Basic Vent Modes MADE EASY - Ventilator Settings Reviewed

Summary

In this ICU Advantage video, Eddie Watson explains the fundamental modes of mechanical ventilation: volume control and pressure control. He details settings like tidal volume, respiratory rate, and positive end expiratory pressure (PEEP). Eddie also covers modes from most to least supportive, including assist control (AC), synchronized intermittent mandatory ventilation (SIMV), and pressure support, emphasizing their impact on patients' work of breathing and the importance of monitoring parameters like minute ventilation and peak inspiratory pressure.

Takeaways

• 🌟 Eddie Watson introduces the lesson on basic ventilator modes, emphasizing their importance for understanding mechanical ventilation.
• 📚 The two main categories of ventilator modes are Volume Control and Pressure Control, each with different modes and settings.
• 🔍 Volume Control modes ensure a set volume of breath is delivered to patients, with pressure varying depending on patient needs.
• 🛠️ Pressure Control modes focus on maintaining a constant pressure, with the volume delivered changing based on patient factors.
• 🌡 Key settings in Volume Control include Tidal Volume (VT), Respiratory Rate (F or RR), Oxygen Concentration (FiO2), and Positive End Expiratory Pressure (PEEP).
• 🆘 Positive End Expiratory Pressure (PEEP) is crucial for maintaining open alveoli and improving oxygenation, with typical settings ranging from 5 to 20 cm H2O.
• 💪 Pressure Support (PS) acts like a 'spotter' in the gym, providing an extra push of air to assist patients during spontaneous breaths.
• 📊 Monitoring parameters include Minute Ventilation (VE), Peak Inspiratory Pressure (PIP), and Plateau Pressure (Pplat), indicating lung compliance.
• 🔄 Assist Control (AC) mode provides full control over ventilation, delivering a set volume and rate, but can lead to excessive ventilation.
• 🔄 Synchronized Intermittent Mandatory Ventilation (SIMV) allows for patient-initiated breaths between mandatory breaths, facilitating weaning from the ventilator.
• 🔄 Pressure Support mode is a form of spontaneous breathing with no mandatory breaths, relying on patient effort and PS settings.

Q & A

What are the two main categories of ventilator modes discussed in the video?

The two main categories of ventilator modes discussed are volume control and pressure control.

What is the fundamental difference between volume control and pressure control modes?

In volume control modes, the volume of air delivered is constant while the pressure changes. Conversely, in pressure control modes, the pressure is constant while the volume of air delivered changes.

What is the purpose of the tidal volume (VT) setting in volume control modes?

The tidal volume setting determines the volume of air that is delivered with each breath to the patient.

How is respiratory rate, or frequency (F or RR), calculated in terms of breaths per minute on a ventilator?

Respiratory rate is the number of breaths delivered per minute, calculated by dividing the set respiratory rate into 60 to determine the time interval between each breath.

What does FIO2 represent and how is it expressed?

FIO2 stands for fraction of inspired oxygen, and it represents the concentration of oxygen in the air mixture a patient receives. It is expressed as a fraction or a decimal.

What is the significance of Positive End Expiratory Pressure (PEEP) in a ventilator setting?

PEEP is a constant pressure applied throughout expiration to help keep alveoli open, improving oxygenation. It's similar to CPAP or BiPAP in non-invasive ventilation.

Why is Pressure Support (PS) used in volume control modes?

Pressure Support provides an extra push of air to assist patients during spontaneous breaths, similar to a gym spotter, helping them overcome the resistance of breathing through an ET tube.

What is minute ventilation (VE) and why is it important?

Minute ventilation is a measure of the amount of air delivered to a patient per minute, calculated by multiplying tidal volume by respiratory rate. It's crucial for understanding how much air is being delivered and for adjusting CO2 clearance.

What does Peak Inspiratory Pressure (PIP) indicate and what is the target range for it?

PIP indicates the maximum pressure reached during inspiration. The target is to keep it below 35 cm H2O to prevent lung injury.

