The Goldilocks Rule for Ventilation

A successful resuscitation requires a well-executed bundle of interventions that are interdependent. To borrow from Dr. Snyder in Wake County, North Carolina, “there is no silver bullet, but there is a silver chain!”

High quality chest compressions are the foundation of the resuscitation – this includes proper rate of compressions, proper depth, and limiting “no-flow” times. Technological advances in real-time CPR feedback have improved the quality of CPR, and novel approaches to keep the compression fraction above 90 percent are implemented in many systems. Two of the biggest improvements to increase the compression fraction are to limit the peri-shock pause and to de-emphasize airway management. As an example, intubation should be performed without interrupting compressions, or the provider can utilize a blind insertion airway device. The execution of the resuscitation bundle can vary; however, the key is to limit any interruption in compressions. Although compressions precede airway management in a cardiac arrest, we have to remember that ventilation plays a very important role to compliment these compressions and other interventions.

As an example, Idris et al shows that ventilating in cardiac arrest favorably affects hypoxia, hypercarbic acidosis, and acidemia. This has a direct influence on the efficacy of drugs and defibrillation. Lurie et al also showed “that periodic lung inflation maintains the structural integrity of the lungs and lowers pulmonary vascular resistance,” thereby improving blood flow through the lungs.

On the other hand, hypoventilating during cardiac arrest causes detrimental consequences. Lurie et al showed that giving only 2 breaths per minute versus 10 breaths per minute causes the lungs become more atelectatic. The atelectasis is believed to cause a “reduction in the transmission of the energy from the elastic chest-wall recoil during CPR” which decreases blood flow. In addition, pulmonary vascular resistance increases causing trans-pulmonary blood flow to decrease.

Not ventilating also affects medication administration. Idris et al showed that CPP responded better to epinephrine in ventilated animals versus non-ventilated animals. This would suggests that “ventilation may play an important role in regulating CPP and ROSC through the vascular response to catecholamines,” making it more likely to achieve ROSC in a ventilated patient.

Another consequence of improper ventilation in cardiac arrest is hypercarbic acidosis, which causes peripheral vasodilation and “blunts the vasoconstriction response to exogenous epinephrine.” Higher PACO2 also effects cerebral blood flow by increasing cerebral vasodilation secondary to cerebral autoregulatory mechanisms. In addition, if ROSC is achieved, the hypoxia and hypercarbia “profoundly decreases the myocardial force of contraction.” This would make a re-arrest more likely.

In summary, not ventilating has profound and potentially harmful effect on the resuscitation process. When deploying the “silver chain” of resuscitation, we should also follow the “goldilocks rule” of performing interventions correctly. Whether we perform compressions or ventilate the patient, rates that are too fast or too slow are detrimental. We have to do things “just right!”

How about that!

The Goldilocks Rule: Rate Matters

A lot of positive progress has been made in the process of resuscitating cardiac arrest victims. Our understanding of the physiology has improved, the tools at our disposal to successfully intervene in a code are phenomenal, and a cultural philosophy that “it actually works” is sweeping our profession. One of the biggest changes in the process has been a revival on focusing on the basics – and nothing is more basic in a resuscitation than chest compressions.

Chest compressions are the foundation on which a resuscitation is built. And like any foundation, we need it to be of high quality or the entire process will crumble.  I do not care if you have the best drugs, the greatest defibrillator, or the smartest clinician at a code. Without high quality chest compressions, the ultimate outcome will be less than desirable.

In the last few years, there have been some great PSA about performing CPR. My favorite is “Vinnie Jones' hard and fast Hands-only CPR.” Check it out!

Although this PSA is for lay-person CPR, Vinnie hinted at some important aspects of high quality CPR that professional providers need to remember - push hard and fast. However, the actual rate matters.

Think about the baseline in a healthy person. There is a small range in all of our vitals, but a deviation to one extreme or another is a bad thing. A heart rate of 30 or a rate of 240 is a bad thing in a living person. Those rates must be really bad in a person whom we are resuscitating with compressions. Right?

So we do not want a rate that is too slow, nor too fast. We want a rate that is just right! Call it the Goldilocks rule! 100 compressions per minute. That’s the rate! And while we are on the subject of rates, do not breathe too fast for them either! The AHA recommends a rate no faster than 10 breaths per minute.

Build that foundation and watch a real life fairy-tale unfold!

How about it?