Comparison of end tidal CO2 levels between automated head up and conventional cardiopulmonary resuscitation: A pre-post intervention trial

Abstract

Background: The combination of controlled automated head/thorax elevation, active compression-decompression (ACD) cardiopulmonary resuscitation (CPR), and an impedance threshold device (ITD-16), termed AHUP-CPR, lowers intracranial pressure and increases circulation and neurologically-sound survival in pigs versus conventional (C) CPR. This study examined whether AHUP-CPR increased end tidal (ET) CO₂, a non-invasive marker of cardiac output and organ perfusion, compared with C-CPR in witnessed out-of-hospital cardiac arrest patients.

Method: We conducted a prospective, single-arm, pre-post intervention trial in France between October 2019 and October 2022.Firefighters treated patients enrolled during the pre-intervention period with manual C-CPR and with AHUP-CPR during the post-intervention period. Advanced life support was provided by a physician-staffed 2nd-tier response vehicle for the two study periods. The primary outcome was the peak ETCO₂ value measured during CPR.

Results: 122 patients with a mean age of 67 years (standard deviation [SD], 17) were enrolled (59 in the pre-intervention period and 63 in the post-intervention period). Based on an intention-to-treat analysis, mean baseline ETCO₂ values were comparable between pre- (20.1 mmHg, SD,16.3) and post-(19.2 mmHg, SD, 16.3) intervention periods. Mean peak ETCO₂ values during CPR were 30.3 mmHg (SD, 13.1) versus 40.7 mmHg (SD, 17.8) for the pre- and post-intervention study periods (mean difference, 10.6, 95% confidence interval, 4.6 to 16.1, P < 0.001). Mean differences in peak ETCO₂ between study periods did not vary according to the first recorded cardiac rhythm (P for interaction = 0.99). The proportion of return of spontaneous circulation [19 (32.2%) vs. 21 (33.3%)], survival on hospital admission [17 (28.8%) vs. 19 (30.2%)], and 30-day survival with favorable neurological outcome [8 (13.6%) vs. 7 (11.1%)] did not differ between study periods.

Conclusion: ETCO₂ values during AHUP-CPR reached the range of non-arrest normal physiological levels and were significantly higher than with C-CPR, regardless of the presenting cardiac rhythm.

Keywords: Active compression-decompression; Automated head-up positioning CPR; Cardiac arrest; Cardiopulmonary resuscitation; Impedance threshold device; Mechanical CPR.