PsvPRo vs Breathing on the Bag

[jthedestroyr]

So ca1, and I'm interested to get some opinions in psvpro versus purely letting people breath on the bag.

I normally, if i dont need to paralyze or on steep positioning generally like to put people on psvpro then titrate support as needed.

Recently had a few attendings that really hate it, and flip patients to the bag without support as soon as suc wears off s/p intubation or after a LMA is in.

Their reasoning, is you can fine tune your anesthetic better as you can see how deep or light the patient is better off the vent than on.

I have also noticed when you do flip them to bag, it appears a lot harder to titrate to effect. I often feel since theyre breathing against the resistance of the tube without the support of psvpro the patients struggle more to hit that equalibrium point versus giving them that extra support.

Maybe its a comfort thing, but it makes me very, very uneasy seeing tidal volumes of 200-240 (essentially deadspace) with ETco2 40-45 lingering for a bit. Those attendings didnt seem to be bothered by it.

Am i over thinking this? The attendings that like to do this are new from private practice. Our pure academic types never do this (old or new).

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[deleted171991]

You should try using PSV at 4-5 cmH2O, with no PEEP, and titrating meds to breathing as with SV. That's pretty close to normal breathing effort without a tube. I even extubate from there without a problem, if otherwise appropriate (I just want good volumes).

It's very good that you are bothered by the low tidal volumes and high pCO2, just for the sake of having the patient on SV. That's CRNA school style. One can lose lung recruitment on SV, especially during a long emergence in bigger patients.

With an LMA, it's less of a big deal (larger cross-sectional area than a 9 mm ETT).

 

[fakin' the funk]

I have also noticed when you do flip them to bag, it appears a lot harder to titrate to effect. I often feel since theyre breathing against the resistance of the tube without the support of psvpro the patients struggle more to hit that equalibrium point versus giving them that extra support.

Maybe its a comfort thing, but it makes me very, very uneasy seeing tidal volumes of 200-240 (essentially deadspace) with ETco2 40-45 lingering for a bit. Those attendings didnt seem to be bothered by it.

It's totally fine to have an ASA1-2 normal-ish patient breathing 200ml TV's with etCO2s in that range. Patients will tolerate much, much worse for much, much longer and be just fine. While there *is* resistance in the circuit, it's not that much -- certainly not enough to meaningfully reduce TV's. Just try it yourself sometime - see what it feels like to breathe from the circuit elbow, or even better, from a 8, 7, 6, 5.0 ETT.

PSV is a sometimes-useful mode but you have to get your settings dialed in right, especially the flow trigger. It's easy to hyperventilate the patient relative to the paCO2 threshhold that they want to breathe at if your flow trigger is too sensitive (i.e., set too low) and the vent is delivering a supported breath the patient didn't really "want."

Titrating opioids to RR or minute ventilation can be done on either spontaneous or PSV, as long as you "trust" that the patient's ventilatory pattern on PSV is not artifact from messed-up PSV settings.

In my experience the PSV on the Dragers is garbage.

 

[Ezekiel2517]

What you're doing is fine. Leave them on PS, you can still easily tell if they're getting light because their RR and TV's will go up. I typically leave them on PS til I take the LMA out b/c it helps get the gas off quicker. Patients are extubated all the time in the unit on PS.

 

[Ronin786]

One other thing to keep in mind is that your EtCO2 when you're spontaneously ventilating may not necessarily be adequate. You need a full plateau to have a proper EtCo2.

 

[jthedestroyr]

So do any of you just leave them breathing spontaneous on the bag and why ?

I normally start at 15 cm h20 support then titrate down to 4-5. If i can get below 10 cm h20 they tend to tolate breathing without support.

 

[urge]

I have seen patients look good on minimal settings of PSPVpro that go on resp distress quickly after extubation. I would not extubate on it. But carrying the anesthetic on PSPV pro is fine. Just make sure they are breathing fine on the bag before extubating.

 

[urge]

So ca1, and I'm interested to get some opinions in psvpro versus purely letting people breath on the bag.

I normally, if i dont need to paralyze or on steep positioning generally like to put people on psvpro then titrate support as needed.

Recently had a few attendings that really hate it, and flip patients to the bag without support as soon as suc wears off s/p intubation or after a LMA is in.

Their reasoning, is you can fine tune your anesthetic better as you can see how deep or light the patient is better off the vent than on.

