Optimizing preoxygenation in adults

Abstract

Purpose Preoxygenation increases oxygen reserves and duration of apnea without desaturation (DAWD), thus it provides valuable additional time to secure the airway. The purpose of this Continuing Professional Development (CPD) module is to examine the various preoxygenation techniques that have been proposed and to assess their effectiveness in healthy adults and in obese, pregnant, and elderly patients. Principal findings The effectiveness of preoxygenation techniques can be evaluated by measuring DAWD, i.e., the time for oxygen saturation to decrease to\90%. Clinically, preoxygenation is considered adequate when end-tidal oxygen fraction is[90%. This is usually achieved with a 3-min tidal volume breathing (TVB) technique. As a rule, asking the patient to take four deep breaths in 30 sec (4 DB 30 sec) yields poorer results. Eight deep breaths in 60 sec (8 DB 60 sec) is equivalent to TVB 3 min. The DAWD is decreased in obese patients, pregnant women, and patients with increased metabolism. Obese patients may benefit from the head-up position and positive pressure breathing. A TVB technique is preferable in the elderly. Failure to preoxygenate is often due to leaks, which commonly occur in edentulous or bearded patients. In cases of difficult preoxygenation, directly applying the circuit to the mouth might be a useful alternative. Supplying extra oxygen in the nasopharynx during apnea might increase DAWD. Conclusion Since ventilation and tracheal intubation difficulties are unpredictable, this CPD module recommends that all patients be preoxygenated. The TVB 3 min and the 8 DB 60 sec techniques are suitable for most patients; however, the 4 DB 30 sec is inadequate. Continuing Professional Development objectivesAfter reading this review, the reader should be able to:• understand the physiological principles of preoxygenation;• describe the slow and fast techniques for preoxygenating patients; • apply the proper techniques in healthy adults with normal weight; • modify these techniques in obese patients, pregnant women, and the elderly; • briefly describe preoxygenation devices other than the face mask.The purpose of preoxygenation is to increase the oxygen reserves of the body, thus preventing hypoxia during a planned or unexpected period of apnea. The term ''denitrogenation'', indicating that nitrogen in the lungs is replaced by oxygen, is sometimes used instead of ''preoxygenation''. However, the latter is generally preferred because the primary goal is to provide oxygen, not to remove nitrogen. With adequate preoxygenation, patients can tolerate a longer period of apnea, and an increased margin of safety is created between induction of anesthesia and the moment the airway is secured. This extra time may prove particularly valuable if mask ventilation is difficult or contraindicated and if laryngoscopy and tracheal intubation are more difficult than expected.The purpose of this Continuing Professional Development (CPD) module is to summarize the physiological principles 123Can J Anesth/J Can Anesth (2009...

S1 guidelines on airway management

“…Various techniques are possible: 8 maximum deep breaths within 60 s and preoxygenation for 3-4 min or until the expiratory oxygen concentration exceeds 90 % [19][20][21].…”

La prise en charge des voies aériennes et l’oxygénation du patient obèse

“…32 Preoxygenation is considered to be sufficient when the end-tidal oxygen fraction is [ 90%. 33 Tidal volume breathing through a well-sealed face mask for three minutes or four vital capacity breaths are common techniques of preoxygenation. Evidence suggests that obese patients desaturate faster with the latter technique.…”

“…32 La préoxygénation est considérée comme suffisante lorsque la fraction d'oxygène télé-expiratoire est [ 90 %. 33 La respiration en volume courant via un masque facial bien scellé pendant trois minutes ou quatre respirations en capacité vitale sont deux techniques de préoxygénation courantes. Les données probantes laissent penser que les patients obèses désaturent plus rapidement avec la seconde technique.…”

Intubation in the ICU: We Could Improve our Practice

“…Several maneuvers in spontaneous ventilation (e. g., 3-8 vital capacities vs 3 minutes tidal volume breathing) exist to improve pre-oxygenation before intubation and seem to be almost equally eff ective [8]. Some technical details, however, can make a signifi cant diff erence.…”