Temporal Trends in Bag-Valve-Mask End-Tidal Capnography and Outcomes in Out-of-Hospital Cardiac Arrest

Among advanced airway (AA) devices, capnography trajectory has been associated with outcomes in out-of-hospital cardiac arrest (OHCA). Limited data describe bag-valve-mask (BVM) end-tidal capnography (EtCO2) trajectories. We aimed to characterize EtCO2 trajectories during BVM ventilation and associations with outcomes.

We analyzed data from the Pragmatic Airway Resuscitation Trial (PART), which evaluated advanced airway strategies and associations with 72-hour survival in OHCA. We classified subjects by AA first pass success: 1) AA successfully placed 2) AA unsuccessfully placed 3) BVM-only (no AA attempted). Emergency medical services collected continuous EtCO2 recordings using standard defibrillator monitors. We summarized EtCO2 values per ventilation into 1-minute epochs using previously validated automated signal processing techniques. We defined EtCO2 slope as the change in capnography over time (mmHg per minute) using at least 2 epochs over resuscitation. We compared slopes between ROSC and non-ROSC groups using Mann-Whitney testing. Outcomes included return of spontaneous circulation (ROSC) and 72-hour survival (secondary). Using airway stratified regression models, we determined the association between EtCO2 trajectory and outcomes.

Among 3,004 patients, 1,401 had available EtCO₂ data, including AA successful (n=1,026), AA unsuccessful (n=346), and BVM-only (n=29). ROSC and 72-hour survival did not differ across airway groups. In all airway strata, patients achieving ROSC demonstrated increasing EtCO₂ over time as demonstrated by positive slopes vs non-ROSC patients with negative slopes [(1) AA Successful: 0.61 [-0.40, 2.35] vs -0.28 [-0.94, 0.17]; p<0.001 (2) AA Unsuccessful: 0.63 [-0.19, 2.06] vs -0.32 [-1.34, 0.20]; p<0.001) (3) BVM-only: 1.13 [0.20, 1.81] vs -0.60 [-1.75, -0.17]; p=0.011)]. In all 3 strata, capnography trajectory was associated with outcomes (ROSC: AA successful 1.36 [1.26, 1.48], p<0.001; AA unsuccessful 1.44 [1.23, 1.70], p<0.001; BVM-only 3.04 [1.07, 8.58], p=0.036; 72-hour survival: AA successful 1.33 [1.23, 1.45], p<0.001; AA unsuccessful 1.40 [1.16, 1.70], p=0.001; BVM-only 3.18 [1.02, 9.92], p=0.047).

Capnography trajectories are associated with outcomes in all ventilation strategies. This supports that BVM capnography trajectory may be reliable in cardiac arrest.