Mysterious Pop-off valve???

[suckstobeme]

OK. Perhaps a stupid question but I'll ask anyway. What the heck does the pop-off valve do? What is it a valve between? What does it mean to have it totally open, partially open, or closed? How can I make it work for me?

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[UTSouthwestern]

OK. Perhaps a stupid question but I'll ask anyway. What the heck does the pop-off valve do? What is it a valve between? What does it mean to have it totally open, partially open, or closed? How can I make it work for me?

We do not speak of it in public. To do so will bring down the curse of the gods!!!


It is merely a figment of your imagination.








Hypothetically speaking of course, it is the valve that lies between the expiratory limb of the of the breathing circuit and the scavenging system. In most machines, when the selector is set to ventilator mode, the APL (adjustable pressure limiting, i.e. pop-off, valve) is no longer part of the circuit and has no real function (exceptions include the older Modulus 1 machine).

During manual ventilation (i.e. hand bagging a patient), the valve can be adjusted to allow build up of positive pressure in the breathing circuit to force more flow to the patient by decreasing or restricting flow to the scavenging system. At the limit of the pressure you dial in, flow begins to spill over to the scavenging system through the valve. If it is totally closed, all flow will have to be vented to the patient (bad idea but sometimes you forget that and a lung goes POP!).

If a patient is spontaneously breathing on an ET tube or LMA, you can dial up the APL and create a little positive end expiratory pressure to help inflate the lungs/keep the lungs inflated.


You must now deny ever having read this document or risk having your eyeballs spontaneously combust.

 

[dr_bigmac]

Try the breathing machine simulator on the website below. There's a also a checklist there which lets you answer the questions by doing simulations.

http://vam.anest.ufl.edu

 

[colchicine]

I'm a bit confused about this since I've had different attendings tell me different things ???

During mask ventilation at induction, how fast and how much volume am I supposed to give. Some attendings told me to bag slowly but give big volumes, some attendings told me to give small volumes not to inflate the stomach, and some attendings told me to bag really fast in order to give the patient some reserve in order to have more time for laryngoscopy....so which on eir right and why ?

Also we use mask ventilation for D&C's. In this case it does make sense to bag the patient every 5 or 6 seconds and give them big tidal volumes to mimic what the ventilator would do...but maybe I'm really wrong...

Also we had a really sick trauma patient the other day who was on the vent but still her sats were dropping so I tried then the senior resident tried to manually ventilate the patient with 100% O2 to increase the patient's saturation back to 100% without success and finally the attending took over and was able to bag her in a way to get her sats back up to 100%...however I couldn't telll how he was doing it and before I could ask him he put her back on the vent and added 5 of Peep and left the room...the patient did fine afterwards...so how did he do it ?

Can someone please explain all this to me...as u can tell, I am really confused ???

Thanx

 

[colchicine]

I'm a bit confused about this since I've had different attendings tell me different things ???

During mask ventilation at induction, how fast and how much volume am I supposed to give. Some attendings told me to bag slowly but give big volumes, some attendings told me to give small volumes not to inflate the stomach, and some attendings told me to bag really fast in order to give the patient some reserve in order to have more time for laryngoscopy....so which one is right and why ?

Also we use mask ventilation for D&C's. In this case it does make sense to bag the patient every 5 or 6 seconds and give them big tidal volumes to mimic what the ventilator would do...but maybe I'm really wrong...

Also we had a really sick trauma patient the other day who was on the vent but still her sats were dropping so I tried then the senior resident tried to manually ventilate the patient with 100% O2 to increase the patient's saturation back to 100% without success and finally the attending took over and was able to bag her in a way to get her sats back up to 100%...however I couldn't telll how he was doing it and before I could ask him he put her back on the vent and added 5 of Peep and left the room...the patient did fine afterwards...so how did he do it ?

Can someone please explain all this to me...as u can tell, I am really confused ???

Thanx

 

[VentdependenT]

attending probably had a better mask position in regards to the airway and as a result was able to get better ventilation.

As for the apl and induction basically there is no one correct way to perform mask ventilation. However it is all about position. Get a good fit and a solid jaw thrust (get that pinky under the angle of the mandible and lift for the stars), get the "face to fit into the mask" vs smashing the mask down into the face.

Then just twist the apl valve in the direction that makes the bag harder to squeeze. Keep tinkering with the valve until you get a good chest rise, a decent co2 waveform, and good spo2 sats. A goal of bagging is to check out your pressure meter and try and keep the needle from rising above 20mmhg (lower esophageal sphincter pressure) in order to minimize insufflating the stomach. Sometimes you cant help it. Some peeps have poor compliance for whatever reason and you gotta crank that apl down to deliver adequate tidal volumes.

If you cant get a good tidal volume and air is squeeling outta the sides of the mask throw in an oral airway. just make sure you snake that sucker past the tongue without folding it back on itself or things will be even more difficult.


righty tighty lefty loosey
vent

 

[colchicine]

Thanx, that helped...

I just realized in that example of that trauma patient, I forgot to mention that the patient was intubated on the vent and sats started dropping to low 90%'s and the attending was bagging while patient was intubated and was able to get the sats back up giving 100% O2, which actually seemed easy but both me and the senior were not able to bring the sat back up to 100% with positive pressure ventilation for some reason ?

Also what would be your differential of a patient on the ventilator who's sats are dropping assuming there's no leak in the circuit and machine working fine ???
The senior attending did mention PE as part of the differential...

 

[VentdependenT]

Hypoxia is broken down into four main categories:

Hypoventilation: think kinks in tube, pt biting, secretions in tube, circuit disconnect, cuff leak, stiff chest from inadequate depth/relaxation, bronchospasm can decrease compliance and increase airtrapping causing this and deadspace.

Deadspace: Think hypOperfusion and PEEP/AUTOPEEP. Hypoperfusion increases west zone one. Other things include EMBOLI:fat, thrombus, air, etc. In these situations Co2 may drop as well. Thats a real bad sign.

Shunt: Think crud in your alveoli. Pneumonia, pulmonary edema, aspiration...

DLCO2: Pulmonary fibrosis, etc.