The answer to the above question is that home sleep testing (HST) has the potential to be either, neither, or both. HST can bring both accessibility and affordability for detection and treatment to the 90% of OSA patients who have not yet been identified. On the other hand, if applied and interpreted improperly, it can result in CPAP treatment for those who don’t require it. Of much greater concern is the withholding or withdrawal of CPAP in those who may suffer dire consequences without it. Such misuse could also lead to the improper management of other varieties of sleep-disordered breathing (SDB) besides OSA, such as central sleep apnea (CSA), complex sleep apnea, obesity-hypoventilation syndrome, Cheyne-Stokes respiration, and hypoventilation due to severe COPD and neuromuscular disease.
Limiting our sleep focus to only HST and OSA can lead to the “demedicalization” of other important sleep disorders such as insomnia, sleep deprivation, and shift work disorders. The narrow-minded notion that if it’s not apnea, it’s not important is erroneous. This also holds true for the automatic assumption that an individual’s sleep symptoms must be due to their apnea. Countless patients have the incidental presence of OSA (which may indeed require therapy), but their presenting symptoms remain in spite of optimal CPAP. These co-existing non-OSA sleep problems not only impair quality of life, but the sleep fragmentation that results may actually have cardiovascular morbidities similar to those in apnea. Overlooking these patients provides a real disservice in their care.
EVOLUTION OF HST: WHY NOT EARLIER?
In many patients, any sleep study may be difficult to obtain. In-lab testing, in particular, adds even greater impediments. Patients may be reluctant to sleep or try to get sleep (“first-night effect”) in a strange place. For some people, reluctance may be due to geographic distance or inability to schedule an available time, due to work and family responsibilities. For others, there is hesitation in leaving a spouse, other family member, or even a pet for an overnight absence. Still others are institutionalized in hospitals, nursing homes, rehabilitation units, or other assisted-living settings, where they are not able to travel to an off-site sleep center.
Another obstacle to the performance of an in-lab sleep test is the risk of incurring high personal medical cost. This is a fear not only for patients, but for their primary care physicians (PCPs) as well. It is not an ungrounded fear. Many physicians feel that every patient they refer to the sleep center always undergoes a baseline full night sleep study, and is (automatically) diagnosed as having OSA. The patient is then asked to return for another full night of study for CPAP titration. A CPAP device is dispensed, often from the same facility. A report may not reach the PCP, and the patient may never return for follow-up, becoming rather a patient of the sleep center. Other perhaps more pressing medical issues are lost in the shuffle, as the OSA takes on “a life of its own.” I’ve heard many physicians lament, “I know I’m good, but I can’t be THAT good [in OSA diagnosis].” It sometimes appears that the same labor-intensive, time-consuming, and costly approach is applied in the same manner to every patient.
But why not perform ambulatory polysomnography to improve access and decrease cost? Many of the aforementioned obstacles to in-lab sleep studies could be readily overcome. However, the sleep specialist’s approach to the OSA suspect has changed little in the last 25 years. Pragmatism and expedience have infiltrated and even overtaken our disease management approach to such chronic illnesses as asthma, diabetes, and hypertension, but not OSA. Application of the principles of evidence-based medicine, disease management, outcomes modification, and cost-effectiveness has not had a sufficient opportunity to evolve and be applied in a mature fashion, in the rapidly developing field of sleep medicine.
In past years, technology for home testing was rudimentary. Little data was published assessing it. The sleep establishment opposed it. Reimbursers couldn’t force it. Stakeholders flourished.
But the most important obstacle to HST was that it could not (and still doesn’t) meet the “acid test” of all acceptable screening tests, ie, there must be no false negatives. HST typically doesn’t incorporate sleep time, stage, and quality, as reflected in the EEG, EOG, and EMG. Therefore, we don’t have the all-important denominator of an in-lab study. Our apnea-hypopnea index (episodes per hour of sleep) is replaced by a respiratory disturbance index (RDI = episodes per hour of recording). Therefore, a patient with a low RDI on a home study may still suffer from significant OSA, but may have diluted their AHI by a good bit of wake time. Furthermore, hypopneas generating <4% desaturation cannot be scored, even though undetected microarousals may have been present. Actual AHI on an in-lab study may be much higher than the RDI on a patient’s type III or IV recording. Therefore, a negative HST doesn’t exclude significant OSA, especially if clinical suspicion was present. It would not be a diagnostic endpoint, whereby the patient can be deemed safe and in no need of CPAP. In fact, if the patient is symptomatic, a complete PSG would be essential to exclude OSA and deliver the 100% sensitivity expected of a satisfactory screening test.
