Wednesday, March 20, 2013


This is a pulse oximeter. It is a self-contained model for use in the home. The top number is the oxygen saturation. It reads ninety-eight percent. The bar to the left of that number jumps up and down with each heart beat, and lets you know how the signal is 'good'. The number on the bottom is the number of times it 'jumps' a minute, or, more simply put, the pulse.

Before this was invented, death was common in the Operating Room due to Anesthesia mishaps. Hypoxemia, or low oxygen level in the blood, was detected late, sometimes almost until it was 'too late'. The only way to detect it was if the patient turned blue. I have seen them turn the color of that plastic on that finger. It is not a pretty sight. They pink right back up once you get the oxygen in them. But with the pulse-ox, you can 'head it off at the pass' before it gets really low enough to compromise the brain and the heart.

I have been through many generations of pulse-oximeters in my clinical practice. Here are the first ones that were invented and mass-produced, the Nellcor:
What is cool about the Nellcor is that the pitch of the beep of each heartbeat drops with a decrease in the oxygen saturation. Beep beep beeeeeeep beeeeeeep booooop boooooop...this is what 'bad' sounds like to an anesthesiologist. When you hear this, you focus one-hundred percent on the airway. You open it, hand on tight with the mask, up the flows of oxygen, tighten the pop-off valve, and bag like crazy. I often smash the bag with my hand against my right leg to really squeeze it hardest. Sometimes I hang on to the mask with both hands and someone else has to squeeze the bag to get the air in.

What is the worst that can happen? Well, I got called in to help a colleague in trouble who had just put someone to sleep. No air would pass. I looked at the surgeon, right in the eye, and said, 'cut the neck'. Immediately a trach tray was brought to the room, the instruments opened, and the surgeon obtained a surgical airway in less than thirty seconds. The tube went in (technically this is a cricothyrotomy, not a trach, when done emergently), and the sats picked up.

When the sats are low, the EKG widens, then goes agonal, and the heart dies. That is what is going on in those four to eight minutes between lack of air exchange and death. At four minutes there is irreversible brain damage; even if the patient does survive, pretty much all they are able to do at that point is have siezures. Quality of life is nil.

This is funny! Why? Because it is a pediatric-sized wrap around sensor on an adult! The real one for the adult is white and goes over the top of the finger front to back. The cord side sticks on first. 

What about fingernail polish? That is a good question. (You see, the whole thing works on the principle of two different wavelengths of light absorbed by hemoglobin. Oxygenated absorbs a different wavelength than de-oxygenated. The difference between the two divided by the oxygenated and multiplied by one hundred gives the percent oxygen saturation. I like my patients over 95%, but anything over 90% will keep your patient out of trouble until you can figure out how to raise it. Below 80%, people start to look blue in the lips and get a ghastly pallor. In the 30% range, most devices are not accurate, and people look like blue jeans. The first time you see it, you sort of really freak out. All of this can reverse in a few moments, once there is a direct supply of air.) I simple twist the probe to read from side to side through the finger, instead of the finger nail. In the old days we used to remove the polish with a little wipe.

 Check this out! This is a typical re-useable probe. I clean mine between patients. Not everyone does. And the OTHER thing is an invasive arterial monitoring line. It reads the blood pressure, and also permits for the sampling of blood for tests such as arterial blood gas (ABG) , Hemoglobin and hematocrit (H and H--to measure anemia), chemistries, and coagulation.  I put these monitoring lines in. I like it when the blood spurts out the hub of the catheter right before I connect it to the line because I know it is in the right place and I am going to keep my patient safe with good blood pressure data no matter what goes on in surgery!

The other thing to note about this picture is the placement of the probe on the non-index finger. Today one of my patients had his on the index finger, woke up, and almost poked his eye out when he went to scratch his nose! Quick thinking on my part saved his sight--and possibly a painful corneal abrasion.

What do you think goes on in places of poverty in third world countries when it comes to surgery? Do you think they have pulse oximetry there?

When I went on a medical mission to Mexicali, we only had one to share between two pediatric patients. Since we worked on cleft lips and palates, and there were many cases, like, six going on in one room (but only three pulse ox's), we alternated the probe between children on both sides of the pulse ox.

I stopped doing medical mission work like that because it hurt too much to see sub-optimal care being given to the children, compared to what it available to kids that come through my O.R. back home. On this mission we ran out of morphine, even though it was only given to the ones that had a bone graft from the hip to close the defect in the palate. After we left, A fellow stayed in town one extra day, and then the kids were on their own with their families and a lot of tylenol with codeine syrup. There was no follow up, and to me, this felt irresponsible. Although life-changing and life-saving, in a sense, re-used endotracheal tubes that were washed in a sink, and ER nurse doing manual blood pressures, no anesthesia machine, and a halothane stand-alone vaporizer just was not 'safe enough' for me to participate. If any of those kids died I could not live with myself!, One of them came close--the halothane got too deep and I heard the 'muffled heart sounds' they talk about on the anesthesia boards. I have a stethoscope that is molded to my ear, and connects to a 'bell' that is placed directly on the chest throughout surgery.

How about the people IN those countries providing anesthesia for surgery? Typically an anesthetic is just ketamine (dissociative--think 'frontal lobotomy in a vial'--temporary of course. Ketamine is also used as an animal tranquilizer. Remember Wild Kingdom and Jim with the tranquilizer darts? That was Ketamine in those darts.) and local anesthesia.

Is that safe?A group of anesthesiologists don't think it is. And instead of complaining, they organized and formed this wonderful group 'Lifebox'.  On their website, they state:

  • Surgical safety knows no religion, nationality or race, and we are proud to collaborate with a range of secular and faith-based organizations that share this principle.
If you want to help change the world, know that each of these indestructible pulse ox's cost two-hundred fifty dollars. And instead of just equipments, the group is committed to raising awareness, providing education on respiratory physiology (sat of sixty is not good!), and maintaining support of these places they help. There is a map of all the places in need of a Lifebox pulse-oximeter. Together we can fill the dots with Life one by one.

By the way, the best pulse ox on the market now is Masimo. That is what is standard of care in the O.R.'s today. Next time you are at the hospital, and they put a pulse ox on you, check it out. Is it Masimo?

Take care and have a great rest of your day. Thank you for reading this message. I know it was technical. But sometimes, technical is good for you--like your vegetables!


Reiki Doc