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The simplest description of CPR would be, "You blow in their mouth, and push on their heart." From that over simplistic concept, we need to answer some additional questions like, When,? or Where,? or How Many,? or How Hard?
When?
Well when someone isn't breathing, you should breathe for them. And when they don't have a pulse (or are not showing any "signs of circulation,") you should "give" them a pulse (or circulate their blood.)
Where?
If it's breathing that you need to "replace" then that's accomplished by breathing into the mouth of the patient. If it's a heartbeat that needs to be replaced, you should push on the center of the chest at, or just slightly below, a line drawn between the nipples on the chest of a male (or an equivalent position on the chest of a female,) in a spot that you believe is directly above the heart of the patient (keep in mind that the heart lies in the center of the chest, directly behind the breastbone, NOT off to the left as is commonly thought.) If it is both functions that must be replaced, then you will have to alternate between the two locations.
If it is just the breathing that you are doing for this patient (Rescue Breathing,) you should blow into the mouth of an adult patient about once every 5 seconds (12 times a minute) or into the mouth of a child or infant about once every 3 seconds (20 times a minute.) These numbers are offered as guidelines and should not be assigned more value than was intended. By that we mean, that it is important to ventilate a patient that is not breathing. If the ventilations are performed a little too frequently, or a little too infrequently, it is still better than what the patient is capable of doing on their own. It is very unlikely that you will have a stopwatch (or someone to operate it) in order to assure that the patient is being ventilated every 3 seconds or every 5 seconds. With that in mind, I would suggest that if you can't remember how often to ventilate this particular patient, then just try ventilating at a rate that you consider to be a "normal" breathing rate. Said differently, you should exhale (or blow) into the mouth of this patient right after you have the "urge" to satisfy you own need to inhale. Do me a favor, inhale........we'll wait......... Now, notice that the inhalation was nice and slow, nice and even, not quick or 'explosive.' When ventilating a patient you should take care to re-create the same kind of "inhalation" for the patient as the one you just took, by blowing nice and even, nice and slow. (Return To Respiratory Distress, if you just came from there.)
If it is the heartbeat that is being replaced by your effort, then it will in fact be a combination of breathing and pushing (CPR,) because someone who has lost their pulse has also lost the ability to breathe. In this case, you are going to push 15 times on the chest of an adult (5 times on the chest of a child or infant,) ventilate the patient twice (once for a child or infant.) This needs to be done at a rate of about 100 times a minute for adults, children and infants (120 times a minute for a newborn infant.) But, as with the ventilation rate above, there will not be a stopwatch available to "time" the compression rate. And I don't believe that any of us has an intrinsic understanding of "100 times a minute," so much so that if I asked you to tap your foot at 100 times a minute, I don't believe you could do it with any certainty. But, if I asked you to tap your foot at a "normal adult heart rate," I think you would immediately start tapping your foot at a rate that probably came close to your own heart rate, because that concept (your heart rate) is one that is very intrinsic to you (it's a concept that you have lived with all of your life,) and that rate is normally between 60 and 100. So if you are doing chest compressions on a unresponsive patient, do them at a normal adult heart rate (or go slightly faster if the patient is a newborn infant.)
How Hard?
So, just how hard should you blow into the lungs of another person if they are not breathing? Well the textbooks say that the rescuer should blow hard enough to cause chest rise in the patient. I can see where that description might lead to a dangerous outcome. Mainly, because the individual interpretation of "chest rise" tends to approach what one experiences when he/she inhales, and this, unfortunately, is more motion than you can expect to achieve when ventilating a patient. If you attempt to achieve the same degree of chest rise in this patient, there is a good possibility of causing some gastric distention (see "Gastric Distention" for further explanation.) My experience as a provider tells me that if you are relatively attentive, you will "feel" the lungs comply to your effort to ventilate and you will perceive an end point to that ventilation, just don't look for a whole bunch of "chest rise.".
Finally, how hard should you push on the chest of someone who doesn't have a pulse? Well, the textbooks suggest that the sternum (that's the breastbone in the center of the chest) should be displaced about 1½ - 2 inches for an adult, 1 -1½ inches for a child, and ½ - 1 inch for an infant. But, if there wasn't a stopwatch available to time the ventilations, you can be absolutely certain that there will not be a ruler to measure the depth of compressions. And, besides, from what reference would you measure? And so, again, I find myself adding to the published suggestions of the American Heart Association.® (Shhh! Please don't tell them. I wouldn't want to upset them, because the suggestions that they make are the gold standard in this industry.) While reading the Journal of the American Medical Association (JAMA), I came across a statement (in the section pertaining to pediatric CPR) that suggested that the sternum of a child should be displaced about ⅓ - ½ of the patient's total body width. I took this information back to the field with me and applied it to the patients for whom I provided CPR. What I found was that the estimate was very appropriate, and that it seemed to apply to all patients, not just the children. It also represents a suggestion that is easily remembered and doesn't need much more than common sense to apply (no rulers, no stopwatches.) From a conceptual point of view, I would just remind you that we are trying to "squeeze" the heart between the breast bone (sternum) and the back bone (spinal column) and the sternum needs to be pushed down far enough to accomplish that goal. Just a word of caution, here. It is likely (and becomes more likely as the age of the patient increases) that "displacing" the sternum may break some ribs. It is also likely that you will hear and/or feel those ribs breaking as you push the sternum down (especially the initial "push".) If you feel or hear some "crunching" as you push down on the chest, DO NOT STOP what you are doing. Simply make certain that you are in the correct position as explained in "Where?" and continue.
The foregoing represents a conceptual interpretation of CPR and does not include any of the mechanics of, or the techniques for determining the necessity for CPR. CPR - "In-Depth" will address those issues.
