Is an increased PaO2 in a normobaric state safe in acute CO poisoning?

Abstract

Our objective was to determine how much PaO2 levels increase after normobaric oxygen (NBO) therapy and whether NBO therapy exerts therapeutic effects regardless of the PaO2 level. We suggest the optimal PaO2 level to use during NBO therapy for the acute treatment of carbon monoxide (CO) poisoning. This retrospective study included 311 patients who received oxygen administration after CO poisoning and had a measurable PaO2 level upon arrival. Baseline characteristics, clinical courses and long-term neurological outcome were collected and compared. The PaO2 level upon arrival was 192 (161-225) mmHg, and 272 (87.5%) of the patients presented with hyperoxia. The incidence of poor long-term neurological outcome was 11.3% at a median follow-up period of 35months. PaO2 levels upon arrival were higher in patients with good long-term neurological outcome than in those with poor outcome. The incidence of poor long-term neurological outcome was significantly dependent on the PaO2 level when patients were stratified at 100-mmHg increments. A multivariate regression analysis showed that PaO2 levels, when considered a continuous, interval or ordinal variable, were associated with long-term neurological outcome in separate models. According to the three models, a PaO2 level of 200-300mmHg has the lowest risk of poor long-term neurological outcome. The results of the analysis of the predicted probability of poor long-term outcome according to the PaO2 level exhibited a U-shaped curve. Further large-scale studies are needed to confirm the association between 200-300mmHg of PaO2 and long-term neurological outcome and evaluate the impact of PaO2 levels above 300mmHg on acute CO poisoning outcome.