Vent Modes

cointosser13

cointosser13

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This more pertains to critical care paramedicine, but I was wondering: how do you remember what each vent mode (A/C PRVC SIMV etc) does when ventilating a patient? Any tricks (or charts) to remembering what each one does?
 
@VentMonkey

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cointosser13 said:
This more pertains to critical care paramedicine, but I was wondering: how do you remember what each vent mode (A/C PRVC SIMV etc) does when ventilating a patient? Any tricks (or charts) to remembering what each one does?
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There are apps that I carry, and peruse from time to time on my phone (basics of mechanical ventilation is the one I review the most from time to time, and it has the modes you've listed in your post). Just know with ventilator management there is no one-size fits all approach.

I also recommend giving Eric Bauer's book on prehospital ventilator management a look, as well as his, and Weingart's podcasts. They have some stuff that is unconventional though, and requires quite a bit of experience (many of it far beyond even my comfort zone, and level), and may not be well received by the masses at your particular program. YouTube, and Google also did wonders---and still do---when I first began delving into vent management.

If you have any RRT/ RCP colleagues, pick their brains; if you run into any pulmonologists pick theirs as well. Understand everything there is about the respiratory system to the best of your ability from basic adjuncts (e.g., never not transport your vented patients without a BVM/ mask at the ready, and easily accessible to you), get familiar with ABG's, and different formulas that may benefit certain patient types (e.g., Winter's Formula for a critically ill intubated, and ventilated metabolically acidotic patient), and get familiar with the ARDS net group, their literature, and publications.

Also, consider the type of ventilator you use, and get to know it back, and forth, play with it, do routine vent checks til you're comfortable with the basic set ups and modes. As far as when to use to different modes/ what they do, again, you will hear 10 different people cite 10 different uses. If your ventilator has PRVC, then you're well ahead of most of the soon-to-be phased out prehospital vents as this is a combination mode which as the name implies offers volume-control ventilation while calculating the patients initiated pressure limits so to speak. You may also see CMV-assist listed as AC, CMV alone is a pretty obsolete mode that has very limited use at least at my program. I hope this helps you some:).
 
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https://www.openanesthesia.org/modes_of_mechanical_ventilation/

No sure if there are many tricks to learning vents other than just remembering the information and the physiology behind it.


Maybe something like this would help.
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...aaand one more link added to my "work" folder, thanks @Chase.
 
I'm not really sure if there are any tricks to learning the modes, it's probably just one of those things that need memorization. There are tons of YouTube videos, power points, podcasts, etc... to answer pretty much any question you have.

I'd also suggest buying Eric Bauer's book on ventilator management. That said, I don't agree with his SIMV only strategy for all patients. Ventilator management can vary so much from patient to patient that it's dangerous to teach modes as a "one size fits all" approach, like VentMonkey said above.
 
RocKetamine said:
That said, I don't agree with his SIMV only strategy for all patients.
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I think it's a fail safe option for providers lacking the dual encompassing PRVC mode, however, I think you're right in that it should not be used on every patient given the likelihood of damage that one can inflict with the incorrect mode of an acutely ill patient that may require more ventilator dependency; he's a big proponent of patient comfort, and what I would presume to be less ventilator dependency in an effort to encourage weaning sooner rather than later, which I don't necessarily disagree with, but each mode is certainly circumstantial to the patient at hand.

I sure do find ASV an interesting mode for most patients, but again, it is not an all encompassing ventilatory mode, just one intended to get us from the scene post induction/ intubation to the ED; it seems sufficient as more often than not the patients we're picking up from scenes, and placing on our vent are most likely not going to experience any acute deleterious effects of this mode, or any of the ones we use for them (PRVC being the other go-to) in a routine 15-30 minute flight to our regional ED's.
 
VentMonkey said:
(e.g., never not transport your vented patients without a BVM/ mask at the ready, and easily accessible to you),
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I learned the importance of this the other week. I had a BVM, I keep a mini airway bag stocked on the stretcher all the time anyway. However, we ended up needing to pull out the BVM for quite a while. Definitely an important reminder for me. Otherwise, I am going back to lurking, because I am interested in seeing what pops up here.
 
StCEMT said:
I learned the importance of this the other week. I had a BVM, I keep a mini airway bag stocked on the stretcher all the time anyway. However, we ended up needing to pull out the BVM for quite a while. Definitely an important reminder for me. Otherwise, I am going back to lurking, because I am interested in seeing what pops up here.
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I like threading the oxygen tubing through the mask itself and setting it on their lap, and/ or next to my person in flight; it serves as a good visual reminder for me. We do have the BVM behind the paramedic seat, but it can be a PITA for me to reach, so I try and leave the BVM where myself, or partner(s) can grab it in a pinch.

