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Respiratory diseases, like Asthma, COPD, have been a significant public health challenge over decades. Portable spirometers are effective in continuous monitoring of respiratory syndromes out-of-clinic. However, existing systems are either costly or provide limited information and require extra hardware. In this paper, we present mmFlow, a low-barrier means to perform at-home spirometry tests using 5G smart devices. mmFlow works like regular spirometers, where a user forcibly exhales onto a device; but instead of relying on special-purpose hardware, mmFlow leverages built-in millimeter-wave technology in general-purpose, ubiquitous mobile devices. mmFlow analyzes the tiny vibrations created by the airflow on the device surface and combines wireless signal processing with deep learning to enable a software-only spirometry solution. From empirical evaluations, we find that, when device distance is fixed, mmFlow can predict the spirometry indicators with performance comparable to inclinic spirometers with <5% prediction errors. Besides, mmFlow generalizes well under different environments and human conditions, making it promising for out-of-clinic daily monitoring. 

The rapid evolution of the telehealth industry, accelerated recently by stay-at-home directives, has created a demand for more ubiquitous health-sensing tools. One such tool is the Spirometer. Spirometers have been used in traditional clinics to measure lung capacity (volume) as well as airflow (flow rate) and have wide applicability in the diagnosis of Asthma, COPD, and other pulmonary diseases. In addition, they can be used to diagnose Dyspnea, i.e., shortness of breath, one of the symptoms of the COVID-19 virus. Several spirometers are available commercially for home-use, but they are either costly, cumbersome or provide limited flow information. We propose SpiroMilli, a low-barrier means to performing spirometry at home using the millimeter-wave (mmWave) technology in 5G-and-beyond devices. To perform a test, users will hold the device in front of their mouth, fully inhale, then sharply exhale. The system will then output seven key indicators, e.g., Forced Vital Capacity (FVC), Peak Expiratory Flow (PEF), etc., along with a flow-volume curve. SpiroMilli’s key idea is intuitive: Strong airflow in front of the mmWave antenna creates tiny vibrations, and these vibrations affect the phase of reflected signals from nearby objects. For example, a 79 GHz device (wavelength: 3.79 mm) will register a 5 µm displacement as a 1◦ phase change.