C. F. Ryan

Impact of Continuous Positive Airway Pressure Therapy on Blood Pressure in Patients with Obstructive Sleep Apnea Hypopnea: A Meta-analysis of Randomized Controlled Trials

Patients with untreated obstructive sleep apnea hypopnea (OSAH) are predisposed to developing hypertension, and therapy with continuous positive airway pressure (CPAP) may reduce blood pressure (BP). The purpose of this study was to assess the impact of CPAP therapy on BP in patients with OSAH. We performed a comprehensive literature search up to July 2006 [Medline, PubMed, EMBASE, Cochrane Database of Systematic Reviews (CDSR), Cochrane controlled trials register (CCTR), and Database of Abstract and Reviews of Effect (DARE)] to identify clinical studies and systemic reviews that examined the impact of CPAP on BP. Studies were included if they (1) were randomized controlled trials with an appropriate control group, (2) included systolic and diastolic BP measurements before and after CPAP/control in patients with OSAH, and (3) contained adequate data to perform a meta-analysis. To calculate pooled results, studies were weighted by inverse variances, with either a fixed or a random effects model used depending on the presence of heterogeneity (assessed with Q test). Ten studies met our inclusion criteria (587 patients): three studies were crossover (149 patients) and seven were parallel in design. Seven studies (421 patients) used 24-h ambulatory BP and three used one-time measurements. Two studies were of patients with heart failure (41 patients). Overall, the effects of CPAP were modest and not statistically significant; CPAP (compared to control) reduced systolic BP (SBP) by 1.38 mmHg (95% CI: 3.6 to −0.88, pxa0=xa00.23) and diastolic BP (DBP) by 1.52 mmHg (CI: 3.1 to −0.07; pxa0=xa00.06). Six of the trials studied more severe OSAH (mean AHI > 30/h, 313 patients); in these six trials, CPAP reduced SBP by 3.03 mmHg (CI 6.7 to −0.61; pxa0=xa00.10) and DBP by 2.03 mmHg (CI: 4.1 to −0.002; pxa0=xa00.05). There was a trend for SBP reduction to be associated with CPAP compliance. In unselected patients with sleep apnea, CPAP has very modest effects on BP. However, we cannot exclude the possibility that certain subgroups of patients may have more robust responses—this may include patients with more severe OSAH or difficult-to-control hypertension. Future randomized controlled trials in this area should potentially concentrate on these subgroups of patients.

Mandibular advancement oral appliance therapy for obstructive sleep apnoea: effect on awake calibre of the velopharynx

BACKGROUND The mechanisms of action of oral appliance therapy in obstructive sleep apnoea are poorly understood. Videoendoscopy of the upper airway was used during wakefulness to examine whether the changes in pharyngeal dimensions produced by a mandibular advancement oral appliance are related to the improvement in the severity of obstructive sleep apnoea. METHODS Fifteen patients with mild to moderate obstructive sleep apnoea (median (range) apnoea index (AI) 4(0–38)/h, apnoea-hypopnoea index (AHI) 28(9–45)/h) underwent overnight polysomnography and imaging of the upper airway before and after insertion of the oral appliance. Images were obtained in the hypopharynx, oropharynx, and velopharynx at end tidal expiration during quiet nasal breathing in the supine position. The cross sectional area and diameters of the upper airway were measured using image processing software with an intraluminal catheter as a linear calibration. RESULTS AI decreased to a median (range) value of 0 (0–6)/h (p<0.01) and AHI to 8 (1–28)/h (p<0.001) following insertion of the oral appliance. The median (95% confidence interval) cross sectional area of the upper airway increased by 18% (3 to 35) (p<0.02) in the hypopharynx and by 25% (11 to 69) (p<0.005) in the velopharynx, but not significantly in the oropharynx. Although in general the shape of the pharynx did not change following insertion of the oral appliance, the lateral diameter of the velopharynx increased to a greater extent than the anteroposterior diameter. Following insertion of the oral appliance the reduction in AHI was related to the increase in cross sectional area of the velopharynx (p = 0.01). CONCLUSIONS A mandibular advancement oral appliance increases the cross sectional area of the upper airway during wakefulness, particularly in the velopharynx. Assuming this effect on upper airway calibre is not eliminated by sleep, mandibular advancement oral appliances may reduce the severity of obstructive sleep apnoea by maintaining patency of the velopharynx, particularly in its lateral dimension.

