By Adem Lewis / in , , , , , , , , , , , /


Ventilator Safety Assessment, by Kevin Bullock.
Health care workers in all health care settings should always adhere to the latest World Health
Organization guidelines on hand hygiene and barrier precautions before and after contact
with a patient, bodily fluids or patient surroundings. For more information, please watch your video
entitled hand hygiene. Hi, my name is Kevin Bullock. I’m a clinical
supervisor in the department of respiratory care at Boston Children’s Hospital. And this
will be a lecture on the comprehensive patient ventilator safety assessment that will be
broken up into two parts– the patient and the ventilator. Overview. The purpose of the ventilator safety assessment
is to ensure proper humidification and circuit function, ensure appropriate ventilator function,
ensure that the settings are appropriate for the patient’s size and disease state, also
again to ensure optimal patient ventilator interaction, and most importantly to ensure
changes in status will alert clinicians or our alarm assessment. Circuit Function. We will start with assessment of the ventilator
circuit. Is it the appropriate size for the patient? We have three ranges of ventilator
circuits available to us– the neonatal size, the pediatric size, and the adult size. Circuit sizes may coincide with the patient
mode selection on our ventilators. The neonatal circuit may be used in premature infants less
than 1 kilogram up to patients weighing 15 kilograms. At 15 kilograms we may move up
to the pediatric tubing and the pediatric mode selection. Pediatrics circuits and mode selection may
be used up to the 35 kilogram mark. At 35 kilograms we move up to the adult circuit
and mode selection. Depending on the ventilator model used at your institution, you may have
various circuits sizes and patient modes to choose from. It is always best to consult
the operator’s manual for patient mode selection and governing parameters. Next we need to assess if our ventilator circuit
is a heated wire circuit or a non-heated wire circuit. Does it contain a water trap and
temperature probes? We will assess if the connections are tight so that we do not have
any undue leaks in the system. Part of this circuit assessment when you initially
set up your patient on the ventilator is to conduct a pre-use check. This pre-use check
generally encompasses a leak check, a pressure performance check to assess circuit integrity. It will also calculate your tubing compliance
and compressible volume loss so that you may calculate effective tidal volume. The pre-use
check will also assess the pneumotachometer within the ventilator. It will zero it and
ensure that it is functioning properly. The last stage of a pre-use check is to assess
oxygen cell function. A zero must be conducted. If it is an internal analyzer this procedure
will be done within the ventilator during the pre-use check. If it is an external analyzer
it is up to the clinician to calibrate their oxygen sensor. I recommend that any FiO2 greater
than 60% be calibrated to 100%, and if it is less than 60% to calibrate to room air,
or 21%. There are also analyzers available that may
require a two point calibration, in which case the clinician would conduct both a 100%
FiO2 calibration as well as a 21% room air calibration. As part of our circuit assessment,
we may have adjunct monitoring and/or equipment attached to the ventilator circuit. These
are all sources of a leak and should be considered for erroneous measurements or collection of
condensate. Many institutions monitor end-tidal CO2. We
should perform a functional verification of the end-tidal C02 monitor by zeroing and referencing.
We also may use an in-line suction catheter on our patients. We need to ensure that this
is the appropriate size for the endotracheal tube, that all the connections are tight,
the installation ports are closed, and that the suction button is turned to the locked
position when not in use. We may also add nebulizers to our ventilator
circuit. We need to assess that they are functioning properly and their connections are tight so
they are not a source for a leak. Furthermore, we may be conducting metabolic studies on
our patients. And these metabolic carts need to be connected to our ventilator circuit.
They will have a sample rate depending on the device used, and also be a source of leaks. As we assess our integrity of our circuit
we also need to note circuit positioning and support. This needs to be optimized to reduce
torque on the airway, pressure on the skin, and drainage of condensate away from the patient. Humidification. Once we have assessed that
our circuit is intact, the position is appropriate, we move on to assessing our humidifier function.
