Transcript pslocum/RET 2284 Mod 3.0 Modes of Ventilation

Principles of Mechanical Ventilation
RET 2284
Module 3.0
Modes of Ventilation
Modes of Ventilation
Mode
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Description of a breath type and the timing of
breath delivery
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Terms or acronyms used to describe the way a
ventilator performs in a particular situation; often
invented by physicians, therapists, or manufacturers
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Basically there are three breath delivery techniques
used with invasive positive pressure ventilation
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CMV – controlled mode ventilation
SIMV – synchronized
Spontaneous modes
Modes of Ventilation
CMV
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Continuous Mandatory Ventilation
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All breaths are mandatory and can be volume or
pressure targeted
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Controlled Ventilation – when mandatory breaths are
time triggered

Assist/Control Ventilation – when mandatory breaths
are either time triggered or patient triggered
Modes of Ventilation
CMV
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Continuous Mandatory Ventilation
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Controlled Ventilation – when mandatory breaths are
time triggered
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Mandatory breath – ventilator determines the start time
(time triggered) and/or the volume or pressure target
Modes of Ventilation
CMV
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Controlled Ventilation
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Appropriate when a patient can make no effort to
breathe or when ventilation must be completely
controlled
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Drugs
Cerebral malfunctions
Spinal cord injury
Phrenic nerve injury
Motor nerve paralysis
Modes of Ventilation
CMV
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Controlled Ventilation
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In other types of patients, controlled ventilation is
difficult to use unless the patient is sedated or
paralyzed with medications
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Seizure activity
Tetanic contractions
Inverses I:E ratio ventilation
Patient is fighting (bucking) the ventilator
Crushed chest injury – stabilizes the chest
Complete rest for the patient
Modes of Ventilation
CMV
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Controlled Ventilation
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Adequate alarms must be set to safeguard the patient
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E.g., disconnection
Sensitivity should be set so that when the patient
begins to respond, they can receive gas flow from the
patient
Do not lock the patient out of the ventilator!
Modes of Ventilation
CMV
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Assist/Control Ventilation
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A time or patient triggered CMV mode in which the
operator sets a minimum rate, sensitivity level, type of
breath (volume or pressure)
The patient can trigger breaths at a faster rate than
the set minimum, but only the set volume or pressure
is delivered with each breath
Modes of Ventilation
CMV
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Assist/Control Ventilation
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Indications
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Advantages
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Patients requiring full ventilatory support
Patients with stable respiratory drive
Decreases the work of breathing (WOB)
Allows patients to regulate respiratory rate
Helps maintain a normal PaCO2
Complications
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Alveolar hyperventilation
Modes of Ventilation
CMV
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Volume Controlled – CMV
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Time or patient triggered,
volume targeted, volume
cycled ventilation
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Graphic (VC-CMV)
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Time-triggered, constant
flow, volume-targeted
ventilation
Modes of Ventilation
CMV
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Volume Controlled – CMV
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Time or patient triggered,
volume targeted, volume
cycled ventilation
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Graphic (VC-CMV)
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Time-triggered,
descending-flow, volumetargeted ventilation
Modes of Ventilation
CMV
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Pressure Controlled – CMV
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PC – CMV (AKA – Pressure control ventilation - PCV)
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Time or patient triggered, pressure targeted
(limited), time cycled ventilation
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The operator sets the length of inspiration (Ti), the
pressure level, and the backup rate of ventilation
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VT is based on the compliance and resistance of the
patient’s lungs, patient effort, and the set pressure
Modes of Ventilation
CMV
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Pressure Controlled – CMV
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Note inspiratory pause
Modes of Ventilation
CMV
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Pressure Controlled – CMV
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Note shorter Ti
Modes of Ventilation
CMV
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Pressure Controlled – CMV
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Airway pressure is limited, which may help guard
against barotrauma or volume-associated lung injury
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Maximum inspiratory pressure set at 30 – 35 cm H2O
Especially helpful in patients with ALI and ARDS
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Allows application of extended inspiratory time, which
may benefit patients with severe oxygenation
problems
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Usually reserved for patient who have poor results
with a conventional ventilation strategy of volume
ventilation
Modes of Ventilation
CMV
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Pressure Controlled – CMV
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Occasionally, Ti is set longer than TE during PC-CMV;
known as Pressure Control Inverse Ratio Ventilation
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Longer Ti provides better oxygenation to some patients
by increasing mean airway pressure
Requires sedation, and in some cases paralysis
Modes of Ventilation
IMV and SIMV
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Intermittent Mandatory Ventilation – IMV