Risk and severity of motor vehicle crashes in patients with obstructive sleep apnoea/hypopnoea

Background: Obstructive sleep apnoea/hypopnoea (OSAH) appears to be associated with an increased risk of motor vehicle crashes (MVCs). However, its impact on crash patterns, particularly the severity of crashes, has not been well described. A study was undertaken to determine whether OSAH severity influenced crash severity in patients referred for investigation of suspected sleep-disordered breathing. Methods: Objective crash data (including the nature of crashes) for 783 patients with suspected OSAH for the 3 years prior to polysomnography were obtained from provincial insurance records and compared with data for 783 age- and sex-matched controls. The patient group was 71% male with a mean age of 50 years, a mean apnoea-hypopnoea index (AHI) of 22 events/h and a mean Epworth Sleepiness Scale score of 10. Results: There were 375 crashes in the 3-year period, 252 in patients and 123 in controls. Compared with controls, patients with mild, moderate and severe OSAH had an increased rate of MVCs with relative risks of 2.6 (95% CI 1.7 to 3.9), 1.9 (95% CI 1.2 to 2.8) and 2.0 (95% CI 1.4 to 3.0), respectively. Patients with suspected OSAH and normal polysomnography (AHI 0–5) did not have an increased rate of MVC (relative risk 1.5 (95% CI 0.9 to 2.5), pu200a=u200a0.21). When the impact of OSAH on MVC associated with personal injury was examined, patients with mild, moderate and severe OSAH had a substantially higher rate of MVCs than controls with relative risks of 4.8 (95% CI 1.8 to 12.4), 3.0 (95% CI 1.3 to 7.0) and 4.3 (95% CI 1.8 to 8.9), respectively, whereas patients without OSAH had similar crash rates to controls with a relative risk of 0.6 (95% CI 0.2 to 2.5). Very severe MVCs (head-on collisions or those involving pedestrians or cyclists) were rare, but 80% of these occurred in patients with OSAH (pu200a=u200a0.06). Conclusion: Patients with OSAH have increased rates of MVCs, and disproportionately increased rates of MVCs are associated with personal injury.

The Impact of a Telemedicine Monitoring System on Positive Airway Pressure Adherence in Patients with Obstructive Sleep Apnea: A Randomized Controlled Trial

STUDY OBJECTIVESnFirst-line therapy for patients with moderate to severe obstructive sleep apnea (OSA) is positive airway pressure (PAP). Although PAP is a highly efficacious treatment, adherence to PAP is still a substantial clinical problem. The objective of this study was to determine whether PAP adherence can be improved with a telemedicine monitoring system.nnnDESIGNnA nonblinded, single-center, randomized controlled trial that compared standard PAP treatment versus PAP treatment and a telemedicine monitoring systemnnnSETTINGnUniversity sleep disorders program in British Columbia, CanadannnPATIENTSnAdult patients (≥ 19 yr of age) with moderate to severe OSA (apnea hypopnea index (AHI) ≥ 15 events/hr determined by polysomnography) prescribed PAP INTERVENTIONS: Patients were randomized to either standard care with an autotitrating PAP machine or an autotitrating PAP machine that transmitted physiologic information (i.e., adherence, air leak, residual AHI) daily to a website that could be reviewed. If problems were identified from information from the website, the patient was contacted by telephone as necessary.nnnMEASUREMENTSnPAP adherence after 3 mo, subjective sleep quality, and side effectsnnnRESULTSnSeventy-five patients were enrolled; 39 were randomized to telemedicine and 36 to standard care. The mean age ± standard deviation (SD) was 53.5 ± 11.2 yr, mean AHI was 41.6 ± 22.1 events/hr, and 80% of patients were male. After 3 mo, mean PAP adherence was significantly greater in the telemedicine arm (191 min per day) versus the standard arm (105 min per day; mean difference = 87 min, 95% confidence interval (CI): 25-148 min, P = 0.006, unpaired t test). On days when PAP was used, mean adherence was 321 min in the telemedicine arm and 207 min in the standard arm (difference = 113 min, 95% CI: 62-164 min, P < 0.0001). Significant independent predictors of adherence included age, baseline Epworth Sleepiness Scale score, and use of telemedicine. On average, an additional 67 min of technician time was spent on patients in the telemedicine arm compared with the standard arm (P = 0.0001).nnnCONCLUSIONSnPAP adherence can be improved with the use of a web-based telemedicine system at the initiation of treatment.

