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Ambulatory Management Strategies for Obstructive Sleep Apnea Ching Li Chai-Coetzer, MBBS, FRACP, GCPH, PhD1,2 Nick A. Antic, MBBS, FRACP, PhD1,2 1 Adelaide Institute for Sleep Health, Repatriation General Hospital,
Daw Park, SA, Australia 2 Flinders University, Bedford Park, SA, Australia
Vinod Aiyappan, MBBS, MD, MRCP, FRACP1,2
Address for correspondence Ching Li Chai-Coetzer, MBBS, FRACP, GCPH, PhD, Adelaide Institute for Sleep Health, Repatriation General Hospital, Daws Road, Daw Park, SA 5041, Australia (e-mail: [email protected]).
Abstract
Keywords
► obstructive sleep apnea ► polysomnography ► ambulatory model ► portable monitoring ► home diagnosis ► screening questionnaires ► autotitrating continuous positive airway pressure
The prevalence of obstructive sleep apnea (OSA) has been steadily rising over recent decades and patient access to laboratory-based sleep services and specialist consultations have become increasingly limited, resulting in potential delays in treatment. As a result, there has been growing interest in the use of non-sleep laboratory methods for diagnosing and managing OSA, including the use of screening questionnaires, portable sleep monitoring devices, and home autotitrating continuous positive airway pressure. There is also evidence in support of a role for alternative health care professionals, such as sleep-trained nurses and primary care physicians in the diagnosis and treatment of OSA. In this review, we compare the different types of home monitoring devices, discuss the limitations of portable monitoring compared with full laboratory polysomnography, and summarize the results from published comparative effectiveness studies which have evaluated ambulatory models of care for the management of OSA. We also consider how future models of care that may be needed to deal with the burden of disease will evolve and some of the issues that prevent the translation of such models of care in many countries.
Obstructive sleep apnea (OSA) is characterized by recurrent occlusion of the upper airway during sleep and is associated with repetitive oxygen desaturations, frequent arousals, and complaints of excessive daytime sleepiness. Symptomatic OSA was estimated to affect 2 to 4% of middle-aged adults in the early 1990s.1 However, since this time, there has been a dramatic increase in obesity rates worldwide2 and as a result the prevalence of OSA has risen in parallel, with more recent studies reporting moderate-to-severe disease in at least 15% of middle-aged adults.3 Untreated OSA has been associated with several adverse health consequences, including motor vehicle accidents,4,5 hypertension,6 and cardiovascular disease,7,8 with the risks of disease being minimized by the use of effective therapies, such as continuous positive airway pressure (CPAP)9–11 and mandibular advancement splints.12–14 Laboratory-based polysomnography (PSG) is the current gold standard for the diagnosis of OSA and for the determi-
Issue Theme Clinical Consequences and Management of Sleep Disordered Breathing; Guest Editors, Ravi Aysola, MD, and Teofilo L. Lee-Chiong Jr., MD
nation of appropriate CPAP therapy pressure settings. However, patient access to laboratory-based sleep studies and/or sleep physician consultations can be limited, with some centers reporting extensive waiting times for sleep services.15 Furthermore, laboratory PSG requires overnight attendance and monitoring by sleep technician staff, which can be expensive, labor intensive, and time consuming. As a result, in recent years there has been growing interest in homebased sleep monitoring for the identification and treatment of OSA, including the use of devices with limited recording channels and automatically titrating CPAP. The results of several comparative effectiveness studies evaluating ambulatory models of care for OSA compared with usual laboratory-based management have now been published, including studies which have involved alternative health care providers in disease management such as specialist sleep-trained nurses and primary care physicians
Copyright © 2014 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.
DOI http://dx.doi.org/ 10.1055/s-0034-1390139. ISSN 1069-3424.
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Semin Respir Crit Care Med 2014;35:545–551.
Ambulatory Management Strategies for Obstructive Sleep Apnea (PCPs). In this article, we discuss non-sleep laboratory strategies for the diagnosis and treatment of OSA and review the results of randomized, controlled studies which have assessed the clinical efficacy and cost-effectiveness of ambulatory care models versus laboratory-based management.
Portable Monitoring There are four levels of sleep studies, as classified by the American Academy of Sleep Medicine (AASM), based on the number of parameters recorded and the presence or absence of an attending technician. Type 1: Standard in-laboratory PSG with a technician in attendance, at least seven recording channels and body position sensor. This is considered the gold standard to which the other types of studies are compared. Type 2: Comprehensive, unattended, portable PSG with at least seven recording channels and optional body position sensor. This is the most common type of ambulatory diagnostic study conducted by tertiary sleep units. Type 3: Portable sleep study with at least four recording channels (ECG, oxygen saturation monitor, two channels for airflow and/or respiratory movements). Type 4: Continuous recording of one or two signals (usually oxygen saturation monitor and airflow). Types 2, 3, and 4 represent the different portable diagnostic devices available for the investigation of OSA. Portable tests were developed as an alternative to the laboratorybased PSG, with the aim of reducing costs and improving patient access to diagnostic sleep services; however, their initial use was limited due to lack of data regarding efficacy. With time, these devices have gained wider acceptance and multiple studies have now been published which support their role in the diagnosis of OSA. In 2007, the AASM published new guidelines regarding the use of portable devices for the diagnosis and management of OSA.16 These guidelines are specifically aimed at Type 3 devices, as they are the ones most commonly used for this purpose. These guidelines suggest the following: • Portable monitoring (PM) can be used in the place of laboratory PSG for the diagnosis of OSA for patients with a high pretest probability for OSA. • PM should be used only in conjunction with comprehensive sleep evaluation. • PM should not be used for screening. • PM is not recommended in patients with comorbid diseases (COPD, CHF, neuromuscular disease, etc.) or when other sleep disorders (central sleep apnea, periodic limb movement disorder, narcolepsy, circadian rhythm disorder, etc.) are suspected. • PM may be used in patients who cannot attend laboratory PSG (immobility, critical illness, etc.) and for monitoring response to non-CPAP treatment (surgery, weight loss, MAS, etc.). With the increasing prevalence of OSA and rapid advancements in technology, newer portable devices are flooding the market with considerable differences in the number and type Seminars in Respiratory and Critical Care Medicine
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of monitoring channels. In this setting, Collop et al have developed an alternate classification for the portable devices.17 This system categorizes portable devices based on measurements of sleep, cardiovascular, oximetry, position, effort, and respiratory (SCOPER) parameters. This classification does not include devices that did not have an oximetry channel. The PM devices are judged on whether the PM has a positive likelihood ratio of at least 5 and a sensitivity of at least 82.5% (coinciding with an in-laboratory polysomnography generated apnea–hypopnea index [AHI] 5/hour).
