Contents I. Introduction
RESPIRATORY rate is considered the next critical vital sign and yet often goes under measured or ignored primarily due to shortcomings of the currently used measurement methods. Respiratory rate provides important information on a person's health condition and physiological stability, and an abnormal respiratory rate is a strong indicator that a health crisis is imminent [1]. In fact, a sudden change in respiratory rate is one of the strongest predictors of mortality [2]–[3]. Current methods to collect respiration data include use of respiration belts, impedance through EKG electrodes, spirometers, or clinical observation/counting. These techniques have drawbacks that limit the frequency and convenience of the respiratory monitoring. Recognizing that closer respiration monitoring can save lives and improve quality of life, reduce hospital stays, and lower medical costs [3], the heath care industry is seeking improved respiration monitoring products.
