I-Corps: Ambient Sleep Architecture Monitor

San Diego State University Foundation, San Diego CA

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project is to monitor sleep quality of individuals and report sleep quality index and sleep architecture using an ambient connected sensor. This project will potentially improve quality of care in some patient populations such as Alzheimer/Dementia patients and infants by enabling sleep quality assessment using a non-intrusive technology. The passive sensor we have developed can precisely detect entire sleep stages as well as any abnormalities related to breathing or movement during sleep. The sensor is placed outside of bed and does not pose discomfort to the patient. It is our goal to offer a sleep sensor that will be an essential part of our healthy lifestyle choices. The sensor must be non-intrusive and ambient to be widely accepted. Wearable or body-contact sensors take away from the natural sensation of sleep and might create a feeling of being monitored. For this reason, we believe an ideal sleep monitor should be ambient and easily blend in with the accessories on the bedside table. This monitor will enable the same kind of diagnostic power available in a hospital, to the comfort of our bedrooms. This I-Corps project proposes a sleep monitor based on a passive infrared sensing technology which utilizes a pyroelectric material for temperature sensing. The material is lithium tantalate, a crystal that has pyroelectric properties. A change in ambient temperature creates a change in polarization of the crystal. This change creates a potential across the crystal and a charge is generated similar to a capacitor. The generated charge is collected by electrodes thus we obtain the voltage response of the pyroelectric detector. Under constant and ambient temperature, the response quickly approaches steady state. Due to the thermal time constant, the crystal will quickly thermalize to its environment after input. Thus, we observe a 'voltage pulse' mechanism when there is a fast change (physical movement) against the background. This property makes our sensor very sensitive to fluctuations against the background temperature distribution and allows it to accurately detect fine movements such as chest motion during breathing. We use these fine chest movements to detect respiration and heart rate which in turn are used to determine the sleep stage. We use respiration rate variability to determine sleep stages and derive sleep quality index using sophisticated signal processing methods. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.