Toward the Development of a Wearable Optical Respiratory Sensor for Real-Time Use

Respiration rate is an important vital sign that can provide insight into a patient's status and health progression. This information is used from critical care to sports and human performance evaluation. The current state of the art has demonstrated effectiveness in monitoring respiration rate with the use of wearable sensors. However, their form factor, which refers to the embodiment of approach, size, and shape, makes it difficult to implement within a longterm monitoring setting. Problems relating to form factor, such as compliance, are a major issue in collecting useful and actionable data, because they directly impact comfort and ease of wear. We present a new approach based on an optical computer mouse sensor that can be rendered into a slim, wearable device without the need for a harness or shirt to hold the sensor in place. Its main objective is to achieve similar or better readings than those of the state of the art while reducing the overall size and thus, improve compliance by making it easier, more comfortable to wear. The principle of operation of the sensor allows for enhanced signal and computational noise reduction for movement artifacts. The sensor was tested to determine its limits of detection and was calibrated to expected distance of movement. Then, observations were made under normal breathing conditions, apnea, deep breathing, and hyperventilation covering a spectrum of 0 to 45 breathings per minute (BPM). The performance of the device was described by using the mean average error which was 0.37 and 0.83 under deep breathing and hyperventilation, respectively. Testing revealed that the device produces the best results when worn over the diaphragm and that its readings are comparable to the industry gold standard. The future version we are developing incorporates a slimmer, lighter design, Bluetooth data communication to remove leads and wires, adhesive electrodes and a reusable adhesive that is also waterproof.