Portable Devices Used for Home Testing in Obstructive Sleep Apnea

Jeffrey A. Tice, M.D.


May 18, 2010

In This Article


The 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.


Obstructive Sleep Apnea (OSA)

Untreated, OSA is associated with significant morbidity and mortality including excessive sleepiness, poor memory, poor quality of life, hypertension, sudden death, stroke, congestive heart failure, myocardial infarction, and automobile and work-related accidents.[2,3,4,5,6,7,8,9,10] Apnea is usually defined as a cessation of airflow for >10 seconds, and hypopnea, as a reduction of >50% in thoracoabdominal movements for >10 seconds or as a discernable reduction in respiratory airflow for >10 seconds and accompanied by a decrease of >4% in SaO2 and/or an arousal.[11] The apnea-hypopnea index (AHI) is calculated as the average number of apneas plus hypopneas per hour of sleep. The cut-off for the diagnosis of OSA for the AHI has varied from study to study. Recent studies using a “liberal” definition of OSA—an AHI of greater than five events per hour—have found that up to 24% of men and nine percent of women have OSA. Using a more “conservative” diagnostic criterion—an AHI of at least 15 events per hour plus a history of daytime somnolence—up to two percent to four percent of adults have obstructive sleep apnea syndrome.[12,13] Treatment of OSA syndrome with nasal continuous positive airway pressure (nasal CPAP), dental devices, surgery, and weight loss improves patient daytime somnolence, cognitive dysfunction, and overall survival[3,14,15,16,17,18,19] Although there have been few comparative studies, the consensus is that CPAP should be the first line therapy for OSA.

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.[20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38]

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 in-laboratory PSG in the diagnosis of OSA.[39,40,41] 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:

  1. Excessive daytime sleepiness that is not better explained by other factors

  2. Two or more of the following that are not better explained by other factors:

    1. Choking or gasping during sleep

    2. Recurrent awakenings from sleep

    3. Unrefreshing sleep

    4. Daytime fatigue

    5. Impaired concentration

  3. Overnight monitoring demonstrates five or more obstructed breathing events per hour during sleep

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[48,49,50,51] with different diagnostic goals. Simple, inexpensive devices have been developed to screen or to case-select 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 time-consuming.[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.[50,60,61,62] 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.


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