Why is Plateau Pressure important in volume control modes?

Plateau Pressure is an indication of lung compliance. It is measured at the end of inspiration and should be under 30 cm H2O to prevent barotrauma.

How does Assist Control (AC or VC) mode differ from Synchronized Intermittent Mandatory Ventilation (SIMV) mode?

In AC mode, the ventilator delivers a full set tidal volume for both mandatory breaths and spontaneous breaths initiated by the patient. In SIMV mode, the ventilator delivers a set number of mandatory breaths, but spontaneous breaths can vary in volume and are assisted by pressure support.

What is the role of SIMV in the weaning process of a patient from a ventilator?

SIMV allows patients to gradually take over their work of breathing by reducing the number of mandatory breaths, increasing the patient's own respiratory effort, and facilitating the weaning process.

Why is Pressure Support often the last step before extubating a patient?

Pressure Support mode allows patients to breathe spontaneously with only the assistance of the set pressure support, making it a trial to assess their ability to breathe independently before extubation.

Outlines

00:00

😷 Introduction to Basic Ventilator Modes

Eddie Watson introduces the topic of basic ventilator modes, emphasizing the importance of understanding these modes for future discussions on alternative modes. He aims to simplify complex critical care topics through his channel, ICU Advantage. Eddie encourages viewers to subscribe and turn on notifications for new lessons and acknowledges the support of subscribers and the input of 'respiratory coach' in refining the content. The script then transitions into an explanation of positive pressure ventilation, distinguishing between volume control and pressure control modes. Volume control focuses on delivering a set volume of air, with pressure varying, while pressure control does the opposite, maintaining a constant pressure and varying the volume of air delivered.

05:02

🔍 Settings and Concepts in Volume Control Ventilation

The paragraph delves into the specifics of volume control ventilation, starting with the explanation of tidal volume (VT), which is the amount of air delivered per breath. It then moves on to respiratory rate (RR or F), which dictates how many breaths are given per minute. The script discusses oxygen concentration (FiO2) and its representation as a fraction or decimal, and the importance of positive end expiratory pressure (PEEP) in maintaining alveoli open. Pressure support (PS) is introduced as a form of assistance during spontaneous breathing, likened to a gym spotter, with typical settings ranging from five to twenty. The paragraph concludes with a discussion on monitoring parameters such as minute ventilation (VE), peak inspiratory pressure (PIP), and plateau pressure (PLAT), which are crucial for assessing a patient's tolerance to ventilation.

10:03

🛑 Detailed Explanation of Ventilator Modes and Settings

This section provides a deeper look into the volume control modes, starting with Assist Control (AC or VC). It explains how AC delivers a set volume at a set frequency, with no pressure support, and how it can lead to excessive ventilation if the patient has high respiratory drive. Synchronized Intermittent Mandatory Ventilation (SIMV) is then introduced as a mode that mandates a minimum number of breaths but allows the patient to determine the size of their spontaneous breaths, with pressure support assisting these efforts. The paragraph highlights the importance of monitoring the patient's response to the work of breathing and adjusting the mode and settings accordingly to prevent complications like respiratory alkalosis or acidosis.

15:04

🌐 Transitioning from AC to SIMV and the Role of Pressure Support

The script clarifies the operational differences between AC and SIMV, noting that SIMV allows for patient-initiated breaths between mandatory breaths, which can help improve patient-ventilator synchrony. It discusses how SIMV can be used as a weaning tool, gradually reducing the support provided by mandatory breaths to encourage the patient to take over their work of breathing. The paragraph also touches on the risks associated with SIMV, such as the potential for the patient to become tachypneic or hyperventilate, leading to respiratory alkalosis, or to retain CO2, leading to respiratory acidosis.

