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Anaesthesia Deep Dive: Pulse Oximetry

Updated: 1 day ago

Ensuring the health and safety of our patients during medical procedures is a top priority. One critical tool we use to monitor cats during sedation or general anaesthesia is the pulse oximeter. Although it sounds technical, pulse oximetry plays a straightforward yet essential role in keeping your cat safe.


What Is Pulse Oximetry?


Similar to a fitness monitor, this device, known as a pulse oximeter, clips onto a part of the cat's body, often the ear or paw. It uses light waves to detect the pulse rate and the percentage of haemoglobin molecules saturated with oxygen in the blood (oxygen saturation or SPO2)


Iullstration of oxygen molecules in RBCs
Oxygen is transported around the body by attaching to haemoglobin molecules in red blood cells.

Why Is Pulse Oximetry Important?


Cats, like humans, need a steady supply of oxygen for their organs and tissues to function properly. Sedation or anaesthesia can sometimes cause low oxygen or heart rate levels, which can be dangerous if not detected early. The pulse oximeter allows us to keep a constant eye on these levels, ensuring that any drop in oxygen and/or heart rate can be quickly addressed.



How Does It Work?


The pulse oximeter works by shining a light through the skin and measuring how much light is absorbed by the blood. Oxygen-rich blood absorbs more light, and by calculating the difference, the device can determine the SPO2 level. The readings help the us make informed decisions, like adjusting the level of anaesthesia or providing additional oxygen if needed.



A grey cat with pulse oximetry probe on it's foot
The light used by the pulse oximetry proble can be seen shining through the webbing between this cat's toes.


Pulse Oximetry and Your Cat’s Safety


At Melbourne Cat Vets, pulse oximetry is a standard part of monitoring your cat during any procedure that requires sedation or anaesthesia. This tool ensures that your cat’s blood oxygen levels stay within a safe range throughout the procedure. If the oximeter detects a drop in oxygen levels, we can respond immediately, providing interventions that range from adjusting the cat’s position to increasing the oxygen supply.


If a cat’s SpO2 level drops during anaesthesia, it’s a sign that the cat isn’t getting enough oxygen to the body's tissues, which can be serious. Oxygen is crucial for the organs to function properly, and a significant drop in oxygen saturation can lead to complications like organ damage if not addressed promptly.


A multiparameter screen highlighting the pulse ox trace
Pulse oximetry gives a continuous update on the cat's oxygen levels and pulse rate.


Possible Causes of Low Oxygen Saturation


  1. Respiratory Depression: Anaesthesia can sometimes slow down the cat’s breathing, reducing the amount of oxygen taken in.


  1. Respiratory Diseases: It is particularly important to monitor blood oxygen levels in cats with lung issues that may hinder the absorption of oxygen from the inhaled gases.


  2. Airway Obstruction: The cat’s airway could become partially blocked, either by the positioning during surgery or due to secretions like saliva or mucus in the breathing tube.


  3. Inadequate Ventilation: The anesthetic equipment might not be delivering enough oxygen, or the cat’s lungs might not be effectively moving air in and out.


  4. Circulatory Issues: Low blood pressure or other circulation problems can reduce the amount of oxygenated blood reaching the tissues.


Key Points


For cat owners, understanding that pulse oximetry is part of your cat’s care can provide peace of mind. It’s one of the many tools that we use use to ensure that procedures are as safe as possible. By continuously monitoring your cat's vital signs, our team can quickly respond to any issues, helping to keep your cat safe and healthy.


Check out our other blog posts about anaesthesia monitoring to learn more about how we strive to keep your cat safe -



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