95% CI 0.8 to 4.0; p<0.001) as did subjective sleepiness on the Epworth scale (mean difference –6, 95% CI –3 to –9; p = 0.001). Symptom total score also fell with CPAP (mean difference –1.6, 95% CI –2.2 to –1.0; p<0.001). No determinants of these changes with active treatment were identified, and no significant enhancements to cognitive function or psychosocial well being were found in this small sample. CONCLUSIONS These findings provide further evidence for clinically significant benefits to daytime function from CPAP.

Evaluation of a portable device for diagnosing the sleep apnoea/hypopnoea syndrome

Waiting times for hospital-based monitoring of the obstructive sleep apnoea/hypopnoea syndrome (OSAHS) are rising. This study tested whether Embletta, a new portable device, may accurately diagnose OSAHS at home. A synchronous comparison to polysomnography was performed in 40 patients and a comparison of home Embletta studies with in-laboratory polysomnography was performed in 61 patients. In the synchronous study, the mean difference (polysomnography–Embletta) in apnoeas+hypopnoeas (A+H)·h−1 in bed was 2·h−1. In comparison to the apnoea/hypopnoea index (AHI)·h−1 slept, the Embletta (A+H)·h−1 in bed differed by 8·h−1. These data were used to construct diagnostic categories in symptomatic patients from their Embletta results: “OSAHS” (≥20 (A+H)·h−1 in bed), “possible OSAHS” (10–20 (A+H)·h−1 in bed) or “not OSAHS” (<10 (A+H)·h−1 in bed). In the home study, the mean difference in (A+H)·h−1 in bed was 3·h−1. In comparison to the polysomnographic AHI·h−1 slept, the Embletta (A+H)·h−1 in bed differed by 6±14·h−1. Using the above classification, all nine patients categorised as not OSAHS had AHI <15·h−1 slept on polysomnography and all 23 with OSAHS on Embletta had an AHI ≥15 on polysomnography, but 18 patients fell into the possible OSAHS category potentially requiring further investigation and 11 home studies failed. Most patients were satisfactorily classified by home Embletta studies but 29 out of 61 required further investigation. The study suggested a 42% saving in diagnostic costs over polysomnography if this approach were adopted.

The effect of age, sex, obesity and posture on upper airway size

Most patients with sleep apnoea/hypopnoea syndrome (SAHS) are middle-aged men. As there are conflicting data on the effects of age and gender on upper airway calibre, we tested the hypothesis that increasing age and the male sex predispose to upper airway narrowing in normal subjects. We measured upper airway calibre using acoustic reflection in 60 men and 54 women (median 35, range 16-74 yrs) both seated and supine. All upper airway dimensions, except oropharyngeal junction (OPJ), decreased with increasing age in both men and women (r > -0.24, p < or = 0.05) while supine (r2 > 0.06). Men had greater changes in airway area at OPJ on lying down (mean (SEM) 0.5 (0.1), 0.2 (0.1) cm2; p < 0.02). Men had greater body mass indices (mean (SD) 26 (4), 24 (4) kg.m-2; p = 0.04), and larger neck circumferences (mean (SD) 38 (3), 33 (2) cm; p < 0.0001) than women. For any body mass index, neck circumference was larger in men than women (p < 0.001). This study shows that upper airway size decreases with increasing age in both men and women, and that men have greater upper airway collapsibility on lying down at oropharyngeal junction than women.

Daytime sleepiness, cognitive performance and mood after continuous positive airway pressure for the sleep apnoea/hypopnoea syndrome.

