Abstract Body: Background: While prehospital advanced airway devices are commonly used in out-of-hospital cardiac arrest (OHCA), whether gas exchange differs between devices is unknown.
Objective: To characterize arterial blood gas (ABG) differences between patients receiving laryngeal tube (LT) or endotracheal intubation (ETI) in the Pragmatic Airway Resuscitation Trial (PART).
Methods: We included adult OHCA enrolled in PART with first ABG collected ≤ 90 minutes after emergency department (ED) arrival. We identified 1) last prehospital airway technique used (LT vs. ETI), 2) average end-tidal capnography (EtCO₂) values for the last 5 minutes of prehospital care, 3) return of spontaneous circulation (ROSC) in the ED, and 4) ED ABG measurements (pH, PaO₂, PaCO₂). We compared ABG values between LT and ETI using the Mann-Whitney test, stratifying by ROSC vs. non-ROSC. We also determined the correlation between last 5-minute mean prehospital EtCO₂ and PaCO₂ using Pearson’s correlation. We also compared absolute difference between EtCO₂ and PaCO₂ (PaCO₂ - EtCO₂) using the Mann-Whitney test. All blood gas and EtCO₂ values are reported in mmHg.
Results: Of 3004 patients enrolled in the parent trial, 483 had an ABG ≤ 90 minutes after ED arrival; 276 LT, 129 ETI, 76 no advanced airway, and 2 unknown. Among patients with ROSC in the ED, pH did not differ between LT and ETI (7.1 vs. 7.2, p=0.10), PaO₂ showed a tendency toward lower values in LT than ETI (142 vs. 170, p=0.07), and PaCO₂ was significantly higher in LT compared to ETI (59 vs. 50, p=0.002). Among patients without ROSC, pH did not differ between LT and ETI (7.0 vs. 7.0, p=0.55), PaO₂ was significantly lower in LT than ETI (85 vs. 123, p=0.03), and PaCO₂ did not differ between LT and ETI (64 vs. 60.5, p=0.58). EtCO₂ did not correlate with PaCO₂ in any airway device/ROSC combination: [LT+ROSC] r=0.02, [ETI+ROSC] r=0.14, [LT+non-ROSC] r=-0.11, [ETI+non-ROSC] r=0.51. PaCO₂ - EtCO₂ was significantly wider in non-ROSC than ROSC cases (27 vs. 18, p=0.03) but did not differ by airway device.
Conclusions: ABG values may vary by prehospital advanced airway management methods. The correlation between EtCO₂ and PaCO₂ in patients with OHCA remains unclear.