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Professor of Medicine, Brown University School of Medicine, and Director of Sleep Disorders Center of Lifespan Hospitals.
Correspondence to: Richard P. Millman, MD, FCCP, Division of Pulmonary Sleep and Critical Care Medicine, Rhode Island Hospital, 593 Eddy St, Providence, RI 02903-4923
Over the last decade, there has been more evidence that sleep disorders, such as obstructive sleep apnea, are extremely prevalent in the population. There has been a raging debate between proponents of home studies and proponents of in-laboratory full polysomnography with each side proposing that its technology represents "the best test." Proponents for home studies have claimed that a larger number of patients could be better served by studying them at home. Using portable studies, patients can be evaluated in a potentially more comfortable setting at a potentially reduced cost. Advocates of in-laboratory full polysomnography have claimed that these studies provide a greater amount of information. In addition, they allow a technician to be available to adjust signals, potentially start nasal continuous positive airway pressure if the patient meets the criteria for a split night study, and intervene if the patient has a medical problem.
Part of the problem in this debate is that there is probably no single "best text." In fact, the best test really depends on what clinical question is being addressed. Choosing the best test should be based on pretest clinical suspicion for disease.1
For example, if one is evaluating a patient with a high clinical suspicion for obstructive sleep apnea, there may be several alternatives for testing. The patient with a high clinical suspicion for sleep apnea typically complains of extremely loud snoring (frequently in any position), observed apneas or choking arousals during sleep, and excessive daytime sleepiness, and has upper body obesity, and associated hypertension. In this type of patient, the diagnosis of obstructive sleep apnea can probably be made either with full polysomnography or in the home setting using even a four-channel cardiorespiratory recorder. The clinical suspicion for these patients is so high that one would have trouble accepting a normal sleep study. In fact, data are available to show that negative findings on polysomnographic evaluations in the laboratory setting in these patients warrant a second study.2 Negative results from a home study would also necessitate a repeat evaluation.
It becomes more difficult if the pretest clinical suspicion for obstructive sleep apnea is lower as with patients with mild sleep apnea or with the "upper airway resistance syndrome." Sleep centers are seeing more and more of these patients as public awareness of sleep disorders increases. These patients have been shown to require greater technologic assessment. Full sleep stage monitoring is essential to detect EEG arousals. Qualitative respiratory inductive plethysmography or nasal pressure transducers are being used more frequently to assess hypopneas and sensitive changes in upper airway resistance. Some sleep centers also use esophageal balloons, although this is not universally practical.
Though pulmonologists tend to focus on obstructive sleep apnea, there are a large number of sleepy patients in whom snoring is not a major issue. Though a large component of these patients will be suffering from insufficient sleep, others will have organic sleep disorders warranting testing. These include patients with periodic limb movements during sleep, narcolepsy, or idiopathic CNS hypersomnolence. Clearly, these patients need in-laboratory full polysomnography. These patients would require sensitive respiratory monitoring because they might have very subtle obstructive sleep apnea. They also would frequently require multiple sleep latency testing the next day to assess the degree of sleepiness and to help exclude narcolepsy.
The other part of the problem with the in-home vs laboratory debate is that in the past, proponents have been comparing "apples" to "oranges." This is because the technology that has been used in the two settings has been very different. The typical home study was performed with a four-channel cardiorespiratory recorder measuring heart rate, respiratory effort, airflow, and pulse oximetry.3 Although a popular new piece of equipment has added qualitative sleep monitoring and measurement of periodic limb movements,4 it suffers from an inability to detect actual arousals on EEG recording. This makes it difficult to detect subtle respiratory events and determine whether periodic limb movements have any clinical relevance.
The debate would obviously make more sense if the technology in the home environment and in the laboratory were equivalent. The paper by Mykytyn and colleagues that appears in this issue of CHEST (see page 114) tries to compare "apples" to "apples." They compare portable full polysomnography and in-laboratory full polysomnography simultaneously. These studies were done in the laboratory, and to try to simulate the home environment, the authors ignored the portable polysomnographic measuring equipment in half of the studies. Although the study has weaknesses, including the small sample size, no actual in-home evaluation, and failure of both electromyographic and oximetry signals, it does begin to support the authors' conclusion that portable polysomnography may be a viable alternative to in-laboratory polysomnography.
A recent article by Fry et al5 supports this notion. This study also compared simultaneous recording of portable full polysomnography with standard full polysomnography in the laboratory. In addition, these authors performed full polysomnography in the home 1 to 2 weeks after in-laboratory evaluation in 77 patients. Similar results were obtained from both methods. Interestingly, patients preferred the in-laboratory study over the home evaluation (63.6% compared to 33.8%). They felt the equipment was less cumbersome in the laboratory, and they felt they could actually sleep better in the laboratory which obviously is counter to popular belief. With the type of equipment being tested, the patients had to have the sensors applied in the laboratory first, and several patients complained of the travel time and the fact that they had to take too much equipment home.
Obviously there has to be improvement in technology and convenience for full polysomnography to be performed in the home setting with any frequency. Practitioners of sleep medicine have to be confident that the technology answers the clinical questions being posed. One has to be sensitive to the pretest clinical suspicion of disease. In addition, studies need to assess whether home technology actually allows for the assessment of a greater number of patients at a reduced cost. Specifically, we need to assess not only the cost of a single test, but whether there is any additional cost incurred because of equipment failure or because the initial study failed to answer the underlying clinical question.
References
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