Abstract Body: Introduction: During cardiopulmonary resuscitation (CPR), chest compressions induce oscillations in capnography. The relative magnitude of these oscillations can be quantified by the Airway Opening Index (AOI). AOI is hypothesized to be reflective of airway patency and effective ventilation, and may be associated with higher incidence of return of spontaneous circulation (ROSC).

Aim: We sought to determine whether AOI is measurable and associated with ROSC using retrospective analyses of human out-of-hospital cardiac arrest (OHCA) and swine resuscitation.

Methods: Human OHCA cases received attempted resuscitation from a single metropolitan EMS system between 2015-2021. Yorkshire swine received either 5 or 10 minutes of induced ventricular fibrillation followed by mechanical CPR. Cases were excluded if capnography was missing or artifacted. AOI was calculated using 4 established methods (Fig. 1). Median AOI for each AOI method was compared between humans and swine and according to ROSC status using Wilcoxon rank-sum test.

Results: Among the 2095 eligible human cases, 50% (n=1046) achieved ROSC. Among the 37 eligible swine, 70% (n=27) achieved ROSC. Median AOI [Methods 1-4] was higher in humans ([14.9-22.2%]) than swine ([4.1-7.5%], p<0.001). AOI by all 4 methods was higher among those who achieved ROSC compared to No-ROSC for humans (Fig. 2) and for swine (Fig. 3). The difference in AOI according to ROSC was greater in swine than humans ([4.0-8.2%] vs [2.1-3.5%] respectively, p<0.05).

Conclusion: AOI was measured in human OHCA and an experimental swine model. AOI was associated with ROSC in both animals and humans. AOI magnitude was significantly smaller in swine, though swine had a greater AOI difference between ROSC and No-ROSC cases. Further investigation will explore whether these differences are due to different thoracic anatomy and/or experimental conditions between humans and swine. Overall, the results validate the experimental swine model as a platform to investigate whether AOI is a modifiable target to increase the likelihood of ROSC, with a goal to improve outcomes for cardiac arrest.