Humidification can be active or passive. Passive humidification is generally for short term
use and utilizes a heat-moisture exchanger, or HME. When using an HME, we must ensure
that it is being changed routinely, as most can be used safely for up to 48 hours. We
must also assess the that the HME is clear of secretions or excess condensate that may
increase resistance to patient airflow. The majority of mechanical ventilation will
require active humidification. We need to assess that there is sufficient sterile water
for inhalation, and I recommend that it is changed with 10% or less remaining to avoid
running a circuit dry. We also need to ensure that our humidifier is set to the appropriate
mode for the patient application. Nowadays, most humidifiers and mechanical
ventilators can accommodate both invasive and non-invasive ventilation, making this
assessment very important. The choice will dictate our available temperature settings,
and the amount of humidity held by the gas. Remember, the warmer the temperature, the
greater the amount of humidity carried by the gas. The goals of humidification are to reach 100%
relative humidity, with an absolute humidity ranging from 33-44 mg/L. Invasive temperature
settings should be in a range of 34-41 degrees Celsius, and non-invasive temperature settings
should be in a range of 28-34 degrees Celsius. We can set lower temperatures in the non-invasive
mode because the upper airways are available to contribute natural heat and humidification.
The invasive setting requires higher temperatures, because we are bypassing the body’s natural
heat and humidification. We should note minimal condensation in the
tubing, and if there is excess of condensation in the tubing, we should note this and adjust
our humidifier accordingly to try to lessen. Always drain condensate away from your patients,
and make a note if this condensation buildup has contributed to auto-triggering. The final assessment of adequate humidification
for your patient is the secretion assessment. We should assess the relative thickness of
the secretions every time we are suctioning our patients to ensure that they are not getting
too thick or creating plugs. Adjusting our humidification may help to improve the thickness
of these secretions and the ease of removal. Ventilator Function. Next, we move onto assessing ventilator function.
We need to assess if what is set is measured. There may be some variation depending on patient
synchrony and disease state. In general, we should expect to see our peak inspiratory
pressure plus or minus 2 centimeters of water above our set pressure. Our positive end-expiratory
pressure should also be plus or minus 2 centimeters of water around our set positive end-expiratory
pressure. Our frequency should also be plus or minus
2 breaths from our set mechanical frequency. This will certainly vary with a spontaneously
breathing patient. Our pressure support value should also be plus or minus 2 centimeters
of water around our set pressure support value. Our fraction of inspired oxygen should be
plus or minus 6%. Most ventilators have internal alarms that will alert us of a discrepancy
in measured versus set FiO2. If you have an external analyzer, you may set those alarms
on your own. If we are in a volume-controlled mode of ventilation, tidal volume assessment
should be plus or minus 10% of the set tidal volume. We need to assess if these settings and monitored
values are appropriate for patient size and disease state. I will refer you to Barry Grenier’s
OPENPediatrics lecture on initial ventilator settings for guidance on appropriate settings
for disease state and patient size. Perhaps most importantly in this assessment
is, are the tidal volumes appropriate? Can the waveforms tell you about the patient and
the patient ventilator interaction? Is the end-tidal CO2 appropriate for the patient’s
disease state? Do we understand the arterial to end-tidal CO2 gradient and what may be
causing it? Alarms. Finally, we will move on to our alarms.
We have assessed that the ventilator is functioning properly and there are no major leaks in our
system, so we should be able to appropriately set our alarms. Each institution should standardize
alarm settings based on ventilator settings and monitored parameters. First and foremost,
alarm settings should be safe for the patients. However, alarm settings should be adjusted
in such a way that nuisance alarms are reduced to prevent alarm fatigue for clinicians. And
here’s a chart of suggested alarm settings based on your measured values. Also a part
of your alarm assessment should be to test the disconnect alarm of the ventilator. This
is important to alert clinicians in case of an inadvertent disconnection of any portion
of the ventilator circuit or an unplanned extubation. Lastly, we should conduct a battery test if
the ventilator has an internal battery. We do this by unplugging the ventilator from
the wall and ensuring that the ventilator alarms to alert clinicians that it is now
in battery operation. We will then plug the ventilator back in. Patient-Ventilator Interaction. Next we will assess the integrity of our ventilator
circuit and its attachment to our patient’s endotracheal tube. We want to ensure that
it is tightly connected to the endotracheal tube and all fittings at the Y are tightly
in place. This is a heated wire circuit so it has a proximal temp probe closest to the
patient at the Y. We need to ensure the cap is on any adjunct pressure monitoring ports
and then work our way down the circuit towards the humidifier. Next, we’ll move onto assessment of the humidifier.