A lesser concern, but one not to be ignored, is the occurrence of a false-positive HST. A variety of sleep-disordered breathing and cardiac and pulmonary diseases have mimicked OSA when testing is limited. Additionally, CPAP titration remained an in-lab exercise, due to the required dynamic interaction between the technologist and the patient’s upper airway and quality sleep.
EVOLUTION OF HST: WHY NOW?
In spite of these obstacles, a number of factors have now converged to make home testing a valuable additional tool in the management of sleep patients. The Institute of Medicine (IOM) has recently made the observation that health care in the field of sleep medicine has progressed quite slowly over the last several decades. The sleep establishment’s very conservative and traditional approach has directed the major portion of time and money toward the in-lab diagnosis and then titration of CPAP in the OSA suspect. Continuity of care with emphasis on actual treatment and outcome has been neglected. The approach to these patients has not changed substantially in the last two and half decades.
In addition to the IOM, another federal institution, the Centers for Medicare and Medicaid Services (CMS), has finally approved reimbursement for CPAP based on a HST. Their efforts have been largely motivated by a desire to decrease the overall cost of OSA care, while actually increasing volume, by identifying undiagnosed apnea patients.
Another factor that has made HST almost inevitable is increasing awareness by patients, families, and caregivers not only of the possible presence of sleep apnea, but the attendant risk. These groups are becoming more aware of its cardiovascular sequelae (even anesthetic risk) and the mitigating effect of treatment. Perhaps the major factor contributing to the move toward HST for a subset of our patients is the advances that have been made in technology (see Sleep Review, June 2008, “Portable Monitoring Pathways“). While technology has made many advances in medicine inaccessible and unaffordable, progress in home testing can do exactly the reverse in the field of sleep. Advances in technology have made extremely sophisticated monitoring quite feasible in the home. Analysis of ECG algorithms may even allow sleep staging without EEG monitoring.
While these advances in technology have taken place, more and more data regarding the specific roles of ambulatory testing have entered the medical literature. Evidence-based medicine has become the order of the day in the use of diagnostic tests and interventions. CMS used much of that information to support their stance on the approval of HST for CPAP reimbursement. Efficiency in diagnostic testing and cost-effectiveness have become paramount.
The final factor that contributed to this ultimate approval was the fashion in which medical practice has changed in the last several decades. Patient comfort, convenience, and affordability have been shown to improve patient compliance. Patient compliance, in turn, has been shown to improve outcomes in a variety of disease management models including asthma, hypertension, and diabetes. Improvement in outcome and continuity of care has been both the trademark and battle cry of an effective program. Shifting of emphasis from expensive and time-consuming diagnosis toward therapy and therapeutic outcomes has changed our paradigm in OSA.
The ambulatory sleep study is an idea whose time has come. It can improve patient access to sleep care, and make such care affordable. Careful patient selection requires concentrating on OSA suspects, and particularly those who do not have complicating cardiopulmonary disorders. Other types of sleep-disordered breathing, such as central and complex apnea, Cheyne-Stokes respiration, pickwickian syndrome, and other causes of hypoventilation, are better served on an in-lab study. CPAP titration is also best performed in a laboratory setting. Still, HST permits multinight and longitudinal studies to provide objective support for adequacy and continuity of care.
USING HST FOR OBJECTIVE VALIDATION OF EFFICACY
According to the new CMS guideline, after 12 weeks of CPAP use, validation of efficacy is now a mandate. Since fewer channels are available on the baseline type III and IV tests, the diagnosis of OSA is less certain, and this confirmation of benefit supports proper initial diagnosis. Unfortunately, there is no simple way to document efficacy at the 12-week time frame. Symptoms and use, in fact, are poor barometers and don’t reflect the appropriateness of CPAP therapy. Improvement in symptoms and/or faithful use of the device does not ensure that the initial diagnosis was correct. It does not confirm that CPAP is truly benefiting the patient, or that CPAP has alleviated cardiovascular morbidity.
