Non-contact Doppler radar screening system for the detection of COPD

Abstract

Background: Chronic Obstructive Pulmonary Disease (COPD) is characterized by irreversible airflow obstruction and commonly assessed by pulmonary function tests. A previous epidemiology report states that the prevalence of airflow limitation in Japan is higher than previously reported, suggesting a higher degree of under-diagnosed COPD. Thus, enhanced screening efforts are needed for earlier interventions and treatment.

Objectives: To evaluate the efficacy of a Doppler radar screening system for the detection of COPD.

Methods: A newly developed non-contact COPD screening system (COPD-SS) incorporates a Doppler radar with 10mW-low output power. COPD-SS radiates 24 GHz imperceptible microwaves from a distance of 35cm from the thorax. COPD-SS monitors motion in real-time by receiving reflected microwaves from the thorax. COPD-SS then converts thoracic motion into a single waveform.

We measured forced vital capacity (FVC) using spirometry in patients simultaneously with COPD-SS. We calculated the change of chest displacement in 1 second then divided by the total motion of the thorax. We then compared the ratio of forced expiratory volume in one second to forced vital capacity (FEV1/FVC) with COPD-SS data.

Results: COPD screening was performed on 58 COPD patients and 26 normal control subjects. Of these, 37 patients and 16 control subjects underwent COPD screening analysis. The percentage of chest displacement in 1 second was significantly correlated with FEV1/FVC (r=0.775, P<0.0001) in all subjects. COPD-SS revealed a high accuracy rate (86.7%) in the detection of airflow limitation.

Conclusions: COPD-SS appears promising as an efficient screening system for the detection of COPD.