I have also noticed when you do flip them to bag, it appears a lot harder to titrate to effect. I often feel since theyre breathing against the resistance of the tube without the support of psvpro the patients struggle more to hit that equalibrium point versus giving them that extra support.

Maybe its a comfort thing, but it makes me very, very uneasy seeing tidal volumes of 200-240 (essentially deadspace) with ETco2 40-45 lingering for a bit. Those attendings didnt seem to be bothered by it.

Am i over thinking this? The attendings that like to do this are new from private practice. Our pure academic types never do this (old or new).

Don't dismiss right away the PP attendings. Those guys have been thru Vietnam, Korea, Iraq, and perhaps even the Clone Wars. Academic attendings have a difficult time stepping out of their comfort zone. PP is more about efficiency.

 

[Hoya11]

So ca1, and I'm interested to get some opinions in psvpro versus purely letting people breath on the bag.

I normally, if i dont need to paralyze or on steep positioning generally like to put people on psvpro then titrate support as needed.

Recently had a few attendings that really hate it, and flip patients to the bag without support as soon as suc wears off s/p intubation or after a LMA is in.

Their reasoning, is you can fine tune your anesthetic better as you can see how deep or light the patient is better off the vent than on.

I have also noticed when you do flip them to bag, it appears a lot harder to titrate to effect. I often feel since theyre breathing against the resistance of the tube without the support of psvpro the patients struggle more to hit that equalibrium point versus giving them that extra support.

Maybe its a comfort thing, but it makes me very, very uneasy seeing tidal volumes of 200-240 (essentially deadspace) with ETco2 40-45 lingering for a bit. Those attendings didnt seem to be bothered by it.

Am i over thinking this? The attendings that like to do this are new from private practice. Our pure academic types never do this (old or new).

Let me explain why I sometimes hate PSV. PSV is very useful when used correctly (as mentioned overcoming tube resistance, imperfect LMA seal, on and on) but I cant tell you how many times this has happened to me while supervising:

I walk into the room and an LMA is in, PS of 17, PEEP of 3, Backup set Rate of 6, patient breathing at 13 TVs 400s

"PS of 17 with an LMA, thats kind of high, did you try to ween that down?"

"Yeah he was taking volumes of like 100-150 without it, he needs PSV"

" Oh OK go to lunch Ill see what I can do"

Turn off vent, yes patient initially takes 100-150 but then over the next 2 minutes slowly and consistently picks up TVs to 400s just as before but now without all the PS.

"Look I got them off PS"

"Oh wierd he wouldnt do that for me" --> THIS IS WHAT DRIVES ME CRAZY.. the inability to understand that you have to give the person time to come back from apnea to normal volumes and rate. PS is thrown on after two small breaths when, if they just gave the patient time without support, the patients own body would self regulate the volumes to normal levels in a few minutes.

So while it might make you feel uncomfortable letting those small volumes be at first, its the better thing to do for the patient compared to inappropriately giving PPV for the entire case. If you have given them time to get their own breathing pattern down and they cannot, then that is a different story. Then either support their spontaneous mode if you think that is advantageous for whatever reason or paralyze/cause apnea and ventilate for them at that point. But give them a chance to come back, not everybody needs it. I do put on at least 5 for an ETT though for resistance.

 

[PainDrain]

"Oh wierd he wouldnt do that for me" --> THIS IS WHAT DRIVES ME CRAZY.. the inability to understand that you have to give the person time to come back from apnea to normal volumes and rate. PS is thrown on after two small breaths when, if they just gave the patient time without support, the patients own body would self regulate the volumes to normal levels in a few minutes.

.

I believe there is some evidence to support the theory that the body senses the inspiratory resistance and compensates its effort accordingly. There are afferent fibers in the chest wall that sense respiration and the theory goes that signals from mechanoreceptors in the chest wall sense resistance and compensate by recruiting accessory respiratory muscles. You can see this in practice where you dial back pressure support until they are breathing on their own and easily overcoming the resistance of the tube.

I use PSV sparingly at the end of the case with intubated patients and rarely with LMAs. I use it to build up some CO2 to trigger their respiratory drive and once they are taking breaths on their own I turn it off. HOYA is correct in that the vast majority will take lousy volumes for the first minute or so and the reflex is to say "they are not ready to breath on their own" but if left alone once they hit a certain threshold they begin breathing normally.

