Okay... so here is the message that I sent out. Hopefully there aren't any inaccuracies in it, let me know if anybody has any questions or comments. I realize that this is pretty basic information, but that is all it was supposed to be.
Do you work in a hospital where the RT's are pretty well respected? I know where I work we teach a class for all the interns when they rotate through pulmonary. That doesn't happen everywhere, though.
I would be more than happy to go over some things, but it really works better if you get with somebody who really knows the machines and theories and can go over it with the machine right in front of you.
A real rough rundown, though, is as follows:
CPAP: This stands for "continuous positive airway pressure". This is a therapy that is adequate for obstructive sleep apnea, acute exacerbation of CHF with some pulmonary edema, etc. It is usually delivered by a face mask and is measured in cmH2O. This is a STRICTLY spontaneous mode: meaning that the patient is not getting ANY ventilatory support. If you have a patient whose ABG shows "normal" acid-base/CO2, but hypoxemia (that is refractory to increased FiO2) then CPAP might be a good place to go.
BIPAP: This stands for "Bilevel positive airway pressure". This is basically the same as having 2 levels of CPAP, a high and a low. The notation is usually written as follows: "Bipap 14/6" where 14 is the high level of pressure and 6 is the low (14 and 6 are just examples!). You can think of there being a base level of 6 cmH2O, but then when the patient either triggers a breath, or the machine is time cycled (a set rate), then the machine "kicks it up a notch" to the higher level of 14 cmH2O. This mode can be used with a facemask to provide NIPPV (non-invasive positive pressure ventilation). You can also set a back up rate, so your order would look like this: Bipap 14/6 rate of 12 FiO2 of 60%. If somebody is a DNR/DNI but wants to have something done to help alleviate work of breathing, then this is a good choice (say they had some respiratory acidosis perhaps with some hypoxemia). This can also get you through a CHF exacerbation while you pump out the Lasix! A big issue with this is the fact that a lot of people won't tolerate the mask (has to be very snug fit).
If the patient can't maintain their own airway, then obviously we have to put in an artificial airway (ET tube/trach/etc). Then you have to go to the vent terminology.
PEEP: The same as CPAP... just on a vent!
FiO2: Hopefully self explanatory!
Rate: Minimum frequency that the vent provides.
Tidal Volume: Vt - size of breath delivered (usually in mL)
CPAP trial: used as a weaning strategy to see how the patient can breathe spontaneously. CANNOT be sedated for this. Some people like to work patients daily (if they are stable enough), others like less frequently. I, personally, believe that daily CPAP trials aren't a bad thing if the patient is stable (as tolerated)... but I ALSO believe in NOT getting an ABG (unless pt has an A-line) on daily CPAP trials - judge them clinically. Usually a CPAP of 5 cmH2O is used, either with or without pressure support.
Pressure support: Basically the same as BIPAP on the vent. There is a set level of PEEP (low level of CPAP) and Pressure support (like the high level of CPAP in BIPAP). The pressure support helps the patient overcome the resistance of the ETT. This can also be used with higher levels for patients who might not be QUITE strong enough to completely support their own ventilation. Also, BE SURE NOT TO USE ON SOMEBODY WHO IS SEDATED!
Assist Control: Abbreviated AC, A/C, CMV (Not 100% accurate name, but is used now). This is the basic mode of mechanical ventilation where we are doing ALL the work for the patient. You set a rate, tidal volume, PEEP and FiO2. If you have a set rate of 12 and the patient is breathing 16, then that is okay - the machine will give them 16 fully supported machine breaths a minute. There is also pressure control, where you set a inspiratory pressure instead of a tidal volume. On this mode the patients muscles aren't doing any work at all (even if they are over breathing the vent, the vent is still doing the work for them). You want to be sure to keep your plateau airway pressures below 30 cmH2O and also keep your tidal volume less then 10 ml/kg.
SIMV: This stands for "synchronized intermittent mechanical ventilation". This is like a mix between assist control and pressure support. You set a tidal volume (or pressure), a rate, PEEP and FiO2 for the machine breaths... but then you ALSO set a pressure support for if the patient over breathes the vent. EXAMPLE: You write an order "SIMV rate of 8, Vt: 750, PEEP: 5, FiO2: 60% Pressure support: 10" This means that the machine will give 8 breaths a minute at 750mL tidal volume. If the patient wants more than that then they can trigger more breaths, but they won't be 750ml breaths... they will be pressure supported at 10 cmH2O (like bipap).
That is all that I can write now... I worked all day today and tomorrow and have had a couple glasses of wine
. There are more modes, but they are a bit more advanced. This is a good place to start. There is also a good website that I recommend:
http://www.ccmtutorials.com/rs/mv/index.htm
I probably should have just given you this website instead of writing everything that I did... would have been more coherent, I imagine!
Let me know if this helps, or if you have any questions! Good luck to you!
-RT2MD
