Diagnosis and Treatment of Sleep Breathing Disorders: 
Choosing the Best Sleep Test

Mansoor Ahmed, M.D, FCCP.
Director, Cleveland Sleep Center. 
Asst. Professor of Medicine, Case Western Reserve University, Cleveland, Ohio.

Accumulating evidence over the last decade or so indicates that Sleep Breathing Disorders (SBD). including Obstructive Sleep Apnea Syndrome (OSA) are quite common ( 1 ). 

SBD are associated with increased morbidity and mortality and has been shown to have adverse impact on health care economics. SBD are chronic and very often under- diagnosed. An estimated 80-90% of persons with OSA have not received a clinical diagnosis (2). In fact, the increased recognition that SBD are common and under- diagnosed disorders, has changed the entire spectrum of Sleep Medicine Practice and demand for the diagnostic sleep labs. 

The growing demand for sleep studies has led to the introduction of newer diagnostic approaches, including ambulatory home monitoring devices to diagnose SBD that might be cheaper and provide an alternative to conducting full, in-laboratory sleep studies. Right now, the debate about the issues related to the cost-effectiveness of these newer sleep diagnostic technologies versus sleep laboratory based studies is raging across the continent. To my knowledge no systemic studies involving a large number of patients have been conducted to evaluate the issue of cost- effectiveness by comparing in-lab diagnostic studies with ambulatory monitoring to diagnose SBD. So, as we stand now, the issue of cost-effectiveness is unresolved. 

From a technical point of view, there are few good studies which are well designed and are conducted to determine the accuracy, validity and reproducibility of the ambulatory sleep technologies (3 ). However, the issue involves not only the technology/equipment used, but also encompasses the issues like the type of recording protocol selected, expertise of technical staff and the knowledge of the person interpreting the tests performed.

Before we enter into any further debate about the practical role of sleep-lab facilities versus ambulatory technologies for the diagnosis of SBD, we must ask ourselves a basic question, as Dr. Guilleminault put it (4): "What do we do a test for?" 

The correct answers to all these legitimate questions by this world renowned sleep specialist is: ALL OF THE ABOVE. For now at least, it than appears that, only a lab-based sleep test may have capability of providing the answer to all of the above.

Nevertheless, the issues of health economics are perhaps more complex and demand flexibility in order to accommodate the equation of supply & demand without compromising the quality of care. In this context, the studies from UK perhaps provide some scientific evidence and a moral support to achieve this goal. A provocative study by NJ Douglas raises the fundamental issues about the importance of measuring sleep parameter in-patients with OSA (5): What is the diagnostic and therapeutic value of sleep parameters in the management of OSA? According to the author, the answer was -NONE. Indeed, if we really take the sleep parameters out of the diagnostic sleep loop (although we may not call them "Sleep Study", for the diagnosis of OSA, it may become cheaper and less cumbersome to diagnose OSA. And now of course we also have all types of auto-PAPs, directly available at the pharmacy store to resolve the expensive issue of sleep laboratory based titration CPAP studies. And still if patient continues to be sleepy then what do we do. ..than of course we have now a new stimulant Modafanil! to take care of rest. In fact this afro mentioned algorithms, in some form or the other is being promoted.

So where do we go from here i.e. issues of appropriate sleep diagnostic strategy? A recent, well worded, ASDA executive summary to some extent clarifies some of these issues (6).

"Based on a review of the available literature, unattended Portable Recording may be effective for the diagnosis of severe SDB, when used by a qualified sleep-specialist as a part of a comprehensive sleep evaluation. Portable recordings used as an isolated procedure by unqualified clinicians may result in improper care and higher health care cost due to its application for inappropriate diagnostic indications."

In summary, ambulatory-monitoring devices has the potential to improve access and lower the cost of care for patients with sleep breathing disorders. However one of the major challenges to achieve these goals is to develop clinical guidelines and ensuring appropriate utilization. In future, ambulatory studies are expected to become more acceptable to diagnose OSA and it is unlikely that there will be a continued demand for a large numbers of standard laboratory based sleep studies primarily addressing sleep apnea. 

From the therapeutic perspectives, because of the automation of CPAP titration equipment (7), titration in the ambulatory settings will increase and may obviate the need for sleep-lab based titration for a majority of uncomplicated OSA patients. However, sleep laboratory based studies will be needed to diagnose and treat patients with polymorbidity and complicated SBD. As a result, future sleep laboratories will evolve into more comprehensive sleep diagnostic centers rather than the typical "apnea sleep lab", addressing the clinical issues related to sleepiness, circadian rhythm and insomnia rather than the OSA only.

References: 
1. T Young et al: The occurrence of sleep-disordered breathing among middle age adults: N Engl J Med; 328: 230-235, 1993. 
2. T Young et al: Estimation of the clinically diagnosed proportion of sleep apnea syndrome in middle aged men and women. Sleep 20: 705-706, 1997. 
3. S Redline et al: Measurement of sleep-related breathing disturbances in Epidemiological study: assessment of the validity and reproducibility of a portable monitoring device. Chest, 100: 1281-86, 1991. 
4. C Guilleminault: Suspicion of sleep-disordered breathing: which test to perform? Sleep Medicine, 1: 73-75, 2000 
5. NJ Douglas et al: Clinical Value polysomnography. Lancet, 339: 347-50, 1992. 
6. Indications for the clinical use of unattended portable recording for the diagnosis of sleep-related breathing disorders. ASDA News, Volume 6, No1, 1999. 
7. H Teschler et al. Automated continuous positive pressure titration for obstructive sleep apnea syndromes. Am J Respir Crit Care Med, 154: 734-40 

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