 

[deleted171991]

The point of using PSV is not to compensate for the lousy volumes (those can be fixed with some PEEP, or just waiting for the patient to open up some lung - which sometimes doesn't happen). The point of PSV is to decrease respiratory muscle work, especially in heavy patients. For emergence, it doesn't really matter which one is used, but for longer periods it may. I have seen CRNAs run patients on SV for hours; the fact that one could doesn't mean that one should.

 

[Planktonmd]

I use PSV on every spontaneously breathing patient unless the case is really short.
It's a very useful tool and in my opinion decreases post op atelectasis especially in obese patients.
On the other hand I have seen CRNAs who actually dial PSV too early before return of spontaneous ventilation, and as a result the backup PCV mode kicks in, but the CRNA never notices and the whole case is done on PCV !

 

[Nivens]

Out of curiosity, what mode do yall typically default to immediately after intubation: pcv vs vc? Does it make much of a difference? A lot of our attendings like PCVG, which feels a bit like cheating/inelegant.

 

[vector2]

Out of curiosity, what mode do yall typically default to immediately after intubation: pcv vs vc? Does it make much of a difference? A lot of our attendings like PCVG, which feels a bit like cheating/inelegant.

pcv-vg. it's actually much more elegant than having the rest of your anesthetic constantly interrupted because you're adjusting PC pressures to get your target Vt. that being said, there's probably not a difference between vc or pc unless your patient has severe pulmonary disease

 

[pgg]

Ask 10 anesthesiologists how to manage a vent and you'll get 15 good answers ...


VC vs PC makes absolutely no difference at all under any circumstances, provided you pay attention when setting parameters and alarms.

SV through a tube for prolonged periods or in patients with respiratory dysfunction is unwise but lots of people get away with it, because most patients have plenty of reserve to spare.

For patients I plan to extubate, I generally don't try to get them spontaneously ventilating. I find it easier to time wakeups if I'm the one in control of minute ventilation. If you don't overdo the opiates, they'll breathe when they wake up.

In particular, I think "titrating opioids to respiratory rate" is a poor approach, since volatiles themselves affect rate and tidal volume, and the volatile is going to be gone when they're awake. Anecdotally, I find that if I'm going to try to titrate opioids to a spontaneously ventilating patient prior to wakeup, ignoring rate and targeting an ETCO2 in the 40s is a better method.

 

[Arch Guillotti]

Maybe its a comfort thing, but it makes me very, very uneasy seeing tidal volumes of 200-240 (essentially deadspace) with ETco2 40-45 lingering for a bit.

It's very good that you are bothered by the low tidal volumes and high pCO2, just for the sake of having the patient on SV.

What's the harm with an ETCO2 of 40-45?

 

[pgg]

What's the harm with an ETCO2 of 40-45?

Surely FFP was being sarcastic.

I think what jthedestroyer was getting at is that if TV is very low, ETCO2 might not be an accurate reflection of PaCO2 and maybe that 45 is really 75. But I wouldn't expect that unless TV was a lot lower than the 200-240 he cited.

 

[deleted171991]

What's the harm with an ETCO2 of 40-45?

Nothing, if real. (Good anesthetic depth, spontaneous ventilation, low CO2, choose two.) But one could argue that at Vt of 200 ml, there is a good amount of dead space ventilation (like @jthedestroyr suggested) so the real EtCO2 might be actually higher.

I like when a resident pays attention to the CO2, and doesn't chase SV at any price, even an EtCO2 of 50+, like some CRNAs do.

On the other hand, it's regrettable that the local culture does not encourage a discussion between attending and resident about the (dis)advantages of both approaches.

 

[deleted171991]

Surely FFP was being sarcastic.

I think what jthedestroyer was getting at is that if TV is very low, ETCO2 might not be an accurate reflection of PaCO2 and maybe that 45 is really 75. But I wouldn't expect that unless TV was a lot lower than the 200-240 he cited.

The average anatomic dead space is 2 ml/kg. So a Vt of 200 ml (3 ml/kg) is low for the average adult and, exactly as you pointed out, the measured EtCO2 might not be the real one.

 

[GravelRider]

10,000 ways to skin a cat. There is probably no right answer...especially in a healthy patient. It's probably ok if they hypoventilate a bit while breathing spontaneously. I just make sure there is a little PEEP or do a recruitment maneuver every so often to prevent the atelectasis. For sicker patients or patients with pulmonary disease, it obviously gets more complicated.

