Ventilators

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can anyone give me a lucid understandable discussion on the different vent settings seen in the unit and what they mean and what their significance is?
I have seen pts in the unit while I was on a surgery month, I'm an intern, and we read of the vent numbers and I have no clue what it all means, I have read about a few differents times on up to date, the icu book, and in lange anesthesia, but it doesnt seem to stick. I was hoping someone here can put it in real understandable terms and hopefullly it will stick with me.
As an example we walk into a pts icu room and we say
he is on a psv 12/5 fio2 of 40% down from 15/10 from yesterday. The day before he was on an AC of 12. I just sit there and am like??? I figure the lower pressure support is good but what the heck does it mean? I am guessing that being on AC is worse than PSV but that is b/c a resident told me that, but didnt explain why.
 
MeaCulpa said:
can anyone give me a lucid understandable discussion on the different vent settings seen in the unit and what they mean and what their significance is?
I have seen pts in the unit while I was on a surgery month, I'm an intern, and we read of the vent numbers and I have no clue what it all means, I have read about a few differents times on up to date, the icu book, and in lange anesthesia, but it doesnt seem to stick. I was hoping someone here can put it in real understandable terms and hopefullly it will stick with me.
As an example we walk into a pts icu room and we say
he is on a psv 12/5 fio2 of 40% down from 15/10 from yesterday. The day before he was on an AC of 12. I just sit there and am like??? I figure the lower pressure support is good but what the heck does it mean? I am guessing that being on AC is worse than PSV but that is b/c a resident told me that, but didnt explain why.
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yeah I can but thankfully Mil is our resident CCM instructor so i will defer to him. And with this statement i have saved myself a lot of grief and time trying to explain it.
 
I also found the ccmtutorials to be helpful, but one important thing to remember is that people sometimes use these setting terms interchangeably, and sometimes one mode seems to have two names or at least two ways of describing it. when you're trying to figure out a new mode one of the best things to do is look at what is set by the user (ie, in AC you get rate, TV, PEEP where in APRV/bivent you have P1/P2 and T1/T2). it's confusing but once you get it it's like a lightbulb. good luck!
 
MeaCulpa said:
can anyone give me a lucid understandable discussion on the different vent settings seen in the unit and what they mean and what their significance is?
I have seen pts in the unit while I was on a surgery month, I'm an intern, and we read of the vent numbers and I have no clue what it all means, I have read about a few differents times on up to date, the icu book, and in lange anesthesia, but it doesnt seem to stick. I was hoping someone here can put it in real understandable terms and hopefullly it will stick with me.
As an example we walk into a pts icu room and we say
he is on a psv 12/5 fio2 of 40% down from 15/10 from yesterday. The day before he was on an AC of 12. I just sit there and am like??? I figure the lower pressure support is good but what the heck does it mean? I am guessing that being on AC is worse than PSV but that is b/c a resident told me that, but didnt explain why.
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Quick, dirty, and only half correct:
Assist Control: Gives a full breath every time the pt spontaneously breaths. The rate setting is how many breaths he gets if aint breathing (paralyzed). FIO is the percent of the air going thru the tubes that is oxygen.

SIMV: Dude gets a full breath a set number of times per minute while spontaneously breathing. So if it is set at 10 and he breates at 20 tiny shallow breathes, 10 will be big full breaths the other 10 will be little. If you use pressure support, then each breath will be bigger cause the remaining 10 little breathes will be provided extra pressure. Eventually at some pressure (in a normal pt) SIMV w/ pressure support will be basically the sme thing as AC.

PS: Vent provides pressure with spontaneous breates. If dude aint breathing, vent wont help on PS alone.

Your people on PS alone or decreasing PS with SIMV might be those who are being weaned. Your AC and SIMV with PS people are sick and have respiratory failure or paralyzed, and not being weaned. That may be why your friend said that AC is worse than PS...who knows....really dont know what to make of that statement.

Clear? Like mud?
 
Sounds like you need a good critical care nurse.😉
 
your question is very broad.

The answer would require a 3hour lecture to properly address it.

Try narrowing down your question a little.
 
militarymd said:
your question is very broad.

The answer would require a 3hour lecture to properly address it.

Try narrowing down your question a little.
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Or you could have johnnywad explain it in 10 minutes!😱
 
Areyoudouble hit the highlights well.
 
Or you could have johnnywad explain it in 10 minutes!😱
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1. Respiratory rate: This setting simply refers to the number of breaths per minute that the ventilator delivers.

2. FiO2: This indicates the amount of oxygen the ventilator delivers, expressed as a percentage.

3. Volume control: Mechanical ventilation is volume controlled. This setting means the ventilator is programmed to deliver a preset volume of oxygen and air, called the tidal volume (VT), regardless of the amount of pressure required to deliver the volume (a positive pressure alarm protects patients from dangerously high pressures).

