Benefits of Pulse Oximetry vs Arterial Blood Gas in Small Animal Research

Blood gas and pulse oximetry are two types of measurements that provide insight into blood gas exchange.  There are significant differences in how each is measured. 

Blood gases are measured by removal of a small sample of blood, which is then delivered into a device that measures parameters directly from the blood.  Blood gas machines conduct basic measurements on 3 parameters: 

  1. Dissolved oxygen 
  2. Dissolved carbon dioxide 
  3. pH

Pulse oximetry on the other hand, measures the amount of oxygen attached to hemoglobin.  Because 97% of oxygen carried to tissues is attached to hemoglobin, this measurement effectively records the total content of oxygen in the blood.

Why Blood Gas over a Pulse Ox? 

Most of the time, pulse oximetry will be the best solution, but that won’t be the case if you are looking for insight into your subjects’ blood chemistry.  

A pulse ox measures at least heart rate and arterial saturation. While some small animal pulse oximeters can also provide breath rate and effort and some other cardio-pulmonary parameter, it can’t provide all the blood chemistry values that an arterial blood gas does.  

The one thing that pulse oximetry does not provide insight into the level of arterial carbon dioxide or pH, so if knowledge of these is required, a blood gas becomes necessary.   

Pulse Oximetry Benefits  

The real advantage to pulse oximetry however is that it is completely non-invasive.   

It can be measured with a simple clip that attaches to an appendage on the animal’s body.  The advantages of using the MouseOx® Plus over blood gas measurements are as follows:    


  1. no adhesives, needle sticks, catheters, IVs, surgery 
  2. can be repeated as often as desired enabling serial measurements over life span of mouse(longitudinal study) 
  3. no need for blood draws enables use on tiny animals 
  4. no disturbance of physiology from occlusions or changes in blood volume or hematocrit 
  5. no special care for catheters 
  6. lower mortality reduces number of animals required to complete a study 


Pulse oximetry allows you to monitor vital signs continuously during research study or surgical procedures.


  1. Low-cost hardware 
  2. No maintenance or upkeep on primary measuring device 
  3. No service contracts 
  4. No consumable items 
    • pipettes
    • cal fluids/gases
    • syringes
    • anesthesia
    • surgical supplies
    • catheter care materials
  5. Sensor is only semi-consumable item – 100 hours use per sensor


  1. No expensive calibration fluids or gas tanks 
  2. No daily, weekly or monthly cal procedures 

Recapping the Benefits of a Pulse Oximeter 

The biggest benefit of a pulse oximeter when compared to arterial blood gas is that it is noninvasive. And, when you are consider the blood volume of small animals such as a mouse, you only have a finite source of blood to test.  

Invasiveness also disqualifies arterial blood gas for use in studies on conscious subjects.  

At the end of the day, pulse oximetry is the noninvasive and cost effective, making it a win-win when it comes to monitoring arterial saturation.  

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