Efficacy and patient satisfaction with autoadjusting CPAP with variable expiratory pressure vs standard CPAP: a two-night randomized crossover trial

Expiratory pressure relief (C-Flex) technology monitors the patient’s airflow during expiration and reduces the pressure in response to the patient. Increased comfort levels associated with C-Flex therapy have potential to improve patient adherence to therapy. The purpose of this study was to assess the combination of autoadjusting CPAP (APAP) and C-Flex in terms of (1) treatment efficacy, and (2) patient preference when compared to standard CPAP. Fifteen patients who had previously undergone formal CPAP titration polysomnography were treated with either one night of the APAP with C-Flex or one night of conventional CPAP, in a crossover trial. Patient satisfaction levels were recorded using visual analog scales (VAS) on the morning after the study. Mean patient age was 50u2009±u200912xa0years, body mass index (BMI) was 36u2009±u20096xa0kg/m2, baseline AHI was 53u2009±u200931xa0events/h, and CPAP Pressure was 11u2009±u20092xa0cm/H2O. APAP with C-Flex was as effective as CPAP, with no differences detected in sleep latency (17u2009±u20095 vs 12.3u2009±u20093xa0min, pu2009=u20090.4), or respiratory indices (AHI of 4.2u2009±u20092 vs 2.4u2009±u20090.7xa0events/h, pu2009=u20090.1). VAS scores (scale 0–10) indicated a trend towards increased patient satisfaction while using APAP with C-Flex (7.9 vs 7.2, pu2009=u20090.07). 10 patients expressed a preference for APAP with C-Flex (VAS, 0 to10) over standard CPAP (total positive score of 68, mean score of 4.8u2009±u20094.3). One patient expressed no preference. Four patients expressed a preference for CPAP (total positive score of 13, mean score of 0.9u2009±u20091.9) (APAP with C-Flex vs standard CPAP, pu2009<u20090.01 paired t test). APAP with C-Flex eliminates sleep disordered breathing as effectively as standard CPAP. Patients indicated a preference for APAP with C-Flex suggesting a possible advantage in terms of patient adherence for this mode of treatment.

Energy Expenditure in Obstructive Sleep Apnea

Patients with obstructive sleep apnea (OSA) are often obese and, in common with obese patients generally, find it difficult to lose weight. Obstructive sleep apnea may be associated with changes in total daily energy expenditure that could contribute to obesity and complicate its management. To determine whether resting metabolic rate and the thermogenic effect of food are reduced in OSA, we have compared postabsorptive resting energy expenditure (REE) and dietary thermogenesis (DT) in 14 patients with moderate to severe symptomatic OSA and 14 control subjects matched for obesity. Anthropometrics, body composition analysis using bioelectrical impedance and indirect calorimetry using a metabolic cart and canopy system were performed in all subjects. Dietary thermogenesis after a liquid meal equivalent to 35% of REE was measured in 13 patients and 8 control subjects. Measurements were repeated after chronic (mean +/- SD 12 +/- 5 weeks) nasal continuous positive airway pressure (CPAP) therapy in 10 patients with OSA. Energy expenditure was expressed in terms of metabolic body size. The patients with OSA were heavier and had larger necks and a larger lean body mass (LBM) than controls, but the two groups were well matched for body mass index (BMI) and percent body fat. REE was greater in OSA patients than controls, but when corrected for LBM there was no difference between the two groups (27 +/- 3 vs. 28 +/- 4 kcal/kg). DT was similar in patients and controls (17 +/- 6 vs. 15 +/- 10%). REE/LBM was quite consistent among patients with OSA, regardless of body weight. REE and DT did not change following chronic nasal CPAP therapy. (ABSTRACT TRUNCATED AT 250 WORDS)

