CPR and Ventilation Rate: “What does a yellow light mean?”
Myron Yaster MD, Jayant K. Deshpande MD, and Justin L. Lockman, MD MSEd
As virtually all of my former residents, fellows and colleagues know, and now many of you, the readers of the Pediatric Anesthesia Article of the Day also know, I am a firm believer that we routinely over-ventilate patients in the OR and that we should instead allow pCO2 to be in the 50s – definitely not the low 30s or high 20s as is so common. I discussed this in the PAAD “CO2 is good for you” (July 18, 2022). To refresh your memory: Hyperventilation resulting in hypocarbia produces alkalosis which, with very few exceptions, is never normal. Alkalosis shifts the oxyhemoglobin dissociation curve to the left thereby preventing the unloading of oxygen to the tissues. It also decreases blood flow to the brain and heart, in addition to depressing/stopping spontaneous minute ventilation. For intubated patients, mechanical hyperventilation additionally decreases systemic venous return by increasing mean intrathoracic pressure. On the other hand, acidosis is very common and occurs every time we exercise. It produces many salutary effects, including increased cardiac output, blood pressure, and heart rate, as well as increased blood flow to organs that are vulnerable to ischemia, such as the brain, heart, and kidneys. Perhaps most importantly to the anesthesiologist, acidosis causes a rightward shift in the oxyhemoglobin dissociation curve, which improves oxygen unloading to every cell in the body, and because hydrogen ion is the primary driver of ventilation at the chemoreceptor in the brainstem, it is the primary driver of spontaneous ventilation.
These physiologic principles are also true during CPR, and perhaps even more so. But during CPR, the team is so relieved when they have an endotracheal tube (“advanced airway device” in American Heart Association (AHA) speak) in place to deliver oxygen, the natural tendency is to squeeze the resuscitation bag as fast as possible almost to the point of hand tetany. You and your team have had to learn how to overcome this tendency and to slow down (“what does a yellow light mean”? see video at the end of the PAAD) just as you learned that chest compressions require pushing fast and pushing hard. Indeed, the AHA changed its thinking about ventilatory rates in the last version of the pediatric life support guidelines. I’ve asked Justin Lockman, the PAAD’s ICU reviewer, and Jay Deshpande, from Wake Up Safe to assist me with this review.
What should the chest compression and ventilatory rates be? Well first, a word from the AHA on chest compression only CPR:
Original article
Jennifer D Chapman, Andrew S Geneslaw, John Babineau, Anita I Sen. Improving Ventilation Rates During Pediatric Cardiopulmonary Resuscitation. Pediatrics. 2022 Sep 1;150(3):e2021053030. PMID: 36000325
In-hospital pediatric cardiac arrest and how and where CPR is performed is NOT what it used to be. Primarily because of rapid response teams,[1] almost all pediatric in-hospital cardiac arrests are witnessed and monitored and occur in the ICU rather than on the medical and surgical wards.[2] Perhaps because of this change, immediate survival rates are vastly improved. Indeed, “As many as 80% to 90% survive the event, but most patients do not survive to hospital discharge”.[2, 3] In 2010, the AHA identified 5 components of high-quality cardiopulmonary resuscitation (CPR), including minimizing interruptions in compressions, providing compressions of adequate rate and depth, allowing full chest recoil for venous return, and avoiding excessive ventilation.[4] Furthermore, the AHA emphasized the utility of monitoring, feedback, and CPR quality improvement (QI) to maximize resuscitation success. As a result, the AHA recommends “avoiding hyperventilation to improve the chance of successful resuscitation”. [5][6] Of these 5 components, avoiding hyperventilation remains perhaps the most challenging in practice – is this because, as one of us (JLL) often teaches, “Epinephrine is a neurotoxin for CPR providers.”?
Chapman et al.[5] in “a QI initiative focused on education of CPR team members, CPR leader feedback, and use of CPR ventilation rate tools decreased the proportion of CPR time with clinically significant hyperventilation rates (defined as ≥30 bpm) from 51% to 29%”.[5] The team used a tool (CPR Metronome) that includes a heart rate metronome at 110 beats per minute and an audible bell every 5 seconds (12 times per minute) to signal when to give a breath. The tool is available from the Apple and Android app stores for a fee if you are interested… but be aware that 12 breaths per minute is not recommended for pediatric patients anymore (see below).
So, what should the ventilation rate be? In prior AHA guidelines the suggested ventilatory rate has ranged from 6-12 breaths/minute, but the 2020 update to AHA guidelines raised the rate 20-30 breaths/minute for infants and young children patients with advanced airways in place.[4, 7] Perhaps the next version of SPA’s PediCrisis app could include a CPR metronome for children? Or let us know if you have one already that you like to use.
Also, although end-tidal CO2 was the method used to measure ventilation rates in this study, CO2 was not used as an endpoint. It would be nice to be able to target a CO2 level, particularly for those with advanced skillsets (like pediatric anesthesiologists), but doing so is limited by the effects of low cardiac output (during CPR) on pulmonary blood flow and thereby on end-tidal CO2 readings. One thing we do know: the presence of high enough end-tidal CO2 (at least 15) during CPR is a marker for adequate compressions and correlates with survival.
One final thought. This paper was about ventilatory rates and not oxygenation and oxygen delivery. Remember that hyperoxia is also something to avoid during CPR and like hyperventilation is quite common.[8] Goal SPO2 (based on current data) should be 94-99%, particularly for post-resuscitation care. In an ideal world, we would like to use an oxygen blender for titration of oxygen to every patient’s needs during and immediately following CPR… but then again, in an ideal world children would never need CPR and there would be no such thing as a children’s hospital!
PS from Myron: One of the funniest TV scenes EVER “what does a yellow light mean”? from the old TV show TAXI is something to think about during CPR. Indeed, I would often tell my colleagues and students during CPR: “What does a yellow light mean”? After watching this video you may do this too!
References
1. Brilli, R.J., et al., Implementation of a medical emergency team in a large pediatric teaching hospital prevents respiratory and cardiopulmonary arrests outside the intensive care unit. Pediatr Crit Care Med, 2007. 8(3): p. 236-46; quiz 247.
2. Morgan, R.W., et al., Pediatric In-Hospital Cardiac Arrest and Cardiopulmonary Resuscitation in the United States: A Review. JAMA Pediatr, 2021. 175(3): p. 293-302.
3. Morgan, R.W., et al., A hemodynamic-directed approach to pediatric cardiopulmonary resuscitation (HD-CPR) improves survival. Resuscitation, 2017. 111: p. 41-47.
4. Kleinman, M.E., et al., Pediatric advanced life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Pediatrics, 2010. 126(5): p. e1361-99.
5. Chapman, J.D., et al., Improving Ventilation Rates During Pediatric Cardiopulmonary Resuscitation. Pediatrics, 2022. 150(3).
6. Meaney, P.A., et al., Cardiopulmonary resuscitation quality: [corrected] improving cardiac resuscitation outcomes both inside and outside the hospital: a consensus statement from the American Heart Association. Circulation, 2013. 128(4): p. 417-35.
7. Topjian, A.A., et al., Part 4: Pediatric Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation, 2020. 142(16_suppl_2): p. S469-s523.
8. Marquez, A.M., et al., Oxygen Exposure During Cardiopulmonary Resuscitation Is Associated With Cerebral Oxidative Injury in a Randomized, Blinded, Controlled, Preclinical Trial. J Am Heart Assoc, 2020. 9(9): p. e015032.