Affiliations: Providence, RI
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
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
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.3Although 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
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
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