«AUTHOR: Jeffrey A. Tice, M.D. Assistant Professor of Medicine Division of General Internal Medicine Department of Medicine University of California ...»
TITLE: Portable Devices Used for Home Testing in Obstructive Sleep
AUTHOR: Jeffrey A. Tice, M.D.
Assistant Professor of Medicine
Division of General Internal Medicine
Department of Medicine
University of California San Francisco
PUBLISHER: California Technology Assessment Forum
DATE OF PUBLICATION: March 11, 2009
PLACE OF PUBLICATION: San Francisco, CA
PORTABLE DEVICES USED IN HOME TESTING FOR OBSTRUCTIVE SLEEP APNEAA Technology Assessment
INTRODUCTIONThe California Technology Assessment Forum (CTAF) has been asked to update its review of the scientific literature on the safety and efficacy of portable devices used in the home to diagnose patients with obstructive sleep apnea. Home diagnostic devices for sleep apnea were last reviewed by the Forum in June
2005.1 At that time, the recommendation of the systematic review was that portable devices did not meet CTAF criteria. Since that time, several new studies and reviews have been published and the Centers for Medicare and Medicaid Services (CMS) issued a national coverage decision supporting the coverage of continuous positive airway pressure (CPAP) based on home diagnosis of sleep apnea using portable devices. An updated review was considered in October 2008, but was tabled.
A major advance in the past decade has been the demonstration that CPAP does not need to be titrated in the sleep lab. Multiple studies have demonstrated the equivalence of automated home titration of CPAP (auto-CPAP) to in lab CPAP titration and guidelines have been written by sleep societies supporting its use.20-38 The diagnosis of OSA cannot be made accurately by clinical history or physical examination alone. The “gold standard” for diagnosis of OSA is polysomnography (PSG), a recording of at least seven parameters— electroencephalography (EEG, brain waves), electro-oculography (EOG, eye movements), chin electromyography (muscle activity), electrocardiography (ECG), respiratory effort, airflow, and blood oxygen saturation--that is performed by a trained technologist using dedicated equipment with the patient sleeping overnight in a sleep laboratory. Full PSG also allows calculation of the respiratory disturbance index (RDI), which is the number of sleep-disordered events per hour of sleep including respiratory effort related arousals that don’t qualify as hypopneas or apneas. Consensus standards exist for the proper use of the inlaboratory PSG in the diagnosis of OSA. 39-41. In-laboratory PSG is labor-intensive and long waiting lists are common in sleep laboratories 42. Furthermore, single-night PSG is not perfect, and false-negative results have been reported 43. In addition, night-to-night variability of respiratory abnormalities has been well documented 42, 44 and may give rise to divergent RDIs, causing reclassification of the diagnosis in up to 43% of patients with lower RDIs (5-15 respiratory events/hour) 45. Some do not consider standard PSG to be the “gold standard” for the diagnosis of OSA 46; instead, they suggest that therapeutic response to treatment (e.g., with nasal CPAP) might be a better “gold standard” 47.
The American Academy of Sleep Medicine recommends using the following definition for the diagnosis of
obstructive sleep apnea hypopnea syndrome.41 A patient must meet either criterion A or B plus criterion C:
A. Excessive daytime sleepiness that is not better explained by other factors
B. Two or more of the following that are not better explained by other factors:
The report also recommends the following terminology for disease severity: mild = 5-15 events per hour;
moderate = 15-30 events per hour, severe = more than 30 events per hour.41 A major advance in the past decade has been the demonstration that CPAP does not need to be titrated in the sleep lab. Multiple studies have demonstrated the equivalence of automated home titration of CPAP to in lab CPAP titration.
Portable Devices for Home Diagnosis of OSA Over the past twenty years, numerous portable devices have been developed that can record sleep, nocturnal breathing and oxygenation at home. A large number of portable sleep monitors are now available 48-51 with different diagnostic goals. Simple, inexpensive devices have been developed to screen or to caseselect patients with sleep-disordered breathing. More complex equipment has been developed to allow the performance of a study equivalent to full PSG in the home setting 48. A recent review identified an “incomplete list” of 36 portable monitors (PM).52 The portable devices offer several potential advantages compared with in laboratory PSG 53, 54. Home studies might provide a more realistic appraisal of sleep-disordered breathing than can be obtained in the laboratory setting 55. The reduced number of monitors with portable devices may also help with better approximation of the patient’s usual sleep habits. The use of home devices could allow for wider access to sleep studies, as there are not enough sleep centers in the United States to perform full PSG on all at risk patients. In the past, waiting lists at some centers have been six months or longer 56, although recent increases in the numbers of sleep centers has decreased wait times in most areas of the United States.57 The data from these portable devices are relatively easy to interpret and data analysis is less timeconsuming 58.
Potential disadvantages include lack of feasibility due to patient disability or transportation problems;
possible unsatisfactory results obtained because of faulty placing of sensors or poor quality signals 58, 59;
inability to diagnose position dependant OSA; and inaccurate diagnoses. Most portable devices are not able to diagnose other sleep disorders such as narcolepsy and restless leg syndrome. Thus, most studies of portable devices exclude patients with a high likelihood of sleep disorders other than obstructive sleep apnea. In addition, many portable home monitoring devices do not actually monitor sleep itself, making it impossible to determine the frequency of apneas and hypopneas per hour of sleep (AHI) 58.