4. Pressure control: An alternative to volume control that's indicated for some patients, pressure control simply means that pressure is the endpoint rather than volume. Thus, inspiration ends when a preset pressure is reached, regardless of the volume delivered.

5. Pressure-regulated volume control (PRVC): This type of mechanical ventilation is an alternative to strict pressure control, representing an attempt to obtain the best of both volume and pressure control. PRVC adapts to changing compliance of the lungs to adjust inspiratory time and pressure to maintain a preset tidal volume.

6. Assist control (AC): In this mode, the ventilator supports every breath, whether it's initiated by the patient or the ventilator. AC is often used to allow the patient to rest, because the ventilator does all the work. This high level of respiratory support is frequently required in patients who have been resuscitated, have acute respiratory distress syndrome, or are paralyzed or sedated.

7. Synchronized intermittent mandatory ventilation (SIMV): In this mode, not all spontaneous breaths are assisted, leaving the patient to draw some breaths on her own. For example, if your patient's ventilator is set on SIMV mode with a respiratory rate of 10 bpm, she will receive a breath roughly once every six seconds. She can also breathe on her own in between the machine-assisted breaths. Patients who need short-term ventilation benefit most from SIMV, but the choice of mode should be an individual decision.

8. Pressure support: Used alone or added to SIMV, this provides a small amount of pressure during inspiration to help the patient draw in a spontaneous breath. Pressure support makes it easier for the patient to overcome the resistance of the ET tube and is often used during weaning because it reduces the work of breathing.

Took about 5 minutes 😉

aredoubleyou did a fine job too.
 
It's sad that an Intern was not taught anything about ventilators before being thrown in an ICU rotation.
It's even worse that someone is suggesting to him to seek advice from an ICU Nurse!
I know it's not rocket science, but Interns should be taught by faculty not by nurses!
 
Planktonmd said:
It's sad that an Intern was not taught anything about ventilators before being thrown in an ICU rotation.
It's even worse that someone is suggesting to him to seek advice from an ICU Nurse!
I know it's not rocket science, but Interns should be taught by faculty not by nurses!
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Agree with the basic premise, but CCM nurses are actually good sources to learn from regarding vents, they work with them every day, especially on the basics of vents. You gotta respect people for the knowlegde and experience they have. The questions that meaculpa was asking, any icu nurse could easily explain...and prossibly better than the pulmonology attending who will get lost in the details. If u read icu book and an anesthesia text and its still not clicking then I see no prob with going to anyone for some help.

Likewise, you should realize where a subject may be outside a persons knowledgebase. A nurse probably wouldnt be an appropriate person to learn management of vents for asthma vs ards vs pulm oedema vs barotrauma etc, although they may have the right answer for that more times than not either, but often its based on pattern recognition than treating the underlying pathophysiology.
 
Agree with the basic premise, but CCM nurses are actually good sources to learn from regarding vents, they work with them every day, especially on the basics of vents. You gotta respect people for the knowlegde and experience they have. The questions that meaculpa was asking, any icu nurse could easily explain...and prossibly better than the pulmonology attending who will get lost in the details. If u read icu book and an anesthesia text and its still not clicking then I see no prob with going to anyone for some help.

Likewise, you should realize where a subject may be outside a persons knowledgebase. A nurse probably wouldnt be an appropriate person to learn management of vents for asthma vs ards vs pulm oedema vs barotrauma etc, although they may have the right answer for that more times than not either, but often its based on pattern recognition than treating the underlying pathophysiology.
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Nice post. A good respiratory terrorist would be a good resource for this as well....that's what they are paid to do.👍
 
Agree with the basic premise, but CCM nurses are actually good sources to learn from regarding vents, they work with them every day, especially on the basics of vents. You gotta respect people for the knowlegde and experience they have. The questions that meaculpa was asking, any icu nurse could easily explain...and prossibly better than the pulmonology attending who will get lost in the details. If u read icu book and an anesthesia text and its still not clicking then I see no prob with going to anyone for some help.

Likewise, you should realize where a subject may be outside a persons knowledgebase. A nurse probably wouldnt be an appropriate person to learn management of vents for asthma vs ards vs pulm oedema vs barotrauma etc, although they may have the right answer for that more times than not either, but often its based on pattern recognition than treating the underlying pathophysiology.
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DING DING DING DING! Outstanding! Agree with boner....RT could probably really help, especially with putting it all in layman's terms and being practical with it. Vents and boogers.....that's there job.
 
Oxygenation controlled by: PEEP and FIO2

Carbon dioxide levels controlled by: RR, TV, and DEAD SPACE.