BACKGROUND--Patients with the sleep apnoea/hypopnoea syndrome often receive continuous positive airway pressure to improve their symptoms and daytime performance, yet objective evidence of the effect of this treatment on cognitive performance is lacking. METHODS--A prospective parallel group study was performed comparing the change in objective daytime sleepiness as assessed by multiple sleep latency, cognitive function, and mood in 21 patients (mean (SE) number of apnoeas and hypopnoeas/hour 57 (6)) who received continuous positive airway pressure for three months and 16 patients (49(6) apnoeas and hypopnoeas/hour) who received conservative treatment for a similar period. RESULTS--Both groups showed significant within group changes in cognitive function between baseline and three months, but when comparisons were made between groups the only significant difference was a greater improvement in multiple sleep latency with continuous positive airway pressure. However, the improvement in sleep latency with continuous positive airway pressure was relatively small (3.5 (0.5) to 5.6 (0.7) min). The group treated with continuous positive airway pressure was divided into those who complied well with treatment (> 4.5 hours/night) and those who did not. Those who complied well (n = 14) showed significant improvement in mean sleep latency and also in depression score compared with the controls but no greater improvement in cognitive function. CONCLUSION--This study confirms significant improvements in objective sleepiness and mood with continuous positive airway pressure, but shows no evidence of major improvements in cognitive function.

Salmeterol in nocturnal asthma: a double blind, placebo controlled trial of a long acting inhaled beta 2 agonist.

OBJECTIVE--To determine whether inhaled salmeterol, a new long acting inhaled beta adrenergic agonist, reduces nocturnal bronchoconstriction and improves sleep quality in patients with nocturnal asthma. DESIGN--Randomised, double blind, placebo controlled crossover study. SETTING--Hospital outpatient clinics in Edinburgh. SUBJECTS--Twenty clinically stable patients (13 women, seven men) with nocturnal asthma, median age 39 (range 18-60) years. INTERVENTIONS--Salmeterol 50 micrograms and 100 micrograms and placebo taken each morning and evening by metered dose inhaler. Rescue salbutamol inhalers were provided throughout the run in and study periods. MAIN OUTCOME MEASURES--Improvement in nocturnal asthma as measured by peak expiratory flow rates and change in sleep quality as measured by electroencephalography. RESULTS--Salmeterol improved the lowest overnight peak flow rate at both 50 micrograms (difference in median values (95% confidence interval for difference in medians) 69 (18 to 88) l/min) and 100 micrograms (72 (23 to 61) l/min) doses twice daily. While taking salmeterol 50 micrograms twice daily patients had an objective improvement in sleep quality, spending less time awake or in light sleep (-9 (-4 to -44) min) and more time in stage 4 sleep (26 (6-34) min). CONCLUSIONS--Salmeterol is an effective long acting inhaled bronchodilator for patients with nocturnal asthma and at a dose of 50 micrograms twice daily improves objective sleep quality.

Sleep-disordered breathing after stroke: a randomised controlled trial of continuous positive airway pressure

Background: Sleep-disordered breathing (SDB) is common after stroke, but it is unclear whether it should be treated. Objective: To conduct a randomised controlled trial of continuous positive airway pressure (CPAP) after stroke. Methods: Patients with stroke with ⩾30 apnoeas and hypopnoeas per hour ((A+H)/h) with predominant obstructive sleep apnoea or hypopnoea were randomised to either CPAP treatment or conservative treatment for 8 weeks. Outcomes were measured blind to treatment allocation at 8 weeks and 6 months after the stroke. The primary outcome was physical function on the Nottingham Extended Activities of Daily Living Scale. Results: Of 658 patients with stroke screened, only 71 (10.7%) were eligible and consented to a sleep study 14–19 days after stroke. 66 patients completed the sleep study (21 women; mean age 72 years), 33 (50%) had ⩾30 (A+H)/h that were predominantly obstructive. 15 were randomised to CPAP treatment and 15 to conventional treatment. Despite intensive efforts, objective use of CPAP was poor, averaging 1.4 h a night. CPAP treatment resulted in no significant improvements (p>0.1) in the primary outcome or in neurological function or sleepiness, and in poorer health status on some measures. Conclusions: This trial showed no benefit from CPAP treatment, the relevance of the observed detrimental effects is questionable. Even in our highly selected patients with stroke, use of CPAP was poor. At present, CPAP treatment should be advocated for patients with stroke only if they have symptoms of SDB.

