Minerva Anestesiol. 2015 Jun 5. [Epub ahead of print]
Three minutes of spontaneous breathing at FiO2=1 allows denitrogenation with FAO2 close to 95% in patients with normal lung function. Tolerable apnea time, defined as the delay until the SpO2 reaches 90%, can be extended up to almost 10 minutes after 3 minutes of classic pre-oxygenation. Eight deep breaths within 60 seconds allow a comparable increase in O2 reserves. For effectiveness, the equipment must be adapted and tightly fitted.
Inadequate pre-oxygenation (FeO2 < 90% after three minutes tidal volume breathing) is frequently observed. Predictive risk factors for inadequate pre-oxygenation share overlap with criteria predictive of difficult mask ventilation. In cases of respiratory failure, oxygenation can be improved by positive end expiration pressure or by pressure support. In morbidly obese patients, pre-oxygenation is enhanced in a seated position (25°) and by use of positive pressure ventilation. O2 can also be administered during the intubation procedure; techniques include pharyngeal O2, special oxygen mask, or even pressure support ventilation for patients with spontaneous ventilation or positive pressure ventilation to the facial mask for apneic patients. Clinicians (especially anesthesiologists trained in ENT and traumatology) must be prepared to handle life-threatening emergency situations by alternate methods including trans-tracheal ventilation. The availability of equipment and training are two essential components of adequate preparation.