20:06

💨 Understanding Pressure Support and Its Role in Ventilation

The final paragraph discusses pressure support as a mode of spontaneous breathing that is not technically a volume control mode, as it does not set a specific volume but rather assists the patient's effort. It explains that in pressure support mode, only FiO2, PEEP, and pressure support are set, with a backup rate provided as a safety measure. The script notes that pressure support is often used as a trial before extubating patients, with settings typically at 10 over 5 (10 cm H2O pressure support and 5 cm H2O PEEP). The paragraph concludes by summarizing the progression from the most to the least supportive modes, reflecting the transition from full mechanical support to full patient effort.

Keywords

💡Ventilator Modes

Ventilator modes refer to the different settings and operations of a mechanical ventilator used to assist or control ventilation in patients who cannot breathe adequately on their own. In the video, the speaker discusses various basic ventilator modes, emphasizing the importance of understanding these modes for healthcare professionals dealing with critical care. The ventilator modes are divided into volume control and pressure control categories, each with different modes affecting the patient's work of breathing.

💡Volume Control

Volume control is a category of ventilator modes where the primary focus is on setting and controlling the volume of air that patients receive. The ventilator delivers a set volume of air with each breath, and the pressure required to deliver this volume can vary from patient to patient. The video explains that volume control modes ensure a constant volume is delivered, with pressure being the variable that changes.

💡Pressure Control

Pressure control is another category of ventilator modes where the ventilator controls the pressure delivered to the patient's lungs. Unlike volume control, where volume is constant, in pressure control, the pressure is constant, and the volume can change. This mode is discussed as having benefits that will be covered in a future lesson, indicating its importance in advanced respiratory care.

💡Tidal Volume (VT)

Tidal volume refers to the amount of air inhaled and exhaled in a single breath, measured in milliliters (mL). In the context of the video, tidal volume is a key setting in volume control modes, determining the volume of air delivered with each breath to the patient. The script mentions that this setting is crucial for maintaining proper ventilation.

💡Respiratory Rate (RR or F)

Respiratory rate, also known as frequency, is the number of breaths taken per minute. The video explains that this setting is essential as it dictates how often the ventilator delivers the set tidal volume to the patient. The rate is used to calculate the time interval between breaths, which is critical for maintaining the patient's ventilation.

💡Fraction of Inspired Oxygen (FiO2)

FiO2 represents the concentration of oxygen in the air being delivered to the patient. The video script mentions that FiO2 is crucial for improving a patient's oxygenation and is set as a fraction or decimal, not as a percentage. For example, 50% oxygen is set as 0.5 in the ventilator.

💡Positive End Expiratory Pressure (PEEP)

PEEP is a setting on the ventilator that maintains a constant positive pressure in the lungs at the end of exhalation. The video script describes PEEP as helping to keep alveoli open, similar to CPAP or BiPAP in non-invasive ventilation. It is an important setting for managing a patient's oxygenation and preventing lung collapse.

💡Pressure Support (PS)

Pressure support is a setting that provides additional pressure to assist the patient during spontaneous breathing efforts. The video likens it to a 'spotter' at the gym, giving an extra push of air to help the patient with their breath. It is used in modes that allow for spontaneous breathing and is set to overcome the resistance of the endotracheal tube.

💡Assist Control (AC or VC)

Assist control is a ventilator mode that ensures the patient receives a set volume of breaths per minute, whether initiated by the ventilator or the patient. The video explains that in assist control, every breath is a full mandatory breath, which can lead to excessive ventilation if the patient has an increased respiratory drive.

💡Synchronized Intermittent Mandatory Ventilation (SIMV)

SIMV is a mode that provides a minimum number of mandatory breaths set by the ventilator, but also synchronizes with the patient's spontaneous breaths. The video script explains that SIMV allows the patient to take over some of the work of breathing, which is beneficial for weaning patients off the ventilator and for those who need partial support.

💡Minute Ventilation (VE)

Minute ventilation refers to the total volume of air inhaled or exhaled per minute. In the video, it is described as one of the most important parameters to monitor because it reflects the effectiveness of the ventilator in delivering the set tidal volume multiplied by the respiratory rate. It is a key indicator of the patient's CO2 clearance.

