General Ventilator Set-up, by Nancy Craig.
Hello, I'm Nancy Craig.
I'm one of the Respiratory Therapists here at Children's Hospital in Boston, and I'm
here to review some of the general setups of an ICU ventilator.
Ventilator Preparation.
This first chapter will demonstrate how to attach the components of a ventilator, prior
to patient use.
Most of the ventilators will have some sort of an expiratory filter for exhaled gases.
The humidifier that all ICU ventilators will have to warm up the gas, delivers humidity
to the patient.
The tubing is either disposable or non-disposable.
If it's disposable, it will be thrown away after each patient use.
If it's non-disposable, it will be sent to be cleaned.
The inspiratory end of the ventilator is connected to the humidifier.
The expiratory end is connected to that expiratory filter.
And there is a piece of tubing that goes from the inspiratory end of the ventilator to the
top of the humidifier.
The circuit then will require a temperature probe for use with the humidifier, which monitors
the temperature back at the ventilator, and then close to the patient's airway.
Now I'm going to show you how to turn the ventilator on and hook it up to the patient.
All ICU ventilators -- I'll turn it around here -- require a power source.
Most of them do have batteries, but the power supply is fairly limited.
And they all will require a high-pressure oxygen source.
This particular ventilator has an air compressor, so it doesn't necessarily need a high-pressure
air source.
If your ventilator does not have a compressor, for it to function you'll need a high-pressure
air hose as well.
The oxygen and the air get hooked up to a 50 PSI source.
The power knob is generally on the back of the machine.
High-pressure Leak Test.
When powering up a ventilator, it will typically ask you to perform a high-pressure leak test,
so that we make sure that the ventilator is good to go before placing on a patient.
I'm going to perform an EST, which is a high-pressure leak test, to make sure that the tubing has
no leaks.
The ventilator instructs you to make sure that you're not on a patient, that your wye
is capped, and it will prompt you to proceed with the high-pressure test.
Here, the extended system test is checking for leaks in the circuit; it's performing
a circuit compliance test to see what the distensibility of the tubing is; and it's
also performing a test of the oxygen sensor.
If there are any leaks in the circuit, then the ventilator will not pass its EST.
If it does not pass its extended system test, then we'll systematically go through and see
where the sources of leaks may be.
Those leaks may be in the humidifier, they may be in some of the connections to the ventilator,
or it might be that the leaks are in the circuit itself.
So there's lots of places where pieces are put together that could be prone to leaks.
Once your ventilator has passed the test and you are assured of its integrity, then we
can continue on.
This particular ventilator asks you to input a patient weight, so that it can figure out
some calculations related to tidal volume.
Initial Ventilator Settings.
After the patient is intubated, there's a period of time where the patient is manually
ventilated and pressure is monitored so that you can have a sense of how much pressure
it takes to visibly move the chest.
So here, it's taking about 25 cmH2O to move the chest, so that is where I will start my
ventilator initially.
I have chosen a pressure control mode for this patient that's just been intubated, and
I'm going to set some, just sort of, initial settings before placing the patient on the
ventilator.
So on this ventilator, typically we start -- depending on the disease state of the patient
-- at 5 cmH2O of PEEP.
To set my pressure, I'm going to -- as I said, it took about 25 cmH2O to move the chest.
On this ventilator I'm setting a change in pressure; so I'm going to start here at 25
cmH2O of PIP and 5 cmH2O of PEEP.
The breath rate is generally based on the size of your patient.
This is a smaller patient, so I'm going to start with a higher rate, something like 18
breaths/minute.
Inspiratory times, again, depending on the size of the patient, should be in the range
of about 0.5-0.8 seconds.
My patient is not breathing, but I'll add a little bit of pressure support ventilation
just in case there is a spontaneous effort.
And that amount of pressure support is generally initially based on the size of the endotracheal tube.
I will set a flow trigger, here, so that the ventilator and the patient are interacting
with each other, in terms of spontaneous breathing.
And after a patient is initially intubated, it's fairly typical to start the fraction
of inspired oxygen at 100%.
So now I'm ready to place the ventilator on the patient.
End-tidal CO2 Monitoring.
Ventilator is ready to go; I'm going to actually attach the end-tidal CO2 monitor next.
This is the cable to monitor end-tidal CO2, and this is the adapter that gets fit onto
the airway.
Depending on the patient's size, you'll have a different size end-tidal CO2 monitor.
The adapter is then positioned between the ventilator circuit and the airway of the patient.
The end-tidal CO2 monitor is placed in line with the ventilator circuit to not only non-invasively
monitor end-tidal CO2, but also to monitor the integrity of the airway.
When I'm monitoring end-tidal CO2, I'm looking at not only the value itself, but also the
shape of the end-tidal capnogram.
