Sham continuous positive airway pressure for placebo-controlled studies in sleep apnoea

Heart failure and sleep apnoea: to sleep perchance to dream

Heart failure and sleep apnoea are major health problems with an increasingly recognized association; evidence suggests that sleep apnoea may play a role in the progression of heart failure. However, confounding factors such as obesity, hypertension and coronary heart disease make this relationship uncertain and an independent correlation remains unproven. Diagnosis of sleep apnoea is suboptimal, as it is often asymptomatic and polysomnography is expensive and time-consuming. A simple and reliable screening protocol is required. All heart failure patients should be considered to be at high risk of sleep apnoea, as this association might be linked to adverse outcome. Continuous positive airway pressure has shown some beneficial effects, but long-term outcome and improvement in survival remains to be demonstrated. Despite recent advances in the understanding of the complex relationship between heart failure and sleep apnoea, there are a number of areas requiring further investigation, which may have important implications for the management and prognosis of a significant number of patients.

Obstructive Sleep Apnea Syndrome Affects Left Ventricular Diastolic Function

Background— The purpose of this study was to determine the role of obstructive sleep apnea syndrome (OSAS) as an independent risk factor for the development of left ventricular diastolic abnormalities. Moreover, we tested the hypothesis that nasal continuous positive airway pressure (nCPAP) improves such alterations in OSAS patients by eliminating apneic events.

Methods and Results— In this prospective, randomized, placebo-controlled, double-blind crossover study, 27 consecutive newly diagnosed middle-aged OSAS men with neither controllable factors nor conditions affecting left ventricular diastolic function and 15 healthy control subjects were selected. OSAS patients were randomized to 12 weeks on sham nCPAP and 12 weeks on effective nCPAP application. Echocardiographic parameters, blood pressure recordings, and urinary catecholamine levels were obtained at baseline and after both treatment modalities. At baseline, an abnormal left ventricular filling pattern was present in 15 of the 27 OSAS patients and only in 3 of the 15 control subjects ( P =0.020). Impaired relaxation was by far the most common abnormal pattern in both groups (11 and 3 patients, respectively). In OSAS patients, 12 weeks on effective nCPAP induced a significant increase in E/A ratio ( P <0.01), as well as reductions in mitral deceleration ( P <0.01) and isovolumic relaxation ( P <0.05) times.

Conclusions— OSAS can affect left ventricular diastolic function independently of other possible factors. Chronic application of nCPAP could avoid the progression of diastolic abnormalities, and indeed, it might reverse these alterations, at least in the initial stages before severe structural changes can be developed.

Randomised controlled crossover trial of humidified continuous positive airway pressure in mild obstructive sleep apnoea

BACKGROUND

It is unclear whether continuous positive airway pressure (CPAP), the treatment of choice for severe obstructive sleep apnoea (OSA), is effective at improving outcomes in mild OSA.

METHODS

To help define the role of humidified CPAP in mild OSA, a randomised crossover study was undertaken of patients with an apnoea hypopnoea index (AHI) of 5-30/hour. Subjective sleepiness, objective wakefulness, mood, reaction time, and quality of life were measured at baseline, after 3 weeks treatment with humidified CPAP and 3 weeks sham CPAP (2 week washout).

RESULTS

Twenty nine of 31 enrolled patients (age 25-67 years, seven women, mean (SD) body mass index 31.5 (6) kg/m2) completed the protocol. Humidified CPAP improved polysomnographic indices of OSA and Epworth Sleepiness Scale (2.4 points (95% CI 0.6 to 4.2)). Objective wakefulness (modified maintenance of wakefulness test) showed a trend towards improvement (5.2 minutes (95% CI -0.6 to 11)). Mood (Hospital Anxiety and Depression Scale), quality of life (SF 36, Functional Outcomes of Sleep Questionnaire), and reaction times (Psychomotor Vigilance Task) were not improved more than sham CPAP. Compliance with humidified and sham CPAP both averaged 4.9 hours/night. Placebo effects were evident in many outcomes and there was no clear treatment preference.

CONCLUSIONS

Humidified CPAP improves subjective sleepiness and possibly objective wakefulness but not reaction times, quality of life, or mood. These results do not support the routine use of CPAP in all patients with mild OSA, but offers some support for the trialling of CPAP in those with severe sleepiness.

Long-term cardiovascular outcomes in men with obstructive sleep apnoea-hypopnoea with or without treatment with continuous positive airway pressure: an observational study

BACKGROUND

The effect of obstructive sleep apnoea-hypopnoea as a cardiovascular risk factor and the potential protective effect of its treatment with continuous positive airway pressure (CPAP) is unclear. We did an observational study to compare incidence of fatal and non-fatal cardiovascular events in simple snorers, patients with untreated obstructive sleep apnoea-hypopnoea, patients treated with CPAP, and healthy men recruited from the general population.