I think this is also illustrative of how a CA1 needs to figure out which attendings you can question and challenge and which ones you just smile and do what they say to get through the day. You'll figure it out. By the time you are a CA2, the management will be all yours to fiddle with.

 

[btbam]

Can someone give a real explanation on the flow trigger setting in PSV-pro? I have heard numerous people say it does not actually correlate with the pt's MV, i.e. a flow trigger of 0.6 doesn't equal 600 ccs generated by the pt. In the peds world I always dial the flow trigger down from the default setting 0f 2.0, am I wrong for doing this?

 

[vector2]

Can someone give a real explanation on the flow trigger setting in PSV-pro? I have heard numerous people say it does not actually correlate with the pt's MV, i.e. a flow trigger of 0.6 doesn't equal 600 ccs generated by the pt. In the peds world I always dial the flow trigger down from the default setting 0f 2.0, am I wrong for doing this?

Either I don't understand the question or you're not understanding what a flow trigger is. The flow trigger has nothing to do with the tidal volume or minute ventilation, but rather how the ventilator senses whether to start administering a supported a breath. Triggers on most ICU ventilators are set either by pressure or flow. The patient has to generate negative pressure (-x CmH20) or a negative flow deflection (-x L/min) before the ventilator senses and does its job...

 

[btbam]

Either I don't understand the question or you're not understanding what a flow trigger is. The flow trigger has nothing to do with the tidal volume or minute ventilation, but rather how the ventilator senses whether to start administering a supported a breath. Triggers on most ICU ventilators are set either by pressure or flow. The patient has to generate negative pressure (-x CmH20) or a negative flow deflection (-x L/min) before the ventilator senses and does its job...

Ok so I guess what I'm asking is how you define "negative flow deflection" then..

 

[vector2]

Ok so I guess what I'm asking is how you define "negative flow deflection" then..

Modern ventilators have a flow sensor at both the inspiratory and expiratory limbs. There is usually a base flow of O2/Air running (say 5L/min). On GE Aestivas, I believe the range for the psvpro flow trigger is something like 0.6L/min to 2. With an apneic patient, the machine will sense an inspiratory flow of 5L/min and expiratory flow of 5L/min. This is a grossly simplified explanation, but say a patient generates an inspiratory pressure that causes a flow rate of -1L/min, the machine will sense 5 at the inflow and 4 at the outflow and trigger a breath. It takes varying degrees of inspiratory force to generate various flows, so the machine lets you set flow triggers that vary because, for instance, a pt who is fully reversed from NMB might easily generate -2L/min flow, whereas someone who is incompletely reversed or has a significant amount of volatile onboard might only be able to generate -0.6L/min.

 

[Iso4ane]

So ca1, and I'm interested to get some opinions in psvpro versus purely letting people breath on the bag.

I normally, if i dont need to paralyze or on steep positioning generally like to put people on psvpro then titrate support as needed.

Recently had a few attendings that really hate it, and flip patients to the bag without support as soon as suc wears off s/p intubation or after a LMA is in.

Their reasoning, is you can fine tune your anesthetic better as you can see how deep or light the patient is better off the vent than on.

I have also noticed when you do flip them to bag, it appears a lot harder to titrate to effect. I often feel since theyre breathing against the resistance of the tube without the support of psvpro the patients struggle more to hit that equalibrium point versus giving them that extra support.

Maybe its a comfort thing, but it makes me very, very uneasy seeing tidal volumes of 200-240 (essentially deadspace) with ETco2 40-45 lingering for a bit. Those attendings didnt seem to be bothered by it.

Am i over thinking this? The attendings that like to do this are new from private practice. Our pure academic types never do this (old or new).

Just as new as you and I to keep volumes stable, so when I use PSVPro, I start with Psupport+PEEP=Ppeak (from prior to switching to PSVPro), then titrating down, and flipping over at when either the Psupport is minimal or they are more responsive.

 

[BLADEMDA]

For the first 10-12 years of my career our ventilators didn't have PS or a PEEP setting for Spontaneous ventilation. Some simply dialed in PEEP manually with the pop off valve. The vast majority of the patients did fine with these "old" ventilators. I'd say the subgroup which needed the PS mode the most was the obese population. Back then we didn't LMA as many obese patients as we do today.

