Angela J. Campbell

Continuous positive airway pressure reduces daytime sleepiness in mild to moderate obstructive sleep apnoea: a meta-analysis

Background: Obstructive sleep apnoea syndrome (OSAS) affects an estimated 2–4% of the middle aged population. Meta-analyses of randomised controlled trials have shown that the severe presentation of the syndrome (apnoea hypopnoea index (AHI) >30/hour) is effectively treated with continuous positive airway pressure (CPAP). Until recently there have been insufficient data to determine whether CPAP improves sleepiness in the larger subgroup with mild to moderate OSAS (AHI 5–30/hour). Methods: A systematic search of Medline and a hand search identified seven randomised controlled trials where CPAP was compared with either a placebo or with conservative management in the treatment of mild to moderate OSAS (AHI 5–30/hour). All trials used the Epworth Sleepiness Scale (ESS), four used the Multiple Sleep Latency Test (MSLT), and three used the Maintenance of Wakefulness Test (MWT) to measure sleepiness. Results: Meta-analyses indicated that CPAP significantly reduced subjective daytime sleepiness (ESS) by 1.2 points (95% CI 0.5 to 1.9, p = 0.001), improved objective daytime wakefulness (MWT) by 2.1 minutes (95% CI 0.5 to 3.7, p = 0.011), but did not affect objective daytime sleepiness (MSLT, mean benefit −0.2 minutes, 95% CI −1.0 to 0.6, p = 0.6). The two significant effects were small (effect size <0.30). Conclusions: CPAP elicits small improvements in subjective sleepiness and objective wakefulness in people with mild to moderate OSAS. However, the effects on sleepiness are of limited clinical significance.

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.

Home set‐up polysomnography in the assessment of suspected obstructive sleep apnea

Home set‐up polysomnography (PSG) has advantages over other portable monitoring devices, but remains unendorsed by professional bodies despite excellent utility in the Sleep Heart Health Study (SHHS). The study aims to determine technical reliability and diagnostic accuracy of unattended, home set‐up versus attended laboratory‐based PSG in patients with suspected obstructive sleep apnea (OSA). Thirty patients with suspected OSA without significant co‐morbidity were recruited. After initial lab‐PSG (Compumedics S series), patients underwent home set‐up PSG (Compumedics Siesta) and lab‐based PSG in random order. Studies were compared for study success, signal loss and likelihood ratio for OSA diagnosis [apnea–hypopnea index (AHI) >10]. Thirty subjects (mean age 49 ± 13.8 years, body mass index 31 ± 6.1 kg m−2) completed investigations. SHHS technical acceptability criteria were met by all lab‐based PSGs and 90% of home‐based PSGs (93% clinically acceptable). Signal loss was higher at home (P = 0.008). Sleep efficiency was similar between sites, but more preferred home‐based PSG (50%). ancova revealed AHI was significantly different if initial AHI >26 per h (P = 0.006), with an average underestimate of 5.1 per h at home. In technically acceptable studies the likelihood ratios to ‘rule in’ and ‘rule out’ OSA were 8.1 and 0.1, respectively. Unattended, home set‐up PSG is technically reliable and achieves excellent diagnostic utility. Signal loss was higher at home but mitigated by multi‐channel redundancy. Success rate was similar to SHHS and superior to laboratory set‐up home studies. Home set‐up PSG is a valid alternative to laboratory‐based PSG for suspected OSA.

Ethnic Disparities in CPAP Adherence in New Zealand: Effects of Socioeconomic Status, Health Literacy and Self-Efficacy

STUDY OBJECTIVES We aimed to investigate the influence of ethnicity on adherence with continuous positive airway pressure (CPAP) in a sample of New Zealand patients. DESIGN Observational study over one month. SETTING A university-based sleep laboratory. PATIENTS 126 consecutively consenting CPAP-naïve patients (19.8% Māori, mean±SD apnea-hypopnea index 57.9 ± 38.9 events/h, CPAP 11.1 ± 3.1 cm H2O). INTERVENTIONS Patients underwent a 4-week supervised home trial of CPAP following pressure titration. MEASUREMENTS AND RESULTS Self-identified ethnicity (Māori/non-Māori), Epworth Sleepiness Scale, Self-Efficacy Measure for Sleep Apnea, Rapid Estimate of Adult Literacy in Medicine, New Zealand Deprivation Index (calculated from residential address), New Zealand Individual Deprivation Index (validated 8-item questionnaire), educational history, income, and employment assessed at baseline were compared to objective CPAP adherence after one month. Māori demonstrated significantly lower usage than non-Māori (median 5.11, interquartile range 2.24 h/night compared with median 5.71, interquartile range 2.61 h/night, P = 0.05). There were no significant relationships between adherence and subjective sleepiness, health literacy, or self-efficacy. In a multivariate logistic regression model incorporating 5 variables (ethnicity, eligibility for government-subsidized healthcare, individual deprivation scores, income, and education), non-completion of tertiary education, and high individual socioeconomic deprivation remained significant independent predictors of average CPAP adherence not reaching ≥ 4 h (odds ratio 0.25, 95% CI 0.08-0.83, P = 0.02; odds ratio 0.10, 95% CI 0.02-0.86, P = 0.04, respectively). The overall model explained approximately 23% of the variance in adherence. CONCLUSIONS The disparity in CPAP adherence demonstrated between Māori and non-Māori can be explained in part by lower education levels and socioeconomic status.