Placebo effect does occur with CPAP, which may in part be due to relief of snoring. It has been demonstrated that even in the 15% of patients with complex sleep apnea for whom CPAP is only partially beneficial, compliance is at least as good as in those who have true obstructive apnea. These patients are left with a significant number of central respiratory episodes that have not been dealt with, yet may be compliant and subjectively better. Even patients on subtherapeutic CPAP for OSA enjoy some subjective benefit and may use the device regularly.
Reasons for Nondiagnostic Home Studies
In contradistinction, many of the patients who are in most need of CPAP are unable to use it. Therefore, noncompliance does not overturn the OSA diagnosis. This may be related to some other factor such as an uncomfortable mask, mask leak, or mouth leak. It may also be related to hypoxemia that has not been dealt with by the CPAP alone. Or failure of use may simply be due to the air hunger generated by complicating cardiopulmonary disease, leading to a sensation of suffocation and precluding CPAP use. Many patients with potentially harmful apnea are unaware of symptoms at baseline, and even those with symptoms may not notice a change on CPAP therapy. Therefore, the use of patient improvement and/or compliance or the lack of it does not document or refute the need for continued therapy.
The ease of application and low cost make HST ideal to document objective efficacy at the 12-week milestone. It also can be used to validate efficacy of other sequential therapies such as weight loss, oral appliances, or upper airway procedures, such as the pillar procedure. HST also allows the patient to be monitored over time to follow progression or lack of it in the untreated patient. It also allows one to identify changes in CPAP requirements objectively. Therefore, repeat HST can markedly improve patient follow-up and continuity of care. Just as we use spirometry longitudinally in the management of COPD, HST can validate the efficacy of OSA care.
Studies have shown that even in typical OSA, initial CPAP levels may no longer be optimal on subsequent testing. Additionally, an efficacious pressure in the lab may not meet the therapeutic goals required for treatment to be deemed effective. With the shift in emphasis by reimbursers from diagnosis toward treatment and follow-up, repeat HST to validate efficacy and effectiveness can be extremely useful. Accessibility and affordability of HST allow it to be a tool that can be applied when needed as opposed to in-lab testing. More precise individualization of care and tailoring of multimodal treatment are possible.
IS HST ADEQUATE FOR HOME TITRATION?
Great advances have been made in the last two decades that have made HST a viable and potentially valuable addition to the sleep center’s armamentarium for baseline testing. Unfortunately, auto-titration of CPAP in the home has not yet become technologically advanced enough to supplant in-lab titrations. Fortunately, CMS has not accepted CPAP titration in the home to replace in-lab testing. Therefore, for the foreseeable future, titrations need to be done in a supervised, attended, and monitored setting and include sleep stage and microarousal monitoring.
Often restoration of normal sleep architecture and alleviation of arousals are the last remnant of upper airway resistance to remit as the optimal CPAP level is reached on a type I in-lab titration. Having said that, the use of Auto-PAP in tandem with type III monitoring may eventually allow home titration to become a predictably accurate and useful endeavor (see Sleep Review, June 2008, “Portable Monitoring Pathways“). Just as is currently possible with baseline HST screening, multiple nights and sequential testing may become feasible for more accurate determination of the ideal CPAP level. Selection of alternative positive airway pressure modes such as adaptive servo ventilation and bilevel positive airway pressure, and the setting of their parameters, may even become possible.
Joseph Golish, MD, is a board-certified specialist in sleep medicine and author of more than 300 publications on sleep. He is a member of the Sleep Steering Committee for the ACCP. After 35 years as a professor at Cleveland Clinic and head of sleep medicine, he has left academic medicine to advance a new paradigm in sleep medicine, focusing on accessibility and affordability. His goals are the proper use of HST and fostering continuity of care, in an efficient and cost-effective manner, while preserving high quality. He is currently the medical director of Cleveland Medical Devices (CleveMed) and codirector of Parma Community Sleep Lab in Cleveland. He can be reached at [email protected].