Advantages and Disadvantages of Portable Monitoring Although laboratory-based, full PSG (Type 1 study) is considered the gold standard test to which portable devices are compared, this is by no means the perfect investigation. There are different schools of thought regarding the appropriate cutoff points for defining the diagnosis and severity of OSA. It has also been shown that there could be significant differences in the AHI,18 based on the criteria used for scoring (1994 AASM Chicago criteria vs. 2007 AASM recommended and alternate criteria). Even with Type 1 studies, there could be night-to-night variability in AHI19 and inter- and intrascorer variability.20 Laboratory PSG is also considerably expensive and labor intensive. Patients are required to sleep in a foreign environment, which can potentially cause sleep fragmentation and poor sleep quality, and the sleep sample studied may not be representative of the patient’s normal sleep in their usual environment. Laboratory PSG has the advantage of being performed in a controlled setting, with ability to intervene if necessary (lead displacement, medical emergency, etc.). The laboratory PSG also enables us to couple the study with video monitoring (e.g., for detection of parasomnias, nocturnal epilepsy) and transcutaneous CO2 measurements (e.g., in sleep hypoventilation). It is also an important tool for the investigation of hypersomnolence states (e.g., before a multiple sleep latency test or maintenance of wakefulness test). Type 2 PM devices are often used as an alternative to laboratory PSG, as they provide most of the data that can be obtained from laboratory PSG21 while sampling the patients’ sleep in their normal surroundings. Upfront costs are also less expensive than with an attended, laboratory PSG.22 However, this type of PM tends to overestimate mild-to-moderate OSA and underestimate severe OSA.23 There is also a failure rate of up to 20%, due to loss of data.24 Real-time telemonitoring of unattended PSGs has been shown to reduce the failure rates albeit with higher costs.25 With the advent of cheaper telemonitoring services, this could emerge as a real contender for laboratory-based PSG. Type 3 devices are the most commonly used PM and the 2007 AASM guidelines16 (as discussed earlier) are specifically aimed at this group of devices. These devices have high sensitivity and specificity when used in patients with a high pretest probability for moderate-to-severe OSA.26 Type 4 devices usually measure oximetry and/or airflow. Although the 2007 AASM guidelines concluded that there was insufficient evidence in support of the use of Type 4 PM in the diagnosis of OSA, emerging studies suggest that they could be
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useful in improving the management of OSA in the community if used in appropriately selected patients with a high pretest probability of disease detected by a screening questionnaire.27 Type 3 and 4 devices measure the events per hour of recording rather than per hour of sleep and hence can potentially underestimate the severity of OSA if there are prolonged periods of wakefulness at night. There is also the issue of data loss. The usefulness of these devices in people with other comorbidities is unclear, as the studies have shown mixed results.28–30
The Role of Screening Questionnaires Several screening questionnaires have been developed to identify patients with OSA. These questionnaires have been developed from samples of patients with suspected OSA, who have had diagnostic tests and use anthropometric measurements and/or symptoms to predict the probability of the disease. The Berlin Questionnaire uses body mass index (BMI), the presence/absence of hypertension, and symptoms (snoring, witnessed apneas, and fatigue/sleepiness) and has been validated in primary care, with the ability to identify patients with OSA (AHI > 5) with a sensitivity of 86% and specificity of 77%.31 The STOP-BANG Questionnaire was developed and validated in preoperative clinics and uses eight different variables (snoring, tiredness, witnessed apneas, blood pressure, BMI, age, and neck circumference) to predict the probability of OSA (sensitivities for AHI greater than 5, greater than 15, and greater than 30 as cutoffs were 83.6, 92.9, and 100%, respectively).32 We have recently developed and validated a simple 4-item screening tool for OSA in primary care setting. This tool (OSA50 Questionnaire) uses obesity (waist circumference), troublesome snoring, witnessed apneas, and age 50 and has high sensitivity for detection of moderate-to-severe OSA.27 The screening questionnaires are very important to risk stratify patients and are helpful tools in the diagnostic pathway. They are an inherent part of PM to identify patients with high probability for OSA, as recommended by the AASM. But the current available tools are very heterogeneous and the results are inconsistent.33,34 Hence, there is a need for a standardized screening tool to allow greater comparability between various studies. The screening questionnaires used with the appropriate diagnostic algorithm are useful in the management of patients with OSA, but cannot replace the existing diagnostic tests, due to their poor specificity.
Autotitrating Continuous Positive Airway Pressure In-laboratory CPAP titration is the current standard for initiating CPAP treatment in patients with OSA. With the advent of smarter machines, autotitrating CPAP (APAP) devices which can detect changes in the upper airway that might lead to airway collapse and adjust pressure delivery accordingly have been developed. These devices use various types of sensors and algorithms to calculate the appropriate therapeutic pressure. In general, these devices measure snor-
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ing, flow limitation, hypopneas/apneas, or impedance with forced oscillatory techniques. Devices using flow-based algorithms have been shown to be superior to devices using a forced oscillation technique.35 As upper airway resistance is dynamic and can change from night to night depending on body position, sleep stage, use of alcohol/sedatives, etc., it is likely that the therapeutic CPAP is prone to night-to-night variability. Theoretically APAP devices can, by automatically adjusting the pressure, deliver the most appropriate therapeutic pressure. Although previous studies have shown that the compliance to treatment is similar in APAP and fixed CPAP users, a recent meta-analysis has suggested that compliance is significantly better with APAP when compared with fixed CPAP.36 Studies have shown that APAP is noninferior to standard CPAP in the control of sleep disordered breathing, and symptom improvement.37–39 Based on current data, the AASM guidelines have recommended that APAP devices can be used to initiate and continue treatment for patients with moderate-to-severe OSA without comorbidities.40 The use of APAP has been shown to result in cost savings by eliminating the need for laboratory-based PSG.41 However, these devices are more expensive than standard, fixed pressure devices. APAP devices can potentially deliver inappropriately high pressures in patients with central sleep apnea, but a recent study has shown that this can be avoided by incorporating an obstructive pressure peak signal into the algorithm.42 Although there have been reports showing good correlation between AHI measured by APAP devices and PSG,43 the 2007 AASM practice guidelines do not recommend the use of APAP devices for the diagnosis of OSA. APAP titration and treatment is not recommended in patients with CHF, COPD, obesity hypoventilation syndrome, and central apneas.40 Although APAP devices have been shown to have comparable outcomes in improving OSA symptoms, their long-term impact on cardiovascular outcomes are unclear.
