Ventilator Auto-Triggering and Brain Death

Tammy Kundinger RRT
UWHC Respiratory Therapy Supervisor
Paula Breihan RRT
UWHC Respiratory Therapy Supervisor
Identify how impaired brainstem function alters
respiratory drive
Identify causes of auto triggering with mechanical
Understand recommendations to eliminate autotriggering
The act reads as follows: “An individual who has
sustained either
1) Irreversible cessation of circulatory and
respiratory functions, or
2) Irreversible cessation of all functions of the
entire brain, including the brain stem, is dead.”
*It serves as a
between the
brain and other
organs of our
*It’s made up of
three parts:
oblongata and
The movement of eye muscles
The movement of voluntary muscles
The respiratory muscles
It also…
◦Regulates autonomic functions and awareness
◦Regulates body temperature
Respiratory Center
◦Controls the movement of respiratory muscles
◦Regulates the rate of respiration
Vasomotor Center
◦Regulates blood pressure
Reflex Center
◦Regulates reflex actions like sneezing, coughing,
swallowing, etc
Regulates sleep patterns
Controls arousal functions like waking up or
being alert
Establish irreversible and proximate cause of coma
Achieve normal core temperature
Achieve normal systolic blood pressure (> 100
Perform one neurologic exam
*Usually several hours after brain insult
*Some state statutes require 2 examinations
These three parameters are necessary to confirm
irreversible functions of the brain:
Absence of brainstem reflexes
Coma: Patients must lack all evidence of
Absence of brainstem reflexes:
§ No pupillary response
§ No ocular movements
§ No corneal reflex
§ No facial muscle movements
§ No pharyngeal and tracheal reflexes
Positive Apnea Test
movements are
◦Arterial PCO2 is > 60
mmHg (or 20 mmHg
increase in arterial
PCO2 over baseline)
Inconclusive Apnea
◦No appropriate rise
in PCO2 over the
◦If the patient is
stable during the
procedure the test
may be repeated for
a longer period of
time (10-15 minutes)
1. Obtain baseline ABG and normalize PaCO2
(34-45mmHg) prior to testing
2. Preoxygenate for at least 10 minutes with
100% oxygen.
3. Disconnect patient from the ventilator
4. Preserve oxygenation by inserting a catheter
into the endotracheal tube delivering 6 l/min
5. Monitor patient closely for respiratory
movement for 8-10 minutes
6. If no respiratory drive is observed, repeat blood
after approximately 8 minutes.
Cerebral Angiography
Nuclear Scan
Transcranial Doppler
Prolonged ICU stay for patients’ families
Confusion for family
◦Ventilator triggering may question the diagnosis
of brain death
◦Cardiac autotriggering may raise false hope of
◦May lead to increased ICU costs
Longer ICU time may lead to losing potential
transplantable organs
◦Formal brain death protocols may take as long
as 6-24 hours
What should you do if the neurologic
assessment has been completed and the
patient has met all criteria for brain death but it
looks like ◦The patient has finger tremors?
◦The patient has toe/plantar flexions?
◦The patient has an intrinsic respiratory drive?
Transient bilateral
finger tremor
simultaneous toe
Retained flexion
stimulation (plantar
◦Occurs in more than
50% of patients
The AAN attests that autotriggering (or ventilator
self-cycling) occurs when a ventilator breath is
triggered in the absence of effort by the patient.
Extrinsic Causes
Random artifact in the
ventilator circuit
Water condensation in
the ventilator circuit
Ventilator circuit leak
Endotracheal tube cuff
Excessive retraction of
an inline suction
Intrinsic Causes
Cardiogenic oscillations
Bronchopleural fistula
Chest tube leak
Ventilator artifact?
Condensation in ventilator circuit?
Leak in ventilator circuit?
ETT cuff leak?
Misplaced inline suction catheter?
Cardiogenic oscillations
◦Is it fixable?
Bronchopleural fistulas
◦How can you correct? Optimize your ventilation
Chest tube leak
◦Reposition chest tube, obtain CXR to determine
position, redress chest tube site, and increase
bias flow on ventilator
End result…intrinsic factors may prove to be
more difficult to correct or even identify.
Physical changes associated with brain death
*Hyperdynamic cardiovascular state
*Altered vasomotor tone
This may produce a
hyperdynamic pericardium
which can be mistaken
for respiratory movement
Hyperdynamic cardiovascular state
Displace intrathoracic volume & lung tissue
Causing cardiogenic oscillation beyond the
set trigger sensitivity
Triggering ventilator breaths in the absence
of an intrinsic respiratory drive
Fluctuations in ventilator airway pressure, flow
and potentially volume waveforms in time with
the cardiac cycle
Cardiogenic oscillations may be seen in greater
amplitude in patients with a more hyperdynamic
cardiovascular system.
83 patients
◦4 patients occasionally triggered the ventilator
Autotriggering was eliminated by the adjustment
of ventilator trigger or by changing the trigger
from flow to pressure.
Pressure Triggered
◦ The patient’s
inspiratory effort
causes a drop in
pressure within the
breathing circuit
Flow Triggered
◦ The ventilator detects a
drop in flow through
the patient circuit
during exhalation
Flow Triggered
◦ Between breaths, the flow coming out of
the main flow control valve and the flow
going through the exhalation valve are
◦ During the patient’s inspiratory effort, the
flow through the exhalation valve falls
below the flow from the output valve
◦ The difference between these two flows is
the flow trigger variable
flow through
circuit: “Base
Normally, a ventilated patient would be set on flow
triggered sensitivity
Flow triggering is more sensitive than pressure
Flow triggering is designed to ease the patient’s
work of breathing by requiring less inspiratory
An appropriate neurologic assessment
Working together and utilizing the expertise of the
interdisciplinary team, the organ procurement
process can be improved
Early identification of potential ventilator
autotriggering can –
◦Minimize ICU stay
◦Reduce costs of care
◦Decrease family stress
◦Facilitate recovery of transplantable organs
UWHC Practice Implementations for
Successful Organ Procurement
End of Life Sustaining Measures Order Set
Donation after Cardiac Death Order Set (DCD)
Brain Dead Donor Order Set (BDD)
These order sets have specific algorithms that RT
uses as a guide for the type of end of life ventilator
management that is indicated in each patient
UWHC Respiratory Care Brain Dead
Ventilator Management Algorithm
Example patient scenario of how the
BDD lung protective algorithm helps
guide the RT in their management of the
ventilator and
assessment of the patient in preparation
organ procurement.
•12/5 at 1800 arrived in ED &
then transferred to ICU
•12/5 at 2220 apnea test ordered
•12/6 at 0410 patient pronounced brain
•12/6 at 0432 BDD order set initiated
•12/6 at 0916 bronchoscopy ordered
•12/6 at 2001 oxygen challenge
•12/7 at 0140 patient taken to
for organ donation
In this example, the process
took a
very short amount of time from
when the patient was admitted
to actual OR time for organ
procurement. Behind the
scenes, this algorithm helps the
flow more smoothly and
eliminates questions and
reduces response time to new
Tammy Kundinger
UWHC RT Supervisor – Neuro ICU
[email protected]
Paula Breihan
UWHC RT Supervisor – TLC ICU
[email protected]
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