Abstract: Objective To study the expression of serum caveolin-1 (Cav-1) in patients with pulmonary hypertension (PAH) associated with chronic obstructive pulmonary disease (COPD), and to analyze its clinical significance. Methods According to whether combined with PAH, a total of 65 stable COPD patients were divided into COPD group [pulmonary systolic blood pressure (PASP) ＜40 mmHg, 35 cases] and COPD-PAH group (PASP ≥40 mmHg, 30 cases). Thirty healthy volunteers who received physical examination in our hospital during the same period were selected as normal control group. Baseline data, blood gas analysis, lung function indicators, and expression levels of Cav-1, IL-6, and TNF - α were compared. The receiver operating characteristic curve (ROC curve) was plotted and the optimal cut-off value for Cav-1 diagnosis of COPD combined with PAH was analyzed. Results The first second forced respiratory volume (FEV1)/forced vital capacity (FVC), FEV1 percentage of predicted value (FEV1%), and oxygen partial pressure [p(O2)] were lower in the COPD-PAH group and the COPD group than those in the control group, and the partial pressure of carbon dioxide [p(CO2)] and PASP were higher than those in the control group (P＜0.01). The p(O2) was lower in the COPD-PAH group than that in the COPD group, and the p(CO2) and PASP were higher than those in the COPD group (P＜0.01). The expression levels of Cav-1 were decreased gradually in the control group, COPD group and COPD-PAH group, while the expression levels of IL- 6 and TNF-α were increased gradually (P＜0.01). For predicting the risk of COPD combined with PAH, the area under the ROC curve was 0.902, the optimal cut-off value was 6.66 ng/ml with a sensitivity of 76.7% and a specificity of 85.7%. Cav-1
was consistent with the PASP results measured by Doppler ultrasound (Kappa value = 0.627). Conclusion The serum
expression of Cav-1 is down-regulated in the patients with PAH associated with COPD, and Cav-1 can be a novel serum
marker for the diagnosis of PAH associated with COPD.

Key words: pulmonary disease, chronic obstructive, hypertension, pulmonary, caveolin 1, serum, inflammation