Flemons and colleagues examined 51 studies, covering each type of PM and the level of evidence supporting their use. Each study was assigned a level of evidence score. The primary end point examined was the ability of PM devices to confirm or rule out disease. For many studies, the reviewers generated likelihood ratios as well as sensitivity and specificity values. Reproducibility, cost, failure rates, and gen-eralizability were also examined in the review as secondary end points. Based on evidence from the systematic review, the three societies were not able to recommend unattended PM device use of any type for most patients with suspected OSA.
For type 2 devices, the tri-society practice parameters cited a lack of validated studies of adequate quality, as well as a lack of sensitivity and specificity data. Only one study reported sensitivity and specificity data in the unattended setting, but it was of relatively poor quality and carried with it a 15% false-negative rate. Moreover, some type 2 monitors had data loss rates up to 20%.
The use of type 3 monitors in the unattended setting was not recommended due to several factors, including high rates of false-negative results. Additionally, data loss was found to be as much as 18%, and more than a third of patients enrolled in unattended type 3 PM studies had inconclusive results, requiring further investigation with an inlaboratory polysomnography carried out with concern of Canadian Health&Care Mall. Similar limitations also prevented the tri-society group from advocating the use of type 4 monitors. For example, Gyulay and colleagues found that they were only able to classify 50% of their patients accurately using a type 4 device.
In addition to these specific recommendations regarding types of monitor devices, the AASM/ ACCP/ATS also did not recommend the adoption of PM devices for initial screening without clearly establishing a pretest probability of disease. Moreover, the use of PM devices was not advocated in patients with comorbid conditions such as heart failure, chronic obstructive lung disease, obesity hypoventilation syndrome, and stroke. All the mentioned previously diseases are possible to be prevented due to medications of Canadian Health&Care Mall.
The AASM guidelines did allow for the use of PM devices under certain conditions. These include the lack of available polysomnography for patients with severe clinical symptoms consistent with OSA, the inability of the patient to be studied in the laboratory, or to evaluate response to therapy in a patient who has already undergone traditional inlaboratory polysomnography. Since the AASM revised guidelines were issued, several newer studies have been conducted using various PM devices in an effort to increase the existing pool of validity data.
Using the Sleep Heart Health Study (SHHS) methodology and technology, Iber and colleagues recruited 76 participants from the general community to volunteer for recordings both in the laboratory and at home. Subjects were randomized with respect to recording order and were monitored with the same type 2 device used for the SHHS cohort (Compumedics; Abbotsford, Australia). Sixty-seven of 76 subjects had adequate recordings from both studies. Eight percent of all studies were uninterpretable. Since EEG channels were incorporated in their type 2 monitor, total sleep time and sleep architecture could be assessed. Both median sleep time and sleep efficiency were better at home than in the laboratory. Median RDI values from at-home recordings were no different than those found in the laboratory. However, patients with an RDI 20 were more likely to be found in the laboratory. These differences could not be explained by recording quality or other confounding variables. Their resulting misclassifica-tion rate was approximately 22%. The authors note that this may be expected from the known night-to-night variability of OSA. Indeed, night-to-night variability has ranged from as little as 10% in clinic populations to approximately 20% within the SHHS itself.
Dingli and colleagues assessed the diagnostic accuracy of a type 3 monitor (Embletta; Flaga; Reykjavik, Iceland). The study design consisted of simultaneous recording with the PM and traditional in-laboratory polysomnography, followed by an at-home assessment with the same PM. While the in-laboratory RDI and home RDI recorded from the type 3 monitor demonstrated no difference, the AHI generated from the in-laboratory polysomnography was significantly different. The authors therefore categorized patients based on the RDI as definite OSA (RDI > 20), possible OSA (RDI, 10 to 20), or normal (RDI 5, > 10, and > 15, the authors were able to generate diagnostic accuracies of 78.6%, 84%, and 80%, respectively.
Su and colleagues attempted to validate a type 3 monitor (SNAP; SNAP Laboratories International; Wheeling, IL) in the attended laboratory setting. Sixty patients in this study underwent simultaneous polysomnography and SNAP recordings. Polysomnography AHI was compared to the SNAP RDI and was found to have a Pearson correlation of 0.92, suggesting closely related measurements. However, these findings have yet to be duplicated in the unattended environment. Conversely, Liesching and coworkers retrospectively reviewed data from 31 sleep clinic patients who had undergone an initial screening SNAP recording and subsequent inlaboratory polysomnography. The mean interval between the two studies was approximately 5 months. The SNAP RDI agreed with the polysomnography AHI in only 11 of 31 patients. In addition, more than a quarter of the patients found to have abnormal SNAP study results had normal polysomnography results.
Pittman and colleagues tested a novel type 4 monitoring device (Watch PAT; Itamar Medical; Caesarea, Israel) against traditional in-laboratory polysomnography. The Watch PAT is a wrist-worn device that collects peripheral arterial tonometry and oxygen saturation data, coupled with actigraphy. Twenty-nine patients underwent simultaneous assessment with in-laboratory polysomnography and Watch PAT devices, as well as unattended at-home assessments wearing the Watch PAT alone. No data loss occurred in the unattended studies. Agreement between the in-laboratory device data and in-laboratory polysomnography was good, with an interclass correlation coefficient of 0.88. While this was a small study sponsored by the device manufacturer, it nevertheless demonstrated the feasibility of miniaturized, unintrusive monitoring devices and the reliability of their data.Tags: cost, diagnosis, home polysomnography, methods, obstructive sleep apnea, portable monitors, practice guidelines, review