B. Wireless Sensors

In order to maintain a closed HIPAA compliant system design, data was encrypted on the firmware and sent to the smartwatch using the BLE stack. This level of encryption was deemed sufficient, as BLE encrypts data using 128-bit Advanced Encryption Standard (AES) cryptography [18], which meets the HIPAA requirement to have at least 128-bit encryption to protect electronic protected health information [19].

The wireless dust sensor used a compact optical dust sensor (Sharp Corporation, Osaka, Japan) for dust density measurements, which was validated against a Dylos professional air quality monitor (DC1100 Pro, Dylos Corporation, Riverside, CA) for sensitivity and accuracy under several different air quality conditions. To allow the dust sensor to be portable, it was integrated with a BLE module (ARM Cortex-M0 microcontroller with integrated Bluetooth 4.0 LE, RFDigital Corporation, Hermosa Beach, CA) and power supply board (PowerBoost 500C, Adafruit Industries, New York, NY). A circuit diagram of the wireless dust sensor can be seen in Fig. 2.

Circuit diagram of the wireless dust sensor.

To collect physiological measurements of individuals, a Vitalograph Asthma-1 electronic peak flow meter (Vitalograph Ltd., Buckingham, England) was used to obtain spirometry data. Spirometry information is an important physiological measurement for the treatment of asthma, as it can assess the severity of the individual’s asthma [20]. More specifically, peak expiratory flow (PEF) and forced expiratory volume in one second (FEV₁) information are most important for the clinical assessment of asthma, as a reduction in these values from age and height-matched healthy individuals’ averages indicates the overall severity of the asthma at a particular time [20].

Spirometry data was sent to the cloud immediately after the individual took measurements by pressing the “spirometer” button on the watch (see Fig. 3 below). The smartwatch app then parsed and read these data using the information provided in the device’s API developer’s toolkit, and sent this information to the cloud for real-time feedback of the current asthma attack risk.

Asthma app risk value user interface, showing the overall asthma risk and button to collect spirometer data on the smartwatch. Green risk level represents a low overall asthma risk, yellow risk level represents a moderate asthma risk, while red represents a high asthma risk.