Substrate-integrated waveguide (SIW) based antenna in remote respiratory sensing

In a hospital environment, continuous monitoring of respiratory activity in a patient moved from intensive care unit may prevent incidence of central sleep apnea (CSA). CSA is difficult to predict and can be life-threatening. Some of the existing respiratory monitoring methods require direct contact with the patient; such as placing electrodes on the skin or wearing a monitoring belt around the chest. Other monitoring devices are bulky and invasive such as the spirometer which involves the patient breathing through a mouthpiece; and is thus, inconvenient. Additionally, the aforementioned monitoring methods/ devices are not suitable for critically ill patients that may not tolerate a mouthpiece, or burn-injured patients that cannot tolerate wearing a monitoring belt. Consequently, there is a need to develop remote/non-contact devices to continuously monitor respiratory activity in a reliable and non-invasive way. Optical techniques have been utilized for remote respiratory monitoring with reported high sensitivity; however, they cannot penetrate clothing. Therefore, microwave techniques have been explored due to their inherent advantage of penetrating clothes.