Highlights

Introduction to different basic ventilator modes commonly used in critical care.

Importance of understanding basic modes for comprehending alternative ventilation modes.

Eddie Watson's goal to simplify complex critical care topics.

Encouragement for viewers to subscribe and select notifications for updates.

Acknowledgment of subscribers and Respiratory Coach for their support and contributions.

Explanation of positive pressure ventilators and their various modes.

Two main categories of ventilator modes: volume control and pressure control.

Volume control focuses on setting and controlling the volume of air delivered to patients.

Pressure control focuses on controlling the pressure delivered to patients.

Key difference between volume control and pressure control: constant volume vs. constant pressure.

Discussion of volume control modes and their impact on patient's work of breathing.

Explanation of tidal volume (VT) as the volume of air delivered with each breath.

Frequency (F or RR) determines the number of breaths per minute.

Oxygen concentration (FiO2) is crucial for patient oxygenation.

Positive end expiratory pressure (PEEP) helps keep alveoli open.

Pressure support (PS) assists patients during spontaneous breaths, likened to a gym spotter.

Monitoring parameters include minute ventilation, peak inspiratory pressure, and plateau pressure.

Assist Control (AC or VC) mode provides full control over patient's minute ventilation.

Synchronized Intermittent Mandatory Ventilation (SIMV) allows patient-initiated breaths.

SIMV is beneficial for weaning patients off the ventilator.

Pressure Support mode relies on patient effort with assistance from set pressure support.

Progression from most supportive to least supportive modes in terms of patient's work of breathing.

Invitation to support the channel through Patreon for additional content.

Transcripts

[Music]

all right you guys welcome back to

another video lesson in this lesson

we're gonna be taking a look at the

different basic ventilator modes that

you're commonly gonna come across these

are the modes that you're gonna see more

often than not and it's gonna be

imperative that you guys have a good

understanding of these so that in the

future when we talk about and you also

come across some other alternative modes

of ventilation you have this as a

baseline in which to understand some of

these other modes and my name is Eddie

Watson and I welcome you to ICU

advantage my goal here with ICU

advantage is to take these complex

critical care topics and really break

them down for you and make them easy to

understand for you guys I hope that I'm

able to do just that and perhaps by the

end of this video I'll have learned a

subscription from ya if you do make sure

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never miss out on a new lesson as always

a special shout out to all of our

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watch like and support our Channel

