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Veterinarian Anesthesia Machine (Gas Machine)

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The Purpose of a veterinarian anesthesia machine is to provide pain management, sedation and anesthesia to the animal during interoperative veterinarian cases by use of anesthetic vapors. IT is the main medical device that the anesthetist operates. An anesthesia machine is a complicated machine, but simply put, it is a system comprised of various components and devices aimed to deliver anesthetic gas. We will go over the basic functions of this machine for an understanding of how this device functions.

Breathing System Components

Firstly, for the anesthesia machine to function, a supply source of fresh gas is needed to drive the machine. This is delivered gas supply system delivery through a gas supply wall outlet. At times when supply is not stable, backup cylinder tanks are used. It is important to have a wall supply of 55-60PSI. The flow of the fresh gas supply and managed and controlled for the O2 flow meter. Once the desired flow has been achieved, next is the Vaporizer.

The Veterinarian Anesthesia machines utilize inhaled anesthetic vapours to anesthetize the animal patient. The component that controls this is the Vaporizer. The Vaporizer controls the concentration of agents to be used as well delivers the agent in the veterinary anesthesia machine. This is normally fixed on the machine and controls the amount of anesthetic agent delivered to the animal patient for sedation. The fresh gas flows into the vaporizer input chamber and is saturated with the agent and out the other side into the patient’s inhalation for sedation. In many cases, these Vaporizers have a fill system that is dedicated to the type of anesthetic agent used and manufacture.

Breathing control in anesthesia with either use of a mechanical ventilator or by manually squeezing the breathing bag. And flow direction is controlled by the Inhalation and exhalation valves. These open and close depending on the breathing phase, directing gas flow into the patient during the inspiratory phase and out of the system into the rebreathing system or scavenging during the expiratory phase. The flush O2 button is utilized to wake up the patient by flush the system with 100% oxygen bypassing the Vaporizer, saturating and reducing agent concentration in the breathing. The breathing system manometer the amount of pressure


During a case, the patient exhales CO2 waste excess agent gases. The soda-lime absorbs the CO2 and removing from the breathing system. During absorption and with CO2 reacting soda lime, the pellets will change the colour from white to purple. Indicating that it has reached absorption capacity. Although it has been noted that if the machine has not been in use for a long period of time, the colour may revert to white or will dry and not absorb. Therefore, it is recommended to have the soda lime change between 12-14 hours of anesthesia use, or the time frame specified by the brand of soda lime used. A scavenging system is use to expel from the system and patient breathing system. The amount is controlled by the Pressure APL valve or a pop off valve. The APL or pop off valve, releases anaesthetic gases into the scavenging system and is intended to provide pressure control in the breathing circuit during manual bag ventilation.



In some vet applications, a vital sign monitor with airway gas monitoring is used in conjunction with the anesthesia machine.  With airway gas monitoring the anesthetist can monitor gasses and concentration that is being exhaled from the animal patient such as End tidal CO2, O2 concentration and anesthetic agents. This serves to assess ventilation, pulmonary function, and as well as condition of breathing circuit.  Alongside from gas analysis capabilities, a vital sign are monitor provide visual and auditory cues and alarms of all vitals of the animal during the case.


System Checks and Maintenance.

Leak in the system can occur and is not uncommon. Thus, It is good practice to do a system check and leak test before starting a case. By closing the APL valve, shorting the inspiratory and expiratory ports, inflating the system with the O2 flush, and waiting to see the rate the barometer drops will indicate how well sealed the system is. By using visual and audible cues to listen and look for leaks can determine where the source of the leak is coming from. Most leak problems can be resolved by replacing the breathing bag or checking the breathing circuit. Sometimes leaks can from from the soda lime canister. Lastly To prevent major issues from occurring it is highly recommended to have a preventative maintenance to be conducted annually. A preventative maintenance, also known as a “PM” consists of routine tests, replacement of maintenance parts, and proactively looking for signs of failure and repair. Testing all the entire system for leaks, fresh gas flows, agent concentration and scavenging systems of the machine.