Outcomes of acute exacerbations in COPD in relation to pre-hospital oxygen therapy

Pre-hospital, high-concentration oxygen therapy during acute exacerbation of chronic obstructive pulmonary disease (AECOPD) has been associated with increased mortality. Recent COPD guidelines have encouraged titrated oxygen therapy with a target saturation range of 88-92%. Oxygen therapy leading to saturation above 92% is defined as 'inappropriate oxygen therapy'.

To examine the frequency of inappropriate oxygen therapy and whether inappropriate oxygen therapy in the ambulance in an urban area with short transit time to hospital was associated with poor outcome.

In an audit of 405 consecutive patients with AECOPD arriving by ambulance to Hvidovre Hospital, details of transit time, oxygen administration, saturation, and arterial blood gases were registered. Outcomes were respiratory acidosis, need of supported ventilation, length of hospitalisation, and in-hospital mortality.

Only 15 patients were not treated with oxygen and information on oxygen flow was missing in seven patients and on saturation on one patient. Altogether, 352 (88.7%) of 397 patients received inappropriate oxygen therapy. Patients on 'inappropriate oxygen therapy' (saturation ≥92%) had a high frequency of respiratory acidosis at hospital admission, 108 (33.5%) of 324 patients, length of stay was on average 5.1 days, 12.5% of the patients needed ventilatory support, and in-hospital mortality was 3.4%.

The majority of patients with AECOPD received inappropriate oxygen therapy in the ambulance, but their need of ventilatory support, length of stay, and mortality were low. Randomised studies are needed to clarify the optimal pre-hospital oxygen therapy.