Oxygenation strategies prior to and during prehospital emergency anaesthesia in UK HEMS practice (PREOXY survey)

Abstract

Background Maintaining effective oxygenation throughout the process of Pre-Hospital Emergency Anaesthesia (PHEA) is critical. There are multiple strategies available to clinicians to oxygenate patients both prior to and during PHEA. The optimal pre-oxygenation technique remains unclear, and it is unknown what techniques are being used by United Kingdom Helicopter Emergency Medical Services (HEMS). This study aimed to determine the current pre- and peri-PHEA oxygenation strategies used by UK HEMS services. Methods An electronic questionnaire survey was delivered to all UK HEMS services between 05 July and 26 December 2019. Questions investigated service standard operating procedures (SOPs) and individual clinician practice regarding oxygenation strategies prior to airway instrumentation (pre-oxygenation) and oxygenation strategies during airway instrumentation (apnoeic oxygenation). Service SOPs were obtained to corroborate questionnaire replies. Results Replies were received from all UK HEMS services (n = 21) and 40 individual clinicians. All services specified oxygenation strategies within their PHEA/RSI SOP and most referred to pre-oxygenation as mandatory (81%), whilst apnoeic oxygenation was mandatory in eight (38%) SOPs. The most commonly identified pre-oxygenation strategies were bag-valve-mask without PEEP (95%), non-rebreathable face mask (81%), and nasal cannula at high flow (81%). Seven (33%) services used Mapleson C circuits, whilst there were eight services (38%) that did not carry bag-valve-masks with PEEP valve nor Mapleson C circuits. All clinicians frequently used pre-oxygenation, however there was variability in clinician use of apnoeic oxygenation by nasal cannula. Nearly all clinicians (95%) reported manually ventilating patients during the apnoeic phase, with over half (58%) stating this was their routine practice. Differences in clinician pre-hospital and in-hospital practice related to availability of humidified high flow nasal oxygenation and Mapleson C circuits. Conclusions Pre-oxygenation is universal amongst UK HEMS services and is most frequently delivered by bag-valve-mask without PEEP or non-rebreathable face masks, whereas apnoeic oxygenation by nasal cannula is highly variable. Multiple services carry Mapleson C circuits, however many services are unable to deliver PEEP due to the equipment they carry. Clinicians are regularly manually ventilating patients during the apnoeic phase of PHEA. The identified variability in clinical practice may indicate uncertainty and further research is warranted to assess the impact of different strategies on clinical outcomes.

Large variations of oxygen delivery in self-inflating resuscitation bags used for preoxygenation - a mechanical simulation

“…SIRBs are used for positive pressure ventilation in patients with insufficient breathing but also for preoxygenation of the spontaneously breathing. For patients undergoing anaesthesia with no access to ventilators or anaesthetic machines there are few practical alternatives to a SIRB [1][2][3].…”

“…The gold standard for preoxygenation is a tight sealed mask connected to an anaesthetic machine, with close to an FiO 2 of 1.0 [1,2]. Outside of the OT and ICU the most common devices used for preoxygenation are SIRBs, freeflow oxygen masks, flow-dependent Mapelson systems or high-flow nasal cannulas [1][2][3]7]. The ability to manually ventilate apnoeic patients and limited oxygen supply typically makes a SIRB the preferred choice [3].…”

Incidence of hyperoxia in trauma patients receiving pre-hospital emergency anaesthesia: results of a 5-year retrospective analysis

“…Examples of these include thoracostomies to relieve a tension pneumothorax, the transfusion of blood products to treat ongoing blood loss, and pre-hospital emergency anesthesia (PHEA) to definitively manage the airway or to optimise ventilation. To prevent hypoxia during PHEA, patients are normally pre-oxygenated with a high FiO 2 and oxygen administration is continued thereafter [ 2 , 3 ].…”

Optimising preoxygenation in critically ill patients. A comparative analysis of the self-inflating bag valve mask and the Mapleson C circuit

“…Boulton et al . [ 13 ] reported that the most common preoxygenation stra-tegy from all UK Helicopter Emergency Medical Services was a BVM with a PEEP valve.…”

“…BVMs facilitate positive pressure ventilation for apnoeic patients and are also commonly employed for preoxygenation in spontaneously breathing patients both during transport and in intensive care units (ICU) [11,12]. Boulton et al [13] reported that the most common preoxygenation strategy from all UK Helicopter Emergency Medical Services was a BVM with a PEEP valve.…”