In 1994 and 1999, a Task Force of the Standards of Practice Committee of the American Academy of Sleep Medicine reviewed the role of portable recording devices in the diagnosis of OSA in adults. Ferber et al 55 subsequently published a comprehensive review of published literature concerning the validity, clinical utility, advantages, and limitations of portable sleep monitoring devices. In 1996, an updated summary was published by Broughton et al 48. More recently both the Agency for Health Care Research and Quality and a joint task force of the American Academy of Sleep Medicine, The American College of Chest Physicians, and the American Thoracic Society updated systematic reviews on home diagnosis of sleep apnea and were unable to identify any clearly effective portable home devices.50, 60-62 Many different (and constantly upgraded) systems employing different technologies to obtain, store, and analyze data have been marketed.
These devices use various sensors in a variety of combinations; they measure different physiological parameters depending on the model. Because each portable device measures a unique set of parameters and use proprietary algorithms to calculate an approximation of the AHI, the devices should not be evaluated as a class. Each unique device should be evaluated on its own merits.
TECHNOLOGY ASSESSMENT (TA)
There are many portable devices approved by the FDA through the 510K program as substantially
equivalent to predicate devices. There are at least two devices specifically noted in this assessment:
The Remmers Sleep Recorder (formerly SnoreSat) (SageTech Electronics Inc., Calgary, Alberta) received FDA 510(k) clearance in June 2002.
The Apnea Risk Evaluation System (ARES, Advanced Brain Monitoring, Carlsbad, CA) received FDA 510(k) clearance in October 2004.
The WATCH-PAT 100 (Itamar Medical, Inc) received FDA 510(k) clearance in November 2001. Several updated versions of the WATCH-PAT have received FDA 510(k) clearance.
TA Criterion 1 is met.
The Medline database, Cochrane clinical trials database, Cochrane reviews database, and the Database of Abstracts of Reviews of Effects (DARE) were searched using the key words sleep apnea, sleep study, polysomnography, home sleep study, home polysomnography, portable sleep study, portable polysomnography and sleep disorder breathing. The search was updated for the period from March 1, 2005 through January 21, 2008. The bibliographies of systematic reviews and key articles were manually searched for additional references.51, 52, 60-63 Further references were also solicited form the manufacturer, local experts and sleep societies. The abstracts of citations were reviewed for relevance and all potentially relevant articles were reviewed in full.
Full details of the search terms are included in Appendix 1. Figure 1 describes the search results. In brief, a total of 502 references were reviewed (199 from Embase, 128 from PubMed, 80 from the combined Cochrane databases, 95 from reference lists of articles and manufacturers).
Figure 1: Study Selection
Most studies of PM have had serious methodological flaws 64. First, often the validation data for these portable devices designed for unattended home use have been generated with the patient sleeping in the sleep laboratory in the presence of a technologist.55, 65, 66 The best validation studies compare data from portable devices used at home with data from full PSG as a “control” and have blinded the scoring of the full polysomnographic tracing to this study results of the home device under evaluation. Second, confounding some research studies are the long intervals between the full PSG and the home monitoring by portable devices. Third, studies have generally not included patients with few symptoms of OSA (and thus low pretest probability of disease), so the utility of the devices as a screening tool in such cases cannot be determined.
In 1994, the American Sleep Disorders Association published standards 47 for the conduct of research studies investigating new diagnostic systems. These included: an independent, blind comparison with a reference standard; an appropriate spectrum of patients; avoidance of work-up bias; adequate detail regarding methods for performing the test; an adequate description of the study population; adequate sample size (estimated to be 200 patients); avoidance of selection bias; and an adequate description of the study setting. No new studies were identified comparing in laboratory PSG to home testing with at least 200 patients and the majority of studies evaluated in the prior study failed to meet this standard. The tables of studies evaluated in our 2005 review and the list of new, small studies investigating portable devices is included as Appendix 2.
Experts have noted a number of inherent difficulties in trying to compare one sleep diagnostic system to another. The most important problems are: (1) the lack of a true “gold standard” in assessing respiration during sleep and thus difficulties in detecting apneas and hypopneas; (2) the absence of a well-accepted cutoff for apnea-hypopnea frequency to make the diagnosis of obstructive sleep apnea; and (3) the night-tonight variability in measures of sleep and respiration that makes comparisons of home assessment versus in-laboratory evaluation difficult 44, 58, 67, 68. PSG results also can vary significantly from night to night. In one recent study, home monitoring had less variability over time than PSG.69. Given the high night-to-night variability of in-lab PSG, it is clear that the results from home monitoring cannot be expected to precisely match those of PSG. The more important question is whether a home-based test and treat strategy can improve outcomes in patients with suspected obstructive sleep apnea to the same degree (or more) than a strategy based on in-lab polysomnography and CPAP titration.