Ambulatory Models of Care for Obstructive Sleep Apnea There is a growing body of literature reporting on the clinical effectiveness of ambulatory care models for the management of OSA, involving the use of screening questionnaires, portable sleep monitoring, and/or autotitrating CPAP. Recently, these models of care have also involved health care professionals other than sleep specialists as the principal providers of care for OSA patients, including sleep-trained nurses and PCPs. The first randomized, controlled study to evaluate an ambulatory approach to the management of OSA was conducted by Canadian investigators Mulgrew et al,44 with results published in 2007. In their study, a total of 68 patients who were found to have a high pretest probability of moderate-to-severe OSA based on an Epworth Sleepiness Scale (ESS) score 10, Sleep Apnea Clinical Score 15, and respiratory disturbance index (RDI) 15/hour on overnight oximetry were randomly allocated to either laboratory-based PSG and CPAP titration or home autotitrating CPAP and overnight Seminars in Respiratory and Critical Care Medicine
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Ambulatory Management Strategies for Obstructive Sleep Apnea
Ambulatory Management Strategies for Obstructive Sleep Apnea oximetry. After 3 months of follow-up, they found no difference in their primary outcome, the residual AHI on CPAP (median difference, 0.8/hour; 95% confidence interval [CI], 0.9–2.3; p ¼ 0.31), and no differences in the change in ESS or Sleep Apnea Quality of Life Index (SAQLI) from baseline. Interestingly, CPAP adherence was found to be greater in the ambulatory management arm (difference, 1.12 hour/ night; 95% CI, 0.2–2.0; p ¼ 0.021). A similar study was conducted by Berry et al45 involving 106 U.S. Veterans who had presented to a sleep center with an ESS 12 and reported at least 2 of the following: loud snoring, witnessed apneas or gasping, and/or treatment for hypertension. Patients with significant cardiac failure or respiratory disease, an uncontrolled psychiatric disorder, or who had previously undergone a diagnostic sleep study or received treatment for OSA were excluded from enrolment. Participants were randomized to either portable, level 3 monitoring (WatchPAT 100) and APAP titration or laboratory-based PSG and CPAP titration, with follow-up for a total of 6 weeks. Study investigators found no difference in average nightly CPAP use (portable arm 5.20 SEM 0.28 hour/night vs. PSG arm 5.25 0.38 hour/night), change in ESS or Functional Outcomes of Sleep Questionnaire (FOSQ) scores, CPAP satisfaction, or residual AHI on CPAP. Kuna et al46 conducted a randomized controlled study involving a group of 296 U.S. Veterans and compared portable home testing using a level 3 monitor and APAP titration to set a fixed CPAP pressure with standard, laboratory-based PSG and CPAP titration for the management of OSA. Compared with other published studies, their inclusion criteria were reported to be less restrictive, with all new patients referred for investigation of suspected OSA being potentially eligible to participate. After 3 months of follow-up, the mean change in FOSQ score for the home testing arm was not inferior to the laboratory testing arm (difference, 0.004 [lower bound 95% CI, 0.54]; noninferiority margin, 1.0). Mean CPAP use was also not clinically inferior in the home testing group (difference, 0.55 hour/night [lower bound 95% CI, 0.03]; noninferior margin, 0.75 hour/night), and there was no difference between groups in the change in ESS, psychomotor vigilance task results, Short Form-12 (SF-12), or Center for Epidemiological Studies Depression Scale (CES-D) scores. The results of a study involving 66 patients were reported by Andreu et al47 whereby patients were randomized to one of three groups: (1) home level 3 monitoring and home follow-up; (2) hospital PSG and hospital follow-up; and (3) home level 3 monitoring and hospital follow-up. After 6 months of follow-up, study investigators found no differences between groups in CPAP compliance, ESS, and FOSQ scores, although it is possible due to the small sample size that the study may have been underpowered to detect such differences. Within-trial costs for the hospital PSG and follow-up arm were significantly higher (€849 11) than home testing and follow-up (€590 43) and home testing and hospital follow-up (€644 93). Another study comparing home-based, level 3 testing and APAP titration with attended, laboratory-based management of OSA was published by Rosen et al,48 involving seven Seminars in Respiratory and Critical Care Medicine
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academic sleep centers across the United States. In their study, which included a total of 373 randomized patients, there was no difference in CPAP prescription acceptance rates (94% in the laboratory arm vs. 93% in the home arm, p ¼ 1.0). Similar to the findings of Mulgrew et al,44 CPAP adherence was significantly higher in the home-based arm after 3 months of follow-up, with a difference in average nightly use of 62 minutes (95% CI, 15–108 minutes; p ¼ 0.01). No differences were found between the groups for the change in ESS, FOSQ, SAQLI, or SF-36 vitality subscale scores at 3 months. Their study also included a comparison of within-trial costs, with the results demonstrating that home-based management (US$139,148.48) was 25% less expensive than laboratorybased management (US$186,109.50).
Role of Health Care Professionals Other Than Sleep Physicians In addition to the use of more simplified, non–laboratorybased methods for diagnosing OSA and undertaking CPAP titration, novel models of care have been proposed which involve health care professionals other than sleep physicians as the principal care provider of patients with OSA, including sleep-trained nurses and PCPs. In collaboration with two other Australian sleep centers, we conducted the first randomized controlled trial evaluating a nurse-led, ambulatory model of care for OSA compared with specialist-led, laboratory-based management.49 A total of 195 patients who were confirmed as having moderate-to-severe OSA based on the results of overnight oximetry (> 2% oxygen dip rate > 27/hour) were randomly assigned management by a specialist sleep-trained nurse and home APAP titration, or to standard care by a sleep physician with laboratory-based, full PSG testing and CPAP titration, for a total of 3 months follow-up. The mean change in ESS for the nurse-led group was clinically noninferior to specialist-led management (difference, 0.13 [95% CI, 1.52 to 1.25]; noninferior margin, 2.0), and there was no difference between groups in the change in FOSQ or SF-36 scores, CPAP use, neurocognitive function, or Maintenance of Wakefulness Test results at the conclusion of the trial. Patient satisfaction was higher for nurse-led management for four out of nine components of the Visit-specific Satisfaction Questionnaire (VSQ-9). Furthermore, the analysis of within-trial costs revealed that nurseled management was AUD $1,111 (95% CI $1,084–$1,137) per patient less expensive than specialist-led care.
Primary Care Management of Obstructive Sleep Apnea The promising results of this study led us to consider a potential role for PCPs and their practice nurses in the diagnosis and management of OSA. Using a validated, twostep diagnostic strategy of OSA50 screening questionnaire (score 5/10) and home oximetry ( 3% oxygen desaturation index 16/hour),27 PCPs identified a total of 155 patients with moderate-to-severe OSA and daytime sleepiness (ESS 8) who were randomly assigned to either ongoing ambulatory management by their PCP and a communitybased nurse or to usual laboratory-based care by a sleep
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Ambulatory Management Strategies for Obstructive Sleep Apnea
Limitations of Randomized Controlled Trials Although the results of randomized controlled trials evaluating ambulatory care models for OSA have generally shown comparable or noninferior outcomes to specialist care, it is important to be mindful of the strict selection criteria used in these studies. With the exception of the study by Kuna et al46 which reported to have had less restrictive criteria, patients were excluded from the study if they had medical comorbidities such as cardiovascular disease, heart failure, COPD, neuromuscular disease, and other causes of respiratory failure, psychiatric conditions, or if they were suspected to have a sleep disorder other than OSA. Therefore, study results cannot be generalized to these populations. In addition, participants had a high pretest probability of OSA and PM strategies have been aimed at identifying those with moderate-to-severe OSA. Thus, further research on the effectiveness of ambulatory management strategies is required in patients with milder degrees of OSA and those with medical comorbidities. There has been considerable debate regarding the costeffectiveness of ambulatory diagnostic and management approaches for OSA. Although previous randomized controlled trials have reported cost savings for ambulatory care models compared with usual laboratory-based care,47–50 their results have included calculations for up-front, within-trial costs only and have not factored in the long-term financial implications of potential misdiagnosis when conducting PM. A more detailed economic analysis was conducted by Pietzsch et al51 using a Markov model which compared the cost-effectiveness of full PSG, split night PSG, and unattended, portable home monitoring. Their results revealed that although up-front costs were higher, use of full PSG was cheaper than both split night PSG and portable home monitoring over the longer term because of its superior diagnostic accuracy. However, criticism has been made of the assumptions used in their model which may have magnified the impact of false-positive and false-negative results,52 including the assumption that the risk of cardiovascular disease would be dramatically reduced by CPAP use which
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is yet to be substantiated by randomized controlled trial evidence, and that patients with a false-positive home monitoring result would comply with CPAP to the same extent as those correctly diagnosed. Thus, the overall cost-effectiveness of ambulatory management strategies for OSA is currently unclear, and further research into this area is needed.
