What is a Cuff Manometer and should we be using it?
During a break from the lectures at the last SOMSA one of the first issues identified was the lack of knowledge of PEEP and the absence of PEEP valves on BVMs. Within a few weeks the paper Why we need PEEP valves on BVMs was written, edited and posted for distribution. Our unit ordered the extremely inexpensive valves and they were distributed down to the medics. It is now standard to be using PEEP valves and considered less-than-best practice without.
My idea with the cuff manometer is similar. Among other topics this could potentially improve the outcome of a patient during long evacuation times. From what I understand, a cuff manometer is used to measure the pressure of the cuff on an endotracheal tube. This can be important when ascending in an unpressurized cabin of a non-standard air evacuation platform. As altitude increases the cuff expands and left unchecked can cause trauma to the trachea. A simple device could possibly be used to measure this and make adjustments at altitude and again after descending to the next long leg of the evacuation.
Knowing this I would next ask if anyone has experience using these. I would ask a pulmonologist how important this is. I would ask the experts at one of the 3 Air Force CSTARS training locations if any research has been done. The University of Cincinnati presented 2 research projects this year at SOMSA and they may already have data to support this concern. This could then be presented to the working group for recommendations specific to a prolonged field care situation.
This one of many due-outs that we owe medics. Are there any thoughts on this? Please comment below and read the great discussion.
When you have to prepare your CAX for an (Air)Evac, there’s a lot of thing to check, fix etc. About the cuff, you will replace the air inside by NaCl 0,9% or Water. That procedure is more safe because the fluid expends less than air !
That’s a solution for the “Air Vs Fluid” question in the cuff !
About the question of pressure (when using air) there an interest to have a pressure enough to avoid leaks. But if you have a cuff to inflated (with a pressure to high) you can bring another kind of wound at the place of the cuff (pressure ulcer on the trachea) Actually you can avoid this problem with a pressure control (manometer) or you can highly reduce this risk using a ETT with a “high volume-low pressure” cuff (But you can also fill it with fluid !)
http://www.howequipmentworks.com/images/physics_images/airway_images/ett_images/hi_low_pressure_gaphic.gif
Do you, or anyone else, know how long it takes for a tracheal ulcer to form? Is this something we should even be worried about over a 3 day situation? Also, what is the proper amount of pressure for a tracheal cuff? Does it change depending on what type of patient you have, burn etc. Many times a medic may be initially be using a generic size for all patients on the team, whatever he packed in his aid bag. Is there a no-shit time he has to change it out or lower the pressure before causing damage? These are some questions I have off the top of my head. If we had some research to back up the answers, we would be well on our way to another paper.
I’m aware that in animal studies, significant tracheal lesions have occurred in 48 hours or less, and I recently took an airway con ed class with the local PHI air medical base in which they pointed out that tracheal mucosal damage can occur in just a few hours, but I can’t recall the timeframe they specified. The papers I’ve seen on line seem to agree that cuff pressure should be no more than 30 cm H20 at their highest.
This is an interesting question from a variety of technical perspectives. A couple of thoughts:
1. The cuff exists to prevent aspiration.
2. The cuff exists close an normally open system to ensure adequate pressures for ventilation.
So do we need a manometer or do we need something akin to dive tables that give us a reference point to use our brain and hands to get “good enough” Good enough is the driving force behind PFC because by definition we are temporizing to a hospital where we can achieve “better”.
So the Iranians below seem to think that you can train, albeit with a less than 1 year cycle to skill degradation, tactile measurement to something around 25cm H2O. That’s intriguing but the Nigerians below seem to think you have to have a manometer. I think we need to see it from a different perspective.
If we think about #1. Then we can adjust for that. We can use the multi-taskers and non battery operated NG tube and 60cc syringe to evacuate the gut and avoid a lot of issues. That means we use devices that are not one trick ponies and can end up in a transport/PFC kit for a lot of purposes thus justifying their cube and weight. Leaving an NG in for aerial evac is desirable as well since it will allow for venting of GI tract gases and expansion at altitude.
Then comes #2. Ideally we could use a combination of three things to manage this.
1. We could use an Ambu bag pop off valve. Normally these have relatively high pressure settings, say around 60cm H2O, but it would not be particularly difficult to engineer one to trigger at say 30cm H2O. When checking cuff pressures a provider could manually ventilate the patient and adjust the cuff pressure incrementally until the valve blew. This would mean that the intrapulmonary pressure exceeded 30cm H2O. My thinking is that a cuff that is less than that would allow an air leak prior to the pop off tripping. I am thinking the physics is sound there. Someone might want to critique me on that.
