Gases and the Effects of Analysis Delay and Air Contamination on Arterial Samples in Patients with Chronic Obstructive Pulmonary Disease and Healthy Controls

30 min in patients with COPD exacerbation (p = 0.0042) and 90 min in controls (p ! 0.0001). A clinically significant decline in pH emerged at 73 min in patients with COPD exacerbation and 87 min in controls. Air contamination was associated with a clinically significant increase in P O 2 in all samples, in-cluding those that were immediately analyzed. Conclusions: Arterial and venous pH differ significantly. Venous pH can-not accurately replace arterial pH. Temporal delays in ABG analysis result in a significant decline in measured pH. ABGs should be analysed within 30 min. Air contamination leads to an immediate increase in measured P O 2, indicating that air-contaminated ABGs should be discarded. Copyright © 2010 S. Karger AG, Basel Arterial blood gas (ABG) analysis is an essential tool for the assessment of patients with a wide range of clini-cal presentations. ABGs provide data relevant to acid-base status, ventilation, and arterial oxygenation and may help confirm a clinical diagnosis, ascertain the severity of a clinical condition (decompensated hypercapnic re-spiratory failure, metabolic acidosis, pulmonary embo-lism), the need for further interventions and the intensity Key Words Chronic obstructive pulmonary disease Arterial blood gases Venous blood gas Background: Arterial blood gases (ABGs) are often sampled incorrectly, leading to a ‘mixed ’ or venous sample. Delays in analysis and air contamination are common. Objectives: We measured the effects of these errors in patients with chronic obstructive pulmonary disease (COPD) exacerba-tions and controls. Methods: Arterial and venous samples were analyzed from 30 patients with COPD exacerbation and 30 controls. Venous samples were analysed immediately and arterial samples separated into non-air-contaminated an