The Future In some countries, most notably in the United States, some of these ambulatory models of care have become the preferred first way to approach diagnosis and treatment of OSA. This evolution of clinical care had been dictated by funding models in most cases. The sleep laboratory still has an integral role in the diagnosis and management of OSA. The role of the laboratory is changing, but ambulatory models struggle to deal with complicated sleep disordered breathing patients including those in respiratory failure. Furthermore, as there is wider adoption of these ambulatory models of care and likely more patients diagnosed with OSA, there are patients who have either insufficient information on their diagnostic tests or do not respond to treatment as predicted that will need to be tested in the sleep laboratory conditions to understand the reasons why their treatment is not effective. It is possible that they may have other sleep disorders, insufficient CPAP pressure to overcome upper airway obstruction, or sleep hypoventilation. If other health professionals are to take an increasing lead in the diagnosis and management of uncomplicated OSA, it is mandatory that they have sufficient training to care for such patients. Robust training programs exist for sleep physicians but will need to be developed for other health professionals. Furthermore, it remains to be seen if there are sufficient primary care physicians or specialist nurses with a willingness to pursue further training and make a meaningful difference to the number of skilled health professionals to deal with OSA. They also need to work in an environment where they have support of a sleep laboratory and sleep physicians for advice, laboratory testing, or clinical review when needed, that is, a hub and spoke clinical model. A stepped care model where uncomplicated OSA is managed in such a way with sleep laboratory services for the increasing numbers of complicated sleep disordered breathing patients may be the way of the future.
Conclusion Because of the progressive rise in OSA prevalence and heightened awareness of the potential adverse health consequences of untreated disease, there has been a steady growth in the demand for diagnostic sleep services. As a result, portable sleep monitoring and auto-CPAP titration which can be conducted in the patients’ own homes are increasingly being used to address the issue of long waiting lists and limited patient access to laboratory-based PSG. However, when compared with full PSG, PM has several limitations which need to be acknowledged, such as their limited ability to diagnosis sleep disorders other than OSA, the potential for Seminars in Respiratory and Critical Care Medicine
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specialist.50 Before their involvement in the study, PCPs and community-based nurses were provided with appropriate training on OSA and its management in the form of a 6-hour education module, and nursing staff undertook an additional week of intensive, in-service training at a specialist sleep center. After a total of 6 months follow-up, primary care management was not inferior to specialist management in terms of the primary outcome, the mean change in ESS score, which was 5.8 for the primary care arm versus 5.4 for the specialist arm (adjusted difference, 0.13; lower bound 1sided 95% CI, 1.5; p ¼ 0.43; noninferiority margin, 2.0). Also, no significant difference was found between groups for secondary outcome measures, including disease specific and general quality of life, OSA symptoms, CPAP adherence, and overall patient satisfaction. Comparison of within-trial costs revealed that primary care management was less costly at an average of AUD $1,606 per patient versus $2,576 for specialist care.
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Ambulatory Management Strategies for Obstructive Sleep Apnea inaccurate results, and the current uncertainty regarding their cost-effectiveness. Mounting evidence from comparative effectiveness studies suggests that ambulatory models of care for OSA involving the use of screening questionnaires, home sleep monitoring, and APAP titration in carefully selected patients with moderate-to-severe disease can produce patient outcomes which are comparable to standard sleep laboratory-based care. In addition, there is evidence supporting the potential involvement of health care professionals other than sleep physicians in the diagnosis and management of OSA in both the sleep clinic and primary care settings. Such evidence comes mainly from tightly controlled clinical trials which have incorporated sufficient training and clinical support for other health professionals. Such training and support is a critical part of the feasibility and safety of such models. Further research is needed to evaluate the role of PM in patients with mild OSA and those with medical comorbidities, and to determine the longer term cost-effectiveness of ambulatory management approaches for OSA.
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screen patients for obstructive sleep apnea. Anesthesiology 2008; 108(5):812–821 Fedson AC, Pack AI, Gislason T. Frequently used sleep questionnaires in epidemiological and genetic research for obstructive sleep apnea: a review. Sleep Med Rev 2012;16(6):529–537 Abrishami A, Khajehdehi A, Chung F. A systematic review of screening questionnaires for obstructive sleep apnea. Can J Anaesth 2010;57(5):423–438 Rigau J, Montserrat JM, Wöhrle H, et al. Bench model to simulate upper airway obstruction for analyzing automatic continuous positive airway pressure devices. Chest 2006;130(2):350–361 Xu T, Li T, Wei D, et al. Effect of automatic versus fixed continuous positive airway pressure for the treatment of obstructive sleep apnea: an up-to-date meta-analysis. Sleep Breath 2012;16(4): 1017–1026 Damiani MF, Quaranta VN, Tedeschi E, et al. Titration effectiveness of two autoadjustable continuous positive airway pressure devices driven by different algorithms in patients with obstructive sleep apnoea. Respirology 2013;18(6):968–973 Hertegonne K, Bauters F. The value of auto-adjustable CPAP devices in pressure titration and treatment of patients with obstructive sleep apnea syndrome. Sleep Med Rev 2010;14(2):115–119 Sériès F, Plante J, Lacasse Y. Reliability of home CPAP titration with different automatic CPAP devices. Respir Res 2008;9:56 Morgenthaler TI, Aurora RN, Brown T, et al; Standards of Practice Committee of the AASM; American Academy of Sleep Medicine. Practice parameters for the use of autotitrating continuous positive airway pressure devices for titrating pressures and treating adult patients with obstructive sleep apnea syndrome: an update for 2007. An American Academy of Sleep Medicine report. Sleep 2008;31(1):141–147 Planès C, D’Ortho MP, Foucher A, et al. Efficacy and cost of homeinitiated auto-nCPAP versus conventional nCPAP. Sleep 2003; 26(2):156–160 Ruhle KH, Domanski U, Nilius G. Obstructive pressure peak: a new method for differentiation of obstructive and central apneas under auto-CPAP therapy. Sleep Breath 2013;17(1):111–115
