Inhalation of 50% Oxygen Does Not Impair Respiratory Depression During Midazolam Sedation

To investigate how inhalation of 50% oxygen during intravenous midazolam sedation affects respiratory variables and thus the availability of oxygen.

Study subjects were 21 healthy adult volunteers (American Society of Anesthesiologists physical status I). They were allocated to undergo midazolam sedation during high-concentration oxygen inhalation (group H) or during normal air inhalation (group N) in a single-blinded randomized crossover design, with an interval of at least 3 days between the 2 sedation sessions. In each experiment, midazolam 0.05 mg/kg was administered, after which the following variables were measured for 40 minutes: oxygen saturation by pulse oximetry (SpO2), end-tidal carbon dioxide partial pressure (ETCO2), respiration rate (RR), tidal volume (VT), and minute volume (MV). Subsequently, flumazenil 0.5 mg was administered, and the same variables were measured for 10 minutes.

SpO2 decreased after midazolam administration in the 2 groups. SpO2 in group H was higher than that in group N at all time points. RR increased and VT decreased after midazolam administration in the 2 groups; however, in contrast to SpO2, the levels of these parameters did not meaningfully differ between groups at any time point. MV remained unchanged in the 2 groups. ETCO2 decreased similarly after midazolam administration in the 2 groups.

Inhalation of 50% oxygen during midazolam sedation did not enhance respiratory depression by midazolam. This suggests that high-concentration oxygen inhalation during midazolam sedation could prevent hypoxia.