METHODS

We recruited men with obstructive sleep apnoea-hypopnoea or simple snorers from a sleep clinic, and a population-based sample of healthy men, matched for age and body-mass index with the patients with untreated severe obstructive sleep apnoea-hypopnoea. The presence and severity of the disorder was determined with full polysomnography, and the apnoea-hypopnoea index (AHI) was calculated as the average number of apnoeas and hypopnoeas per hour of sleep. Participants were followed-up at least once per year for a mean of 10.1 years (SD 1.6) and CPAP compliance was checked with the built-in meter. Endpoints were fatal cardiovascular events (death from myocardial infarction or stroke) and non-fatal cardiovascular events (non-fatal myocardial infarction, non-fatal stroke, coronary artery bypass surgery, and percutaneous transluminal coronary angiography).

FINDINGS

264 healthy men, 377 simple snorers, 403 with untreated mild-moderate obstructive sleep apnoea-hypopnoea, 235 with untreated severe disease, and 372 with the disease and treated with CPAP were included in the analysis. Patients with untreated severe disease had a higher incidence of fatal cardiovascular events (1.06 per 100 person-years) and non-fatal cardiovascular events (2.13 per 100 person-years) than did untreated patients with mild-moderate disease (0.55, p=0.02 and 0.89, p<0.0001), simple snorers (0.34, p=0.0006 and 0.58, p<0.0001), patients treated with CPAP (0.35, p=0.0008 and 0.64, p<0.0001), and healthy participants (0.3, p=0.0012 and 0.45, p<0.0001). Multivariate analysis, adjusted for potential confounders, showed that untreated severe obstructive sleep apnoea-hypopnoea significantly increased the risk of fatal (odds ratio 2.87, 95%CI 1.17-7.51) and non-fatal (3.17, 1.12-7.51) cardiovascular events compared with healthy participants.

INTERPRETATION

In men, severe obstructive sleep apnoea-hypopnoea significantly increases the risk of fatal and non-fatal cardiovascular events. CPAP treatment reduces this risk.

Effectiveness of CPAP treatment in daytime function in sleep apnea syndrome: a randomized controlled study with an optimized placebo

Application of continuous positive airway pressure (CPAP) as the standard treatment for sleep apnea/hypopnea syndrome (SAHS) is a moot point. Studies on the effectiveness of this treatment have been challenged because of the lack of a suitable placebo. The recent description of a true placebo (sham CPAP) prompted us to conduct a randomized trial of CPAP or placebo to assess the effectiveness of CPAP in improving SAHS-related symptoms and daytime function in patients with moderate to severe SAHS. Forty-eight patients, stratified in four groups according to severity, were randomly allocated into two treatment groups (optimal and sham CPAP) for a 6-wk period. Of these, 45 completed follow-up (91% males; age: 54 +/- 10 yr; body mass index [BMI]: 32 +/- 6 kg/m(2); apnea-hypopnea index [AHI]: 54 +/- 19 events/h; and Epworth Sleepiness Scale [ESS]: 16 +/- 5). The ESS, a questionnaire on SAHS-related symptoms, Functional Outcomes Sleep Questionnaire (FOSQ), and the Short Form Health Survey (SF-36) were completed at inclusion and after treatment. After 10 d of washout, the placebo group was treated with optimal CPAP and reassessed before and after optimal CPAP. The group receiving optimal CPAP when compared with the group with sham CPAP showed considerably greater improvement in the relief of sleepiness (-9.5 versus -2.3, p < 0.001), other SAHS-related symptoms (-18.5 versus -4.5, p < 0.001), vigilance (+8.5 versus +3.4, p = 0.009), and general productivity (+4.0 versus +0.5, p = 0.04) FOSQ scales. Both groups used a similar number of hours for the optimal and the sham CPAP (4.3 versus 4.5, (p = NS). The patients initially treated with placebo CPAP improved significantly more when optimal CPAP was applied for ESS (-2.3 versus -6.7, p < 0.001) and other sleep apnea syndrome (SAS)-related symptoms (-4.5 versus -11.2, p = 0.02). Our study provides strong evidence of the effectiveness of CPAP treatment in improving symptoms and perceived health status in moderate to severe SAHS.

Neuropsychological effects of one-week continuous positive airway pressure treatment in patients with obstructive sleep apnea: a placebo-controlled study

OBJECTIVE

To determine whether 1-week continuous positive airway pressure (CPAP) treatment, compared with placebo CPAP, improves cognitive functioning in patients with obstructive sleep apnea (OSA).