hypopnea indices determined by the REMstar Auto M series and those determined by standard in-laboratory polysomnography in patients with obstructive sleep apnea. Intern Med 2012;51(20): 2877–2885 Mulgrew AT, Fox N, Ayas NT, Ryan CF. Diagnosis and initial management of obstructive sleep apnea without polysomnography: a randomized validation study. Ann Intern Med 2007;146(3): 157–166 Berry RB, Hill G, Thompson L, McLaurin V. Portable monitoring and autotitration versus polysomnography for the diagnosis and treatment of sleep apnea. Sleep 2008;31(10):1423–1431 Kuna ST, Gurubhagavatula I, Maislin G, et al. Noninferiority of functional outcome in ambulatory management of obstructive sleep apnea. Am J Respir Crit Care Med 2011;183(9): 1238–1244 Andreu AL, Chiner E, Sancho-Chust JN, et al. Effect of an ambulatory diagnostic and treatment programme in patients with sleep apnoea. Eur Respir J 2012;39(2):305–312 Rosen CL, Auckley D, Benca R, et al. A multisite randomized trial of portable sleep studies and positive airway pressure autotitration versus laboratory-based polysomnography for the diagnosis and treatment of obstructive sleep apnea: the HomePAP study. Sleep 2012;35(6):757–767 Antic NA, Buchan C, Esterman A, et al. A randomized controlled trial of nurse-led care for symptomatic moderate-severe obstructive sleep apnea. Am J Respir Crit Care Med 2009;179(6): 501–508 Chai-Coetzer CL, Antic NA, Rowland LS, et al. Primary care vs specialist sleep center management of obstructive sleep apnea and daytime sleepiness and quality of life: a randomized trial. JAMA 2013;309(10):997–1004 Pietzsch JB, Garner A, Cipriano LE, Linehan JH. An integrated health-economic analysis of diagnostic and therapeutic strategies in the treatment of moderate-to-severe obstructive sleep apnea. Sleep 2011;34(6):695–709 Ayas NT, Pack A, Marra C. The demise of portable monitoring to diagnose OSA? Not so fast!. Sleep 2011;34(6):691–692
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Ambulatory Management Strategies for Obstructive Sleep Apnea
Ambulatory Management Strategies for Obstructive Sleep Apnea Ching Li Chai-Coetzer, MBBS, FRACP, GCPH, PhD1,2 Nick A. Antic, MBBS, FRACP, PhD1,2 1 Adelaide Institute for Sleep Health, Repatriation General Hospital,
Daw Park, SA, Australia 2 Flinders University, Bedford Park, SA, Australia
Vinod Aiyappan, MBBS, MD, MRCP, FRACP1,2
Address for correspondence Ching Li Chai-Coetzer, MBBS, FRACP, GCPH, PhD, Adelaide Institute for Sleep Health, Repatriation General Hospital, Daws Road, Daw Park, SA 5041, Australia (e-mail: [email protected]).
Abstract
Keywords
► obstructive sleep apnea ► polysomnography ► ambulatory model ► portable monitoring ► home diagnosis ► screening questionnaires ► autotitrating continuous positive airway pressure
The prevalence of obstructive sleep apnea (OSA) has been steadily rising over recent decades and patient access to laboratory-based sleep services and specialist consultations have become increasingly limited, resulting in potential delays in treatment. As a result, there has been growing interest in the use of non-sleep laboratory methods for diagnosing and managing OSA, including the use of screening questionnaires, portable sleep monitoring devices, and home autotitrating continuous positive airway pressure. There is also evidence in support of a role for alternative health care professionals, such as sleep-trained nurses and primary care physicians in the diagnosis and treatment of OSA. In this review, we compare the different types of home monitoring devices, discuss the limitations of portable monitoring compared with full laboratory polysomnography, and summarize the results from published comparative effectiveness studies which have evaluated ambulatory models of care for the management of OSA. We also consider how future models of care that may be needed to deal with the burden of disease will evolve and some of the issues that prevent the translation of such models of care in many countries.
Obstructive sleep apnea (OSA) is characterized by recurrent occlusion of the upper airway during sleep and is associated with repetitive oxygen desaturations, frequent arousals, and complaints of excessive daytime sleepiness. Symptomatic OSA was estimated to affect 2 to 4% of middle-aged adults in the early 1990s.1 However, since this time, there has been a dramatic increase in obesity rates worldwide2 and as a result the prevalence of OSA has risen in parallel, with more recent studies reporting moderate-to-severe disease in at least 15% of middle-aged adults.3 Untreated OSA has been associated with several adverse health consequences, including motor vehicle accidents,4,5 hypertension,6 and cardiovascular disease,7,8 with the risks of disease being minimized by the use of effective therapies, such as continuous positive airway pressure (CPAP)9–11 and mandibular advancement splints.12–14 Laboratory-based polysomnography (PSG) is the current gold standard for the diagnosis of OSA and for the determi-
Issue Theme Clinical Consequences and Management of Sleep Disordered Breathing; Guest Editors, Ravi Aysola, MD, and Teofilo L. Lee-Chiong Jr., MD
nation of appropriate CPAP therapy pressure settings. However, patient access to laboratory-based sleep studies and/or sleep physician consultations can be limited, with some centers reporting extensive waiting times for sleep services.15 Furthermore, laboratory PSG requires overnight attendance and monitoring by sleep technician staff, which can be expensive, labor intensive, and time consuming. As a result, in recent years there has been growing interest in homebased sleep monitoring for the identification and treatment of OSA, including the use of devices with limited recording channels and automatically titrating CPAP. The results of several comparative effectiveness studies evaluating ambulatory models of care for OSA compared with usual laboratory-based management have now been published, including studies which have involved alternative health care providers in disease management such as specialist sleep-trained nurses and primary care physicians
Copyright © 2014 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.
DOI http://dx.doi.org/ 10.1055/s-0034-1390139. ISSN 1069-3424.
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Semin Respir Crit Care Med 2014;35:545–551.
Ambulatory Management Strategies for Obstructive Sleep Apnea (PCPs). In this article, we discuss non-sleep laboratory strategies for the diagnosis and treatment of OSA and review the results of randomized, controlled studies which have assessed the clinical efficacy and cost-effectiveness of ambulatory care models versus laboratory-based management.
