Does CPR save lives?

In TV land, most people not only survive CPR (cardiopulmonary resuscitation), but they go home from hospital and function normally afterwards (yes, they actually studied this). In reality, less than 10% survive, and for many that do, it’s not a good life. The low number of people that survive and function well after CPR (as low as 2% in some studies) leads to a question: if the results with CPR are so dismal, what would the results be if we did not do CPR? In other words: does CPR itself do anything; were those that survived going to survive anyway?

In-hospital survival is a little better, but interestingly the survival rate did not change over 14 years in this study of over 400,000 patients, despite multiple changes in the way CPR is delivered over that time. I am aware of before-and-after studies where the survival improved after implementing a change in CPR, notably this study from Seattle. But this study used a more aggressive shock protocol (defibrillation) that may have been responsible for the difference (please note: this blog is about CPR, not electrical defibrillation). Also, the biases of before-and-after studies are such that they nearly universally show improvement over time (for many reasons that will be covered in a future blog post). The bias in these studies is so strong, I only sit up and take notice when one of these studies shows no improvement over time.

Other studies have shown that the technique of delivering CPR doesn’t matter. Using fancy devices doesn’t help (Cochrane review). Giving adrenaline (epinephrine) to these patients can improve the chance of restoring circulation prior to arriving at hospital, but to no avail: it makes little difference to the survival, and is associated with worse functional outcomes (here).

It doesn’t even matter if you breathe for them or not (here and here), and I would have considered that to be pretty important. In fact, breathing for the patient is now supposed to be bad, because it increases the pressure in the chest, decreasing the venous flow into the heart. So what does the chest compression do if it doesn’t increase the pressure in the chest? I get confused reading about the mechanics of this stuff (cardiac pump theory vs. thoracic pump theory etc.) but as many of you know by now, I am a pragmatist: I am less concerned with the biological mechanism, and more concerned with whether or not it saves lives.

Is there a downside to CPR?

This study showed a 21% complication rate at autopsy, and an 89% rate of missed diagnoses, many of which would have made the CPR futile. Common complications are rib fractures, lung damage, vomiting and aspiration (gastric contents into the lungs).

While the response to CPR doesn’t depend much on the technique, it might depend on what is wrong with the patient, which could vary from a simple faint to a massive lung clot. In both these extreme cases, it wouldn’t matter whether or not you had CPR. In the first case (fainting) CPR would just add harm until the patient woke up anyway, and in the second case (massive clot) you would be wasting your time because the event is not survivable. In between though, there are other conditions for which it is possible that CPR may be of benefit, and this makes it hard to convincingly state that CPR never works. There may be people wishing to comment, with personal experience of patients surviving after CPR. My question to them will be: When we look at that case objectively, how can we be certain that the patient survived because of the CPR?

The bottom line.

The results of CPR are a lot worse than most people think, and in most cases CPR will not make a difference to the outcome. CPR fits the pattern of treatments discussed in this blog, with overestimated benefits and underestimated harms. Currently, however, the concept of CPR as an effective treatment is so deeply woven into our thinking that it would be impossible to stop doing it, or even to subject it to better scientific testing. Maybe in 50 years we will look back on our vigorous but naïve attempts to reverse death, and on the harms we did to those who were going to live anyway.