really without you guys in your support

this channel would be nothing once again

another quick shout out to respiratory

coach another channel here on YouTube he

was super helpful in reading through the

notes on this lesson and making sure

that I had all of the key points that I

really needed to get across to you guys

if you haven't seen this channel yet

he's got a bunch of really awesome

videos on topics related to respiratory

therapy so make sure you guys head on

over there check out some of his videos

and subscribe to his channel alright and

with that said let's go ahead and get

started here and let's really start this

lesson off and begin with a quick

introduction to the topic of our basic

ventilator modes so in the previous

lesson which if you haven't watched it

yet I'm linking to it up above and down

in the description I provided you guys

with an introduction into the world of

invasive mechanical ventilation in that

lesson I talked about how pretty much

all of the ventilators that we use today

are all forms of a positive pressure

ventilator and within the world of

positive pressure ventilation there

really are many different types or modes

as we call them that our ventilators can

really operate in in this lesson here

I'm gonna be covering the basic vent

modes to try to really give you guys a

good understanding of the most common

modes that you're gonna come across in a

future lesson I am gonna take a look at

some of the more advanced modes that you

may very well come across now when we

take a look at our different vent modes

there's really two main categories that

you're really gonna come across the

first of these is something that we call

volume control and the other is

something that we call pressure control

so first let's take a look at volume

control here and I'm actually going to

take a look at some of these modes here

in just a minute but really the basis of

this category is that we're gonna be

setting and controlling the volume of

air that our patients get and the way

the vent does this is it delivers this

volume by providing pressurized air

causing it to move into the patient's

lungs now depending on many factors the

pressure that's required to deliver this

volume can and certainly will change

from patient to patient and from breath

to breath this right here is a very

important fact for you to remember so

now if we move over and quickly talk

about pressure control here the reverse

is taking place in pressure control

we're going to be controlling the

pressure that we deliver to our patients

and there are many benefits to pressure

control which we are going to discuss in

the next lesson on those advanced modes

but the thinking and understanding of

these modes is different than our

natural intuition now similar to like we

had just talked about with volume

control depending on many factors the

volume of air as opposed to the pressure

of air that is going to be delivered can

and will change from patient to patient

and breath to breath once again this is

going to be a very key point and this

really summarizes the main difference

between our volume control and our

pressure control as I mentioned here

volume control our volume is constant

and our pressure is the changing

variable whereas in pressure control

our pressure is constant and the volume

is our changing variable so a very key

important distinctive concept to know

now within each of these main categories

there really are many different modes

and even some that kind of cross in

between both of these modes here but for

the purpose of this lesson we're gonna

be sticking to just talking about volume

control so like I said the main

principle for volume control here is

that we want to ensure that our patients

are receiving a set volume of breath

each minute and like I said within this

category we have different modes that

are ultimately play a different role in

the impact on our patients work of

breathing in order to understand the

differences between these modes though

we really need to talk about some of the

settings and some of the things that

we're going to be looking at on our vent

alright so the first thing that we're

going to talk about in our settings is

something that we call our tidal volume

and this you'll see in the setting VT

and essentially our tidal volume is the

volume of air that set to be delivered

with each breath to our patient all

right the next setting that I want to

talk about is something that we call

frequency also known as our respiratory

rate and this will no usually find

abbreviated as either F or RR and this

one should be pretty self-explanatory

but it's how many breaths per minute are

being delivered to our patient now it's

important understand how this works and

how this triggers for a breath to be

given is it will actually take the

respiratory rate that you set and divide

that into 60 to figure out the amount of

time that we should have between each

individual breath and we'll talk about

it more here in a minute but when that

amount of time has elapsed then it

triggers another breath to be given all

right the next setting that we're going

to cover here is going to be our oxygen

concentration and this is what we refer

to as our fio2 and fio2 really means our

fraction of inspired oxygen this is

important to know because when we are

referring to our fio2 oftentimes we'll

say we're on 50% we're on 80% but really

we need to understand that this number

is being expressed as a fraction or a

decimal so when we say we're on

fifty percent our fio2 setting is

actually going to be 0.5 if our patients

on a hundred percent fio2 then we have

an fio2 of 1.0 so the next setting that

I want to talk about in the world of

volume control is a setting called

positive end expiratory pressure this is

