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Abstract

Background: Arterial blood gases are necessary for management ofrespiratory failure in patients with acute exacerbation of COPD. Venous bloodgas analysis may be a less invasive potential alternative. The objective of ourstudy was to determine the accuracy of venous blood gases in the diagnosis ofhypercapnic respiratory failure and to determine the correlation betweenarterial and venous PH, PCO2 and HCO3.Methodology: All adult patients presenting to Pulmonology departmentbetween November 2018 and March 2019 with COPD exacerbation havingSPO < 90% were included. Patients in shock, arrhythmia, diabetic 2 ketoacidosis, renal failure, bleeding disorder or unwilling for blood samplingwere excluded. Paired arterial and venous blood samples were obtained andanalyzed on the spot via blood gas analyzer. The sensitivity, specificity anddiagnostic accuracy of VBGs were calculated via SPSS 19, by taking PCO2>45mm of Hg as cut off value to diagnose hypercapnia using ABGs as the goldstandard. Correlation between arterial and venous PH, PCO2 and HCO3 were calculated via Pearson correlation.Results: We enrolled 87 patients, with mean age of 51yrs (+ 8.89 SD) and male to female ratio of 1: 2.2. The mean venous minus arterial PH (7.39-7.40) was -0.13. The mean venous minus arterial PCO (60-54) was 6mm of Hg. The 2sensitivity of venous PCO in the diagnosis of hypercapnia was 97.95%, 2 specificity 66.66%, PPV 80%, NPV 96% and diagnostic accuracy of 82.7%.There was a strong correlation between arterial and venous PH (r =0.83), HCO 3 (r=0.63) and PCO2 (r=0.92). Conclusion: VBGs instead of ABGs can be used as a screening test fordetection of hypercapnia in hemodynamically stable patients presenting withacute exacerbation of COPD and VBGs indices (PH, PCO2 and HCO3 ) can provide guidance about the severity of acid base disturbance.