Initial use of portable monitoring versus polysomnography to confirm obstructive sleep apnea in symptomatic patients: An economic decision model

BACKGROUNDnWhen using portable (level III and level IV) studies to rule in obstructive sleep apnea (OSA) in symptomatic patients, the pre-test probability (P) needs to be sufficiently high to minimize patients with negative tests who require full polysomnography.nnnMETHODSnWe used a theoretical decision analysis model to assess the pre-test probability above which it would be appropriate to use portable studies to rule in disease in symptomatic patients with suspected OSA. For the base case, we considered a symptomatically sleepy patient referred with a probability of OSA of P. We determined the lower threshold of P appropriate for a clinical algorithm based upon an initial ambulatory study compared to initial diagnosis with PSG by comparing costs using the PSG algorithm with a diagnostic algorithm involving initial assessment with a portable study.nnnRESULTSnIn our base case, the pre-test probability above which portable testing would be less costly than initial diagnostic PSG would be 0.47. When an initial split night study was compared to portable testing, the pre-test probability above which portable testing was more economically attractive was greater (0.68). Values of P, however, varied considerably depending on values of many variables, including costs of diagnostic testing and CPAP compliance.nnnCONCLUSIONSnUsing a decision model, we have developed a theoretical framework to ascertain the pre-test disease probability above which portable studies would be economically attractive as an initial test in the assessment of patients with suspected OSA.

Cost-effectiveness of continuous positive airway pressure therapy in patients with obstructive sleep apnea-hypopnea in British Columbia.

BACKGROUNDnObstructive sleep apnea-hypopnea (OSAH) is a common disorder characterized by recurrent collapse of the upper airway during sleep. Patients experience a reduced quality of life and an increased risk of motor vehicle crashes (MVCs). Continuous positive airway pressure (CPAP), which is the first-line therapy for OSAH, improves sleepiness, vigilance and quality of life.nnnOBJECTIVEnTo assess the cost-effectiveness of CPAP therapy versus no treatment for OSAH patients who are drivers.nnnMETHODSnA Markov decision analytical model with a five-year time horizon was used. The study population consisted of male and female patients, between 30 and 59 years of age, who were newly diagnosed with moderate to severe OSAH. The model evaluated the cost-effectiveness of CPAP therapy in reducing rates of MVCs and improving quality of life. Utility values were obtained from previously published studies. Rates of MVCs under the CPAP and no CPAP scenarios were calculated from Insurance Corporation of British Columbia data and a systematic review of published studies. MVCs, equipment and physician costs were obtained from the British Columbia Medical Association, published cost-of-illness studies and the price lists of established vendors of CPAP equipment in British Columbia. Findings were examined from the perspectives of a third-party payer and society.nnnRESULTSnFrom the third-party payer perspective, CPAP therapy was more effective but more costly than no CPAP (incremental cost-effectiveness ratio [ICER] of

Arnold-Chiari malformation presenting as sleep apnea syndrome.

3,626 per quality-adjusted life year). From the societal perspective, the ICER was similar (

Knowledge-Based Data Analysis: First Step Toward the Creation of Clinical Prediction Rules Using a New Typicality Measure

2,979 per quality-adjusted life year). The ICER was most dependent on preference elicitation method used to obtain utility values, varying almost sixfold under alternative assumptions from the base-case analysis.nnnCONCLUSIONnAfter considering costs and impact on quality of life, as well as the risk of MVCs in individuals with OSAH, CPAP therapy for OSAH patients is a highly efficient use of health care resources. Provincial governments who do not provide funding for CPAP therapy should reconsider.