Your pet is about to undergo surgery. You are likely to be worried and confused, especially as the vet bandies about medical jargon unfamiliar to your lexicon. You find yourself looking up words on the Internet dictionary or Web MD or jotting down unknown terms, so you can ask the vet follow-up questions later. Note-taking and personal research are good approaches to have before your pet’s surgery, so you are familiar with all the steps of the procedure and how the vet plans to keep your loved one safe. One such term that may come your way during discussions is pulse oximetry. Below are some details about pulse oximetry and how a vet uses a pulse oximeter, so now you have one less term you have to look up later!

What is Pulse Oximetry and What Does Pulse Oximetry Measure?

In a nutshell, pulse oximetry is a non-invasive approach to measuring the oxygen levels in the blood.  It is an imperfect, yet quick, bedside method of testing. An alternative method, arterial blood gas sampling, is the more precise but also more complex way to test, primarily reserved for seriously ill animals.

How Does a Pulse Oximeter Operate?

A probe connects to a hairless area with minimal pigmentation and a pulsating bed of arteries, such as the lip or the vulva. The probe extends light at two wavelengths—red and infrared—through your animal’s bodily tissues. Hemoglobin, the red protein responsible for transporting oxygen in the blood, absorbs and passes through the light in different ways, depending on the level of oxygen it contains. Essentially, oxygenated hemoglobin absorbs more of the infrared light and allows the red light to pass through. However, deoxygenated hemoglobin absorbs more of the red light and allows the infrared light to pass through. The final calculation for determining oxygen levels is a percentage that comes from the difference in light absorption. The results may appear on the machine as pulse rates or wavelengths, depending on the type of machine the vet uses. A solid result is greater than 95% or 96%, but an ideal result is between 98% and 100% . While 90% may seem like a decent result too (since it’s in the 90s range and not far from 95%), it is actually not so good. 90% means that the animal only has two-thirds of the oxygen it needs.

Detecting Pulse Oximeters’ False Results

As noted above, the pulse oximeter is an imperfect method. Common causes of inaccurate results include the following: the animal’s movements due to seizures or tremors, skin pigmentation where the probe is attached, very thin animal tissues, anemia, and interferences from other electromagnetic energy sources, just to name a few. It is the job of the vet to take into consideration the animal’s health condition along with variables that cause false readings in order to determine the accuracy of the final result. For example, if the animal on the table is breathing normally but the machine reads 60%, then clearly the machine has failed to produce an accurate result. If the possibility of false results scares you, then talk to your vet about the equipment he or she uses. Ultimately, if you trust the vet to make decisions about your pet based on interpretations of imaging and blood work, then you can also trust the vet to correctly determine the pulse oximeter’s results.

A Pulse Oximeter Offers Peace of Mind

Knowing the animal’s oxygen levels can help vets make important decisions during surgery in order to keep your animal oxygenated. Without the pulse oximeter, the vet would have to make guesses that, while educated, would not have the verification and confirmation that a pulse oximeter provides.