Does life depend on the number of compressions a minute? Yes it does. The fact of the matter is that a heart that’s not pumping needs to be manually compressed. It is also important that artificially compressing the heart needs to mimic normal heart beats. A person on cardiac arrest needs the heart to be able to push blood around the rest of the body, where the oxygen and carbon dioxide exchange occurs. Knowing that, there is something called under- compression and over- compression. Understanding this concept and how the body works will be helpful to realize the significance of compression rates.
Prior to the change in 2015 about the number of chest compressions per minute, the wording was that during cardiopulmonary resuscitation (CPR), a rescuer should compress at least 100 per minute. Obviously, the heart does not stop after reaching 100 every minute, and the count begins again. How they came up with that number comes from the average heartbeat of all age groups and who is likely to have cardiac arrests.
Average Heart Beats
Normal heart beats for infants that are less than 1 year of age beat at a rate of 100- 180 per minute. Children from 1 to 8 years of age have a heart beat with a rate of 80- 110 per minute. All other age groups have a heart beat ranging from 60- 100 beats a minute. With these numbers alone, it is reasonable to try to reach the 100 beats a minute threshold. It is also reasonable because the age group that would most likely have a cardiac arrest are adults. Another good reason is the fact that reaching the maximum number of chest compressions a minute is better than the fear of not compressing enough for adequate blood transportation throughout the body.
This leads to another concept that must be understood, which is under- and over- compression. The results of under- and over- compression are the same. They both do not provide enough blood flow throughout the body. Under- compression will cause the heart to fill with blood but the time for it to be pushed out of the heart and travel through the body takes some time and may not be adequate for the organs and their individual cells to exchange carbon dioxide and oxygen. Oxygen is needed to make energy and maintain body functions. On the other hand, over- compression will not give the heart time to fill with blood. So, every compression will pump out less than adequate amount of blood that is needed in the body.
Benefits of a Compression Rate
The words used prior to 2015 was “at least 100…”. AHA has recommended a compression rate of “100- 120 compressions”. Statistically, these numbers are sound. It is within a normal heart rate at rest. Furthermore, people who are not at cardiac arrest can have a heart rate of over 110 beats a minute if they have a fever or are injured. During exercises, such as a long run, heart rates can be as high as 160 beats a minute. The maximum heart rate during an exercise is 175 beats a minute (45 years old). In a traumatic situation such as a cardiac arrest, the body needs the heart to pump at a high rate for more oxygen and other proteins contained in the blood for body maintenance and healing. This compression rate is also beneficial for the lone rescuer because actively doing CPR for just 5 minutes can already be quite tiring. Finally, a compression rate of 100- 120 a minute should provide maximum heart functionality in terms of blood volume filling in the heart and the amount of blood being pumped to the rest of the body.
The use of “at least 100 compressions a minute…” is also correct as it meets criteria for maximizing heart function. However, providing a range can be helpful for rescuers to act towards.
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