Accurate Spirometry with Integrated Barometric Sensors in Face-Worn Garments

Abstract

Cardiorespiratory (CR) signals are crucial vital signs for fitness condition tracking, medical diagnosis, and athlete performance evaluation. Monitoring such signals in real-life settings is among the most widespread applications of wearable computing. We investigate how miniaturized barometers can be used to perform accurate spirometry in a wearable system that is built on off-the-shelf training masks often used by athletes as a training aid. We perform an evaluation where differential barometric pressure sensors are compared concurrently with a digital spirometer, during an experimental setting of clinical forced vital capacity (FVC) test procedures with 20 participants. The relationship between the two instruments is derived by mathematical modeling first, then by various regression methods from experiment data. The results show that the error of FVC vital values between the two instruments can be as low as 2∼3%. Beyond clinical tests, the method can also measure continuous tidal breathing air volumes with a 1∼3% error margin. Overall, we conclude that barometers with millimeter footprints embedded in face mask apparel can perform similarly to a digital spirometer to monitor breathing airflow and volume in pulmonary function tests.

SpiroMask: Measuring Lung Function Using Consumer-Grade Masks

“…We finally had data for 48 participants, out of which 14 had lung ailments. The number of healthy and unhealthy participants in our study is comparable or more than in several similar studies [15,26,38,65,69,72,73].…”

“…A total of 14 participants had lung ailments. The number of healthy and unhealthy participants in our trial is comparable to study population of past studies [15,26,38,65,69,72,73]. For each participant, the study lasted for about an hour.…”

“…Such masks are specially designed for athletes, restricting breathing, making an athlete feel like they are at a high altitude. Accurate wearable spirometry has been performed in athlete masks with error margins of 2.9% and 3.3% for FVC and FEV1 respectively [72]. Researchers have also experimented by integrating an audio sensor inside a surgical mask to estimate FVC from the energy of the audio signal but they have not quantified the error [1].…”

Masquare: A Functional Smart Mask Design for Health Monitoring

“…Most wearable sensing methods can only achieve respiration rhythm level [5,8] or rough intensity level monitoring. Differential embedded barometers were calibrated with a medical spirometer inside a mask design, achieving similar accuracy in deriving clinical pulmonary function test results such as the forced vital capacity (FVC) [10]. In [11], a barometer, a PPG sensor, and a motion sensor (IMU) were integrated in a technical demonstrator CoRSA, to monitor the entire cardio-respiratory functions, which is the technical foundation of our design.…”

“…A pair of differential barometers: BME680 (dedicated module) inside and LPS22HB (integrated on the Arduino Nano Sense) outside, act as the spirometer, which measures the respiratory pressure or lung volume during inhalation and exhalation. According to [10], such a pair of differential baromters paired with a mask chamber can measure transient airflow as precise as a medical spirometer. The BME680 module is placed in the faceguard and held in place by a 3D printed click mechanism as shown in Fig.…”