something that we more commonly referred

to as peep so thinking back to one of

our previous lessons where we covered

non-invasive ventilation think of peep

as being really similar to CPAP or BiPAP

on a BiPAP machine essentially this is a

constant pressure that's going to be

applied throughout expiration to really

help an open and keep open alveoli now

it's peep along with our fio2 which is

how we really help to improve our

patient's oxygenation and so for this

setting it's really important that we

maintain at least 5 centimeters of water

to help to provide what we call

physiological peep and the reason for

this is because of the ET tube that we

have in our patient that this can

actually allow the intrathoracic

pressure to fall to zero which would not

be a good thing now the range of

settings that will usually see for a

peep is typically in the range of 5 to

20 and since they didn't mention in a

minute ago for our fio2 we typically

aren't going to find that any lower than

35% or 0.35 and this can obviously go up

to a hundred percent alright and so the

final setting that i want to talk about

here in this world of volume control is

something that we call pressure support

this one you'll see abbreviated as PS

and the best analogy that I can really

give you for pressure support is if you

really think about this as a spotter at

the gym so this is really an extra push

of air to assist our patients when

they're taking spontaneous breaths so if

you think about that spotter is there to

kind of help provide a little bit of

pressure and support as you're going

through doing some sort of exercise

that's kind of the same thing that's

happening with our pressure support only

in this case we're helping our patients

take a breath so if you really think

about this the more pressure support

that we apply the larger the spontaneous

breath that a patient's going to be able

to take with Morris's

our settings usually for pressure

support you're gonna find in the range

of five to twenty typically though we're

gonna keep it at a minimum of anywhere

from eight to ten and this is really to

help overcome the resistance of having

to breathe through that ET tube actually

out there if you take the time to look

for it there is a chart that does a

breakdown based on the ET tube size and

how much pressure support it really

requires to overcome that resistance if

I happen to find it I'll link to it down

in the description but it's an

interesting chart and it really drives

home the point that just because of the

size and the resistance of that ET tube

we're already gonna have to give them

some sort of assistance because if we

gave them nothing breathing through that

ET tube would actually be harder to

breathe through than if they were

normally breathing alright so those are

all the settings that you're gonna need

to know when we're talking about these

different modes of volume control lastly

I do want to talk about a couple of the

different things that we're going to be

looking for in the monitoring of our

patients on the vent and I'm gonna go

through a couple different parameters

that you're gonna see on your vent but

just know that these parameters that I'm

listing here are far from all of the

parameters that are really important in

truly understanding how your patient is

tolerating being on the vent but again

this is where the respiratory therapist

comes in because this is their area of

expertise over time it certainly is

great to learn about a lot of these

different settings and different numbers

that you get on there but for a basic

understanding I'm gonna give you a

couple things that are going to be

really important the first of these is

going to be something that we call our

minute ventilation and this you'll see

abbreviated as ve now this one's

probably the most important one for you

to understand and that's because this is

a measure of the amount of air that's

being delivered to our patient per

minute so it's important to know how we

get this number and really in a perfect

world our minute ventilation would be

our tidal volume times our frequency and

if you really just kind of think about

that for a minute if we take the volume

of air that we're delivering with each

breath and then multiply that by how

many breaths were giving per minute

should tell us what our volume of air

that we delivered to our patient over

the course of a minute would be now as

we know we don't live in a perfect world

so we have to deal with things like

inefficiencies triggering pressure

limits and really the patient's own

response can and do impact the actual

delivery of air that they get but if you

do have to increase or decrease your

patients minute ventilation to do

something like let's say control our PA

co2 on an ABG then we're going to be

looking to adjust our patients minute

ventilation and again because we should

be keeping our tidal volume set based

off our patients ideal body weight then

really we know that if we need to be

making changes to our minute ventilation

we probably want to be adjusting our

respiratory rate the core concept here

is if we have more minute ventilation

we're gonna have more co2 clearance

hence less minute ventilation less co2

clearance and the goal for a patient's

minute ventilation is going to be from 5

to 10 liters per minute all right the

next thing I want to talk about it's

actually going to be the first of two

different pressures here it's gonna be

something that we call our peak

inspiratory pressure and this one you'll

see abbreviated as our pip now I'm not

going to go too far into some ventilator

Theory here but essentially our pip is

the maximum pressure that's reached

during inspiration and the goal here for

our pip is to have this less than 35

with the goal of preventing lung injury

