A prospective audit of the use of oxygen during the management of patients with acute exacerbations of COPD (AECOPD)

Introduction: The BTS guidelines for the management of COPD recommend that during an acute exacerbation the FiO₂ does not exceed 28% until the result of arterial blood gas analysis is available because it has been suggested that an FiO₂ >28% is associated with acidosis and increased mortality (Jeffrey et al Thorax 1992;47:34-40). Aims: The aims of our audit were to determine the proportion of patients who received an FiO₂ >28%, the stage in the admission process at which it was given, whether patients distinguished between COPD and asthma and whether outcome was affected by an FiO₂>28%. Methods: Over a two month period all consecutive patients with a final diagnosis of AECOPD made by a respiratory physician were included; information was obtained from the ambulance and hospital case records and patient interview. Results: We included 101 patients (mean (SD) age 69.7 yrs (9), 55 male, 37 current smokers). 57 patients received an FiO₂ > 28% at some time during their emergency management. Ambulance transport was used by 65 patients of whom 80% received an FiO₂ >28%. The triage nurse, A&E SHO and the medical SHO administered an FiO₂ >28% to 24%, 39% and 11%, respectively. Only 35 patients identified their lung disease as COPD, whereas 47 patients described it as asthma. In the first group a mean FiO₂ of 45% was administered in the ambulance - but exceeded 28% in 60% of cases - whereas in the second group the mean FiO₂ was 62% (p<0.01). Arterial blood gases were measured in 83 patients. A severe respiratory acidosis (H⁺ >55 nmol/L) was found in 11/51 patients (22%) given FiO₂ >28%, but only in 1/32 (3%) given FiO₂ 528% (p<0.01). In-hospital mortality was 8/57 patients (14%) given FiO₂ >28%, but only 1/44 (2%) given FiO₂ <28% (p<0.05). These two groups were comparable with respect to triage category, age, smoking history, mean dose of inhaled steroids and use of home oxygen. Conclusion: In AECOPD oxygen therapy with an FiO₂ in excess of 28% is common and is initiated predominantly in the ambulance. Strategies to identify patients at risk of uncontrolled oxygen therapy are under review.