Ventilation - pressure support

[bkell101]

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Hey everybody,

Is there a disadvantage to maintaining a an intubated pt on pressure support compared to volume control if the tv and rr are the exact same? Atelectasis, wob?

 

[cchoukal]

Hey everybody,

Is there a disadvantage to maintaining a an intubated pt on pressure support compared to volume control if the tv and rr are the exact same? Atelectasis, wob?

There real question should be whether there is an advantage to doing so. Search for papers on diaphragmatic atrophy and mechanical ventilation.

 

[bkell101]

I'll do some reading....but just yesterday I asked my attending if putting the pt on ps and making them work a little bit during a long case helped fight atrophy...I told her during intern year, the pulm guys were huge on daily weans to avoid atrophy of the diaphragm... I'm not sure if in the acute setting its as beneficial as it is in the icu. I guess it would be a matter of how long it takes for the "use it or lose it" to happen? I'll see what I come across

 

[cchoukal]

You're on the right track!

 

[Idiopathic]

I'll do some reading....but just yesterday I asked my attending if putting the pt on ps and making them work a little bit during a long case helped fight atrophy...I told her during intern year, the pulm guys were huge on daily weans to avoid atrophy of the diaphragm... I'm not sure if in the acute setting its as beneficial as it is in the icu. I guess it would be a matter of how long it takes for the "use it or lose it" to happen? I'll see what I come across

you are unlikely to get atrophy or ventilator induced diaphragmatic dysfunction during an OR case, but more likely to get it after 24 hours on a vent. im not sure if the clinical implications of this atrophy have been fleshed out

 

[bkell101]

This suggests about 16 hours ....http://ccforum.com/content/12/5/R116

 

[bkell101]

Anything wrong with pressure support though? If we used roc to intubate the pt for a 2hr case.... pt starts breathing with an hour to go and doesn't need paralysis for the end of the case, why not just leave him on pressure support for that hour?

 

[BLADEMDA]

Anything wrong with pressure support though? If we used roc to intubate the pt for a 2hr case.... pt starts breathing with an hour to go and doesn't need paralysis for the end of the case, why not just leave him on pressure support for that hour?

Nothing wrong with pressure support provided the surgeon is fine with a spontaneously breathing patient. Most of the time I get the patient breathing at the end if the case if possible.

Our ventilators now have pressure support mode in the operating room. I primarily use Pressure support with some peep for my LMA cases but I have used it for my ETT ones as well.

No proven advantage for pressure support over other ventilation modes for intubated patients in the operating room. Since entering private practice I've yet to do a case anywhere near 16 hrs in duration but a few certainly felt that long. 😉

 

[Idiopathic]

Anything wrong with pressure support though? If we used roc to intubate the pt for a 2hr case.... pt starts breathing with an hour to go and doesn't need paralysis for the end of the case, why not just leave him on pressure support for that hour?

nothing wrong with it per se, as long as the breathing doesnt affect the surgical field, as Blade alluded to,

 

[PMPMD]

Also, pts get more flow w/ PSV vs VCV (flow-limited). PSV is more comfortable for awake ICU pts than VCV, I'm not sure if this translates into reduced GA requirements in OR. Probably not significant beyond academic interest.

 

[Precedex]

Ive always kinda wondered this but what do you think is the difference in the surgical field when the patient is triggering pressure supported breaths vs being controlled fully on the vent?

 

[Idiopathic]

Ive always kinda wondered this but what do you think is the difference in the surgical field when the patient is triggering pressure supported breaths vs being controlled fully on the vent?

if you watch the abdomen of a spontaneously breathing patient in the OR vs one who is on controlled ventilation you will see the difference

 

[Sublimazing]

Why does pressure control produce a sustained pressure (raising Pmean) where as volume control hits a set volume and immediately drops (sometimes producing a higher Pmax)? The flat hill wave form of PC versus the Shark-fin of VC?

 

[PMPMD]

Why does pressure control produce a sustained pressure (raising Pmean) where as volume control hits a set volume and immediately drops (sometimes producing a higher Pmax)? The flat hill wave form of PC versus the Shark-fin of VC?

VCV = delivers constant flow, until volume target hit. Pressure is dependent variable (depends on compliance, etc.).
PCV = delivers set pressure with decelerating flow for set time. Volume is dependent variable (depends on driving pressure, compliance, etc.)

 

[Sublimazing]

VCV = delivers constant flow, until volume target hit. Pressure is dependent variable (depends on compliance, etc.).
PCV = delivers set pressure with decelerating flow for set time. Volume is dependent variable (depends on driving pressure, compliance, etc.)

Thanks, much clearer now.