Background: End Tidal CO2 (ETCO2) has been used as a surrogate for systemic blood flow during CPR. Resuscitation guidelines suggest the use of ETCO2 for assessing chest compression effectiveness. While previous studies have found a relationship between deeper chest compression depth and higher ETCO2, there is paucity of clinical research examining the effect of ventilation parameters on ETCO2 during CPR.
Objective: To quantify the relationship of ETCO2 independently with respiratory rate (RR), minute ventilation (MV) and tidal volume (TV) during clinical CPR.
Methods: We performed an observational study which captured time synchronized respiratory data from adult cardiac arrest events at 2 sites between 02/2015-04/2016 using a respiratory profile monitor (Philips Respironics NM3, Andover, MA). ETCO2, RR, MV and TV were averaged over each minute and analyzed using mixed effects regression modeling to account for patient as a cluster.
Results: 11 subjects had a total of 129 average breaths per min of respiratory data captured, see Table below. Six (55%) subjects had an initial shockable rhythm, 3 (27%) had PEA, 1 (9%) had asystole, and 1 (9%) was unknown. As total RR increased, mean ETCO2 decreased (coef -0.10, p=0.02). The relationship between ETCO2 with MV and with TV was not statistically significant.
Conclusion: This quantitative analysis during clinical CPR suggests that a higher RR is associated with lower ETCO2. MV and TV did not affect ETCO2.