Aim Patients with severe COPD are at risk of CO₂ retention, due to uncontrolled oxygen administration. In Denmark, emergency medical service (EMS) care only offers respiratory support with 100% oxygen and treatment with fractionated oxygen is limited. In this retrospective study we sought to clarify the extend at which patients with hypercapnic acidosis, due to excessive pre-hospital oxygen therapy, were admitted through the emergency department (ED).

Methods Patients admitted through the ED were divided according to triage score. Venous blood samples were collected from all patients and arterialised using the venous to arterial conversion (v-TAC) software. All admissions of patients with CO₂ retention (pCO₂>6.0 kPa) and acidosis (pH<7.35) were identified. Patient records and EMS journals were reviewed to determine out-of-hospital saturation and vital signs.

Results 125 admissions were registered concerning respiratory issues. 11 patients had CO₂ retention and acidosis. Mean pre-hospital saturation was 83.6% at first patient contact. Saturation increased to 95.0% upon arrival at the ED, and when triage took place in-hospital, saturation decreased to 91,1%. Blood gas revealed mean pH 7.29, pCO₂ 8.72 kPa, and pO₂ 10.2 kPa. But pCO₂ values as high as 11 kPa were registered. All blood samples were drawn as part of the triage.

Conclusion Although few patients were identified with CO₂ retention, results indicated that the cause most likely was high oxygenation pre-hospital. Studies exploring optimised pre-hospital oxygen therapy for patients with CO₂ retention tendencies are required.

Conflict of interest None declared.

Funding None declared.