Comparison of the efficacy of two preoxygenation techniques using oxygen reserve index

Preoxygenation is very important to protect the patient from hypoxia before intubation. However, pulse oximetry has some limitations in detecting hypoxia.

We aimed to compare the effectiveness of 2 preoxygenation techniques based on oxygen reserve index (ORI) levels.

Twenty healthy male volunteers were included in the study. They inhaled 100% FiO2 oxygen administered at 5 L/min as the 1st technique (M1) with a ventilation mask as much as their tidal volumes for 3 min. The 2nd technique (M2) applied 100% FiO2 oxygen at 10 L/min flow using the same mask and 8 deep inspiratory volumes, which was aimed to be completed within 1 min. Maximum ORI levels, duration to reach that level, and time needed to reach the target ORI level (0.35) and return back to the "0" were measured.

In the M1 group, ORI levels were significantly higher during and after 60 s, according to post hoc tests. In the M2 groups, ORI levels were significantly higher during and after the 4th inspiration, according to post hoc tests. Oxygen reserve index values at the 60th 2nd (M1) and 8th inspiration (M2) were compared as the 8th inspiration corresponded to the 60th second. The maximum ORI values were significantly lower in the M1 group compared to the M2 group (p < 0.001 and p = 0.006, respectively). Seven volunteers (36.8%) in the M1 group and 2 volunteers (10.5%) in the M2 group could not reach the target ORI (McNemar's test, test statistic 3.2, degrees of freedom (df) = 1, p = 0.063). The time to reach the target ORI value and to reach maximum ORI values was significantly longer in the M1 group than in the M2 group (p = 0.008 and p < 0.001, respectively).

We observed that the 8-deep breath technique is more effective in preoxygenation compared to the 3-min tidal volume technique.