Portable Monitoring There are four levels of sleep studies, as classified by the American Academy of Sleep Medicine (AASM), based on the number of parameters recorded and the presence or absence of an attending technician. Type 1: Standard in-laboratory PSG with a technician in attendance, at least seven recording channels and body position sensor. This is considered the gold standard to which the other types of studies are compared. Type 2: Comprehensive, unattended, portable PSG with at least seven recording channels and optional body position sensor. This is the most common type of ambulatory diagnostic study conducted by tertiary sleep units. Type 3: Portable sleep study with at least four recording channels (ECG, oxygen saturation monitor, two channels for airflow and/or respiratory movements). Type 4: Continuous recording of one or two signals (usually oxygen saturation monitor and airflow). Types 2, 3, and 4 represent the different portable diagnostic devices available for the investigation of OSA. Portable tests were developed as an alternative to the laboratorybased PSG, with the aim of reducing costs and improving patient access to diagnostic sleep services; however, their initial use was limited due to lack of data regarding efficacy. With time, these devices have gained wider acceptance and multiple studies have now been published which support their role in the diagnosis of OSA. In 2007, the AASM published new guidelines regarding the use of portable devices for the diagnosis and management of OSA.16 These guidelines are specifically aimed at Type 3 devices, as they are the ones most commonly used for this purpose. These guidelines suggest the following: • Portable monitoring (PM) can be used in the place of laboratory PSG for the diagnosis of OSA for patients with a high pretest probability for OSA. • PM should be used only in conjunction with comprehensive sleep evaluation. • PM should not be used for screening. • PM is not recommended in patients with comorbid diseases (COPD, CHF, neuromuscular disease, etc.) or when other sleep disorders (central sleep apnea, periodic limb movement disorder, narcolepsy, circadian rhythm disorder, etc.) are suspected. • PM may be used in patients who cannot attend laboratory PSG (immobility, critical illness, etc.) and for monitoring response to non-CPAP treatment (surgery, weight loss, MAS, etc.). With the increasing prevalence of OSA and rapid advancements in technology, newer portable devices are flooding the market with considerable differences in the number and type Seminars in Respiratory and Critical Care Medicine
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of monitoring channels. In this setting, Collop et al have developed an alternate classification for the portable devices.17 This system categorizes portable devices based on measurements of sleep, cardiovascular, oximetry, position, effort, and respiratory (SCOPER) parameters. This classification does not include devices that did not have an oximetry channel. The PM devices are judged on whether the PM has a positive likelihood ratio of at least 5 and a sensitivity of at least 82.5% (coinciding with an in-laboratory polysomnography generated apnea–hypopnea index [AHI] 5/hour).
Advantages and Disadvantages of Portable Monitoring Although laboratory-based, full PSG (Type 1 study) is considered the gold standard test to which portable devices are compared, this is by no means the perfect investigation. There are different schools of thought regarding the appropriate cutoff points for defining the diagnosis and severity of OSA. It has also been shown that there could be significant differences in the AHI,18 based on the criteria used for scoring (1994 AASM Chicago criteria vs. 2007 AASM recommended and alternate criteria). Even with Type 1 studies, there could be night-to-night variability in AHI19 and inter- and intrascorer variability.20 Laboratory PSG is also considerably expensive and labor intensive. Patients are required to sleep in a foreign environment, which can potentially cause sleep fragmentation and poor sleep quality, and the sleep sample studied may not be representative of the patient’s normal sleep in their usual environment. Laboratory PSG has the advantage of being performed in a controlled setting, with ability to intervene if necessary (lead displacement, medical emergency, etc.). The laboratory PSG also enables us to couple the study with video monitoring (e.g., for detection of parasomnias, nocturnal epilepsy) and transcutaneous CO2 measurements (e.g., in sleep hypoventilation). It is also an important tool for the investigation of hypersomnolence states (e.g., before a multiple sleep latency test or maintenance of wakefulness test). Type 2 PM devices are often used as an alternative to laboratory PSG, as they provide most of the data that can be obtained from laboratory PSG21 while sampling the patients’ sleep in their normal surroundings. Upfront costs are also less expensive than with an attended, laboratory PSG.22 However, this type of PM tends to overestimate mild-to-moderate OSA and underestimate severe OSA.23 There is also a failure rate of up to 20%, due to loss of data.24 Real-time telemonitoring of unattended PSGs has been shown to reduce the failure rates albeit with higher costs.25 With the advent of cheaper telemonitoring services, this could emerge as a real contender for laboratory-based PSG. Type 3 devices are the most commonly used PM and the 2007 AASM guidelines16 (as discussed earlier) are specifically aimed at this group of devices. These devices have high sensitivity and specificity when used in patients with a high pretest probability for moderate-to-severe OSA.26 Type 4 devices usually measure oximetry and/or airflow. Although the 2007 AASM guidelines concluded that there was insufficient evidence in support of the use of Type 4 PM in the diagnosis of OSA, emerging studies suggest that they could be
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useful in improving the management of OSA in the community if used in appropriately selected patients with a high pretest probability of disease detected by a screening questionnaire.27 Type 3 and 4 devices measure the events per hour of recording rather than per hour of sleep and hence can potentially underestimate the severity of OSA if there are prolonged periods of wakefulness at night. There is also the issue of data loss. The usefulness of these devices in people with other comorbidities is unclear, as the studies have shown mixed results.28–30
The Role of Screening Questionnaires Several screening questionnaires have been developed to identify patients with OSA. These questionnaires have been developed from samples of patients with suspected OSA, who have had diagnostic tests and use anthropometric measurements and/or symptoms to predict the probability of the disease. The Berlin Questionnaire uses body mass index (BMI), the presence/absence of hypertension, and symptoms (snoring, witnessed apneas, and fatigue/sleepiness) and has been validated in primary care, with the ability to identify patients with OSA (AHI > 5) with a sensitivity of 86% and specificity of 77%.31 The STOP-BANG Questionnaire was developed and validated in preoperative clinics and uses eight different variables (snoring, tiredness, witnessed apneas, blood pressure, BMI, age, and neck circumference) to predict the probability of OSA (sensitivities for AHI greater than 5, greater than 15, and greater than 30 as cutoffs were 83.6, 92.9, and 100%, respectively).32 We have recently developed and validated a simple 4-item screening tool for OSA in primary care setting. This tool (OSA50 Questionnaire) uses obesity (waist circumference), troublesome snoring, witnessed apneas, and age 50 and has high sensitivity for detection of moderate-to-severe OSA.27 The screening questionnaires are very important to risk stratify patients and are helpful tools in the diagnostic pathway. They are an inherent part of PM to identify patients with high probability for OSA, as recommended by the AASM. But the current available tools are very heterogeneous and the results are inconsistent.33,34 Hence, there is a need for a standardized screening tool to allow greater comparability between various studies. The screening questionnaires used with the appropriate diagnostic algorithm are useful in the management of patients with OSA, but cannot replace the existing diagnostic tests, due to their poor specificity.
