Revisions to the practice parameters for the use of portable monitoring (PM) devices for the evaluation of obstructive sleep apnea (OSA) were recently announced in a publication by the American Academy of Sleep Medicine (AASM) Task Force.1 Based upon previous reviews,2,3 and following systematic and extensive data evaluation, the paper outlines the revised parameters and identifies recommended practice parameters for the unattended use of PM devices to study adult patients with possible OSA. Following a long standing debate about the role of PM as a diagnostic tool for OSA, the paper includes a description of limitations applicable to the unattended use of PM devices, instances in which PM are not appropriate, technical considerations for PM and testing recommendations.1
The evidence used in the evaluation of PM devices was based upon the apnea hypopnea index (AHI) compared with in-lab polysomnography (PSG) as the gold standard, and it is use in the evaluation of suspected OSA only. In some patients, the PM may generate an underestimation or overestimation of the AHI resulting in discrepancies between the PM device AHI (based on total recording time) and the in-lab AHI (based on total sleep time). Furthermore, insufficient evidence in the evaluation of other sleep disorders with PM devices limit the use of PM devices to only assess OSA.
Of significance is the new stance that unattended PM devices can be used as an acceptable alternative, in the absence of available PSG, to assess patients at high risk for OSA and when clinical judgment by a physician deems it necessary. PM may be used also as a pre-test to PSG in patients with a high probability of moderate to severe OSA and indicated in patients who may have limited access to in-lab PSG due to immobility, safety or critical illness. Another recommendation permits PM devices to be used to monitor the response to oral appliances, upper airway surgery and weight loss. All of the above recommendations are pre-empted by the condition that PM should be performed ONLY in conjunction with a comprehensive sleep evaluation and must be supervised by a sleep boarded or board eligible physician (Table 1).
The Task Force also describes three instances in which PM is not appropriate for the diagnostic evaluation of suspected OSA: (1) co-morbidity with other sleep disorders (i.e. central sleep apnea, periodic limb movement disorder, insomnia, parasomnias, circadian rhythm disorders or narcolepsy); (2) co-morbidity with medical conditions (i.e. moderate to severe pulmonary disease, neuromuscular disease, or congestive heart failure) and (3) as a general screening tool among asymptomatic populations1 (Table 2).
Furthermore, the Task Force suggested that all sleep laboratories confirm that the commercial PM device that they use has research documenting its performance and that it has the necessary characteristics pertinent to the general category recommended (i.e. Type 3). The ability to review raw data from the PM device by the interpreting physician was highly recommended. The device should also have the option of manual scoring of the raw data. Scoring should be performed by trained and qualified technologist and the raw data reviewed by experienced physicians who are familiar with the PM device.
Technical recommendations for PM devices were based on sensors used for the in-laboratory setting. The Task Force recommended the use of airflow, respiratory effort and blood oxygen measurements for PM devices. The assessment was limited to Type 3 devices, which typically use a minimum of four channels and no electroencephalogram (EEG) recording. As described in the previous review, manual scoring of the PM deviceâ€™s raw data remains a limitation.4
Two sensors are recommended for simultaneous monitoring of airflow. The detection of apneas should be performed with an oronasal thermal sensor and for the detection of hypopneas, a nasal pressure transducer should be used. Respiratory effort can be monitored using esophageal manometry, calibrated or uncalibrated Respiratory Inductance Plethysmography (RIP) and blood oxygen should be monitored using pulse oximetry with a minimum averaging time of â‰¤3 seconds and accommodate for motion artifact5 (Table 3).
The guideline-writing committee called for urgently needed research to address many of the gaps related to PM devices. Recommendations for future research include obtaining data without using a fixed-threshold AHI, evidence from primary-care populations, verification in patients with co-morbid conditions, non-whites and women. The studies should include sufficient sample sizes. The only PM class currently recommended for routine use in the attended setting with the limitations described above is the Type 3 (and Type 2 unattended full PSG).
An example of a portable monitoring Type 3 category device that meets the AASM recommendations is the EmblettaÂ® (Embla, Broomfield, CO). This device provides diagnostic signals of nasal airflow, oral thermistor, two respiratory effort sensors using XactTrace Respiratory Inductive Plethysmography (RIP), pulse oximetry, and optional signals of leg/body movement, heart rate, position and activity. It could be used for the unattended or attended in sleep clinic, hospital, or home setting to rule in or out the diagnosis of sleep disordered breathing. The Embletta can be adapted to a variety of ambulatory and online studies by using its variable proxy connections. This device can be connect directly to a ResMed AutoSetÂ® flow generator so that flow, pressure, leak and events from the AutoSet are recorded. The raw data can be reviewed. The EmblettaÂ® has been validated in studies both in Europe and the US and has been designated by the American Sleep Medicine Foundationâ€™s landmark study for use in Portable Monitoring in the Diagnosis and Management of Obstructive Sleep Apnea.
David Baker, President
and Preetam Schramm, PhD, RPSGT
Embla Systems Inc, Broomfield, CO
1. Collop NA, Anderson WM, Boehlecke B, Claman D, Goldberg R, Gottleib DJ, Hudgel D, Sateia M, Schwab R: Portable Monitoring Task Force on the American Academy of Sleep Medicine. Clinical Guidelines for the Use of Portable Monitoring Devices in the Diagnosis of Obstructive Sleep Apnea in Adults Patients. J Clin Sleep Med, 2007; 3(7):737â€“747.
2. Chesson AL, Ferber R, Fry J, et al. The indications for polysomnography and related procedures. Sleep 1997; 20: 406â€“422.
3. American Sleep Disorders Association Report. Standards of Practice Committee. Practice Parameters for the use of portable recording in the assessment of obstructive sleep apnea. Sleep 1994; 17:372â€“377.
4. Chesson Al, Berry RB, Pack A. Practice Parameters for the Use of Portable Monitoring Devices in the Investigation of Suspected Obstructive Sleep Apnea in Adults. Sleep 2003; 26(7):907â€“913.
5. Iber C, Ancoli-Israel S, Chesson AL, Quan S. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications. AASM Manual for Scoring Sleep, 2007.