We should care about end tidal CO2 during CPR as it can depict the respiratory process (ie, metabolism, transport, ventilation) even in a low perfusion state. As such, there are 3 good reasons (if not more!) to monitor ETCO2 during an arrest.
Monitoring CPR Fatigue
During effective CPR, ETCO2 values are typically 10-20 mmHg. A trend down may indicate fatigue of the person providing chest compressions. I think we’ve all seen when the person providing CPR is sweating and too shy to say they need a rest. Give ’em a break.
<10 for 20? Call it.
Values persistently at 10 mmHg or under for 20 minutes of CPR are 88% sensitive and 77% specific for not obtaining ROSC. The grey area – those between 10 & 20 mmHg, is less clear. There is conflicting literature that 14-15 mmHg should be a stopping point. One study of 737 patients found, “When a 20-minute end-tidal carbon dioxide value of 1.9 kPa (14.3 mmHg) or less was used as a screening test to predict ROSC, the sensitivity, specificity, positive predictive value, and negative predictive value were all 100%” where as another found: “We identified 22 patients, who had an initial end-tidal CO2 at or below 1.3kPa [9.75 mmHg]. Four of these patients achieved return of spontaneous circulation.” No comments on whether or not these 4 patients survived to discharge. Good review found here: http://www.ncbi.nlm.nih.gov/pubmed/23871864
When you see sudden bump- typically 10mmHg or >35mmHg- Congrats! – you’ve got ROSC. Now, no one needs to have their hand in the patients groin to do frequent pulse checks. And no one needs to stop CPR. CAUTION: this is a single study of 108 patients and stands to be the foundation of new dogma.
Final thought, and one that may actually make a difference…
values in mean ± SD (from Resusc 2012 paper below)
The standard deviation numbers have significant overlap. However, a lower ETCO2 after ROSC brings forth the question of thrombolysis for PE. And would you have thrombolysed anyway after a RUSH exam and an EKG showing right sided strain?
The gist: ETCO2 is now in the ACLS guidelines and on the EMS wagons, time to get our EDs up to speed
End-tidal Carbon dioxide and the outcome of out of hospital cardiac arrest. PMID: 9233867
Factors complicating interpretation of capnography during advanced life support in cardiac arrest- A clinical retrospective study in 575 patients. PMID: 22370007
Partial pressure of end-tidal carbon dioxide successful predicts cardiopulmonary resuscitation in the field: a prospective observational study PMID: 18786260
A sudden increase in partial pressure end-tidal carbon dioxide pETCO2 at the moment of return of spontaneous circulation. PMID: 19570645