Apple #315: Xiphoid Process

I realized yesterday that I don't have any entries about topics that begin with the letter "x". So I decided to find out about the xiphoid process.

• The xiphoid process is the little knob that sticks out at the bottom of the sternum, in between the two halves of your ribcage. Technically, it is part of your sternum, the lowest-third, and smallest part.

In this diagram, the xiphoid process is #6. Numbers 1, 2, and 6 are collectively the sternum.
(Image from anatomy.us)

• The word xiphoid comes from the Greek xiphos, which means sword-shaped.
  

• The word "process" is there for its lesser-used meaning of the word: "a prominent or projecting part of an organic structure."

• So, putting the two meanings together, "xiphoid process" essentially means a sword-shaped bone that sticks out.
  

• People who want to get all fancy with it may also call it the xiphisternum, which refers to the fact that the bone is part of the sternum.

• When you are born, the xiphoid process is made of cartilage. As you get older, the places where it attaches to the rest of the sternum slowly harden, so by the time you are roughly 25 years old, they have turned to bone (ossified).

• In some people, the entire thing will turn to bone by the time they are 40 or 50, but in other people, it stays partly made of cartilage. It doesn't mean anything one way or the other, it's just one genetic variation.

• When performing CPR (cardiopulmonary resuscitation) and doing those chest compressions, instructions say to "find the xiphoid process." What that means is to feel the upper abdomen for the place where the fleshy part of the stomach comes up in between where the rib cage comes together (a.k.a. "substernal notch" or "epigastric fossa").
  

• If you probe slightly into that triangle of softness, you can feel some firmness beneath. It's not as hard as bone, but it's definitely firmer than plain flesh and muscle. That's where the xiphoid process is.

If you're going to give someone chest compressions, go up about two fingers' width above the xiphoid process. It will feel like the last firm place before the chest cavity opens up.
(Photo from the Merck Health Handbook)

• The reason they want you to find the xiphoid process is so that you will avoid it when doing the compressions. The whole purpose of doing those CPR compressions is to apply enough pressure to re-start the person's heart and get a pulse going. If you put pressure on the xiphoid process, you could snap it off and plunge it into the lungs or heart tissue and thus kill your patient.

• So you want to make sure your compression hands are located in the center of the chest, not over the xiphoid process.

The correct way to apply CPR compressions to anyone over the age of 8. Use the heel of your hand and your body weight, not your arm muscles. Push at a rate of about 100 compressions per minute, or more than one per second. Do not rock back and forth or bounce up and down, but apply consistent pressure. If the person is a child, use only one hand, not two.
(Diagram from Frontier Lifeline)

For more on CPR see the Mayo Clinic's instructions for performing CPR.

• The xiphoid process is a landmark for another, though less urgent, procedure. Fitness people who measure their body fat -- and are kind of obsessed with that whole body fat ratio business -- take measurements using calipers in various places around the body. One place where they take that measurement is at the axilla (a.k.a armpit).

• Find the axilla by drawing a line beginning at the xiphoid process and around the torso to the side of the body, and keep one finger there. Then with another finger, find the very middle of the armpit on that side and bring it down to intersect with the line you drew from the xiphoid process. That's the axilla.
  

Photo of someone finding the axilla where they will take a body fat measurement. People who are really into this will call it the midaxillary skinfold site.
(Diagram from Lipsified)

• That's the place to pinch the skin and apply those calipers. Experts recommend taking two measurements for accuracy.

• Except measuring body fat only at the axilla won't tell you much. You need to take similar measurements at seven total sites, then use a formula to calculate total body fat percent. Detailed instructions and mathematical calculations are provided at The Build Muscle & Gain Weight Fast Guide.
  

• Or you could just get a body fat scale.

Amazon has this Omron Body Fat Monitor and Scale available for about $35.


I'm not getting a body fat monitor or calipers or anything like that. But I am glad to know where that xiphoid process is. I'm also glad I got to type a word that starts with the letter "x" several times.


Sources
Philip M. Parker, Webster's Online Dictionary, Definition: Sternum
Philip M. Parker, Webster's Online Dictionary, Definition: Xiphoid
Britannica Student Encyclopedia, process
How to Perform CPR - Rescue Breathing - Heimlich Maneuver
Department of Social and Health Services, Washington State, CPR pdf
Global Fitness, The Physiology of Football and Fitness Tests
Topendsports, Fitness Testing, Skinfold sites, Axilla