The objective of this case-based review is to identify and summarize the relevant evidence for the clinical utility of peripheral venous blood gas (pVBG) analyses in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) treated in the emergency department. Relevant studies were identified using the Cochrane Library, Medline, Embase, and CINAHL databases and by hand searching of references of published articles. Included studies were prospective trials comparing arterial and pVBG results in patients with COPD or respiratory distress that reported at least average differences and/or limits of agreement between the two results in English. Outcomes of interest were agreement between arterial and pVBG values for pH, pCO2, pO2, and HCO3. Eighty-nine studies were identified of which six were relevant. The weighted average difference for pCO2 was 5.92 mmHg, whereas those for pH, pO2, and HCO3 were 0.028, 18.65 mmHg, and 1.34 mEq/l, respectively. Using Bland-Altman analysis, the 95% limits of agreement were in the range of -0.10 to 0.08, -17 to 26 mmHg and, -3.5 to 3.5 mEq/l for pH, pCO2, and HCO3, respectively. Reported cutoff pVBG pCO2 values for screening of arterial hypercarbia ranged from 30 to 46 mmHg. No studies investigated the role of pVBG analysis in treatment alteration or clinical outcomes. Available evidence suggests that there is good agreement for pH and HCO3 values between arterial and pVBG results in patients with COPD, but not for pO2 or pCO2. Widespread clinical use is limited because of the lack of validation studies on clinical outcomes.