METHODS

36 OSA patients (aged 32-60 years, respiratory disturbance index [RDI] > 15) were monitored 2 nights with polysomnography, then randomized for 1-week treatment to CPAP or placebo (CPAP at 2 cm H2O with holes in mask). Participants completed Wechsler Adult Intelligence Scale-Revised Digit Symbol and Digit Span, Trailmaking A/B, Digit Vigilance, Stroop Color-Word, Digit Ordering, and Word Fluency tests pre- and posttreatment. These produced 22 scores per participant, which were analyzed by use of repeated-measures analysis of variance (ANOVA) and a rank-sum test.

RESULTS

In ANOVA, only 1 of the 22 scores showed significant changes specific to CPAP treatment, a number that could be expected by chance alone: Digit Vigilance-Time (p = .035). The CPAP group improved their time (from 7.5 to 6.9 minutes. p = .013). The rank-sum test revealed that the CPAP group had significantly better overall cognitive functioning posttreatment than the placebo group (mean ranks of 17.8 vs. 20.2, respectively; p = .022).

CONCLUSIONS

Although results suggest overall cognitive improvement due to CPAP, no beneficial effects in any specific cognitive domain were found. Future studies of neuropsychological effects of CPAP treatment should include a placebo CPAP control group. Placebo studies that use longer-term treatment might demonstrate additional effects. It is also possible that, even at 2 cm H2O, CPAP conveys some beneficial neuropsychological effects.

Effect of nasal continuous positive airway pressure on neuropsychological function in sleep apnea-hypopnea syndrome. A randomized, placebo-controlled trial

A placebo-controlled, partial cross-over, double-blind, randomized study was performed with 46 adults with sleep apnea-hypopnea syndrome (SAHS) to determine the effect of therapeutic and subtherapeutic (0-1 cm H(2)O) nasal continuous positive airway pressure (CPAP) treatment on polysomnographic and neuropsychological testing. The following neuropsychological tests were administered: Geriatric Depression Scale, Trail Making A and B, Digit Span Test Forward and Backward, Epworth Sleepiness Scale, SteerClear, Digit Symbol, Controlled Oral Word Association, and Complex Figure Recall. Compared with results without CPAP, subtherapeutic CPAP did not affect any measured polysomnographic parameter. Comparison of neuropsychological test results obtained between the initial periods of effective treatment (Group 1, 16.1 d; Group 2, 19.6 d; p = NS) in all subjects showed significant improvements in Digit Symbol, Digit Span Backward, and Complex Figure tests. However, there were no group differences in changes in test results during the period when one group was on effective CPAP and the other on ineffective CPAP (Group 1, 16.1 d; Group 2, 13.9 d; p = NS). The results indicate the feasibility and importance of using ineffective CPAP as a placebo treatment and the importance of including a placebo control in studies evaluating the effect of treatment on neuropsychological function in SAHS.

Randomised prospective parallel trial of therapeutic versus subtherapeutic nasal continuous positive airway pressure on simulated steering performance in patients with obstructive sleep apnoea

BACKGROUND

Obstructive sleep apnoea (OSA) impairs vigilance and may lead to an increased rate of driving accidents. In uncontrolled studies accident rates and simulated steering performance improve following treatment with nasal continuous positive airway pressure (NCPAP). This study seeks to confirm the improvement in steering performance in a randomised controlled trial using subtherapeutic NCPAP as a control treatment.

METHODS

Fifty nine men with OSA (Epworth Sleepiness Score (ESS) of > or =10, and > or =10/h dips in SaO(2) of >4% due to OSA) received therapeutic or subtherapeutic NCPAP ( approximately 1 cm H(2)O) for one month. Simulated steering performance over three 30-minute "drives" was quantified as: standard deviation (SD) of road position, deterioration in SD across the drive, length of drive before "crashing", and number of off-road events. The reaction times to peripheral target stimuli during the drive were also measured.

RESULTS

Subtherapeutic NCPAP did not improve overnight >4% SaO(2) dips/h compared with baseline values, thus acting as a control. The SD of the steering position improved from 0.36 to 0.21 on therapeutic NCPAP, and from 0.35 to 0.30 on subtherapeutic NCPAP (p = 0.03). Deterioration in SD of the steering position improved from 0.18 to 0.06 SD/h with therapeutic NCPAP and worsened from 0.18 to 0.24 with subtherapeutic NCPAP (p = 0.04). The reaction time to target stimuli was quicker after therapeutic than after subtherapeutic NCPAP (2.3 versus 2.7 seconds, p = 0.04).

CONCLUSIONS

Therapeutic NCPAP improves steering performance and reaction time to target stimuli in patients with OSA, lending further support to the hypothesis that OSA impairs driving, increases driving accident rates, and that these improve following treatment with NCPAP.