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Periodic volume or pressure targeted breaths occur at
set interval (time triggering)
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Between mandatory breaths, the patient breathes
spontaneously at any desired baseline pressure
without receiving a mandatory breath
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Patient can breathe either from a continuous flow or
gas or from a demand valve
Modes of Ventilation
IMV and SIMV
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Intermittent Mandatory Ventilation – IMV
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Indications
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Facilitate transition from full ventilatory support to
partial support
Advantages
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Maintains respiratory muscle strength by avoiding
muscle atrophy
Decreases mean airway pressure
Facilitates ventilator discontinuation – “weaning”
Modes of Ventilation
IMV and SIMV
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Intermittent Mandatory Ventilation – IMV
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Complications
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When used for weaning, may be done too quickly and
cause muscle fatigue
Mechanical rate and spontaneous rate may
asynchronous causing “stacking”
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May cause barotrauma or volutrauma
Modes of Ventilation
IMV and SIMV
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Synchronized IMV
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Operates in the same way as IMV except that
mandatory breaths are normally patient triggered
rather than time triggered (operator set the volume
or pressure target)
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As in IMV, the patient can breathe spontaneously
through the ventilator circuit between mandatory
breaths
Modes of Ventilation
IMV and SIMV
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Synchronized IMV
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At a predetermined interval (respiratory rate), which
is set by the operator, the ventilator waits for the
patient’s next inspiratory effort
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When the ventilator senses the effort, the ventilator
assists the patient by synchronously delivering a
mandatory breath
Modes of Ventilation
IMV and SIMV
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Synchronized IMV
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If the patient fails to initiate ventilation within a
predetermined interval, the ventilator provides a
mandatory breath at the end of the time period
Modes of Ventilation
IMV and SIMV
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Synchronized IMV
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Indications
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Facilitate transition from full ventilatory support to
partial support
Advantages
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Maintains respiratory muscle strength by avoiding
muscle atrophy
Decreases mean airway pressure
Facilitates ventilator discontinuation – “weaning”
Modes of Ventilation
IMV and SIMV
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Synchronized IMV
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Complications
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When used for weaning, may be done too quickly and
cause muscle fatigue
Modes of Ventilation
Spontaneous Modes
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Three basic means of providing support for
continuous spontaneous breathing during
mechanical ventilation
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Spontaneous breathing
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CPAP
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PSV – Pressure Support Ventilation
Modes of Ventilation
Spontaneous Modes
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Spontaneous breathing
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Patients can breathe spontaneously through a
ventilator circuit; sometimes called T-Piece Method
because it mimics having the patient ET tube
connected to a Briggs adapter (T-piece)
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Advantage
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Ventilator can monitor the patient’s breathing and
activate an alarm if something undesirable occurs
Disadvantage
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May increase patient’s WOB with older ventilators
Modes of Ventilation
Spontaneous Modes
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CPAP
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Ventilators can provide
CPAP for spontaneously
breathing patients
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Helpful for improving
oxygenation in patients with
refractory hypoxemia and a
low FRC
CPAP setting is adjusted to
provide the best oxygenation
with the lowest positive
pressure and the lowest FiO2
Modes of Ventilation
Spontaneous Modes
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CPAP
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Advantages
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Ventilator can
monitor the
patient’s breathing
and activate an
alarm if something
undesirable occurs
Modes of Ventilation
Spontaneous Modes
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PEEP (Positive End Expiratory Pressure)
“According to its purest definition, the term PEEP is
defined as positive pressure at the end of exhalation
during either spontaneous breathing or mechanical
ventilation. However, use of the term commonly
implies that the patient is also receiving mandatory
breaths from a ventilator.” (Pilbeam)
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PEEP becomes the baseline variable during mechanical
ventilation
Modes of Ventilation
Spontaneous Modes
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PEEP
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Helps prevent early airway closure and alveolar
collapse and the end of expiration by increasing (and
normalizing) the functional residual capacity (FRC) of
the lungs
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Facilitates better oxygenation
NOTE: PEEP is intended to improve oxygenation, not to
provide ventilation, which is the movement of air into the
lungs followed by exhalation
Modes of Ventilation
Spontaneous Modes
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Pressure Support Ventilation – PSV
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Patient triggered, pressure targeted, flow cycled
mode of ventilation
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Requires a patient with a consistent spontaneous
respiratory pattern
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The ventilator provides a constant pressure during
inspiration once it senses that the patient has made
an inspiratory effort
Modes of Ventilation