now the last setting and the last

pressure that I actually want to talk

about here is something that we call our

plateau pressure and this one's

abbreviated RP plat and when we talk

about some of these pressures and volume

control the plateau pressure is going to

be probably one of our most important

ones to keep an eye on because this

one's going to be an indication of our

lung compliance so we measure this one

at the end of inspiration with an

inspiratory hold or pause maneuver and

we really want to be shooting to have

our plateau pressure under 30 and this

is really to help prevent Barrow trauma

so important to know plateau pressure

means lung compliance if we see an

increasing plateau pressure this can

signal that there's some sort of problem

with our patient's lung compliance all

right so those are the settings and some

the major important things that we want

to be monitoring for in terms of numbers

on the ventilator and so now let's go

ahead and move on and talk about the

different volume control modes so I'm

going to go through and talk about a few

different modes that we're gonna see

here and it can really help to think

about these modes as being from the most

supportive to the least supportive in

terms of our patient's work of breathing

alright so the first of these modes that

I want to talk about is something that

we call assist control this is something

that you'll see abbreviated either AC or

VC for volume control now you may also

see people interchange this with CMV but

there actually is a very important

distinction and I'll kind of explain

that difference here in a minute when we

get to that so when we talk about assist

control there's a couple settings that

are going to be really important for

this mode obviously we're going to have

because it's a volume control we're

gonna have a predetermined volume set

for each breath so a VT or tidal volume

and we're also going to set the number

of breaths per minute or the frequency

for our patients in addition to that

we're also going to set an fio2 as well

as a peep important distinction here is

we are not going to have a pressure

support now let me try to explain why so

we know based on our tidal volume and

our frequency that every so often we're

gonna give the patient a set volume of

breath so if we had a tidal volume of

let's say 500 and a respiratory rate of

12 we know every five seconds we're

gonna give this patient a breath of 500

MLS and this is essentially what CMV or

control ventilation does whatever the

set number of breaths are and the volume

to be delivered the vent just continues

to pump that out one after another after

another and there is no derivation from

that no matter what the patient needs or

what they're trying to do they're just

going to continue to get at the same

frequency the same volume of breath

where assist control comes in is this

actually will take into account the

patient trying to take their own breath

so what happens here in assist control

is if a patient attempts to take their

own breath this is what we call

spontaneous breath that the ven is gonna

recognize this breath but it's going to

deliver the full set tidal volume so the

vent is either gonna deliver breath to

the patient when it's time or if the

patient tries to initiate their own

breath the vent is going to recognize it

but say I know you want a breath here

have the full breath and because of this

this is why we don't have a pressure

support because we're not gonna aid the

patient in taking a spontaneous breath

we're just going to detect that they

want a breath and then give them a full

breath so this sounds wonderful except

the fact that this can actually lead to

excessive ventilation especially if our

patients are too kipnuk for non

respiratory related reasons so here this

to Kipp Nia will lead to blowing off too

much co2 and ultimately lead our patient

into a respiratory alkalosis if you want

kind of a review on this I'm gonna link

to ABG lesson up above as well as down

in the description but here if you think

about if your patients in pain if they

have anxiety or even if they have some

sort of central nervous system

dysfunction causing them to have this

abnormal - Kipp Nia that this can

ultimately lead to blowing off too much

co2 when we physiologically normally

wouldn't want that now often times

though we will initially use AC when

we're intubating a patient as we really

have the full control over our patients

minute ventilation as well as fully

taking over their work of breathing

alright so because of some of these

problems that we just talked about with

assist control and also because of a

desire to want to be able to have a mode

that can really help with weaning our

patients down off the ventilator

another mode was developed and it's

something that we call synchronized

intermittent mandatory ventilation

something that goes by the name simv so

essentially with simv we're still going

to determine or mandate hence the name

mandatory that a patient gets at least a

set volume and a set number of breaths

per minute again for this we also will

set an fio2 and a peep so so far this is

looking just like a sis control

the big difference now when we compare

this to AC is what happens when a

patient takes their own spontaneous

breath in simv instead of delivering the

set volume of air the patient's actually

going to be allowed to take whatever

size breath they can and so now the

breaths that were delivering through the

vent are actually going to be

synchronized with the patient's own

spontaneous breaths to really help to

increase their vent compliance so

essentially as long as they take a

breath in a predefined window between

each of the two mandatory breaths then

if they go to initiate that breath then

whatever breath they take the size the

