THOMAS PIRAINO: Hello.
My name is Thomas Piraino.
And I'm going to discuss with you extubation.
The number one goal of mechanical ventilation
is to get the patient off of the ventilator.
Assessment for readiness to wean, or liberation of the patient
should be done daily.
The first step in this readiness assessment
is to make sure the patient is medically stable enough to proceed.
A few things need to be considered prior to performing
any readiness to wean tests.
For example, is the patient expected to have a surgical procedure
that requires sedation and for them to remain on the ventilator?
Is the patient currently in respiratory distress?
Are they hemodynamically stable?
Do you suspect myocardial ischemia?
Do they have a depressed mental status?
Do they have a very low drive to breathe with a respiratory rate less than 10?
Are they still requiring a significant amount
of positive and expiratory pressure?
Or do they still require a significant amount of FiO2?
While there are many respiratory system measurements that
can be done to determine strength and breathing capacity of the patient,
the most commonly used test is a simple one called the rapid shallow breathing
index, which is a two-minute spontaneous breathing assessment.
The test does not require the person to be already
on a spontaneous mode of ventilation.
They simply need to meet the criteria I just mentioned.
This two-minute test is done by simply placing the patient onto pressure
support ventilation, if they're not already on that mode,
and turning the settings down to 0 centimeters of water of support
and 0 centimeters of water of PEEP.
Please note, some ventilators will still read a number 1
for centimeters of water of PEEP.
And this is due to the fact that there is
bias flow that can generate at least 1 centimeter of water.
So it's just being honest with the reality of that when you turn it down,
there still may be some pressure in the system.
But this is OK.
At the end of two minutes of the patient breathing
without any support from the ventilator, you divide the frequency
by the tidal volume in liters.
In this example, a respiratory rate of 18 breath per minute with a tidal
volume of 340 mils would be 18 divided by 0.340,
which would give you a number of 53.
If the number is less than 105, it's considered a successful test.
You would continue with a spontaneous breathing trial.
Different techniques have been used for spontaneous breathing
trials in the literature.
The classic method is the T-piece method,
which involves removing the patient from the ventilator
completely and supplying oxygen to the endotracheal tube
with a t-shaped adapter.
Another option is setting 0 centimeters of water of support
and 0 centimeters of water of PEEP as described
in the two-minute rapid shallow breathing index.
This is the most similar to T-piece in terms of work of breathing,
but allows ventilator monitoring of tidal volume, respiratory rate,
and minute ventilation.
It is also the method that best reflects the post extubation work of breathing
experienced by the patient.
Pressure support is another method used, where low settings of support
are used with either no PEEP or very little PEEP.
Automatic tube compensation is available on some ventilators.
And it provides inspiratory support proportional
to the endotracheal tube size.
So it does require proper setup within the ventilator
to tell the machine what size endotracheal tube the patient has.
And finally, some clinicians simply use continuous positive airway pressure
to theoretically maintain a minimum level of end-expiratory lung volume.
For COVID-19 patients, if you want to best reflect
the post-extubation work of breathing and minimize possible exposure
to those caring for the patient, keeping the patient on the ventilator
would be a more reasonable choice than removing the patient.
And the zero level of pressure support with 0 PEEP
would be most likely to demonstrate the true tolerance
of spontaneous breathing.
However, institutional differences exist on the preferred method,
and you must keep this in mind.
The timing of the spontaneous breathing trial is important.
In a recent study that compared two different techniques
of spontaneous breathing trials, they failed
to exclusively address true differences between techniques
because they used two very different timings.
One of the timings was two hours, which data has already suggested
is not necessary and likely too long.
So a spontaneous breathing trial should be a minimum of 30 minutes.
And one hour is more than sufficient.
Extending it to 120 minutes is the maximum
that is recommended in any policy.
However, it is not necessary.
It is important to note, however, that the more support a patient is
provided during a spontaneous breathing trial, the less likely
they will fail it.
And the less likely it will represent the work of breathing
required by the patient after extubation.
So patients that will have a higher post-extubation work of breathing
may not demonstrate this during a spontaneous breathing
trial that provides support.
The following is a list of typical signs of failing a spontaneous breathing
trial.
A respiratory rate greater than 35 breaths per minute,
or an increase in a respiratory rate more than 20%
from baseline with signs of respiratory distress.
