PSG Validation of MATRx Plus AHI

Obstructive sleep apnea (OSA) is a common disease that carries significant risks for cardiovascular disease, mortality, and economic costs. Almost thirty years ago, initial population studies found the prevalence of OSA to be five to nine percent of the adult population. Excess body weight is a risk factor for the development of OSA, and the recent rise in prevalence of obesity has led to revised estimates of OSA prevalence, now at seventeen per cent of the adult population. OSA is poorly recognized clinically; 85% of apneics remain undiagnosed and untreated.

OSA derives fundamentally from structural abnormalities of the pharynx that cause pharyngeal narrowing or closure during sleep and produce recurrent apneas and hypopneas. During wakefulness, compensatory neuromuscular reflexes protect the pharynx from collapse. These reflexes are lost during sleep, leaving the collapsible human pharynx susceptible to narrowing or closure. Owing largely to its association with excess body weight, OSA has arguably become the most prevalent chronic non-communicable disease in industrialized societies, assuming that obesity is not classified a disease. In addition to impairing quality of life, OSA conveys an increased risk of cardiovascular disease and vehicular accidents. The majority of apneics remain undiagnosed and untreated. Thus, OSA has the hallmarks of a major public health problem, affecting all age groups and increasing in epidemic proportions. Unfortunately, current medical practices seem ill-suited to dealing with the challenges posed by OSA.

Perhaps the most unsettling aspect of present medical practices relates to the cumbersome, uninviting, and expensive methods currently used to diagnose the disease. Common clinical experience indicates that individuals often resist undergoing the standard diagnostic test, an overnight in-hospital polysomnogram (PSG), because of the extensive attachments to the body surface. In other words, as public awareness of sleep apnea has increased so also has the negative impression of current testing. Any effective solution to the public health challenges posed by sleep apnea will have to consider the need for less cumbersome and off-putting clinical methods.

Zephyr Sleep Technologies has developed a device that has been approved for use in Canada. The device, MATRx plus, functions as both a Level III sleep recorder (records respiratory airflow, respiratory effort, pulse rate, and arterial oxygen saturation) as well as a home-based system to select patients for oral appliance therapy. The American Academy of Sleep Medicine (AASM) recommends the use of apnea-hypopnea index (AHI) for the diagnosis and categorization of OSA severity. The Level III function of the MATRx plus device is approved for use in Canada with two autoscoring methods: oxygen desaturation index, ODI and apnea-hypopnea index, AHI, but requires further validation of AHI for clearance by the US Food and Drug Administration (FDA).

The proposed research will validate the AHI autoscoring function of the MATRs plus Level III home sleep recorder by comparing it to data recorded in a PSG, which is considered to be the gold standard for sleep testing. Though the effectiveness of the AHI autoscoring algorithm has been previously established, it has not been validated against PSG data. Additionally, other parameters such as snoring will be examined in order to develop scoring algorithms for other facets of sleep disordered breathing.