The Relationship of Partial Pressure of Carbon Dioxide (PaCO2) with Disease Severity Indicators Such as BODE and GOLD in Hospitalized COPD Patients

Abstract

Purpose. This study aimed to investigate the relationship of partial pressure of carbon dioxide (PaCO2) with BODE and GOLD in stable COPD subjects and to explore the predictive value of PaCO2 for severe COPD (BODE index score ≥5 or GOLD index score ≥3). Patients and Methods. In total, 80 participants with COPD and free from other conditions affecting PaCO2 were recruited. Arterial blood gases, BODE, GOLD, SGRQ, lung function, and other data were collected. The BODE index was calculated, and patients were divided into two groups according to the BODE index and PaCO2 median, respectively. We used Pearson’s correlation test and the receiver operating characteristic curves to evaluate the utility of PaCO2. Besides, the univariate and multivariate logistic regression analyses were conducted to verify whether PaCO2 was an independent factor associated with BODE grades. Results. COPD subjects with BODE ≥5 and GOLD ≥3 had significantly higher levels of PaCO2 ( $p$  = 0.004, $p$  = 0.001, respectively). In the high PaCO2 group, patients underwent poorer outcomes than the low PaCO2 group. PaCO2 was negatively correlated with forced expiratory volume in 1 second in percent of the predicted value (FEV1%) (r = −0.612, $p$  < 0.001). The performance of PaCO2 levels in predicting BODE ≥5 and GOLD ≥3 was 0.748 and 0.755, respectively. The logistic regression analyses proved that PaCO2 was associated with BODE ≥5 in COPD patients (odds ratio = 1.160, 95% CI: 1.025–1.313, $p$  = 0.019). Conclusions. A higher level of PaCO2 was associated with a higher index for BODE or GOLD in COPD and had the predictive value for severe COPD.