Abstract
Obstructive pulmonary diseases, such as diffuse panbronchiolitis (DPB), asthma, chronic obstructive pulmonary disease (COPD), and asthma COPD overlap syndrome (ACOS) trigger a severe reaction at some situations. Detecting early airflow limitation caused by diseases above is critical to stop the progression. Thus, there is a need for tools to enable self-screening of early airflow limitation at home. Here, we developed a novel non-contact early airflow limitation screening system (EAFL-SS) that does not require calibration to the individual by a spirometer. The system is based on an infrared time-of-flight (ToF) depth image sensor, which is integrated into several smartphones for photography focusing or augmented reality. The EAFL-SS comprised an 850 nm infrared ToF depth image sensor (224 × 171 pixels) and custom-built data processing algorithms to visualize anterior-thorax three-dimensional motions in real-time. Multiple linear regression analysis was used to determine the amount of air compulsorily exhaled after maximal inspiration (referred to as the forced vital capacity, FVCEAFL–SS) from the ToF-derived anterior-thorax forced vital capacity (FVC), height, and body mass index as explanatory variables and spirometer-derived FVC as the objective variable. The non-contact measurement is automatically started when an examinee is sitting 35 cm away from the EAFL-SS. A clinical test was conducted with 32 COPD patients (27/5 M/F, 67–93 years) as typical airflow limitation cases recruited at St. Marianna University Hospital and 21 healthy volunteers (10/11 M/F, 23–79 years). The EAFL-SS was used to monitor the respiration of examinees during forced exhalation while sitting still, and a spirometer was used simultaneously as a reference. The forced expiratory volume in 1 s (FEV1%EAFL–SS) was evaluated as a percentage of the FVCEAFL–SS, where values less than 70% indicated suspected airflow limitation. Leave-one-out cross-validation analysis revealed that this system provided 81% sensitivity and 90% specificity. Further, the FEV1EAFL–SS values were closely correlated with that measured using a spirometer (r = 0.85, p < 0.0001). Hence, EAFL-SS appears promising for early airflow limitation screening at home.
Highlights
Diffuse panbronchiolitis (DPB), asthma, chronic obstructive pulmonary disease (COPD), and asthma COPD overlap syndrome (ACOS), all known as typical obstructive pulmonary diseases, trigger a severe reaction including death for some situations (Laucho-Contreras et al, 2016)
In physiologically point of view, COPD is diagnosed by the FEV1/forced vital capacity (FVC) ratio (The Global Initiative for Chronic Obstructive Lung Disease [GOLD], 2020)
FEV1% and FEV1 are two dominant parameters to determine airflow limitations induced by asthma, COPD, and ACOS
Summary
Diffuse panbronchiolitis (DPB), asthma, chronic obstructive pulmonary disease (COPD), and asthma COPD overlap syndrome (ACOS), all known as typical obstructive pulmonary diseases, trigger a severe reaction including death for some situations (Laucho-Contreras et al, 2016). Spirometry is useful for early detection of these diseases with airflow limitation, it is not designed for home-use. Airflow limitation detections are critical to stop the disease progression. Respiratory bronchioles without treatment in early stage causes severe obstructive respiratory disorder, bronchiectasis, and death. Asthma is a syndrome of lung dysfunction involving airflow obstruction. Patients with severe COPD require home oxygen therapy, which drastically degrades their quality of life. COPD is characterized by a persistent airflow limitation that is usually progressive. Intervention, such as smoking cessation, it is important to change the natural history of COPD. In physiologically point of view, COPD is diagnosed by the FEV1/forced vital capacity (FVC) ratio (The Global Initiative for Chronic Obstructive Lung Disease [GOLD], 2020). As for COVID-19 hospitalized patients, COPD is the second risk factor (next to malignant tumor) of reaching to the composite end points (admission to Intensive Care Unit, invasive ventilation, or death) (Guan et al, 2020)
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