Fast forward to today and I routinely use PS (typically 4-6) with some low dose PEEP (5 cm) on the vast majority of patients. Has it made a difference? Maybe around the edges particularly with the Obese population.
If you aren't familiar with doing cases without PS I encourage you to do a few with your hand on the bag and the patient spontaneously breathing through the LMA. When you get a healthy ASA1or ASA2 for a simple case this old fashioned technique is a good way to work on your anesthesia skills.

 

[Iso4ane]

For the first 10-12 years of my career our ventilators didn't have PS or a PEEP setting for Spontaneous ventilation. Some simply dialed in PEEP manually with the pop off valve. The vast majority of the patients did fine with these "old" ventilators. I'd say the subgroup which needed the PS mode the most was the obese population. Back then we didn't LMA as many obese patients as we do today.

Fast forward to today and I routinely use PS (typically 4-6) with some low dose PEEP (5 cm) on the vast majority of patients. Has it made a difference? Maybe around the edges particularly with the Obese population.
If you aren't familiar with doing cases without PS I encourage you to do a few with your hand on the bag and the patient spontaneously breathing through the LMA. When you get a healthy ASA1or ASA2 for a simple case this old fashioned technique is a good way to work on your anesthesia skills.

Where I am we have a lot of super-super obese people )At least that's how it's coded in EPIC), with BMIs routinely 50+, and a handful 80+.

 

[ProRealDoc]

Let me explain why I sometimes hate PSV. PSV is very useful when used correctly (as mentioned overcoming tube resistance, imperfect LMA seal, on and on) but I cant tell you how many times this has happened to me while supervising:

I walk into the room and an LMA is in, PS of 17, PEEP of 3, Backup set Rate of 6, patient breathing at 13 TVs 400s

"PS of 17 with an LMA, thats kind of high, did you try to ween that down?"

"Yeah he was taking volumes of like 100-150 without it, he needs PSV"

" Oh OK go to lunch Ill see what I can do"

Turn off vent, yes patient initially takes 100-150 but then over the next 2 minutes slowly and consistently picks up TVs to 400s just as before but now without all the PS.

"Look I got them off PS"

"Oh wierd he wouldnt do that for me" --> THIS IS WHAT DRIVES ME CRAZY.. the inability to understand that you have to give the person time to come back from apnea to normal volumes and rate. PS is thrown on after two small breaths when, if they just gave the patient time without support, the patients own body would self regulate the volumes to normal levels in a few minutes.

So while it might make you feel uncomfortable letting those small volumes be at first, its the better thing to do for the patient compared to inappropriately giving PPV for the entire case. If you have given them time to get their own breathing pattern down and they cannot, then that is a different story. Then either support their spontaneous mode if you think that is advantageous for whatever reason or paralyze/cause apnea and ventilate for them at that point. But give them a chance to come back, not everybody needs it. I do put on at least 5 for an ETT though for resistance.

You're expected to cover lunch breaks for your CRNAs?

 

[Ronin786]

You're expected to cover lunch breaks for your CRNAs?

If they're your employees why wouldn't you?

 

[Arch Guillotti]

If they're your employees why wouldn't you?

Because another CRNA is getting them out.

 

[Psai]

If they're your employees why wouldn't you?

Does the hospital ceo cover your lunches too?

 

[Hoya11]

You're expected to cover lunch breaks for your CRNAs?

often our practice does have CRNAs give the breaks for us, but often I do it myself if necessary. Rarely they will go without breaks if its hectic and sometimes they will get two breaks if its slow... its always changing according to the OR schedule of the day

 

[pjl]

often our practice does have CRNAs give the breaks for us, but often I do it myself if necessary. Rarely they will go without breaks if its hectic and sometimes they will get two breaks if its slow... its always changing according to the OR schedule of the day

We cover the lunches that the "break CRNA" cant get to. Today, that would have been 2 CRNAs for me. Both just told me "no thanks, I'll eat tomorrow."
I now have a complex.


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[deleted171991]

We cover the lunches that the "break CRNA" cant get to. Today, that would have been 2 CRNAs for me. Both just told me "no thanks, I'll eat tomorrow."
I now have a complex.


Sent from my iPad using SDN mobile app

They were afraid you would F up their anesthetic plans, you paper monkey fireperson you. 😛