Anesthesia Circuit Failure: Predictable and Preventable

Failure of the anesthesia circuit, with inability to ventilate, is one of the most frightening anesthetic emergencies. You must act quickly to keep your patient safe and troubleshoot causes of the anesthesia circuit failure. One essential diagnostic and management tool in this emergency is your manual ventilation bag.


The Problem

My patient was a 50 yo, 5’ 11”, 280 lb. hypertensive who was undergoing an anterior/posterior lumbar fusion. I used a total IV anesthetic to allow neuro-monitoring. We finished the anterior portion after 2 hours of uneventful surgery. A flurry of activity ensued as our surgeon, 4 other team members, and I shifted the patient laterally onto a gurney. We then turned him prone onto the OR table for the posterior portion of the case.

I ventilated and listened for breath sounds. All okay. The staff removed the gurney from the room. Multiple helpers reattached monitors, moved the OR table, fine tuned patient position, and moved X-ray equipment closer. After we finished positioning, I again squeezed the ventilation bag. Nothing happened: I couldn’t maintain any pressure and I couldn’t ventilate.

The Solution

I quickly verified that the circuit was connected to the endotracheal tube. It was. I immediately alerted the team that I could not ventilate. My first thought was accidental extubation. My nurse brought the gurney back into the room, preparing for possible supine reintubation.

Using my manual ventilation bag, I discovered that I could easily ventilate the patient. This was not an airway problem, it was a machine problem. Being able to ventilate with an ongoing IV anesthetic gave me time to troubleshoot. I found a disconnected oxygen analyzer — undoubtedly knocked loose while we were moving equipment. Everyone breathed a sigh of relief and surgery continued.

Photo of anesthesia machine manifold with disconnected breathing circuit, causing anesthesia circuit failure.
Oxygen analyzer sensor had been knocked loose, causing anesthesia circuit failure.

Someday this could happen to you. What do you do if you suddenly experience anesthesia circuit failure and can’t ventilate your patient?

Start With The Tube and Anesthesia Circuit

  • Check the circuit connection to the tube. An ETT or LMA disconnection is the most common cause of circuit leak.
  • If the tube is firmly connected, check depth of tube insertion for evidence of extubation.
  • Follow the circuit back to the machine and make sure both circuit limbs are securely attached.
  • Do a quick check for other circuit disconnections.

Is The Ventilator On?

Is your ventilator on? Some machines allow flush-filling and squeezing the ventilation bag during ventilator operation, however, you will NOT be able to ventilate the patient . This “feature” has fooled — and scared — me a couple of times.  

Alert The Team

Don’t wait until your patient starts to desaturate. Alert your team immediately if you still can’t ventilate after 30-40 seconds of searching for a cause. Your team can help problem solve, gather emergency equipment, and bring the gurney back into the room if the patient is prone.

Has The Patient Been Extubated?

Don’t assume the tip of the endotracheal tube is still in the trachea. The tip may have slipped out of position. Ventilate with your emergency manual ventilation bag. If you can ventilate, the problem is in your circuit or machine. If you can’t ventilate, you need concentrate on reestablishing an airway.

Perform a quick manual circuit pressure test. A circuit that holds pressure implies that the problem is with the patient’s airway.

A persistent leak with the ability to ventilate can result from an under-inflated cuff, or having a cuff above the vocal cords. For a discussion of diagnosing and managing persistent endotracheal tube cuff leak see:

Risks of Placing Your Endotracheal Tube Too high

Monitor Your Patient and Maintain Anesthesia

Being able to ventilate gives you time to explore other causes of anesthesia circuit failure, however, first ensure the patient’s safety.

One of your assistants should ventilate while you troubleshoot.

Avoid patient awareness. Use IV agents because your patient is no longer breathing anesthetic.

You may be distracted. Instruct your assistant to help monitor oxygen saturation, blood pressure and pulse.

Finding Anesthesia Circuit Failure Causes

Do a circuit pressure check. Disconnect the breathing circuit, plug the end with your thumb, close the pop-off, flush to fill the bag, and squeeze. a bag that won’t hold pressure means that the leak is in the circuit or the machine. I previously discussed machine failures in:

Help! My Anesthesia Machine Is Not Working!

Anesthesia circuit leaks I have seen include:

  • circuit disconnected from the machine,
  • cracked bacterial filter on the adaptor attaching the circuit to the machine,
  • oxygen sensor disconnected from its port,
  • ETCO2 sample tubing disconnected from the elbow, or at the sampling port,
  • cracked soda lime canister
  • circuit board failure in an electronic anesthesia machine that disabled the ability to maintain manual pressure (and which necessitated swapping out the machine in the middle of the case).
Photo of anesthesia machine manifold with oxygen sensor knocked out of it's holder, causing anesthesia circuit failure
Circuit limb disconnected, causing anesthesia circuit failure
Photo of circuit elbow with disconnected ETCO2 sampling port, causing anesthesia circuit failure.
ETCO2 sample line disconnected, causing anesthesia circuit failure
Close up of CO2 canister showing the impact hole at the bottom, where it was hidden from view during the anesthesia circuit failure emergency.
Close up of CO2 canister showing the impact hole at the bottom, where it was hidden from view during the emergency.

Preventing Anesthesia Circuit Failure

Prevention is the best way to avoid anesthesia circuit failure.

Check Equipment Before Starting

Always perform a circuit pressure check before any anesthetic — even a MAC. By knowing your machine is functional before you start, you are better prepared if something changes. In addition, you may find and solve a problem.

Ensure Tight Connections

Every time you connect two parts together, there is opportunity for accidental disconnection. Connections hidden under the drapes, or near the field, are especially prone to disconnect. Ensure your connections are tight.

Be Prepared For Accidental Extubation

Always have the equipment to reintubate the patient in the room. I have worked in surgery centers that had one laryngoscope handle and blade for each room. Wait until after extubation to send them for cleaning.

If your patient is prone, keep the gurney outside the room. This avoids delays if you need to turn supine in an emergency.

Always Have Emergency Equipment Available

  • Keep your ventilation mask at hand.
  • Have an appropriately sized oral and nasal airway in the room (not necessarily open).
  • Have a laryngeal mask airway. In an emergency it can be placed in a prone patient and buy time.
  • Emergency airway box/cart available.

To be a good anesthesia provider means becoming a catastrophist. You must imagine all of the possible things that can go wrong and have a plan for managing them. Most causes of anesthesia circuit failure are predictable and preventable. For a review on avoiding other anesthetic complications, including an accidental prone extubation, see:

Boredom Interrupted: 10 Causes of Airway Complications And How to Avoid Them

May The Force Be With You

Christine E. Whitten MD, author:

Anyone Can Intubate: A Step-By-Step Guide
Pediatric Airway Management: A Step-By-Step Guide

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