Preoxygenation by 8 deep breaths in 60 seconds using the Mapleson A (Magill), the circle system, or the Mapleson D system

Effect of high fresh gas flow and pattern of breathing on rapid preoxygenation

Background and Aims:

Preoxygenation is supplementation of 100% oxygen prior to induction of general anaesthesia to increase the body’s oxygen stores. Efficacy of preoxygenation can be increased by optimising fresh gas flow (FGF) rate and pattern of breathing.

Methods:

Based on pattern of breathing—Tidal Volume Breathing (TVB) or Deep Breathing (DB) and FGF-10 L/min or 15 L/min—100 subjects of the American Society of Anesthesiologists physical status I/II posted for elective surgery were recruited and randomised into four groups: T10 - TVB with 10 L/min; D10 - DB with 10 L/min; T15 - TVB with 15 L/min; and D15 - DB with 15 L/min. A tight-fitting anaesthesia mask along with continuous positive airway pressure of 5 cm of H₂O with 20° head-up was used for preoxygenation. The total time taken and the total number of breaths required to achieve end tidal oxygen concentration (EtO₂) of 90% were noted. Exhaled tidal volume (Vte), end tidal carbon dioxide, fraction of inspired oxygen, and EtO₂ were recorded at each breath. Analysis of variance (ANOVA) was used for inferential statistics and Tukey’s honestly significant difference (HSD) test was used to calculate mean difference in total time and number of breaths amongst the groups.

Results:

Total time taken was significantly low (P < 0.001) in DB compared to TVB (D10: 70.2 ± 19.91, D15: 68.4 ± 20.27 vs T10: 112.28 ± 47.96, T15: 113.6 ± 48.57 seconds). Number of breaths was significantly high (P < 0.001) in TVB with 22.84 ± 8.73, 23.76 ± 11.64, 10.56 ± 3.69, and 8.32 ± 1.8 in T10, T15, D10 and D15, respectively. Vte was significantly low in TVB (P < 0.001).

Conclusion:

Rapid preoxygenation can be achieved by DB at high FGF of a minimum of 10 L/min.

Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults

These guidelines provide a strategy to manage unanticipated difficulty with tracheal intubation. They are founded on published evidence. Where evidence is lacking, they have been directed by feedback from members of the Difficult Airway Society and based on expert opinion. These guidelines have been informed by advances in the understanding of crisis management; they emphasize the recognition and declaration of difficulty during airway management. A simplified, single algorithm now covers unanticipated difficulties in both routine intubation and rapid sequence induction. Planning for failed intubation should form part of the pre-induction briefing, particularly for urgent surgery. Emphasis is placed on assessment, preparation, positioning, preoxygenation, maintenance of oxygenation, and minimizing trauma from airway interventions. It is recommended that the number of airway interventions are limited, and blind techniques using a bougie or through supraglottic airway devices have been superseded by video- or fibre-optically guided intubation. If tracheal intubation fails, supraglottic airway devices are recommended to provide a route for oxygenation while reviewing how to proceed. Second-generation devices have advantages and are recommended. When both tracheal intubation and supraglottic airway device insertion have failed, waking the patient is the default option. If at this stage, face-mask oxygenation is impossible in the presence of muscle relaxation, cricothyroidotomy should follow immediately. Scalpel cricothyroidotomy is recommended as the preferred rescue technique and should be practised by all anaesthetists. The plans outlined are designed to be simple and easy to follow. They should be regularly rehearsed and made familiar to the whole theatre team.