If my medic bag has to go in our aft compartment for storage my partner or I will pull out the VL as well should the tube become dislodged or what have you in-flight; this is standard for all of us. We have a spare intubation kit in the paramedic door than can be utilized as well, but the VL is only in the medic (first-in) bag so we have to grab it before we're in-flight.
 
While its always a fun debate, really the strategy between A/C and SIMV is based on preference and models of ventilators.

ASV i have no experience with but i hear great things about.

The biggest thing i tell people eager to learn about transport vents, is focus your studying on how to use volume vs pressure modes.

I generally use pressure but when i have the sickest of the sick i will switch to volume
 
Discussion of basic modes here that may be helpful.
 
Brandon O said:
Discussion of basic modes here that may be helpful.
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Thanks for the link. OP, this is an excellent starting point; also added to my work folder on my phone.
 
Maximizing oxygenation/ventilation while minimizing volu/barotrauma is the simple goal, but getting out into the deep weeds isn't that hard sometimes.

If I was only allowed one way to give mechanical ventilation, It would be pressure control (with peep, of course), just because I can give more volume for a given pressure and the patient can over breath the vent without too much difficulty. If it's not objectively clear how to ventilate, I'd default to this and be very comfortable defending it.
 
E tank said:
just because I can give more volume for a given pressure and the patient can over breath the vent without too much difficulty.
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Eh... eh? Not sure I understand the argument for either of these points.
 
E tank said:
Well, what specifically is the question?
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In what respect does pressure control allow you to give more volume for a given pressure or make it easier to overbreathe?
 
Brandon O said:
In what respect does pressure control allow you to give more volume for a given pressure or make it easier to overbreathe?
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Compared to VCV, the decelerating flow pattern in PCV allows for the earlier dissipation of flow resistance which results in lower peak pressures for the same volume. This has all kinds of consequences, not the least of which is lower intrathoracic pressure, better venous return, and less intrapulmonary shunting.

As to the second point, it depends on your ventilator, but when the machine sees the set pressure on bucking, it stops cycling a breath, whereas in VCV (not SIMV) it will continue to attempt to give the set volume until it does. I realize that some ventilators are more sophisticated than others and the ones I use are more forgiving of a breathing/bucking patient. Your results may vary.

Note that in my post I said that if I were allowed only one mode of ventilation, I'd choose PC. I'm not in any way suggesting that other modes have no utility. I just reduced the conversation to that for the sake of simplicity for folks that have not had a lot of experience with mechanical ventilation.
 
E tank said:
Compared to VCV, the decelerating flow pattern in PCV allows for the earlier dissipation of flow resistance which results in lower peak pressures for the same volume. This has all kinds of consequences, not the least of which is lower intrathoracic pressure, better venous return, and less intrapulmonary shunting.

As to the second point, it depends on your ventilator, but when the machine sees the set pressure on bucking, it stops cycling a breath, whereas in VCV (not SIMV) it will continue to attempt to give the set volume until it does. I realize that some ventilators are more sophisticated than others and the ones I use are more forgiving of a breathing/bucking patient. Your results may vary.
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I think it's important to distinguish peak versus plateau pressure.

Most of what you're describing involves higher PEAK pressures. As I'm sure you recognize, the peak pressure (the driving pressure, measured and generated at the ventilator) is produced by a combination of two forces: the resistive pressure and the plateau pressure. The former is purely a dynamic phenomenon created by the resistance of the circuit, ET tube, and large airways (much like blowing through a straw). It is not transmitted or felt in the lung parenchyma, i.e. the alveoli. The latter is reflected by the plateau pressure, usually measured by an end-expiratory hold (although if PCV is configured to allow the flow to fully return to zero by the end of the breath, peak will equal plateau in that case).

Reducing peak flow has very little consequence. It is not lung-protective, because it is not felt by the alveoli, which is the portion of the lung that experiences injury. It probably has no impact on hemodynamics, since the large airways are not very compliant and transmit little pressure. As for plateau pressure, it is largely a consequence of volume, not of flow patterns. I recognize there is an argument that PCV can produce somewhat better recruitment, but this is mostly due to the fact that it is time-cycled, allowing essentially a breath-hold at full pressure, whereas in VCV the breath ends when the full volume is reached. (You can probably adjust VCV flow and use a decelerating-ramp waveform to get close to this if desired.)

If a patient is bucking, peak pressure may be increased, as will plateau. However, the thoracic pressure is equally increased (that's how they're transmitting pressure to the airway), so the transpulmonary gradient is NOT any greater. This is why nobody gets a pneumothorax from playing a trumpet or pooping or lifting weights, even though in that case airway pressures (against a closed glottis) may be tremendous. Pressure is high on both sides of the alveolar membrane.

I think PCV can be more comfortable in some patients due to the variable flow. I doubt there is ever a difference in outcome.
 
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