volume that they get is what they get if

they happen to take that breath right

about the time that another mandatory

breath is going to come the vent is

going to recognize this but similar to

AC is it's then going to go ahead and

give that full set tidal volume this

ensures that we're maintaining at least

that mandatory minimum level of minute

ventilation so because the fact that our

patients are able to take their own

spontaneous breath that this is where we

actually are going to set a pressure

support here and again the point of this

pressure support is to assist them in

taking their spontaneous breath if we

notice that our patient is taking too

small of the spontaneous breath we can

increase this pressure support to really

help them achieve a larger spontaneous

breath so now a quick test of

understanding here let's say you have a

patient who has just been intubated and

they are currently sedated and paralyzed

still from the intubation if you were to

put this patient now in to assist

control or if you were to put this

patient into simv with all of the same

settings other than the pressure support

that you'd set in simv

what would be the difference that you

would see in your patient on the vent

now well hopefully you realize that that

was a trick question

because there's going to be no

difference between these two so if a

patient is taking no spontaneous breaths

simv is going to be indistinguishable

from AC and if you really kind of think

this one through if they're paralyzed

and they're not taking their own

spontaneous breaths we do have a

frequency and a tidal volume set

so again if we think of that example of

a volume of 500 and a frequency at 12

every five seconds we're gonna give this

patient 500 tidal volume and this is

just gonna go over and over and the

patient doesn't take any spontaneous

breath that's all that they're gonna get

well if they were an AC again they're

gonna still be getting every five

seconds of volume of 500 and again

they're not taking any spontaneous

breaths so that's all that they're gonna

get as well and these two modes are

going to be completely indistinguishable

from one another now simv is really good

because it can actually allow patients

to gradually take back over their work

of breathing over time and so the less

support that we give them with the

mandatory breaths the more work of

breathing that the patient is going to

need to take on on their own and so like

I said simv was initially developed with

the help of really weaning patients from

the vent but often we find it as one of

our primary modes of ventilation because

of the fact that some of the work of

breathing is on the patient it really

requires close observation of our

patients physiologically as well as

psychologically to see how they're

responding to this work of breathing now

our patients may be at risk of becoming

tachypneic hyperventilating and leading

themselves into a respiratory alkalosis

but again because we're relying on them

for some of the work of breathing if

they're minute ventilation just isn't

sufficient for what they need they're

not taking enough breaths or large

enough breaths then we can go to the

other side of things and be retaining

co2 leading to a respiratory acidosis

all right so the last mode that i want

to talk about here is something that we

call pressure support now oftentimes

you'll hear this referred to as CPAP let

me tell you this is not CPAP please

don't call it that and in talking about

pressure support this actually

technically isn't a volume control mode

of ventilation because in volume control

we are setting and controlling the

volume that our patient is getting and

pressure support is a form of

spontaneous breathing so for patients in

this mode we're only going to set an

fio2 a peep and a pressure support so

there's not going to be a tidal volume

or a rate set for the

patience although that said most vents

do have a safety mechanism in place

something that we call backup rate so in

the event that our patient goes APNIC

this backup rate is gonna kick in and

take over until we reset it now here in

pressure support minute ventilation and

thus our patients work of breathing will

be almost entirely dependent on the

patient's effort with the assistance of

whatever we set our pressure support at

so oftentimes you'll see this used as

our last step or trial before excavating

patients typically if we do have our

patients and pressure support and we are

doing this spontaneous breathing trial

we usually have them set at 10 over 5

which is 10 of pressure support and five

of PEEP or for a very short run

sometimes we will run them 5 over 5 and

again this is going to be a short run

just prior to excavating all right so

that finishes up our discussion here

talking about the different vent modes

hopefully these modes make sense you can

see that we're looking at some of the

same settings were functioning very

similar in terms of volumes that were

being delivered but where some of the

key differences come in is how we handle

a patient's spontaneous breath from CMV

or control ventilation where we pretty

much don't acknowledge that at all

down through recognizing those breaths

but giving the full breath an AC to simv

where the patient will determine the

size of their breath all the way down to

pressure support where the patient's not

going to get any mandatory breaths and

everything's going to be based on their

own work of breathing like I said it's

sort of this progression from the most

amount of support and the most effort

and the most coverage taking over of our

patients work of breathing down to the

least amount all right and with that

said I do want to thank you guys so much

for watching if you found this lesson

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