A tool and method of continuously assessing sleep disorders in a home environment
OHSU # 1342
OHSU has developed a non-obtrusive system to monitor and diagnose sleep apnea and hypopnea through the use of load cells installed in the supports of a patient’s bed. The load cells continuously and independently measure the weight supported by each leg of the bed, and are sensitive enough to pick up small fluctuations in weight which result from slight mass displacements on the bed due to the patient’s breathing. These movements are converted to a load cell breathing signal which can then be analyzed in the same fashion as traditional polysomnography (PSG) tracing data. OHSU researchers tested the effectiveness of using load cell breathing signals to detect sleep apnea compared to traditional PSG breathing signals. Load cells were able to correctly classify disordered breathing segments with a sensitivity of 0.87 and a specificity of 0.97 for AHI >15.
Sleep Lab Centers - Diagnosis of sleep apnea is most commonly performed using multiple night PSG studies at a sleep center attended by a clinician. Validation studies have found that load cell technology performs comparably to PSG devices when used in a sleep lab setting.
Home Monitoring - Light weight and with the potential for easy setup and transportation, load cells may also be implemented in home monitoring settings. In the comfort of a patient’s home, load cell data can be collected continuously, giving physicians consistent data throughout the night and over multiple days.
Advantages of Load Cells over Competing Technologies
Patients in polysomnographic studies suffer from the first-night effect. Essentially, nasal pressure cannulas, oral thermistors, and belts significantly disrupt a person’s sleep architecture, sleep efficiency, and REM latency and duration. Simply put, patients lay awake and uncomfortable – frustrated by the arsenal of gadgets on their face and chest. Even after the first night, maintaining proper positioning of sensors as patients move around in their sleep is difficult and sometimes impractical.
In contrast, load cells effectively monitor sleep in a non-obtrusive, non-contact manner. Load cells only need to be setup once under the bed posts to provide numerous nights of data collection. They are not inadvertently removed during sleep, as is common with current sensors. Load cells also do not exacerbate claustrophobia or skin sensitivities. Furthermore, computer readouts of load cell data are also very similar to classic PSG readings. Since physicians are accustomed to working with PSG readouts, transitioning to load cells should be straightforward.
Sleep Lab Testing
The total U.S. clinical market size for sleep apnea testing in 2011 was $2.52 billion. We calculated this figure based on an estimated 3,000-3,500 sleep centers in the U.S and each sleep center averaging 140 patients per month. Each sleep center visit costs $2-3,000 and Medicare pays approximately $235 million in reimbursement annually. In 2010, Global Data estimated that 2012 sales of sleep apnea diagnostic equipment sales would approach $225 million and maintain a compound annual growth rate (CAGR) of 4.7% through 2017.
Home sleep apnea testing (HSAT) currently accounts for 10% of the apnea testing market or approximately $252 million annually in the U.S. HSAT is preferred by insurance providers mostly because physician reimbursement is generally in the range of $180, compared with $700 or so for polysomnography. Similarly, HSAT devices are expected to account for 10% of device sales or approximately $22.5 million annually. However, the sale of HSAT devices has seen explosive growth since 2008 and this trend is expected to continue as the industry shifts to a model where 70% of tests are conducted at home by 2027, compared to 10% today.
US Patent 8,905,928
- Tamara Hayes, SM.Biomedical Engineering
- Zachary Beattie, SM.Biomedical Engineering
- Chad Hagen, SM.Psychiatry
- Michael (Misha) Pavel, SM.Biomedical Engineering
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Technology Development Manager