The association between viscera and the body surface remains obscure, but a better understanding of it will maximize its diagnostic and therapeutic values in clinical practice. Therefore, this study aimed to investigate the specificity of the association between viscera and the body surface in the pathological state.

Study subjects included 40 chronic obstructive pulmonary disease (COPD) participants in the COPD group and 40 age-matched healthy participants in the healthy control group. Laser doppler flowmetry, infrared thermography, and functional near-infrared spectroscopy were respectively adopted to measure (1) the perfusion unit (PU), (2) temperature, and (3) regional oxygen saturation (rSO2) of 4 specific somatic sites distributing in the heart and lung meridians. These 3 outcome measures reflected the microcirculatory, thermal and metabolic characteristics of the body surface, respectively.

Inclusion Criteria:

• COPD participants were eligible if they 1) satisfied the diagnostic criteria of COPD; 2) were in the stable phase of COPD; 3) were 20 ≤ age ≤ 75 years; 4) fully understood the study protocol and signed the written informed consent. Healthy participants were eligible if they 1) were healthy subjects who provided a medical examination report within 6 preceding months for confirming their health conditions; 2) were age-matched with the COPD group; 3) fully understood the study protocol and signed the written informed consent.

Exclusion Criteria:

• COPD patients were excluded if they 1) had other major lung diseases, such as bronchiectasis, pneumothorax, and lung tumors; 2) had concomitant heart diseases; 3) had serious concomitant diseases in major systems that were not controlled effectively 4) had mental diseases, history of drug abuse, and alcohol dependence; 5) were lactating or pregnant and 6)had scarring, hyperpigmentation, redness, swelling and heat in the skin around the measurement sites, which would affect the accuracy of examinations. Healthy subjects were excluded if they 1) had mental illness, history of drug abuse and alcohol dependence; 2) were lactating or pregnant; 3) had scarring, hyperpigmentation, redness, swelling, and heat in the skin around the measurement sites, which would affect the accuracy of examinations.

The diagnostic criteria of COPD were based on criteria proposed by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) consensus published in 2017, in which persistent airflow obstruction is confirmed according to the pulmonary function test. Healthy participants were determined by a medical examination report within 6 preceding months for confirming their health conditions.