Haemodynamic effects of a 10-min treatment with a high inspired oxygen concentration in the emergency department: a prospective observational study.

UNLABELLED: Previous studies show that prolonged exposure to a high inspired oxygen concentration (FiO2 ) is associated with unfavourable haemodynamic effects. Until now, it is unknown if similar effects also occur after oxygen therapy of limited duration in the emergency department (ED).

OBJECTIVES: To investigate the haemodynamic effects of a high FiO2 administered for a limited duration of time in patients who receive preoxygenation for procedural sedation and analgesia (PSA) in the ED.

DESIGN, SETTINGS AND PARTICIPANTS: In a prospective cohort study, cardiac output (CO), stroke volume (SV) and systemic vascular resistance (SVR) were measured using the Clearsight non-invasive CO monitoring system in patients who received preoxygenation for PSA in the ED. Measurements were performed at baseline, after 5 min of preoxygenation via a non-rebreathing mask at 15 /L min and after 5 min of flush rate oxygen administration.

OUTCOMES MEASURES: The primary outcome was defined as the change in CO (L/min) from baseline after subsequent preoxygenation with 15 L/min and flush rate.

RESULTS: Sixty patients were included. Mean CO at baseline was 6.5 (6.0-6.9) L/min and decreased to 6.3 (5.8-6.8) L/min after 5 min of oxygen administration at a rate of 15 L/min, and to 6.2 (5.7-6.70) L/min after another 5 min at flush rate (p=0.037). Mean SV remained relatively constant during this period, whereas mean SVR increased markedly (from 781 (649-1067), to 1244 (936-1695) to 1337 (988-1738) dyn/s/cm-5 , p<0.001. Sixteen (27%) patients experienced a>10% decrease in CO.

CONCLUSION: Exposure of patients to a high FiO2 for 5-10 min results in a significant drop in CO in one out of four patients. Therefore, even in the ED and in prehospital care, where oxygen is administered for a limited amount of time, FiO2 should be titrated based on deficit whenever this is feasible and high flow oxygen should not be given as a routine treatment.