Association between end tidal capnography dynamics following vasopressor administration

Dynamic changes in end-tidal CO₂ (EtCO₂) may reflect changes in perfusion and ventilation during cardiopulmonary resuscitation. However, EtCO₂ dynamics following vasopressor administration in out-of-hospital cardiac arrest (OHCA) is unknown. We sought to characterize EtCO₂ variations after single dose vasopressor administration.

We performed a secondary analysis from the Pragmatic Airway Resuscitation Trial. We summarized maximal EtCO₂ values into one-minute epochs using previously validated automated signal processing. We identified vasopressor administration times using patient records and defibrillator timestamps. We studied changes in EtCO₂ morphology after vasopressor administration, including time (minutes) to 15% rise above baseline, time to peak EtCO₂, peak proportional change in EtCO_2, and duration of EtCO₂ over 15%. We compared differences in EtCO₂ morphology between return-of-spontaneous circulation (ROSC) and non-ROSC using Mann-Whitney U tests.

We included 517 patients with EtCO₂ recorded during a single dose of vasopressor. 139 patients (27%) achieved ROSC. Lag time (ROSC: 1.87 min, IQR 0.88-3.38 vs. non-ROSC: 1.93 min, IQR 0.77-3.50; p = 0.177) and peak time (ROSC: 3.43 min, IQR 1.44-6.67 vs. non-ROSC: 2.70 min, IQR 1.10-4.99; p = 0.129) were not associated with ROSC. Proportional change in EtCO₂ (ROSC: 43.33%, IQR 15.01-105.88 vs. non-ROSC: 24.67%, IQR 4.86-64.10; p < 0.001) and rise duration (ROSC: 4.00 min, IQR 0.50-10.00 vs. non-ROSC: 1.00 min, IQR 0.50-5.75; p < 0.001) were associated with ROSC.

Following a single dose of vasopressor, EtCO₂ increased and remained elevated for longer durations in ROSC patients. EtCO₂ changes after vasopressor administration may reflect progression of OHCA resuscitation.