2. We could use the ventilator itself. After confirmation of placement and a good ETCO2 waveform, A combination of chest rise (perhaps even ultrasound evaluation of lung sliding) and gradual decrease in cuff pressure until a reduction in chest rise and fall is observed and then incremental additions to the cuff to return of optimal chest mechanics might allow for a “close enough approximation”
3. The last paper down below looked at CT scanned tracheal cross sectional areas and found that in men there is a relationship between cross sectional area and height. Not so much for women. So since we are dealing with a mostly male population this works out to our favor. The trachea is a fairly rigid tube. If you know your cross sectional area and the surface area of the ET cuff and tube size it should not be terribly difficult math to determine the volume of air infused at a given barometric pressure/altitude to reach an optimal cuff pressure for that combination. This is the “dive table” approach to setting cuff pressures. It needs to be refined and a table constructed and tested in say ICUs and ORs with formal manometry to determine reliability but I think not only would it be an interesting research project but also potentially a very beneficial tool.
I did consider a combination of supraglottic obstruction (say pinching the nose and sealing off the mouth and using the presence of returned air from an indwelling NG tube to help set the cuff pressure to optimal but this seems very cumbersome and crude in the setting we are discussing.
One final thought, we use a “tire gauge” transducer into a smart phone. 0.35 PSI is 25 cm H2O. Seems to me that a very small transducer could be developed with a Luer Lock that could be plugged into the ET cuff balloon port and into a smart phone with a simple app to tell you exactly what cuff pressure is. That means using a gizmo that can fail, but it means that you end up carrying a lightweight transducer in your airway kit and not an actual manometer. The iPhone 6 already incorporates a barometer, so developing an app and transducer to measure pressures doesn’t seem like a huge stretch. 25cm H2O is about 18.4 mmHg. That is less than standard atmospheric pressure but not by much so there may be a simple solution in our smart phones.
Please commence to shredding my thoughts. In the end the manometer might be the simplest of items to pursue.
Iran Red Crescent Med J. 2013 May;15(5):381-4. doi: 10.5812/ircmj.4164. Epub 2013 May 5.
Accuracy of endotracheal tube cuff pressure adjustment by fingertip palpation after training of intensive care unit nurses.
Maboudi A1, Abtahi H1, Hosseini M2, Tamadon A3, Safavi E1.
and to contrast this…
Niger J Clin Pract. 2013 Apr-Jun;16(2):253-7. doi: 10.4103/1119-3077.110139.
Effects of user experience and method in the inflation of endotracheal tube pilot balloon on cuff pressure.
Ozer AB1, Demirel I, Gunduz G, Erhan OL.
Ann Otol Rhinol Laryngol. 2014 Oct 10. pii: 0003489414549154. [Epub ahead of print]
Tracheal Size Variability Is Associated With Sex: Implications for Endotracheal Tube Selection.
Karmakar A1, Pate MB1, Solowski NL1, Postma GN1, Weinberger PM2.
Todd after reading your comment I went searching for devices that you described and this seems to fit the bill. I think even though it may be a one trick pony, it may be worth looking into before going the route of the iphone transducer. We have tried and failed to acquire any subscription based product such as would be required with the iPhone or iPad, despite every medic I know having one. Much of this is all on our own dime unfortunately. I have looked into getting specialized app made as well and the amount of headache is overwhelming. This cuff controller, like a PEEP valve, may be worth the extra ounce or two it weighs to prevent VAP or tracheal ulcers. Does anyone have any experience using this? Is it worth it? Everyone absolutely insisted on us getting PEEP valves, I have yet to hear of similar concern in this realm http://www.smiths-medical.com/plugins/news/2006/oct/pressureeasy-cuff-pressure-controller.html
FYI. I have one of our engineering professors on this and if we can build one for a few bucks it might be worth testing on goats or whatever we have on hand. The gizmo above works with existing tools and without batteries so it is more optimal. Frankly I think the Iranians might be on to something with training to feel.
If we are doing PFC properly then we are doing pulmonary and tracheal toilet and suctioning and doing perioral care. Optimizing by feel and absence of cuff leaks is not elegant but it could be nuanced if you know what I mean and I am not sure that the risk of aspiration is that great from suboptimal cuff pressures if the basic airway care and maintenance is observed.
Just saying. Need to find a paper on that to back myself up.
