Resuscitation and ETCO2: So what’s the use?
Remember back in 2005 when it became ACLS Guideline directed practice to resume CPR immediately after defibrillation. Did that freak you out? Do you still pause after defibrillation, and try to sneak a quick peak at the monitor to check for a life sustaining rhythm? Do you delay chest compressions to quickly feel for a pulse?
If you answered, “yes” to either or both of these questions, perhaps you are doing so propelled by a combination of hope and or fear. Hope that your efforts at defibrillation were successful, and fear that your ongoing resuscitation efforts will cause harm.
Indeed after defibrillation, the curious practitioner is left to wonder “what if our shock was successful and we obtained return of spontaneous circulation [ROSC], could we cause harm with chest compressions or by pushing IV epinephrine?” At first glance delaying a rhythm and pulse check can feel like a great leap of faith, and for some members of the resuscitation community this leap represents a significant clinical hurdle to overcome.
The 2010 ACLS Guidelines have given us a way to jump over that hurdle and keep on running safely through our resuscitations. In this latest iteration, emphasis has been placed on continuous waveform or capnometric ETCO2 monitoring. Achieved in cardiac arrest by inserting a line onto an advanced airway to a receiving monitor, this metric is used not only for ongoing confirmation of advanced airways, but also provides real time breath-by-breath physiological evaluation of patients.
The study of capnography is multi-faceted and as a simplified statement normal values are 35-45 mm/Hg. The waveform below shows a patient with an ETCO2 of 34 mm/Hg:
Naturally a pulseless patient, who has no pulmonary circulation, will in turn have no ETCO2. However when high quality CPR is performed, the exhaled ETCO2 jumps from 0 mm/Hg to greater than 10mm/Hg. If during compressions, the ETCO2 lowers; code team members should turn their attention to the quality of the CPR being given. Rescuer fatigue for instance can dramatically decrease chest compression efficiency. The waveform below shows a patient receiving CPR with an ETCO2 rising from around 10 to 16 mm/Hg:
If during high quality CPR there is a return of spontaneous circulation then the ETCO2 will display “an abrupt sustained increase” and as shown below will jump into the 35-45 mm/Hg range.
This is how employing the use of continuous ETCO2 monitoring during CPR, that resuscitators are provided with insight into the outcome of their defibrillation attempts and with a window to ROSC. Indeed it is this information that allows clinicians to jump over the hurdle described above, and to gain an increased sense of comfort with the decision to resume chest compressions immediately after defibrillation.
Darin Abbey RN
Clinical Nurse Educator
Nanaimo Regional General Hospital