Abstract Body: Background: Automatic oxygenators can be used for ventilation in out-of-hospital cardiac arrest (OHCA) patients. However, their efficacy under different pressure limits is unknown.
Research Question: Does the ventilation efficacy of Ambu bag and automatic oxygenators under different pressure limits differ in OHCA patients during prehospital resuscitation?
Aims: To compare the ventilation efficacy of Ambu bag and automatic oxygenators under different pressure limits and investigate the association of different ventilation settings with patient outcomes.
Methods: This retrospective study included adult patients with non-traumatic OHCA who received prehospital advanced airway in Hsinchu county, Taiwan, in 2023. Patients were categorized into three groups: Group A (ventilated by Ambu bag), Group B (automatic oxygenators, pressure limit at 45 cmH2O), and Group C (automatic oxygenators, pressure limit at 60 cmH2O). Ventilation efficacy was monitored by recording tidal volume using Zoll® X-series monitors. The median and maximum tidal volume and percentage of adequate ventilation (tidal volume between 500-600 ml) of each patient among 3 groups were compared. Associations between ventilation settings, efficacy, and patient outcomes were analyzed using multivariable logistic regression.
Results: Group A, Group B, and Group C consisted of 57 (32.0%), 41 (23.0%), and 80 (45.5%) OHCA patients, respectively. The demographics and prehospital managements, including advanced airway type (laryngeal mask [LMA] or endotracheal tube [ETT]), did not differ between groups. The median tidal volume was highest in Group B, followed by Group A and C (Group A: 363.0 ml, Group B: 403.0 ml, Group C: 275.0 ml, p = 0.016). The median maximum tidal volume was highest in Group A, followed by Group C and B (Group A: 644.0 ml, Group B: 534.0 ml, Group C: 567.5 ml, p = 0.024). The median percentages of adequate ventilation were equally low in 3 groups, (Group A: 5.7%, Group B: 3.1%, Group C: 2.0%, p = 0.372). Different ventilation settings or efficacy were not associated with prehospital or in-hospital return of spontaneous circulation. However, patients receiving prehospital ETT insertion had better outcomes than those with LMA.
Conclusion: This study presents the ventilation efficacy of OHCA patients ventilated by Ambu bag or automatic oxygenators under different pressure limits. Despite slight differences in tidal volumes measured across groups, patient outcomes did not differ significantly.