Using pulse oximetry for obstructive sleep apnea screening has been debated and evaluated for years. As the industry takes on board unattended home sleep tests, this inexpensive and easy-to-use detection device is receiving greater attention.

Overnight in-laboratory polysomnography is the gold standard for OSA diagnosis. However, only a fraction of the estimated 12 million Americans with OSA are being tested for the disorder due to a shortage of sleep centers, the complexity of scheduling, and lack of insurance reimbursement. When patients do come into the lab, their chief complaints are the uncomfortable wiring and unfamiliar atmosphere for sleeping away from home.

The prevalence of undetected and untreated sleep disorders such as OSA not only puts patients at risk for heart disease and stroke, it also costs the overall U.S. economy billions in decreased productivity and work accidents. Proponents of at-home sleep tests suggest the tremendous health, economic, and public safety burdens of OSA could be lifted if patients were identified faster and treated earlier.

Home sleep monitoring devices that incorporate pulse oximetry technology can help in diagnosing far more patients than standard PSG because of its ease of accessibility, set-up, and computerized data analysis. The devices also could be used for augmenting diagnostic decision-making and to evaluate the adequacy of therapeutic interventions.

In addition, portable monitoring can be used for triaging and educating patients for further treatments. In a hospital setting, these devices may be of great value to assess hundreds of patients for OSA at the bedside while they are admitted for other medical issues.

Changes in reimbursement

The Centers for Medicare and Medicaid Services in April decided to reimburse continuous positive airway pressure treatment for OSA patients diagnosed via at-home sleep tests. CMS' policy permits all types of portable monitoring equipment classified by the American Academy of Sleep Medicine. This includes Type 4 devices with at least three channels, which -typically include pulse oximetry.

In July, CMS released a fee structure for three new G-codes for home testing. The payment rates for these services can be found in Addendum B of the July 2008 Hospital Outpatient Prospective Payment System (OPPS).

The G-400 code refers to Type 4 unattended portable monitors with a minimum of three channels. The payment rate set by Medicare is $146.37 with a minimum unadjusted co-pay of $29.27 and national unadjusted co-pay of $53.58.

The potential implications of the new G-codes could be more initial surveillance of patients who otherwise would not have been studied. The addition of more channels with the modern advanced home sleep testing devices available now can provide more frequent testing at a much lower rate, which is easier and more convenient for patients.

Screening with pulse ox

Due to major technical improvements in recent years, pulse oximetry now is accepted by many practitioners for screening lower-risk OSA cases. However, Medicare's coverage determination excludes screening with pulse oximetry alone. The insurer Aetna, which revised its stance to mirror Medicare's coverage determination, considers pulse oximetry used alone for OSA screening and testing "experimental."

Currently, the main limitations of at-home testing with pulse oximetry alone are false-negative or false-positive readings that could lead to a misdiagnosis. To avoid this, overnight sleep diagnostic devices should measure respiratory disturbance index, apnea-hypopnea index, and rapid eye movement percentage, in addition to heart rate and oxygen desaturation levels. Practitioners should follow up with in-lab PSG in cases believed to be false negatives, or for patients with medical conditions rendering the home trial problematic.

Pulse oximetry alone also does not reliably indicate the degree of obstruction or other sleep disturbances that may be present, including narcolepsy, parasomnias, nocturnal seizures, REM behavior disorder, or restless legs syndrome. Pulse oximetry also does not distinguish between OSA and central sleep apnea.

Trends in technology

Within the next several years, however, we will see more evolved types of portable home sleep study devices incorporating pulse oximetry that are increasingly accurate and reliable.

Several such systems already are available. Numerous studies have confirmed that they are fairly accurate in screening and, in some cases, diagnosing patients suspected of having obstructive sleep apnea. These new technologies provide faster signal averaging time, excellent recording of heart rate, pulse oximetry, apnea as well as hyponea index, and percentages of REM. Other features of these portable devices are their small size, ease and accuracy of downloading, effortless use by patients, and inexpensive initial cost for practitioners.

One such system incorporates peripheral arterial tonometry. This self-contained device is worn on the wrist and uses a noninvasive finger-mounted pneuoptical probe to measure the PAT signal. The recorded signals are stored in a removable memory card in the device to be downloaded to a computer for automatic analysis utilizing proprietary algorithms.

In addition to the PAT signal, the system records oxygen saturation and actigraph.

A fourth channel - pulse rate - is derived from the PAT signal. The device was proven to be accurate and easy to use. The results were very much comparable to a comprehensive overnight PSG.

New guidelines

Many sleep practitioners have been slow to warm to the implementation of unattended sleep testing at home. The AASM's clinical guidelines for the use of unattended portable monitors for initial screening and, in some cases, diagnosis of this major illness have recommended that testing with portable monitors be performed only in conjunction with a comprehensive sleep evaluation and testing should be supervised by a board- certified or eligible sleep specialist. The guidelines issued in December also state that home sleep tests are "not appropriate for general screening of asymptomatic population."

These recommendations theoretically are acceptable; however, they may not be practical or financially feasible for every single patient. In fact, the newer overnight monitoring devices are able to fairly accurately analyze and record patients' data, providing easy-to-understand information for any practitioner trained to read those data.

This exciting new era in sleep testing offers hope to thousands of people who previously were unable to obtain treatment to improve their quality of life through early intervention.

Mansoor Madani, DMD, MD, is chairman of the department of oral and maxillofacial surgery, Capital Health Medical Center, Trenton, N.J., and associate professor of oral and maxillofacial surgery at Temple University Hospital, Philadelphia. He also directs the Center for Corrective Jaw Surgery, Bala Cynwyd, Pa.