Autotitrating Continuous Positive Airway Pressure In-laboratory CPAP titration is the current standard for initiating CPAP treatment in patients with OSA. With the advent of smarter machines, autotitrating CPAP (APAP) devices which can detect changes in the upper airway that might lead to airway collapse and adjust pressure delivery accordingly have been developed. These devices use various types of sensors and algorithms to calculate the appropriate therapeutic pressure. In general, these devices measure snor-
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ing, flow limitation, hypopneas/apneas, or impedance with forced oscillatory techniques. Devices using flow-based algorithms have been shown to be superior to devices using a forced oscillation technique.35 As upper airway resistance is dynamic and can change from night to night depending on body position, sleep stage, use of alcohol/sedatives, etc., it is likely that the therapeutic CPAP is prone to night-to-night variability. Theoretically APAP devices can, by automatically adjusting the pressure, deliver the most appropriate therapeutic pressure. Although previous studies have shown that the compliance to treatment is similar in APAP and fixed CPAP users, a recent meta-analysis has suggested that compliance is significantly better with APAP when compared with fixed CPAP.36 Studies have shown that APAP is noninferior to standard CPAP in the control of sleep disordered breathing, and symptom improvement.37–39 Based on current data, the AASM guidelines have recommended that APAP devices can be used to initiate and continue treatment for patients with moderate-to-severe OSA without comorbidities.40 The use of APAP has been shown to result in cost savings by eliminating the need for laboratory-based PSG.41 However, these devices are more expensive than standard, fixed pressure devices. APAP devices can potentially deliver inappropriately high pressures in patients with central sleep apnea, but a recent study has shown that this can be avoided by incorporating an obstructive pressure peak signal into the algorithm.42 Although there have been reports showing good correlation between AHI measured by APAP devices and PSG,43 the 2007 AASM practice guidelines do not recommend the use of APAP devices for the diagnosis of OSA. APAP titration and treatment is not recommended in patients with CHF, COPD, obesity hypoventilation syndrome, and central apneas.40 Although APAP devices have been shown to have comparable outcomes in improving OSA symptoms, their long-term impact on cardiovascular outcomes are unclear.
Ambulatory Models of Care for Obstructive Sleep Apnea There is a growing body of literature reporting on the clinical effectiveness of ambulatory care models for the management of OSA, involving the use of screening questionnaires, portable sleep monitoring, and/or autotitrating CPAP. Recently, these models of care have also involved health care professionals other than sleep specialists as the principal providers of care for OSA patients, including sleep-trained nurses and PCPs. The first randomized, controlled study to evaluate an ambulatory approach to the management of OSA was conducted by Canadian investigators Mulgrew et al,44 with results published in 2007. In their study, a total of 68 patients who were found to have a high pretest probability of moderate-to-severe OSA based on an Epworth Sleepiness Scale (ESS) score 10, Sleep Apnea Clinical Score 15, and respiratory disturbance index (RDI) 15/hour on overnight oximetry were randomly allocated to either laboratory-based PSG and CPAP titration or home autotitrating CPAP and overnight Seminars in Respiratory and Critical Care Medicine
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Ambulatory Management Strategies for Obstructive Sleep Apnea oximetry. After 3 months of follow-up, they found no difference in their primary outcome, the residual AHI on CPAP (median difference, 0.8/hour; 95% confidence interval [CI], 0.9–2.3; p ¼ 0.31), and no differences in the change in ESS or Sleep Apnea Quality of Life Index (SAQLI) from baseline. Interestingly, CPAP adherence was found to be greater in the ambulatory management arm (difference, 1.12 hour/ night; 95% CI, 0.2–2.0; p ¼ 0.021). A similar study was conducted by Berry et al45 involving 106 U.S. Veterans who had presented to a sleep center with an ESS 12 and reported at least 2 of the following: loud snoring, witnessed apneas or gasping, and/or treatment for hypertension. Patients with significant cardiac failure or respiratory disease, an uncontrolled psychiatric disorder, or who had previously undergone a diagnostic sleep study or received treatment for OSA were excluded from enrolment. Participants were randomized to either portable, level 3 monitoring (WatchPAT 100) and APAP titration or laboratory-based PSG and CPAP titration, with follow-up for a total of 6 weeks. Study investigators found no difference in average nightly CPAP use (portable arm 5.20 SEM 0.28 hour/night vs. PSG arm 5.25 0.38 hour/night), change in ESS or Functional Outcomes of Sleep Questionnaire (FOSQ) scores, CPAP satisfaction, or residual AHI on CPAP. Kuna et al46 conducted a randomized controlled study involving a group of 296 U.S. Veterans and compared portable home testing using a level 3 monitor and APAP titration to set a fixed CPAP pressure with standard, laboratory-based PSG and CPAP titration for the management of OSA. Compared with other published studies, their inclusion criteria were reported to be less restrictive, with all new patients referred for investigation of suspected OSA being potentially eligible to participate. After 3 months of follow-up, the mean change in FOSQ score for the home testing arm was not inferior to the laboratory testing arm (difference, 0.004 [lower bound 95% CI, 0.54]; noninferiority margin, 1.0). Mean CPAP use was also not clinically inferior in the home testing group (difference, 0.55 hour/night [lower bound 95% CI, 0.03]; noninferior margin, 0.75 hour/night), and there was no difference between groups in the change in ESS, psychomotor vigilance task results, Short Form-12 (SF-12), or Center for Epidemiological Studies Depression Scale (CES-D) scores. The results of a study involving 66 patients were reported by Andreu et al47 whereby patients were randomized to one of three groups: (1) home level 3 monitoring and home follow-up; (2) hospital PSG and hospital follow-up; and (3) home level 3 monitoring and hospital follow-up. After 6 months of follow-up, study investigators found no differences between groups in CPAP compliance, ESS, and FOSQ scores, although it is possible due to the small sample size that the study may have been underpowered to detect such differences. Within-trial costs for the hospital PSG and follow-up arm were significantly higher (€849 11) than home testing and follow-up (€590 43) and home testing and hospital follow-up (€644 93). Another study comparing home-based, level 3 testing and APAP titration with attended, laboratory-based management of OSA was published by Rosen et al,48 involving seven Seminars in Respiratory and Critical Care Medicine
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academic sleep centers across the United States. In their study, which included a total of 373 randomized patients, there was no difference in CPAP prescription acceptance rates (94% in the laboratory arm vs. 93% in the home arm, p ¼ 1.0). Similar to the findings of Mulgrew et al,44 CPAP adherence was significantly higher in the home-based arm after 3 months of follow-up, with a difference in average nightly use of 62 minutes (95% CI, 15–108 minutes; p ¼ 0.01). No differences were found between the groups for the change in ESS, FOSQ, SAQLI, or SF-36 vitality subscale scores at 3 months. Their study also included a comparison of within-trial costs, with the results demonstrating that home-based management (US$139,148.48) was 25% less expensive than laboratorybased management (US$186,109.50).
Role of Health Care Professionals Other Than Sleep Physicians In addition to the use of more simplified, non–laboratorybased methods for diagnosing OSA and undertaking CPAP titration, novel models of care have been proposed which involve health care professionals other than sleep physicians as the principal care provider of patients with OSA, including sleep-trained nurses and PCPs. In collaboration with two other Australian sleep centers, we conducted the first randomized controlled trial evaluating a nurse-led, ambulatory model of care for OSA compared with specialist-led, laboratory-based management.49 A total of 195 patients who were confirmed as having moderate-to-severe OSA based on the results of overnight oximetry (> 2% oxygen dip rate > 27/hour) were randomly assigned management by a specialist sleep-trained nurse and home APAP titration, or to standard care by a sleep physician with laboratory-based, full PSG testing and CPAP titration, for a total of 3 months follow-up. The mean change in ESS for the nurse-led group was clinically noninferior to specialist-led management (difference, 0.13 [95% CI, 1.52 to 1.25]; noninferior margin, 2.0), and there was no difference between groups in the change in FOSQ or SF-36 scores, CPAP use, neurocognitive function, or Maintenance of Wakefulness Test results at the conclusion of the trial. Patient satisfaction was higher for nurse-led management for four out of nine components of the Visit-specific Satisfaction Questionnaire (VSQ-9). Furthermore, the analysis of within-trial costs revealed that nurseled management was AUD $1,111 (95% CI $1,084–$1,137) per patient less expensive than specialist-led care.
