Date of Award

2025

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Master of Medical and Health Science by Research

School

School of Medical and Health Sciences

First Supervisor

Brennen Mills

Second Supervisor

David Ford

Abstract

Background: Out-of-Hospital Cardiac Arrest (OHCA) is one of the world’s leading causes of mortality. Survival rates are low, ranging from 3.1–20.4% internationally. The most effective oxygenation method for patients during pre-hospital cardiac arrest is ventilating using a self- inflating Bag-Valve-Mask (BVM). Yet, extensive research has identified a lack of compliance with ventilator guidelines during OHCA cardiopulmonary resuscitation (CPR). As a result, clinicians often ventilate patients too aggressively using the BVM, delivering breaths excessively higher than the International Liaison Committee on Resuscitation (ILCOR) recommended rate of 10 breaths per minute (BPM). Hyperventilation can lead to complications such as aspiration, barotrauma, and increased intracranial pressure.

Nevertheless, when utilised correctly, the BVM provides lifesaving respiratory assistance for oxygenation and gaseous exchange and has been the mainstay of prehospital ventilation since its creation in 1956. The Paediatric BVM has been trialled in in-hospital and tabletop studies to assess if the reduced inspired tidal volume decreases inadvertent hyperventilation within adult OHCA, with results indicating the Paediatric BVM may well provide more efficacious ventilations compared to the traditional Adult BVM. The Synchronous Manual Actuation Response Technology (SMART) BVM was subsequently designed with an actuating mechanism inside the neck bushing of the bag to intentionally limit the potential for excessive gas flow into the patient's airway. In-hospital tabletop studies suggest the SMART BVM, on average, provides ventilations and tidal volumes closer to recommended guidelines than other traditional Adult BVMs.

Yet, ILCOR states additional research is required to best inform clinicians on optimal airway practices, ventilation rates and tidal volumes, particularly in prehospital environments. In addition, improvements in CPR outcomes need a high-quality chain of survival from basic to advanced life support, in which clinicians from prehospital and in-hospital provide ventilations from a BVM. The present research investigates which of three established BVMs (SMART, Paediatric and Adult) provides more effective ventilations that align closely with ILCOR guidelines during a simulated OHCA.

Aim: To compare mean ventilation rates, singular inspired tidal volume and one-minute volume of asynchronous ventilations between the SMART BVM, traditional Adult and Paediatric BVM during an OHCA CPR simulation.

Methods: Thirty first-year paramedic students completed three simulated exercises (SIMEXs) utilising each BVM lasting four minutes each. Order of BVM exposure was randomised and participants were given six-minute rest breaks between each SIMEX. Each SIMEX comprised one participant providing two minutes of asynchronous ventilations having been informed the defined efficacy rate was 10–12 BPM, ~500 mLs per singular tidal volume ventilation, and 5,000–6,000 mLs total per one-minute volume, whilst the second participant provided chest compressions at a rate of 100–120 per minute. Participants undertook tasks for two minutes before cardiac defibrillation, then alternating roles for a further two minutes of asynchronous ventilations. All clinical guidelines were in accordance with ILCOR recommendations.

Results: The Adult BVM and SMART BVM mean ventilation rates were within recommended guidelines. While Adult BVM mean singular tidal volume (524 mLs) and one-minute volume (5,894 mLs) were no different to ILCOR recommendations, mean singular tidal volumes for the SMART BVM (443 mLs) and Paediatric BVM (280 mLs) were below ILCOR recommendations, as was the Paediatric mean one-minute volume (2,992 mLs).

Conclusion: Through our contemporary experiment with first-year undergraduate paramedical science students, the SMART BVMs incorporated pressure-response valve designed to limit excessive gas flow produced a singular tidal volume below established ventilatory recommendations. Similarly, the Paediatric BVM produced mean tidal volumes and one-minute volumes that were significantly lower than the recommendations set forth by ILCOR. By comparison, the traditional Adult BVM delivered tidal and one-minute volume more aligned with ILCOR recommendations.

Implications: According to the ILCOR 2015–2020 guidelines, patients experiencing OHCA should receive effective BVM ventilations at a rate of 10 BPM. The recommended tidal volume is approximately ~500 mLs, which equates to a total volume of 5,000–6,000 mLs delivered over one minute. During CPR, supplemental oxygen should be administered at a flow rate of 15,000 mLs/min. Achieving the appropriate one-minute volume and oxygen administration during CPR has been associated with increased rates of return of spontaneous circulation (ROSC) and improved long-term neurological outcomes for patients with OHCA.

Our research presents findings that challenge the conclusions of previous studies, particularly regarding the SMART BVM. The implications of our study could improve ventilatory strategies for BVMs, ultimately enhancing patient outcomes for those experiencing OHCA. We recommend conducting further investigations before ambulance services and other organizations allocate financial resources to alternative BVMs. Such a cautious approach could lead to substantial cost savings and prevent health organisations from making large-scale investments that do not improve OHCA outcomes. Therefore, additional specific research is necessary, comparing BVMs available on the market during adult OHCA CPR and enhancing our understanding of ventilatory parameters. Study findings may contribute to the further development of improved evidence-based guidelines.

DOI

10.25958/2xex-7j61

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