I will start with VOLUME CONTROL PRESSURE LIMITED settings. You set the volume the patient wants. Then you set a pressure maximum that the vent can try and deliver that volume. The volume delivered is LIMITED by the maximum pressure limit you have selected. The danger with this setting is that if you leave the pressure limit high that the patient can get barotrauma.

paralyzed patient: Start them on Assist Control. You set a rate, a tidal volume, and boom there's your minute ventilation. Your patient will ALWAYS RECEIVE AT LEAST that amount of minute ventilation (RR x TV). IF your patient initiates a breath (a negitive pressure sensed by the vent) then the vent will deliver the pre determined tidal volume you have selected EVERY SINGLE TIME.

The good on AC: your patient will always receive a minimum minute ventilation which will be physiologically desired (assuming you know what youre doing). Your patient will always receive a set (and hopefully adequate) tidal volume.
The Bad: Patient can get wayyyyyyy to much minute volume if spont breathing and not properly sedated. If your patient is breathing wildly and sucking like mad on the tube he may either NOT get enough tidal volume OR will stack breaths and get auto peep.


Spontaneously breathing patient: SIMV with PRESSURE SUPPORT and PEEP. Every negative pressure sensed by the vent will deliver an assisted breath. This breath will either be pressure supported OR will be assisted with set tidal volume. HOWEVER if the patient is NOT BREATHING it will work exactly like AC! Heres how it works: You set resp rate of 10 and TV of 700. That vent will deliver 10 700 cc breaths a minute NO MATTER WHAT. They may either be synched with the pt's first 10 breaths (assuming hes making a respiratory effort) or they may just be time triggered by the LACK OF PT BREATHING......So what if the patient breaths 20x a minute? Well, the additional 10 breaths will be SUPPORTED with a pressure of whatever you want. The Pressure Support(PS) will drive up the patients tidal volume to, hopefully, a physiologically desiered level.

The good: Uhh...if your is patient breathing spontaneously it can be a usefull adjunct in that the patient MAY not have excessive minute volume delivered all the while of having vent support. Some additional crap out there on how maybe its "more physiologic" to keep the patient spontaneously ventilating. There ain't nothen physiologically normal about being on PPV with a tube in your throat.

The BAD: If you patient is breathing 30x a minute and getting crappy tidal volumes they are gonna tucker out. You may set a rate of 5 and a TV of 600 with PS of 12 and PEEP of 5 thinking that the patient only needs minimal support. Then something goofy happens and nobody puts things together that the patient is now in respiratory acidosis because of either tiring out or not maintaining respiratory effort (sedation, infarct of something, seizure, whatever).

Is one better over the other? I like AC, its the bomb, its what I learned on. Surgeons like SIMV. It really doesn't matter just as long as you know what you are doing. Remember if you are gonna wean somebody you DONT NEED TO HAVE EM ON SIMV FIRST. Thats some old bs. They used to keep turning down the RR on SIMV until all the patients breaths where just PS with PEEP. Well you just wasted 3 days. Just get em spont ventilating in the AM and get the trial going. that means turning off sedation.

You may also choose PRESSURE CONTROLLED VOLUME LIMITED setting on the vent. This is becomming more popular with ards patients. You want to keep plateaus down as well as tidal volumes. this allows you to really fine tune your vent. Its also great for people with blebs and potential BPF's (think status post lobectomy) where big pressures can get you into big trouble. Mess around with this mode.
The bad: You patient can get MASSIVE VOLUMES if you arent careful. Thus the patient can have VOLUTRAUMA..


PS with PEEP is the same damn thing as BIPAP except its through an ETT and not a mask. Its good for weaning trials in the am to get your RR/TV number and correlate it to the vitals and mental status in order to yank ye tube.

Thats the basics.

Remember sedation is OK in order to get their acid base and respiratory function back to normal while yer fine tuning your patient. Thats why AC is great with sedation. Just set it and ferget it.

Vent
 
you might also see a high PEEP with that PCV in ARDS cases. again, when alveolar recruitment is necessary.

nobody mentioned CPAP. AC to CPAP is not uncommon when weaning in the ICU. some docs like to place them on AC --> SIMV/PS --> CPAP while others just either see if they sink or swim by switching them straight to CPAP after sedation has been weaned off.
 
and please...ask an RT, not a nurse. most nurses get pissy because they think they're busy while many RTs love to talk about snot any day of the week.
 
markneil said:
and please...ask an RT, not a nurse. most nurses get pissy because they think they're busy while many RTs love to talk about snot any day of the week.
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Yeah its tough to find stuff to occupy your time between the q6 hour treatments.
 
Also remember that for spontaneous breaths in SIMV or CPAP, the pt needs pressure support just to "neutralize" the added resistance of an ETT or trach and the tubing of the vent. This requires pressure support settings of 10 for an ETT or 4 for a trach.
 
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