This is important, as some patients may breathe
fast but without any signs of distress.
And oxygen saturation that has fell below 90%.
A heart rate greater than 140 beats per minute, or an increase in heart rate
greater than 20% from baseline with signs of respiratory distress.
Systolic blood pressure changes that are significant.
The presence of somnolence, agitation, diaphoresis, and anxiety.
An increase in vasopressor or inotropic agent support required.
Or chest pain and other limiting pain precluding further continuation.
When a patient fails a spontaneous breathing trial,
it is typical to place them on the previous settings they were on prior
to showing signs of distress.
If this was a control mode or an assist control mode,
it might be worthwhile placing them onto a supportive mode,
like pressure support, and sometimes weaning the patient's level of support
so that it's not so different from a spontaneous breathing
trial can be helpful, provided the patient tolerates this.
Once the patient has passed a spontaneous breathing trial,
other criteria should be considered prior to extubating the patient.
First, are the saturations still above 90%
or are they at the baseline level in chronically hypoxemic patients?
Do they have sufficient cough, enough to clear secretions,
or have they required frequent suctioning?
Are patients hemodynamically stable?
Do they have a level of consciousness sufficient to ensure airway protection?
And is a cuff leak present?
However, a cuff leak should only be considered in patients
at high risk of laryngeal edema.
And it should not be the primary reason to keep a patient intubated.
A number of methods exist for checking for a cuff leak.
The simplest is simply removing air from the cuff
and listening for an audible leak with a stethoscope on the neck of the patient.
Prior to removing the endotracheal tube from a patient,
it's important to understand and to know where
the equipment is that would be required to place the tube back in the patient,
if required.
So understanding where your endotracheal tubes are kept,
having a bag mask with positive end-expiratory valve at the bedside
is helpful.
Know where your airway bougies are; tube exchangers;
traditional direct laryngoscopy; video laryngoscopy; a flexible bronchoscope;
drugs needed for induction; and a suction catheter.
The things that should be readily available at the bedside, of course,
is a bag mask with positive end-expiratory pressure
valve, and the suction catheter.
Everything else, you need to know where it is.
And it should be within a very close distance
to the patient that is being extubated.
For extubation, the patient should be seated as upright as possible.
The oral pharynx should be suctioned clean
and the endotracheal tube securing device
should be removed from around the endotracheal tube,
provided someone has a hold on the endotracheal tube.
Ask the patient to take a deep breath in and give a long exhalation.
Deflate the cuff and remove the endotracheal tube
in as fluid a movement as possible while the patient is exhaling.
Doing this during exhalation prevents the patient
from inhaling any oral secretions above the cuff that can still be present even
after suctioning of the oral pharynx.
Instruct the patient to cough out all other secretions
after the tube has been removed.
Then provide supplemental oxygen.
A modification to this technique for COVID-19 patients
may include applying the oxygen therapy, like nasal cannula,
prior to removal of the tube, and placing
a surgical mask over the patient's face immediately after extubation
prior to instructing the patient to cough, just to minimize some
of the droplets that can be projected.
These are just a few ways of minimizing contamination
of the surrounding area and staff.
Of course, proper PPE should be worn for this procedure
as it is considered high risk in COVID-19 patients.
There are a few things to consider as a risk of extubation failure.
The presence of pneumonia as the reason for intubation;
a weak cough; frequent suctioning; and a rapid shallow breathing index
above 58 breaths per minute per liter.
Although the number less than 105 was considered a successful test,
patients are at higher risk if their values were greater than 58.
A positive fluid balance in the last 24 hours prior to activation
is also a risk factor.
Providing therapy, such as heated high-flow and non-invasive ventilation
have been shown to reduce extubation failure in patients.
However, with COVID-19 patients, it is important to follow proper infection
control guidelines to prevent any spread of infection
from patients that may still be contagious
if these therapies are utilized.
And finally, successful extubation in many studies
was considered if a patient does not require
re-intubation within the first 48 hours post-extubation.
However, some consider time limits of up to five to seven days as
whether or not the patient is successfully extubated.
Re-intubation is associated with worse outcomes in patients.
So optimizing them, and assessment of readiness to wean prior to extubation
is extremely important.