Very interesting reading the discussion about managing ET tube cuff pressure during aeromedical transport. Monitoring ET tube cuff pressure is potentially very important in all prolonged care settings, and fixed wing transport makes it even more so. A few thoughts if I may:
1. The CSTARS-Cincinnati group recently studied this and had some interesting findings (the abstract is here: http://www.ncbi.nlm.nih.gov/pubmed/25159361). First, they again confirmed that pressure increases to dangerous levels (70 mm Hg or about 95 cm H2O) with ascent to 8000 cabin altitude. The tracheal mucosa is susceptible to injury over a short period- probably minutes to hours so this is a big deal. That is not to say that there is an epidemic of tracheal ulceration in our casualties but this is still worth addressing. Second, filling the balloon with saline greatly diminishes the pressure changes with altitude. However, this method was associated with excessive pressure at baseline. They also note that even a small amount of air remaining along with the saline led to significant pressure elevations and that manufacturers recommend against doing this. Third, the Pressure Easy device overcomes the increase in pressure at altitude but results in an under-inflated cuff as the aircraft descends. My takeaway from this study (and practice over the years) is to leave the balloon filled with air and monitor/adjust it regularly using a cuff manometer. Failing to do so at altitude will result in dangerously high pressures and the potential for injury to the tracheal mucosa. Failing to do so during descent and after landing will lead to an underinflated cuff and the potential for loss of airway pressure and aspiration around the cuff.
2. The cuff manometer is a fairly small piece of equipment (think if a dial-type tire pressure gauge with a blood pressure cuff bulb attached)- not small enough that you’ll want to add it to a small ruck but it would be reasonable in a larger pack designed for prolonged care. That said, there are times when it will be impractical to carry or for some other reason you will not have it when needed. In those instances it is worthwhile to regularly palpate the pilot balloon and adjust according to feel. This is not nearly as accurate (demonstrated more than once in the literature) but it is probably better than nothing. Despite the inferiority of this method, it is still very common in anesthesia and ICU practices. It might be worth making a point of palpating pilot balloons during ICU and OR rotations just to get a feel for normal.
Phil, once again, your input is invaluable! (He’s the author of “Why we need PEEP valves”). As an EM doc (only), I just palpate the balloon, and then admit to the ICU. I guess I have something (else) to learn…
Thanks, Sean
They make small solid state digital manometers that weigh almost nothing. After you have used a manometer for a few months and palpate at the same time, palpation again becomes reasonable. Each switch of ETT brands/models negates this knowledge and requires finger retraining. http://miradorbiomedical.com/
no conflicts of interest
Thanks Scott. I was able to get in touch with the head of our RT department at the hospital on Fort Carson, shared your site with him and he actually gave us a cuffolator (with a slightly cracked but working screen) for free! Uniting the tribes in a common goal of better patient care opens doors everywhere. We have also added a portable Capnographer (Massimo EMMA), HMEs, Ballard in-line suctions and the adapter to convert ET Tubes to suction. All of this is on it’s way to Africa or already there for use by our medics. I made a presentation that included most of your recommendations from your “Post Intubation Checklist” show and added the Tactical Airway Algorithm that Rich Levitan and Bob Mabry collaborated on and presented it to the Nordic Special Operations Medic Course as well as our own Special Forces Medics and subsequently put it on YouTube and this site with great feedback.
I wanted to keep everyone apprised of the results of this converstaion and the changes we are making at the operational and tactical levels. Thanks to everyone on this thread who contributed with comments and recommendations. If you are reading this and there is something we missed or you can add that will improve the care of our patients, please speak up and share!
Why not just deflate the cuff and move the ETT down or up a bit while you are reassessing the patient. This could be after 12-24 hours or something. Most guys I have seen carry some assembelence of a cut down ETT. There is plenty of length for small movements back and forth adjustments and you will not right main stem the guy.
This cuff manometer seems more of a gizmo and could be managed with some good nursing care principles.
While depth can also be an issue, I think that my concern is being aware of the potential for the cuff to be over or under inflated. Both are bad and medics haven’t been in the habit of checking the pressure once the tube is in. Over inflated cuffs can cause tracheal pressure ulcers while under inflated cuffs can allow aspiration that could contribute to aspiration or ventilator acquired pneumonia. All of these little things add up to increase the chance of infection and sepsis.
Patients with tubes should have oral hygiene addressed in some manner along with regular suction of the mouth and tube. If this is happening the cuff should also be checked.
When is the last time we trained on replacing an IV or IO placed in the field with a cleaner insertion when possible? I haven’t even though it is probably the right answer in certain situations. It used to be that the number 1 killer of burn patients in the ICU was due to infected IV lines, supporative thromboplebitis. I never even thought about this until listening to ICU Rounds the other day.
All of these things are common sense in the better ICUs because of the training and education the staff are required to have to work in critical care. We can only do so much, but sometimes it’s more than we are currently doing.
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