Measurement of tidal volumes and respiratory rate during regular and asynchronous intra-arrest ventilation using the EOlife X device: A method-comparison study in a porcine cardiac arrest model.

AIM: To evaluate the accuracy of the EOlife X, a ventilation feedback device for training, during regular ventilation and during intra-arrest ventilation with ongoing chest compressions.

METHODS

In this prospective experimental method-comparison study in a porcine cardiac arrest model, EOlife X-derived inspiratory tidal volume (Vti), expiratory tidal volume (Vte), and respiratory rate (f) were compared with sensor-based reference computations. Data were extracted by optical character recognition from screen recording of the EOlife X. Reference metrics were computed from continuous airflow and airway pressure measurements. For each animal, a two-minute-long period before cardiac arrest and a two-minute-long period of cardiopulmonary resuscitation (CPR) were analysed. The animals were mechanically ventilated via an endotracheal tube. Agreement was assessed using Bland-Altman analysis with linear mixed model derived bias and limits of agreement to account for repeated measures. Clinically acceptable differences were prespecified as ±50 mL for tidal volumes and ±3 /min for respiratory rate.

RESULTS

Data from 11 animals, yielding 821 paired ventilations (581 regular, 240 intra-arrest), were analysed. During regular ventilation, EOlife X measurements were within the prespecified clinically acceptable difference for all metrics, while exceeding it for all metrics during intra-arrest ventilation: Bias for Vtiwas -26 mL with limits of agreement (LoA) ranging from -355 to 304 mL, for Vtebias was -281 mL (LoA -599 to 37 mL), and for f23.8 /min (LoA -50.2 to 97.8 /min). The proportions of measurements outside the prespecified clinically acceptable difference during intra-arrest ventilation were 37.1% for Vti, 86.2% for Vte, and 60.4% for f. Waveform inspection suggested that chest compression-induced reverse airflow affects airflow-based measurements.

CONCLUSION

EOlife X showed agreement within predefined clinically acceptable limits during regular ventilation, but not during intra-arrest ventilation with ongoing chest compressions. Chest compression-induced reverse airflow appears to compromise airflow-based calculation of tidal volume and respiratory rate. Devices for ventilatory monitoring should be validated specifically under CPR conditions.