Acute Deterioration in Mechanical Ventilation
This is a repost of one of the chapters in our free book on mechanical ventilation in transport. Fore more on that or to read the whole thing, take a look at out website: https://www.rykerrmedical.com/vent-management
The next thing to chat about is what to do if the patient begins to decompensate while on the vent. Let’s start with a common memory tool to address some of the major causes of acute deterioration of the mechanically ventilated patient:
There are also some variations of this guy, so we may see it out there with an “S” at the end for stacking (i.e. AutoPEEP), an “R” at the end for rigidity of the chest wall (a rare complication of Fentanyl administration), or even with the “P” to represent pain and/ or (Auto)PEEP. It is also sometimes accompanied by another mnemonic called DOTTS which outlines actions that can be taken to fix issues identified by DOPE. Now DOTTS includes a step where we bag the patient with a bag-valve mask (BVM) and we’ve crossed that step out. We don’t recommend routinely taking someone off the vent unless we have good reason to and we’ll get back to this idea in just a little bit. But just so we can see it in its true representation, here it is:
The DOPE mnemonic (with or without DOTTS) is easy to remember and can be used to guide the initial troubleshooting process when the patient starts to deteriorate. Many of these occurrences can be tied to Alarms or other assessment parameters, but that depends on which type of machine we are working on and what tools we have available. For example, a tube displaced too deep will give a high-pressure alarm (and eventually a low minute volume alarm) and a tube displaced out of the airway will likely result in a low-pressure alarm. In regard to other assessments: a tube displaced too deep will lead to a high Mean Airway Pressure or Peak Inspiratory Pressure, low exhaled tidal volume, patient discomfort, etc. and a tube displaced out of the airway causes a low mean airway pressure, drop in EtCO2 with change in waveform, hypoxia, etc.
Because there are so many things to consider, building an algorithm to troubleshoot each possibility gets a bit difficult. We’ll go ahead and do it anyway, we just need to consider a few more things in preparation. First of all is that acute deterioration of the vented patient doesn’t always mean that there is an issue with the vent, it could be some other issue beyond the vent (i.e. endotracheal tube displaced or pathophysiologic process). If it’s a vent thing, then we mess around with the vent; but if it’s another issue, our interventions should focus on drugs and procedures and that sort of thing. Think of it this way:
Now the reality is that it isn’t always so cut and dry. There are times where we do both vents things and other things simultaneously. An example of this would be a patient already on the vent who experiences an allergic reaction to something. In this case we could simultaneously proceed with an Obstruction vent strategy and give drugs to fix the problem. So while our little algorithm may be too simple, it often helps to take a moment to think about which sort of problem we have on hand and act accordingly.
In light of the fact that there are so many variables involved, here’s the stepwise approach we suggest for troubleshooting acute deterioration of a ventilated patient. This approach takes advantage of feedback that we may have available to us from vent alarms and assessment parameters:
And in fact, one could argue that “use alarms to guide treatment” may even be a quicker solve than starting with the ABCs. While we recognize that this is blasphemy in the world of EMS and transport medicine, here’s how that might look:
By working through each of these steps systematically, we hit all of the DOPE things and identify where in the system the issue lies (vent, equipment, physiology). Now, it gets a bit more complicated when we add in specifics for each step along the way, but remember that the basic idea is a simple set of four steps:
A few things to note about this algorithm: with a partially deflated cuff, remove air from the cuff and then re-inflate with an appropriate amount of air. Simply adding volume can contribute to both injury from over-inflation and likelihood of tube displacement. Also consider using a monometer to measure cuff pressure and establish a baseline moving forward if available. And if the cuff is defective, consider utilizing a bougie to exchange it for a new one or take steps to fix the issue temporarily.
There’s no way to accommodate all possibilities in a single algorithm without getting too crazy on the details, but that’s the basic idea. Before moving on, just a few things to note. First is that a low minute volume alarm may also accompany acute deterioration, but it will likely be tied to either a high-pressure alarm (with breaths cycling off due to that alarm getting triggered) or some kind of disconnect (which would likely be indicated by a circuit disconnect or low peak-pressure alarm). We also didn’t include a low-frequency or low-PEEP alarm anywhere in this flowchart, as those probably aren’t tied to an acute deterioration unless accompanied by one of these other trump cards. And then we already showed this before (and recognize that not all of these are acute life threats), but just to clarify again the different lung and airway issues we might come across:
Now let’s summarize what actions to take in the event of an acutely deteriorating patient on the vent. While there is a well-known memory tool (the DOPE mnemonic) to guide us through troubleshooting potential issues, that tool doesn’t consider feedback from the machine (i.e. alarms) and, therefore, we suggest a simple sequence of four steps to work through it all: check the ABCs, look at and address any alarms, review the Three Big Things, then check pressures. If by then we haven’t figured out our problem, we can consider taking the patient off the vent and bagging by hand (still not a great strategy though…) or getting out the ultrasound machine to try and identify an issue (if available).
The final idea here is what to do if the patient goes into cardiac arrest while on the vent. Standard practice in this situation is to take the patient off the vent and have someone ventilate by hand while CPR is initiated. That may be a valid option if we have extra hands, but in transport with only two clinicians it may not be possible. If our particular machine allows us to ventilate without patient triggers (i.e. in controlled mechanical ventilation or intermittent mandatory ventilation), that would be the preferred approach. If not, then we may be able to approximate those Basic Modes of Ventilation by maxing out the sensitivity of our trigger. The reason we turn off the mechanism for patient-triggered breaths is that the machine will likely be triggered to deliver a breath with each chest compression given.
Another consideration in this cardiac arrest situation is that we may need to increase our high-pressure limit so that breaths don’t get cut short early during this time. If the machine is trying to give a breath while we are trying to simultaneously give compressions, we will most definitely exceed a normally-set high-pressure limit with the result that breaths will get cycled off. Ideally we could time our compressions with the machine’s breaths to avoid this, but that would be difficult to accomplish. Increasing the high-pressure limit does predispose the patient to both barotrauma and increased intrathoracic pressure, but it may be the best course of action when working a code with limited resources.
One last recap and then we’ll move on. With a deteriorating patient on the vent, try to keep it simple and work through four steps: ABCs, alarms, Three Big Things, and pressures. If after that you can’t figure out the issue, consider removing the patient from the vent and bagging by hand (with a PEEP valve, if available). And if other assessment techniques such as ultrasound are available, they can also be used to further investigate causes of deterioration. In the event that the patient arrests while on the vent, cancel out patient-triggers and increase your high-pressure limit.