Small Animal Anesthesia Machine Leak Check

Definition(s):

Occlude – stop, close up, or obstruct an opening

Procedure:

1. Securely connect the appropriate anesthetic circuit and reservoir bag to the anesthesia machine.
   
   
2. Fully close the pop-off (APL) valve.
   
   
3. With one hand, place a thumb or palm over the circuit at the patient connection site to fully occlude the opening.
   
   
4. With the other hand, turn the oxygen flowmeter on to increase pressure in the system from 0-20 cmH20 while keeping the circuit occluded. Ensure the manometer needle starts at 0 cmH2O and moves freely without any sticking. 
   
   
5. Once a pressure of 20 cmH20 is achieved on the manometer, turn the oxygen flowmeter off while maintaining the occlusion of the circuit.
   
   
6. Closely watch the needle on the anesthesia machine manometer:
   
   1. If the needle on the manometer maintains a pressure of 20 cmH2O on the manometer without any oxygen flow, there is no leak  in the system.
   2. If the needle on the manometer drops at all (even slowly), there is a leak in the system. 
   1. 1. Quantify the leak – Turn the oxygen flowmeter on and slowly increase the flow rate until the needle on the manometer stabilizes (does not rise or drop) – that oxygen flow rate is equivalent to the leak in the system.
         1. Acceptable leak – If the leak is less than 250 ml/min, it is considered an acceptable leak, and anesthesia may proceed with adequate ventilation in the area
         2. Unacceptable leak – If the leak is more than 250 ml/min the site of the leak must be identified and corrected, and the leak test must be re-performed.
            
            
      2. Determine the site of the leak – Maintain a pressure of 20 cmH2O in the 
         system and inspect for leaks:

   a. Visually inspect the circuit, reservoir bag, and machine
   b. Feel for gas movement from various sites of the anesthesia machine. 
   c. If leaks cannot be felt, a soap solution can be sprayed on the machine at common leak sites. If a leak is present, bubbles will be visible at that site. Ensure the soap solution does not enter any part of the patient’s breathing system.

7. NEVER RELEASE YOUR HAND FROM OCCLUDING THE CIRCUIT DURING A LEAK CHECK. TO COMPLETE THE LEAK CHECK AND REDUCE PRESSURE IN THE SYSTEM, IT IS CRITICAL TO FULLY OPEN THE POP OFF VALVE BEFORE REMOVING THE HAND OCCLUDING THE CIRCUIT AT THE PATIENT CONNECTION SITE. 

1. 1. This assesses the functionality of the pop-off valve, ensures the pop-off is not left closed which CAN RESULT IN PATIENT DEATH, and prevents soda lime dust from being forced along the pressure gradient into the patient circuit where it could be inspired and cause harm.

Note: Common sites for leaks in the anesthesia machine are cracks or holes in the breathing circuit or reservoir bag, misalignment/loose connection at the soda lime canister, or other loose connections in the tubing/piping that carries oxygen and anesthetic gases.

Created: 11/17/2021