Spontaneous Modes
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PSV
Modes of Ventilation
Spontaneous Modes
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PSV
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Indications
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Spontaneously breathing patients who require
additional ventilatory support to help overcome
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WOB, CL, Raw
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Respiratory muscle weakness
Weaning (either by itself or in combination with SIMV)
Modes of Ventilation
Spontaneous Modes
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PSV
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Advantages
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Full to partial ventilatory support
Augments the patients spontaneous VT
Decreases the patient’s spontaneous respiratory rate
Decreases patient WOB by overcoming the resistance of
the artificial airway, vent circuit and demand valves
Allows patient control of TI, I, f and VT
Modes of Ventilation
Spontaneous Modes
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PSV
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Advantages
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Set peak pressure
Prevents respiratory muscle atrophy
Facilitates weaning
Improves patient comfort and reduces need for
sedation
May be applied in any mode that allows spontaneous
breathing, e.g., VC-SIMV, PC-SIMV
Modes of Ventilation
Spontaneous Modes
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PSV
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Disadvantages
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Requires consistent spontaneous ventilation
Patients in stand-alone mode should have back-up
ventilation
VT variable and dependant on lung characteristics and
synchrony
Low exhaled E
Fatigue and tachypnea if PS level is set too low
Modes of Ventilation
Spontaneous Modes
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Flow Cycling During PSV
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Flow cycling occurs when the ventilator
detects a decreasing flow, which
represents the end of inspiration
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This point is a percentage of peak flow
measured during inspiration
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PB 7200 – 5 L/min
Bear 1000 – 25% of peak flow
Servo 300 – 5% of peak flow
No single flow-cycle percent is right for
all patients
Modes of Ventilation
Spontaneous Modes
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Flow Cycling During PSV
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Effect of changes in
termination flow
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A: Low percentage (17%)
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B: High percentage (57%)
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Newer ventilators have an
adjustable flow cycle
criterion, which can range
from 1% - 80%, depending
on the ventilator
Modes of Ventilation
Spontaneous Modes
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PSV during SIMV
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Spontaneous breaths during SIMV can be supported
with PSV (reduces the WOB)
PCV – SIMV with PSV
Modes of Ventilation
Spontaneous Modes
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PSV during SIMV
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Spontaneous breaths during SIMV can be supported
with PSV
VC – SIMV with PSV
Modes of Ventilation
Spontaneous Modes
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PSV
NOTE: During pressure support ventilation (PSV),
inspiration ends if the inspiratory time (TI) exceeds a
certain value. This most often occurs with a leak in
the circuit. For example, a deflated cuff causes a
large leak. The flow through the circuit might never
drop to the flow cycle criterion required by the
ventilator. Therefore, inspiratory flow, if not stopped
would continue indefinitely. For this reason, all
ventilators that provide pressure support also have a
maximum inspiratory time.
Modes of Ventilation
Spontaneous Modes
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PSV
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Setting the Level of Pressure Support
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Goal: To provide ventilatory support
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Spontaneous tidal volume is 10 – 12 mL/Kg of ideal
body weight
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Maintain spontaneous respiratory rate <25/min
Goal: To overcome system resistance (ET Tube, circuit,
etc.) in the spontaneous or IMV/SIMV mode
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Set pressure at (PIP – Pplateau) achieved in a volume
breath or at 5 – 10 cm H2O
Modes of Ventilation
Spontaneous Modes
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PSV
Exercise: Using the PIP and the PPlateau from the pressure
waveform below, recommend a pressure support setting for
this patient (patient is in VC-SIMV mode)
35
25
Answer: 10 cm H2O
Modes of Ventilation
Spontaneous Modes
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PSV - The results of your work
35 cm H2O
10 cm H2O
Modes of Ventilation
Spontaneous Modes
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Bilevel Positive Airway Pressure (BiPAP)
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An offshoot of PEEP/CPAP therapy
Most often used in NPPV
AKA
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Bilevel
Bilevel
Bilevel
Bilevel
Bilevel
Bilevel
CPAP
PEEP
Pressure Support
Pressure Assist
Positive Pressure
Airway Pressure
Modes of Ventilation
Spontaneous Modes
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Bilevel Positive Airway Pressure (BiPAP)
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Commonly patient triggered but can be time triggered,
pressure targeted, flow or time cycled
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The operator sets two pressure levels
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IPAP (Inspiratory Positive Airway Pressure)
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IPAP is always set higher than EPAP
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Augments VT and improves ventilation
EPAP (Expiratory Positive Airway Pressure)
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Prevents early airway closure and alveolar collapse at the
end of expiration by increasing (and normalizing) the
functional residual capacity (FRC) of the lungs
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Facilitates better oxygenation
Modes of Ventilation
Spontaneous Modes
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Bilevel Positive Airway Pressure (BiPAP)
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The operator sets two pressure levels
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IPAP
EPAP
NOTE: The pressure difference between IPAP and EPAP is pressure support
Modes of Ventilation
Questions?