Prone or supine for infants with chronic lung disease at neonatal discharge

Objective:  To determine whether infants with chronic lung disease (CLD), ready for neonatal unit discharge, maintain cardiorespiratory stability while sleeping supine.

Fractal characteristics of breath to breath timing in sleeping infants.

We examined interbreath interval (IBI) time series of 19 term infants during active and quiet sleep for fractal properties using Fano factor analysis. For each time series we calculated the fractal exponent (alpha), comparing alpha for the original time series with two forms of surrogate data, a temporally independent surrogate set and an autoregressive surrogate set. alpha values were normally distributed between 0.79 and -0.22, and did not differ with sleep state. The fractal characteristics of the original time series were not retained in the temporally independent surrogate time series indicating that the distribution of intervals alone was not fractal, but were retained using autoregressive surrogates with an order of 10, suggesting that the fractal properties of the IBI time series were related to correlations between successive breaths. These observations suggest that some of the respiratory variability that occurs during sleep in infants, which in the past has been regarded as stochastic noise, may be the product of deterministic processes.

Responses to an increasing asphyxia in infants: effects of age and sleep state

Infants aged 0-6 months were assessed for respiratory and arousal responses to mild asphyxia during sleep. Ventilatory sensitivity was assessed from the relationship between inspired carbon dioxide (FICO2) and ventilation. Arousal and ventilatory sensitivity were significantly related. Respiratory response increased with age and was greater in quiet sleep than in REM sleep. Arousal occurred more frequently in REM sleep (55/102) than quiet sleep (38/165, P < 0.05) and more frequently at the newborn age (54/117) than at 6 months (13/58, P < 0.05). Arousal in quiet sleep occurred in babies with high ventilatory sensitivities (mean ventilatory asphyxial sensitivity (VAS) 0.476 +/- 0.288) and in REM sleep was more associated with low ventilatory sensitivities (mean VAS 0.194 +/- 0.334, P <0.05). We conclude infants respond to mild asphyxia during sleep with an increase in ventilation, an arousal or both. The exact response is dependent on age and sleep state.

Effect of oxygen versus adaptive pressure support servo-ventilation in patients with central sleep apnoea–Cheyne Stokes respiration and congestive heart failure

Central sleep apnoea with Cheyne‐Stokes respiration (CSA‐CSR) is a common, serious consequence of congestive heart failure. Optimal treatment is yet to be established. We compared two common treatments for CSA‐CSR.

Car seat test for preterm infants: comparison with polysomnography

Objectives: To monitor preterm infants in a cot and a car seat and compare an observed car seat trial with polysomnography (PSG). Design: Non-randomised controlled trial. Setting: Regional neonatal unit. Patients: Preterm infants before discharge. Interventions: Nap PSG respiratory and sleep variables were measured including gastro-oesophageal pH. Nurse observations included respiratory distress, apnoea measured by apnoea alarm, oxygen saturation and heart rate. Infants were studied supine in a cot and then in a car seat. Nursing observations were compared with PSG during the car seat trial only. Criteria for failure of the PSG and observed tests were predefined. Main outcome measures: Difference in respiratory instability between cot and car seat. Concurrence regarding failure of the car seat trial between nurse-observed data and PSG. Results: 20 infants (median gestation 33 weeks (range 28–35 weeks; median postmenstrual age (PMA) at study 36.5 weeks (range 35–38 weeks)) were studied. There were sufficient car seat data on 18 infants for comparison. There were fewer central apnoeas and arousals in the cot than the car seat (p = 0.047 and p = 0.024, respectively). Airway obstruction was not more common in the car seat. Younger PMA at time of study predicted failure in both car seat (p = 0.022) and cot (p = 0.022). The nurse-observed test had low sensitivity for predicting PSG failure but more accurately predicted airway obstruction on PSG. Conclusions: Immature infants exhibit respiratory instability in cots and car seats. A car seat test does not accurately detect all adverse events during sleep in the seat.

Continuous positive airway pressure in heart failure patients with obstructive sleep apnoea.

Background:  The aim of the study was to study the effect of 6 months of continuous positive airway pressure (CPAP) in community heart failure (HF) patients with obstructive sleep apnoea (OSA).