Primary Care Management of Obstructive Sleep Apnea The promising results of this study led us to consider a potential role for PCPs and their practice nurses in the diagnosis and management of OSA. Using a validated, twostep diagnostic strategy of OSA50 screening questionnaire (score 5/10) and home oximetry ( 3% oxygen desaturation index 16/hour),27 PCPs identified a total of 155 patients with moderate-to-severe OSA and daytime sleepiness (ESS 8) who were randomly assigned to either ongoing ambulatory management by their PCP and a communitybased nurse or to usual laboratory-based care by a sleep
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Limitations of Randomized Controlled Trials Although the results of randomized controlled trials evaluating ambulatory care models for OSA have generally shown comparable or noninferior outcomes to specialist care, it is important to be mindful of the strict selection criteria used in these studies. With the exception of the study by Kuna et al46 which reported to have had less restrictive criteria, patients were excluded from the study if they had medical comorbidities such as cardiovascular disease, heart failure, COPD, neuromuscular disease, and other causes of respiratory failure, psychiatric conditions, or if they were suspected to have a sleep disorder other than OSA. Therefore, study results cannot be generalized to these populations. In addition, participants had a high pretest probability of OSA and PM strategies have been aimed at identifying those with moderate-to-severe OSA. Thus, further research on the effectiveness of ambulatory management strategies is required in patients with milder degrees of OSA and those with medical comorbidities. There has been considerable debate regarding the costeffectiveness of ambulatory diagnostic and management approaches for OSA. Although previous randomized controlled trials have reported cost savings for ambulatory care models compared with usual laboratory-based care,47–50 their results have included calculations for up-front, within-trial costs only and have not factored in the long-term financial implications of potential misdiagnosis when conducting PM. A more detailed economic analysis was conducted by Pietzsch et al51 using a Markov model which compared the cost-effectiveness of full PSG, split night PSG, and unattended, portable home monitoring. Their results revealed that although up-front costs were higher, use of full PSG was cheaper than both split night PSG and portable home monitoring over the longer term because of its superior diagnostic accuracy. However, criticism has been made of the assumptions used in their model which may have magnified the impact of false-positive and false-negative results,52 including the assumption that the risk of cardiovascular disease would be dramatically reduced by CPAP use which
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is yet to be substantiated by randomized controlled trial evidence, and that patients with a false-positive home monitoring result would comply with CPAP to the same extent as those correctly diagnosed. Thus, the overall cost-effectiveness of ambulatory management strategies for OSA is currently unclear, and further research into this area is needed.
The Future In some countries, most notably in the United States, some of these ambulatory models of care have become the preferred first way to approach diagnosis and treatment of OSA. This evolution of clinical care had been dictated by funding models in most cases. The sleep laboratory still has an integral role in the diagnosis and management of OSA. The role of the laboratory is changing, but ambulatory models struggle to deal with complicated sleep disordered breathing patients including those in respiratory failure. Furthermore, as there is wider adoption of these ambulatory models of care and likely more patients diagnosed with OSA, there are patients who have either insufficient information on their diagnostic tests or do not respond to treatment as predicted that will need to be tested in the sleep laboratory conditions to understand the reasons why their treatment is not effective. It is possible that they may have other sleep disorders, insufficient CPAP pressure to overcome upper airway obstruction, or sleep hypoventilation. If other health professionals are to take an increasing lead in the diagnosis and management of uncomplicated OSA, it is mandatory that they have sufficient training to care for such patients. Robust training programs exist for sleep physicians but will need to be developed for other health professionals. Furthermore, it remains to be seen if there are sufficient primary care physicians or specialist nurses with a willingness to pursue further training and make a meaningful difference to the number of skilled health professionals to deal with OSA. They also need to work in an environment where they have support of a sleep laboratory and sleep physicians for advice, laboratory testing, or clinical review when needed, that is, a hub and spoke clinical model. A stepped care model where uncomplicated OSA is managed in such a way with sleep laboratory services for the increasing numbers of complicated sleep disordered breathing patients may be the way of the future.
Conclusion Because of the progressive rise in OSA prevalence and heightened awareness of the potential adverse health consequences of untreated disease, there has been a steady growth in the demand for diagnostic sleep services. As a result, portable sleep monitoring and auto-CPAP titration which can be conducted in the patients’ own homes are increasingly being used to address the issue of long waiting lists and limited patient access to laboratory-based PSG. However, when compared with full PSG, PM has several limitations which need to be acknowledged, such as their limited ability to diagnosis sleep disorders other than OSA, the potential for Seminars in Respiratory and Critical Care Medicine
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specialist.50 Before their involvement in the study, PCPs and community-based nurses were provided with appropriate training on OSA and its management in the form of a 6-hour education module, and nursing staff undertook an additional week of intensive, in-service training at a specialist sleep center. After a total of 6 months follow-up, primary care management was not inferior to specialist management in terms of the primary outcome, the mean change in ESS score, which was 5.8 for the primary care arm versus 5.4 for the specialist arm (adjusted difference, 0.13; lower bound 1sided 95% CI, 1.5; p ¼ 0.43; noninferiority margin, 2.0). Also, no significant difference was found between groups for secondary outcome measures, including disease specific and general quality of life, OSA symptoms, CPAP adherence, and overall patient satisfaction. Comparison of within-trial costs revealed that primary care management was less costly at an average of AUD $1,606 per patient versus $2,576 for specialist care.
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Ambulatory Management Strategies for Obstructive Sleep Apnea inaccurate results, and the current uncertainty regarding their cost-effectiveness. Mounting evidence from comparative effectiveness studies suggests that ambulatory models of care for OSA involving the use of screening questionnaires, home sleep monitoring, and APAP titration in carefully selected patients with moderate-to-severe disease can produce patient outcomes which are comparable to standard sleep laboratory-based care. In addition, there is evidence supporting the potential involvement of health care professionals other than sleep physicians in the diagnosis and management of OSA in both the sleep clinic and primary care settings. Such evidence comes mainly from tightly controlled clinical trials which have incorporated sufficient training and clinical support for other health professionals. Such training and support is a critical part of the feasibility and safety of such models. Further research is needed to evaluate the role of PM in patients with mild OSA and those with medical comorbidities, and to determine the longer term cost-effectiveness of ambulatory management approaches for OSA.
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