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Post: Blog2_Post

Coca-Cola Lung and ETT Clamping

Updated: Aug 25, 2023

“Mom! Can we go to the store please!?”

I ran into the kitchen and was greeted by my inquisitive mother.

“What do you need at the store?”

I had just finished watching a video where the “scientist” had mixed some mentos with coke and created a near immediate explosion. My mind began racing with the potentials of completing an experiment for this in my backyard.

I soon suppressed this memory, filling its void with lyrics to Nickelback, until one of my early critical care transfers.

We had been tasked with transporting a young lady with a diagnosis of ARDS. She had some fairly high PEEP requirements on the sending hospital ventilator, was at 100% FiO2 and was being transferred for the potential of going on V-V ECMO for refractory hypoxia. I was fairly nervous, being that this was one of my first truly ill patients that I was transferring under the watchful eye of my preceptor.

I prepared our ventilator and was ready for the swap from the sending facilities to my trusty LTV. I reached my hand toward her ET tube, ready to perform a quick change. Before the tips of my fingers touched the plastic, my preceptor bellowed “STOP!” I jumped 3000 feet in the air, nervous I had killed her with my slight movement.

“Before you do that, we need to clamp her ET tube so we don’t lose recruitment!”

He pulled out a pair of Kelly clamps like a field surgeon in World War One, clasped them on her ETT then performed the swap. I imagined him preventing the air from throttling out of the bottle, similar to my coke experiment as a child.

Logistically, this made perfect sense to me and seemed like some hidden cool party trick within the critical care world. I soon wielded the trusty Kelly clamps, awaiting my opportunity to impress the hospital staff.

But, I was given a lesson without perceptive, or knowledge of its true use, which certainly has the potential to cause problems. So, before we go too far, let's review what I’m actually talking about here.

Clamping the endotracheal tube refers to a maneuver of utilizing a pair of Kelly clamps, or manually bending the tube, prior to removing one ventilator and replacing another. The belief is that any build-up recruitment/PEEP will be lost near immediately when the circuit is disconnected. This practice has been used for many years relating to ARDS patients but gained quite a bit of traction during COVID19 (1). Clamping the ETT prior to any disconnection reduced the risk of aerosolizing particulates.

Here is a photo and animation of the typical setup:

After tube clamping you may notice some remaining marks from the clamps:

Given the visible marking I have been concerned about damaging the tube and have added a gauze 4x4 for padding in the past:

Unfortunately, like everything in medicine, this does not come without risk. In the patient who has the potential to spontaneously breathe the biggest risk is Negative Pressure Pulmonary Edema (NPPE). The presumed pathophysiology for this disease is fluid shifting from massive pleural pressures caused by attempting to overcome the airway obstruction (aka your clamps) (2). Think of drinking a large sip of iced coffee. Suddenly your loving friend comes over and kinks the straw mid-sip. Your cheeks cave in and you feel the pressure within your mouth. Translate that pressure to your lungs, without the ability to resolve it and it's possible to see how this can cause problems.

Based on this potential, ensuring your patient has no recent spontaneous breaths, is densely sedated, and potentially neuromuscularly blocked is key.

But Shane, does this actually make a difference? This answer is…kind of. Let's take a look at a paper researching this. This paper looked at the utilization of three styles of clamps: metal, plastic and ECMO. You’ll see a photo of ECMO clamps below. As a brief summary, imagine Kelly clamps but quite a bit larger (picture later). What did the paper show?

First up for our plastic clamps. They sucked. Volumes were lost nearly immediately after disconnection from the ventilator and there was no true benefit.

What about standard metal Kelly clamps? As you can see in the chart below most of the volumes were lost within 30 seconds. There was some maintained volume within 5 seconds, but this is likely an unreasonable amount of time to do a swap.

That leaves the ECMO clamps. Accessibility is probably limited for many EMS systems based off their specific use but as you can see in the chart below they did a fantastic job maintaining the volumes and, in theory, recruitment.

Why the difference? Both are metal and have similar locking mechanisms. The difference is in the length. The length of the clamp theoretically allows for a more complete block of the ETT.

So, what’s the bottom line? There seems to be value in this practice for patients on high levels of recruitment. There are some risks that require calculation and, if you are going to do it, you should have a long pair of clamps to allow absolute closure of the ETT.

1. An Innovation for Airway Management in the COVID-19 Era. (n.d.).

2. Lemyze, M., & Mallat, J. (2014, August). Understanding negative pressure pulmonary edema. Intensive care medicine.,upper%20airway%20obstruction%20(UAO)


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