What is the goal ETCO2 measurement while performing quality CPR?

Ever since The Joint Commission issued revised requirements on resuscitation in early 2022, more and more hospitals are starting to take a closer look at their Code Blue practices and ask some key questions. How are we currently supporting our Code Blue teams to perform at their best? What types of trainings, resources, and feedback should we incorporate to maximize performance? Are there new tools we should invest in, or existing ones that we’re not fully optimizing?

One such tool that often falls into the latter category: end-tidal carbon dioxide (ETCO2) monitoring. Despite being simple, noninvasive, and multi-purpose, it’s often overlooked and underutilized for in-hospital cardiac arrest. In this article, we’ll cover the basics of ETCO2 and why it’s worth measuring, plus highlight 3 ways it can be used during a Code Blue.

• Measures the amount of carbon dioxide released at the end of an exhaled breath
• Indicator of a patient’s metabolism, circulation, and ventilation1
• Average reading for a healthy adult: 35-45 mmHg

Clinicians can use ETCO2 to gauge patient status in all kinds of clinical scenarios. But the readings can be particularly valuable in a high-stakes event like cardiac arrest, where monitoring quality indicators is crucial to guide and inform care.

There are also some practical benefits to consider:

• Easy and noninvasive: Waveform capnography measures ETCO2 continuously and portrays the readings visually as a waveform. Whether your hospital uses a handheld device, bedside monitor, or defibrillator attachment, these devices are simple and noninvasive. This means that there’s very little risk that use of the device will interfere with the code or add unnecessary burden to the team.

• Worth the investment: Like anything else, these devices come with a cost. But since ETCO2 levels yield insight into patient status and can guide care in a critical, life-or-death event like cardiac arrest, the small investment of a monitoring device is well worth it.

• Multi-purpose: Depending on the circumstances, ETCO2 readings can be used in more than one way during a code. From confirming correct placement of an endotracheal tube to helping clinicians recognize return of spontaneous circulation (ROSC), let’s take a closer look at the top 3 ways Code Blue responders can get the most out of this quality indicator.

Recommended by both the American Heart Association and the International Liaison Committee on Resuscitation,2 waveform capnography is the most reliable way to verify that an endotracheal tube is positioned correctly in the trachea. This is true not only for initial placement of the tube, but also for ongoing monitoring to ensure it doesn’t become dislodged during resuscitation. For instance, if no ETCO2 recordings are traced during cardiopulmonary resuscitation (CPR), it’s a signal to the team to re-evaluate the tube location.3

Study after study has shown the importance of high-quality CPR, but it can prove challenging and elusive to even the most experienced clinicians. Manual CPR is both physically and mentally demanding, as responders strive to repeatedly execute compressions at the optimal depth and rate throughout the code.

ETCO2 monitoring doesn’t make the task itself any easier, but it does offer in-the-moment feedback about the team’s efforts. And since clinicians are often relying on muscle memory when performing CPR, the value of a real-time, objective measure of compression quality really can’t be overstated.4-5 During CPR, code teams are aiming for ETCO2 readings greater than 20 mmHg. Readings between 10-20 mmHg are acceptable, and anything less than 10 mmHg is associated with poor outcomes. 4, 6-7 These guidelines help code teams quickly assess the effectiveness of their efforts and make changes as needed.

For example, a notable dip in ETCO2 can indicate that a compressor is tiring, or that some other controllable factor is hindering compression quality. And if the patient’s reading is less than 10 mmHg, the team needs to make an adjustment to get back on track. In manual CPR, this could mean switching out a compressor. For teams using mechanical CPR, it’s a good idea to check to ensure the device is positioned correctly.

A sharp increase in ETCO2 — from the teens to around 40 mmHg, for example — is unlikely to be achieved through CPR alone and is a reliable sign of ROSC. Importantly, it’s often the earliest indicator of ROSC in a cardiac arrest patient, occurring before any other signs of life.8-9 This is particularly useful because response teams can identify ROSC as soon as it happens — versus waiting for the next pause in compressions to check for a pulse.10 Plus, it may help minimize delays and interruptions to CPR that can occur while response teams are feeling for a pulse.

• Keep up with the fast pace of the code using real-time electronic documentation
• Accurately document every detail with a simple, intuitive user interface
• Stay on track with dynamic software guidance based on ACLS algorithms
• Receive immediate feedback with an auto-generated hot debrief report

OVERVIEW

• Current ILCOR guidelines advise that capnography is useful during cardiac arrest resuscitation
• ETCO2 can be used as a surrogate marker of cardiac output

USES

Uses during cardiac arrest:

• gradual fall in ETCO2 suggests compressionist fatigue during CPR -> time to change compressionists
• abrupt increase in ETCO2 suggests ROSC during CPR (detectable before pulse check)
• ETCO2 at 20 minutes of CPR is prognostically useful

Prognosis

• >20 mmHg at 20 minutes CPR -> higher chance of ROSC
• <10 mmHg at 20 minutes CPR -> almost no chance of ROSC

CONFOUNDERS

Confounders include:

• respiratory causes of arrest
• PE
• disconnection of BVM/ ventilator
• disconnection or obstruction of capnograph detector
• dislodgement or malposition of endotracheal tube
• bystander CPR

VIDEO

References and Links

• Heradstveit BE, Sunde K, Sunde GA, Wentzel-Larsen T, Heltne JK. Factors complicating interpretation of capnography during advanced life support in cardiac arrest–a clinical retrospective study in 575 patients. Resuscitation. 2012 Jul;83(7):813-8. PMID: 22370007.
• Kolar M, Krizmaric M, Klemen P, Grmec S. Partial pressure of end-tidal carbon dioxide successful predicts cardiopulmonary resuscitation in the field: a prospective observational study. Crit Care. 2008;12(5):R115. PMC2592743.
• Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. N Engl J Med. 1997 Jul 31;337(5):301-6. PMID: 9233867. [Free Full Text]

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

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