Efficacy of preoxygenation using tidal volume and deep breathing techniques with and without prior maximal exhalation

We evaluated the influence of prior maximal exhalation on preoxygenation in 15 adult volunteers using tidal volume breathing (TVB) for five minutes and deep breathing (DB) for two minutes with and without prior maximal exhalation.

Inspired and end-tidal oxygen, nitrogen and carbon dioxide were monitored continuously and recorded during room air breathing and at 30-sec intervals during 100% oxygen TVB or DB (rate of 8 breaths.min(-1)).

Tidal volume breathing with prior maximal exhalation resulted in an end-tidal oxygen concentration (ETO(2)) slightly higher (P = 0.028) at 0.5 and 1.0 min as compared with TVB without prior maximal exhalation at the same time periods. Regardless of whether TVB was preceded by maximal exhalation or not, 2.5 min was required to reach a mean ETO(2) value of 90% or higher. With DB, there were no differences in ETO(2) values at any time period and 1.5 min was required to reach an ETO(2) of 90% or greater, with or without prior maximal exhalation.

Maximal exhalation prior to TVB slightly steepens the initial rise in ETO(2) during the first minute, but confers no real benefit if maximal preoxygenation is the goal. Maximal exhalation prior to DB has no added value in enhancing preoxygenation.