So I should see a nice exhaled wave that flattens out at the top, to know that my patient is
fully exhaling.
If there is a sudden loss of end-tidal CO2, that will alert me to a problem with the integrity
of the endotracheal tube.
The first thing I would do is to make sure that the ventilator components are hooked
up to the airway.
If they're hooked up to the airway and I still do not have an end-tidal CO2 tracing, then
the next thing I would assume is that I've lost the endotracheal tube from the patient.
Initial Patient Assessment.
When I initially place the ventilator circuit on the patient's endotracheal tube, I'm looking
immediately for chest rise.
Here I'm seeing the patient's chest is visibly rising, and then I come back to the ventilator
to look at some of my parameters.
I would like to set a goal for mechanical breaths of about 8-10 cc/kg.
So that is where I'm monitoring here.
So I'm just a little bit below my target, but looks like the patient is doing okay right now.
Ventilator Alarms.
Once I have established the patient on the ventilator and I'm happy with the way the
patient looks, then I'm going to set my alarms on the ventilator.
The alarm screen is accessed here and these alarms are fairly typical of all ICU ventilators.
I'm going to want to set a high respiratory rate so that I am alerted to a change in the
patient's condition, in terms of how fast they're breathing.
Typically -- the patient is not breathing now -- you would set that alarm at about twice
what the respiratory rate is.
So here I'm going to set it just around twice of the rate of 18. The next very important
alarm limits are the low and high minute ventilation alarms.
I'm going to take you back to this screen.
And remember that minute ventilation is a calculation of respiratory rate times tidal
volume.
So on this ventilator, I will set a low and high minute ventilation to alert me to some
change in the patient's condition, in terms of monitored tidal volumes.
Then I'm going to set it roughly half for the lower limit and twice for the upper limit.
Then it's very important to set a low peak pressure in case there is a leak in the circuit,
and the pressure does not reach what is set, then the alarm will alert you to a low pressure
situation.
And this I set somewhere between the PEEP and the peak inspiratory pressure.
And then the next alarm is the high peak pressure.
This is a very important alarm as well because this will alert the clinician to a change
in peak pressure that's high -- maybe an obstructed airway or a lot of secretions in the tube.
If there's any reason that the peak pressure is higher than what you have set, you would
want to troubleshoot that condition.
That alarm is typically set about 5-10 cmH2O above your monitored peak pressure.
And then I'm going to set an apnea interval.
The apnea interval is going to be based on the size of your patient.
So if your patient is not on a rate, and breathing all on their own, then I would want to be
alerted to a time when there is a pause in spontaneous respirations.
On a bigger patient, I might set it around 20 seconds.
On a smaller patient, I might set it closer to 10 seconds.
So if my apnea interval alarms, then I know that there's a period of time that the patient
has not made a spontaneous effort.
On this ventilator, if the apnea interval alarms it will switch to back up ventilation.
I have a low PEEP alarm, which alerts me to a potential leak in the circuit, and I'm not
maintaining a baseline pressure.
So I will typically set that about 2 cmH2O below my set PEEP.
The other two alarms I set are low end-tidal CO2 and high end-tidal CO2.
A low end-tidal CO2 may alert me to a situation where the patient's status is improving, or
they're breathing faster and their end-tidal CO2 is a little bit lower.
Or if they're not getting an adequate amount of ventilation and their end-tidal CO2 rises,
I would want to know that as well.
Assessment and Monitoring.
There should be an assessment of the monitor parameters and alarm settings at least every
3 to 4 hours.
So on this patient, I'm in a pressure control mode, so I'm going to very closely monitor
the exhaled tidal volume parameters.
And I'm going to set my alarms to alert me if my tidal volume parameters are lower.
In a volume-targeted mode, then I'm going to closely monitor my peak inspiratory pressures
because that value will change, and I will closely monitor and alarm for a high peak
inspiratory pressure.
Depending on the severity of the patient and depending on the frequency by which you're
making changes in the parameters on the ventilator, will determine if you would be doing an assessment
more frequently.
In addition to the parameters that I'm monitoring on the ventilator, when I do an assessment
of the patient, I'm going to be monitoring breath sounds, the integrity of the airway
in terms of its patency, and where it is fixed on the patient in terms of airway position.
And the patient will be continuously on a monitor monitoring heart rate, blood pressure,
and I'll be looking at the oxygen saturations as a guide for my FiO2.
Disassembling the Ventilator.
When the patient is extubated, the ventilator is powered down and disassembled for cleaning.
Any non-disposable parts, like the temperature sensor, are sent down for cleaning.
The disposable parts are disassembled and thrown away, and the ventilator itself is
wiped down in its entirety with a cleaning solution before it is assembled again, ready
for another patient use.
This concludes our session today on the general assembly and set-up of a mechanical ventilator.
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