When we assess our humidifier function, we first need to start by assessing the amount
of sterile water for inhalation available. Once we have determined the is water sufficient,
we can move on to ensure that it is in the appropriate mode, the invasive or non-invasive
mode. Our patient is intubated in this particular humidifier indicates an endotracheal tube.
We must also assess the temperature setting and ensure that is appropriate for the mode
that it is in. Lastly, our temp probe must be assessed on the top of our humidifier column. When we assess the temperature probe on our
humidifier column, we are ensuring that it is adequately placed within the circuit to
prevent leaks. And we can also eyeball the beginning of our circuit for the collection
of a minimal amount of condensate. Depending upon the humidifier used at your institution,
your humidifier may automatically adjust the temperature gradient between your column and
your circuit or you may manually adjust that gradient between the column and the circuit
to minimize rainout. When conducting our ventilator safety assessment,
we want to ensure that a pre-use check has been conducted and a circuit integrity test
has been completed. Ventilators have very specific procedures to conduct these tests
and you will refer to the user manual of the ventilator at your institution. If this is
an assessment on a patient already being ventilated, we just would like to ensure that the pre-use
check had been conducted prior to initiation of ventilation. Before we begin ventilating our patient, we
want to ensure that the appropriate patient size mode has been selected. In this case
it is the Adult mode. Ventilators will have various user interfaces. These user interfaces
allow us to assess our set ventilator settings, our monitor parameters, and our wave forms.
As part of our ventilator safety assessment, we want to ensure that our set parameters
are monitored. In this case, we are on a peak inspiratory
pressure of 25/5 of positive end expiratory pressure. Looking at our monitored values
the peak inspiratory pressure is 26, which is within our standard of plus or minus 2
centimeters of water. Our monitor PEEP is 5 centimeters of water, which is what is set.
Our monitored respiratory rate is 16, which is what is set. Our monitored FiO2 is 41%
set at 40, within our standard of plus or minus 6%. You may also note on this ventilator, in our
tidal volume readings and our minute ventilation, there is an orange C, in an orange box around
these, indicating that two ring compliance is being compensated for. Also another indication
that a pre-use check has been completed. The final portion of our ventilator safety assessment
is to adjust our alarms based on our monitored parameters. On this particular ventilator,
are monitored parameters are displayed as we adjust our alarms. You may use a peak inspiratory
pressure alarm five to 10 centimeters above your set PEEP. In this case we are set at
25 and my alarm is set at 35. For minute ventilation of 2.1, we will set
our low minute ventilation alarm at half of the minute ventilation or one liter per minute.
In our high minute ventilation at two times our minute ventilation or four liters per
minute. We are also on a set respiratory rate of 16 and we will use half of that for our
lower respiratory rate alarm and twice that for our high respiratory rate alarm. For our
positive end expiratory pressure alarms, we should set those 2 centimeters of water above
and below are set PEEP. In this case, we are set to five, so our alarms are set at three
and seven centimeters of water. On most ventilators you may also adjust the
alarm volume. In this case we are set at 100%. And a final safety check is your Apnea time.
In the case that your patient to spontaneously breathing and has an apneic episode. As another
part of our alarm assessment and our ventilator safety check, we must assess the disconnect
alarm to alert us of any disconnections in our patient circuit. If your patient is stable enough you may conduct
this safety check at any time. However, if your patient is on a substantial amount of
support and does not tolerate disconnection, you may wait for this check until you are
suctioning the patient or they require manual ventilation. If they are stable, you may disconnect
at any point on the circuit. As part of our safety inspection we should make note of the
last preventative maintenance inspection performed by a biomedical engineering and when the next
assessment is due. Clinicians should pull or not use any machine
that has gone beyond its preventative maintenance or safety inspection. Proper function and
performance testing is necessary to ensure the highest quality of care and safety is
provided to our patients. The last portion of our ventilator safety assessment, is to
assess the function of the internal batteries, if applicable. To do this, we must unplug
the ventilator from the wall and assess that the ventilator alarms and tells us battery
operates has taken over. And this concludes our ventilator safety assessment. Please help us improve the content by providing
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