An Electric-Field Based Breathing Rate Monitor

Breathing rate is a significant vital sign. Growing evidence suggests that it may be one of the best early predictors of decline of health. Breathing rate trends enables neonatal care, home monitoring of the chronically ill, sleep studies to detect sleep apnea, ascertaining deception via polygraph and long term tracking of health conditions of invalids. Contact methods to determine breathing rate are fraught with limitations such as restricting patient's mobility, causing physiological discomfort and psychological stress, all of which can detrimentally affect the reading. Also these ways of monitoring are not suitable for neonatal patients and burn victims. Thus non-contact techniques are preferred. However, most of these measurement paradigms are error-prone by virtue of design, e. g., infrared-based non-contact sensors are highly sensitive to even slight change in position, pressure, etc. These systems (e. g. radar-based) are often expensive and involve complex signal processing. Recently textile-based sensors for breathing rate monitoring have gained popularity. But these are generally developed as wearables. In this paper we propose a novel, low-cost, non-invasive, non-contact, electric-field based sensing sheet which can be used on hospital beds. The electrodes for breathing rate measurement are designed, as part of the sheet, using conductive fabric. It functions on less power and has simple measurement and signal processing requirements. It determines the breathing rate by measuring the capacitance values that vary in accordance to the respiration of the subject lying on the sheet. The sheet is washable and reusable.