Correlation of Arterial Blood Gas (ABG) with Venous Blood Gas (VBG) in Patients Presenting with Exacerbation of Chronic Obstructive Pulmonary Disease (COPD)

Background and Aim: Arterial blood gas analysis is the gold standard for assessing acid-base balance and gas exchange in acute exacerbations of chronic obstructive pulmonary disease (COPD), but venous sampling may offer a less invasive alternative. This study aimed to evaluate the correlation between arterial and venous blood gas parameters in patients with COPD exacerbation. Material and Methods: An analytic cross-sectional study was conducted in the Pulmonology Department of Lahore General Hospital, Lahore, over 3 months (January to April 2025). Sixty adult patients with acute COPD exacerbation were enrolled using consecutive sampling. Demographics, comorbidities, and clinical history were recorded. Simultaneous arterial and venous samples were analyzed, and correlation assessed using Pearson’s coefficient. Results: The mean age was 59.7±11.4 years; 63.3% were male. Most were active smokers (73.3%), and 46.7% had comorbidities. The mean arterial pH was 7.37±0.05, while venous pH was 7.33±0.05 (r = 0.85, p = 0.5641). For pCO₂, arterial mean was 47.10±7.40 mmHg and venous 52.30±7.90 mmHg (r = 0.92, p = 0.6245). HCO₃⁻ values were 25.20±3.20 mEq/L (arterial) and 26.50±3.50 mEq/L (venous), with strong correlation (r = 0.88, p = 0.7803). The mean arterial pO₂ was 63.40±8.20 mmHg and venous 39.60±6.50 mmHg (r = 0.45, p = 0.0167). Subgroup analysis showed consistent results by gender, age, and respiratory failure type. Conclusion: Venous blood gas analysis can reliably estimate pH, pCO₂, and HCO₃⁻ in patients with COPD exacerbation, though arterial sampling remains necessary for accurate assessment of oxygenation.