Obstructive sleep apnea (OSA) is associated with reduced quality of life, excessive daytime sleepiness and fatigue. Cardiovascular consequences include aggravation of hypertension, ischemic heart disease, congestive heart failure, cardiac arrhythmia, and cerebrovascular disease. Obstructive sleep apnea is also implicated in diabetes mellitus, pulmonary hypertension, and metabolic syndrome. Untreated obstructive sleep apnea represents a significant health risk. Effective treatment for obstructive sleep apnea has been demonstrated to improve quality of life, improve blood pressure control, congestive heart failure and rate of all cause mortality (moderate-severe obstructive sleep apnea).

The prevalence of obstructive sleep apnea appears to be increasing in association with the increase in obesity. Presently, approximately one third of US citizens are obese with BMI > 30 kg/m2. It is estimated that 80% of individuals with obstructive sleep apnea remain undiagnosed. The current gold standard for the evaluation of OSA utilizes in-laboratory testing for both diagnosis and treatment (most commonly when positive airway pressure is the treatment of choice). This can be a costly and time consuming process for patients with the potential for delay in treatment. In addition, there are areas of the country where access to in-laboratory testing is limited due to a lack of sufficient sleep laboratory facilities. The present number of accredited sleep centers is insufficient to address the large number of individuals who would benefit from evaluation and treatment. There is a need to expand our testing beyond the sleep center so as to improve access, while maintaining appropriate quality of testing.

Home sleep testing (HST), also called out of center sleep testing (OCST), and portable monitoring (PM) provides the opportunity to improve access to diagnostic testing. Based on the Executive Summary on portable sleep testing published in 2004, sleep testing devices are graded from I-IV based on the number of channels which are utilized for testing. The current “gold standard” of data collection devices (Type I) is the traditional in-laboratory test. This includes a minimum of four channels of EEG; electro-oculogram (EOG), and electromyogram (EMG), all of which are used to determine sleep stage. In addition, measures include electrocardiogram (ECG), airflow, respiratory effort, body position and oxygen saturation. A sleep technician (attended) is physically present in the sleep center to correct any technical difficulties with data acquisition as well as respond to patient needs. A Type II sleep testing device is similar to the Type I without direct technician supervision (unattended). A Type III sleep testing device monitors a minimum of four channels that must include one or more channels of respiratory effort, airflow, oxygen saturation, and heart rate/ ECG. A Type IV sleep testing device by Medicare criteria requires three channels usually consisting of airflow, pulse/heart rate, and oxygen saturation. The majority of current home sleep testing devices are Type III. The American Academy of Sleep Medicine (AASM) has recently introduced a new classification system based on the method of signal acquisition (SCOPER). This may replace the current classification system over time. The reference has been provided for your review.

Advantages with HST are many, including the ability of the patient to sleep in their most familiar setting. HST increases flexibility for patients that require evaluation but may not have access to a sleep center due to geography, physical or social reasons. These devices utilize fewer monitoring channels which may be less disruptive to sleep. In addition, there is the potential for multiple nights of study with some devices. HST devices are less costly and less technically complex than in-laboratory testing equipment. In many instances the patient can place the appropriate sensors without technician intervention. Most importantly evaluation of “at risk” patients is not limited by the number or location of in-laboratory diagnostic sleep beds.

There are several limitations to home sleep testing. The diagnosis and severity of sleep apnea traditionally relies on the Apnea Hypopnea Index (AHI) which is determined by the number of apneas and hypopneas divided by the total sleep time. As not all home sleep tests evaluate sleep by using EEG, the total sleep time is often overestimated. Because of this, the determination of a severity rating in home sleep testing may underestimate the true severity of sleep disordered breathing. In the home setting the severity is typically described as a Respiratory Disturbance Index (RDI), calculated as the number of apneas and hypopneas divided by the recording time. The recording time may include an indeterminate amount of wake time in addition to sleep time. Some devices have added actigraphy (a measure of activity/movement) as an estimate of sleep time; however, the overestimation issue remains even with this added technology. If there is concern that the HST is not valid for the reasons above, the patient may be referred for in-laboratory evaluation. As these studies are completed without direct technician support the potential for lost or incomplete data is higher (15%-20%). This can lead to the need for multiple studies or ultimately an in-laboratory evaluation. Other concerns with home testing are the potential loss or damage to the home sleep testing devices. Although less complex than in-laboratory testing, the process of distribution of the equipment, testing/data acquisition, retrieval of the data, analysis and report generation requires well-trained personnel. In symptomatic patients with a high pre-test probability for OSA, a negative home sleep study will require an in-laboratory evaluation. Lastly, HST does not typically have the technology needs to evaluate for the presence of sleep disorders other than sleep apnea.

Home sleep testing has been compared with in-laboratory polysomnography in a number of studies. The largest study to date the HomePAP study demonstrated no difference in acceptance of positive pressure therapy (PAP) therapy, titration pressures, and subjective improvement as measured by Epworth Sleepiness Scores (EES) / Functional Outcomes of Sleep Questionnaire (FOSQ) at three months follow-up. In this study, PAP usage was slightly improved in the home testing group. Similar equivalence in PAP adherence and subjective outcomes has been obtained in additional studies. It is important to note the subject population in each of these studies was highly selected; patients with co-morbid conditions were excluded. These co-morbid conditions included congestive heart failure, moderate to severe obstructive airway disease, neuromuscular disease, hypoventilation syndromes or hypoxemia with sleep requiring oxygen. The studies were carried out under the direction of comprehensive sleep centers with evaluation performed by sleep medicine physicians. It is unknown whether these results could be applied to an unselected primary care population, particularly as relates to cardiology and patients with congestive heart failure. More recently Kuna et al. evaluated home sleep testing comparing to standard in-laboratory testing using consecutive patients who were enrolled without exclusion of co-morbid conditions. As in the previous studies there was no difference in CPAP adherence or functional outcome. Interestingly, both arms of the study showed poor CPAP adherence (3.49 hours per night-home tested; 2.92 hours per night-laboratory tested). Further research in HST for patients with co-morbid conditions is necessary in order to determine the utility of home testing in complicated patients with co-morbid conditions.

The American Academy of Sleep Medicine published clinical guidelines for the use of unattended portable monitors (PM) in 2007. Recommendations include home sleep testing as an alternative to in-laboratory polysomnography in individuals with a high pretest probability for obstructive sleep apnea and without co-morbid conditions. These conditions include, but are not exclusive to, moderate to severe obstructive airways disease, neuromuscular disease, and congestive heart failure. Other clinical situations in which in-laboratory testing is recommended would include atrial fibrillation, chronic narcotic use, hypoventilation syndromes, nocturnal oxygen use, and BMI > 40 kg/m2. The guidelines also consider home sleep testing as an alternative to in-laboratory testing in assessing response to non-PAP treatment to include dental appliances, surgery, or weight loss. HST is also an option for individuals for whom in-laboratory testing is difficult related to illness, immobility or transportation.

HST should be utilized in the structure of a comprehensive sleep evaluation and include appropriate longitudinal care. A comprehensive assessment increases the likelihood of appropriate health care utilization, adequate diagnostic assessment, accurate data collection, and effective patient management.

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References

1. Executive Summary on the Systematic Review and Practice Parameters for Portable Monitoring in the Investigation of Suspected Sleep Apnea in Adults. Am J Respir Crit Care Med 2004;169:1160-1163. 

Keywords: Sleep Apnea, Obstructive, Quality of Life

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