CPR Quality Series Part 2: Compression Depth

Welcome to the second installment of our cardiopulmonary resuscitation (CPR) quality series! If you missed it, part 1 focused on the basics of high-quality CPR and how CPR feedback technology can help code teams stay on track.

Next up, we’ll take a deeper dive into one of the components of high-quality CPR: compression depth. Why focus on compression depth? Put simply, compressions are the mainstay of CPR. They supply oxygenated blood to vital organs when the heart has stopped — and targeting the right depth is a crucial piece of that. Without compressions, responders wouldn’t be doing much to help patients in cardiac arrest.

American Heart Association (AHA) guidelines recommend that compressions should be performed at a depth of at least 2 inches in adults (but no more than 2.4 inches) and at least one-third the anteroposterior dimension of the chest for infants and children.^1,2 This equates to approximately 1.5 inches in infants and 2 inches in children.²

But where do the guidelines come from, are there any exceptions, and how can providers stay on track to meet these goals? Keep reading to find out.

Where do the guidelines for compression depth come from?

In short: the guidelines are based on anatomy. The longer answer requires a quick refresher on the goal and mechanism of compressions.

The goal of each compression is to press down on the left ventricle to force out the blood. Then the recoil allows the blood to fill back up in the ventricles, priming the next compression to support further squeeze mechanism of the heart. In between the anteroposterior diameter and the anterior chest wall diameter lies the space that is considered the compressible diameter. This is where responders can compress to achieve that squeezing mechanism and provide blood flow to vital organs during an arrest.²

So what is the right amount of force needed to compress the left ventricle appropriately? To answer that question, researchers have relied on CT scan measurements of the chest and heart wall diameter. Obtaining these measurements from various patients has helped determine the optimal depth needed, leading to the current guidelines.^3,4

Are there any exceptions?

Interestingly, recent studies have found that the suggested depth may be too deep for young children and not deep enough for geriatric patients with comorbidities.^3,5 For instance, in the latter case, the anteroposterior diameter of the chest increases because of dorsal kyphosis, senile emphysema, poor lung compliance associated with aging, and other comorbidities.⁵ This explains why deeper compressions may be more appropriate for that particular population.

That said, the AHA guidelines are just that: guidelines. Thanks to different body structures and different comorbidities, no two patients are the same. But on average, the current guidelines are a good reference point to target and work toward for most patients.

Tips to stay on track

Now that we know where the recommendations come from, what can responders do to help themselves stay on track?

• Place a backboard as soon as possible. The backboard gives responders a harder surface to work against, making it easier to reach and maintain the target depth for compressions.⁶ Since patients are typically on a bed or stretcher — and since the first clinician on the scene may need to wait for other responders to arrive for support — the backboard is not often used right when CPR starts. But the sooner it is placed, the easier it will be to maintain the targeted compression depth.
• Use arterial waveforms or end-tidal carbon dioxide tracings, if possible, to provide real-time feedback on depth.
• Allow for full chest recoil. Per AHA guidelines, avoid leaning on the patient’s chest between compressions. Allowing complete chest re-expansion improves blood flow to the heart during CPR.^1,2

Key takeaways

When it comes to compression depth during codes, here’s our bottom line:

• Compression depth is a crucial component of high-quality CPR. Targeting the right depth helps to ensure blood flow to vital organs during cardiac arrest.
• Although every case is different and there may be exceptions, the guidelines are anatomy-based and appropriate for most patients.
• Strategies to help clinicians maintain an appropriate compression depth include targeting the guidelines, placing a backboard as soon as possible, using real-time feedback, and allowing for full chest recoil. Putting these tips to use can help support an optimal CPR response for the patient.