Morbidity in nocturnal asthma: sleep quality and daytime cognitive performance.

Most patients with asthma waken with nocturnal asthma from time to time. To assess morbidity in patients with nocturnal asthma nocturnal sleep quality, daytime sleepiness, and daytime cognitive performance were measured prospectively in 12 patients with nocturnal asthma (median age 43 years) and 12 age and intellect matched normal subjects. The median (range) percentage overnight fall in peak expiratory flow rate (PEF) was 22 (15 to 50) in the patients with nocturnal asthma and 4 (-4 to 7) in the normal subjects. The patients with asthma had poorer average scores for subjective sleep quality than the normal subjects (median paired difference 1.1 (95% confidence limits 0.1, 2.3)). Objective overnight sleep quality was also worse in the asthmatic patients, who spent more time awake at night (median difference 51 (95% CL 8.1, 74) minutes), had a longer sleep onset latency (12 (10, 30) minutes), and tended to have less stage 4 (deep) sleep (-33 (-58, 4) minutes). Daytime cognitive performance was worse in the patients with nocturnal asthma, who took a longer time to complete the trail making tests (median difference 62 (22, 75) seconds) and achieved a lower score on the paced serial addition tests (-10 (-24, -3)). Mean daytime sleep latency did not differ significantly between the two groups (2 (-3, 7) minutes). It is concluded that hospital outpatients with stable nocturnal asthma have impaired sleep quality and daytime cognitive performance even when having their usual maintenance asthma treatment.

Bispectral index values and spectral edge frequency at different stages of physiologic sleep.

Bispectral index (BIS) and spectral edge frequency (SEF) are used as measures of depth of anesthesia and sedation. We tested whether these signals could predict physiologic sleep stages, by taking processed electroencephalogram measurements and recording full polysomnography through a night’s sleep in 10 subjects being investigated for mild sleep apnea/hypopnea syndrome. Computerized polysomnograph signals were analyzed manually according to standard criteria, classifying each 30-s epoch as a specific sleep stage. The BIS and SEF values were taken at the end of each period of sleep when the same stage had lasted for at least 2 min. Before sleep, median values for BIS were 97 ± 12.1 and for SEF 23 ± 4.2 Hz. After sleep initiation, the median BIS values for arousal, light, slow wave, and rapid eye movement sleep were 67 ± 20.2, 50 ± 16.5, 42 ± 11.2, and 48 ± 7.1, respectively, and the median SEF values were 20 ± 4.7, 15 ± 3.6, 10 ± 2.6, and 19 ± 4.1 Hz, respectively. Although both BIS and SEF decreased with increasing sleep depth, the distribution of values at each sleep depth was considerable, with overlap between each sleep stage. Neither BIS nor SEF reliably indicated conventionally determined sleep stages. In addition, the response of the BIS was slow and patients could arouse with low BIS values, which then took some time to increase.

Does arousal frequency predict daytime function

Patients with the sleep apnoea/hypopnoea syndrome (SAHS) have impaired daytime function with demonstrable sleepiness and impaired cognition. The hypothesis that brief arousals from sleep cause these daytime impairments was tested. One hundred and fifty patients with sleep disordered breathing were studied prospectively, comparing overnight polysomnography with daytime measures of objective sleepiness, psychological well-being and cognitive performance. Significant, but weak (r2<0.1), relationships were seen between several nocturnal measures (apnoea/hypopnoea index, arousals and desaturation variables) and daytime measures of quality of life, well-being, subjective sleepiness, symptoms and cognitive performance. The only significant relationship between nocturnal variables and objective sleepiness was a very weak correlation (r2<0.05) between the lowest oxygen saturation and mean maintenance of wakefulness test (MWT) result. The MWT was better correlated with daytime function than the multiple sleep latency test. This study shows a lack of strong relationships between conventional nocturnal measures and daytime function in patients with sleep disordered breathing.