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Bourns BP200 (neonates) PC-IMV CPAP Bourns LS 104-150 (pediatrics) VC-CMV assist/control VC-IMV CPAP. 1979 Ventilator Mode Options. CMV CMV + ASSIST CMV + AUTOFLOW CMV + PRESS LIMIT SIMV SIMV + PRESS SUPPT SIMV + AUTOFLOW SIMV + PRESS SUPPT + AUTOFLOW + ATC PCV PCV + AUTOFLOW.

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1979 Ventilator Mode Options

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Bourns BP200 (neonates)

PC-IMV

CPAP

Bourns LS 104-150 (pediatrics)

VC-CMV assist/control

VC-IMV

CPAP

1979 Ventilator Mode Options


CMV

CMV + ASSIST

CMV + AUTOFLOW

CMV + PRESS LIMIT

SIMV

SIMV + PRESS SUPPT

SIMV + AUTOFLOW

SIMV + PRESS SUPPT + AUTOFLOW + ATC

PCV

PCV + AUTOFLOW

MMV

MMV + PRESS SUPPT

MMV + AUTOFLOW

APRV

CPAP

CPAP + PRESS SUPPT

2005 Ventilator Mode Options


Key Ideas for Understanding Mechanical Ventilation

  • Mathematical Models

    • Equation of motion

    • Time constant

    • Mean airway pressure

  • Control Variables

    • Pressure, volume, dual

  • Breath Types/Patterns

  • Optimum Mode Selection


transairway

pressure

transrespiratory

pressure

transthoracic

pressure

volume

elastance = Dpressure / Dvolume

Lung Mechanics

resistance = Dpressure / Dflow

flow


Equation of Motion

ventilation

pressure

(to deliver

tidal volume)

elastic

pressure

(to inflate lungs

and chest wall)

resistive

pressure

(to make air flow

through the

airways)

=

+

Pmus + Pvent = Pelastic + Presistive

Pmus + Pvent = E x V + R x V


Uses for the Equation of Motion

  • Classify ventilators and modes

    • ventilator controls only one variable at a time

    • pressure, volume, or flow

  • Monitor lung mechanics

    • resistance & elastance (compliance), time constant

  • Basis of newest modes

    • proportional assist

    • automatic tube compensation

    • adaptive support


Paw

Paw

Volume/Flow Control Pressure Control

Inspiration

Expiration

Inspiration

Expiration

20

20

Pressure

0

0

2

2

1

0

1

20

20

Volume

0

0

2

2

0

1

0

1

3

3

Flow

Time (s)

Time (s)

0

0

-3

-3


Dual Control

  • Use of both pressure and volume signals to control the breath

  • Example: CMV+AutoFlow

    • every breath is mandatory

    • every breath is pressure limited, time cycled

    • pressure limit is automatically adjusted to meet set tidal volume target using compliance measurements

  • Contraindicated if large leaks


Dual Control Advantages

  • Stable minute ventilation

    • as with volume control

  • Better patient synchrony

    • as with pressure control


Characteristics of a Mode

  • Breathing Pattern

    • Control variable

    • Breath sequence

  • Control Type

    • Setpoint, servo, adaptive, optimal

  • Specific Control Strategy

    • Phase variables

    • Operational logic


Breathing Pattern

  • Control Variable

    • Pressure

    • Volume

    • Dual


Breathing Pattern

  • Control Variable

    • Pressure

    • Volume

    • Dual

  • Breath Sequence

    • Mandatory vs spontaneous


Breath Types

  • Spontaneous Breath

    • Patient sets frequency and tidal volume

    • Both patient triggered and patient cycled

  • Mandatory Breath

    • Machine sets frequency and/or tidal volume

    • Machine triggered and/or machine cycled


Breath Sequences

  • Continuous Mandatory Ventilation

    • CMV

    • all breaths mandatory

  • Intermittent Mandatory Ventilation

    • IMV or SIMV

    • mandatory and spontaneous breaths

  • Continuous Spontaneous Ventilation

    • CSV

    • all breaths spontaneous


Basic Breathing Patterns

Control VariableBreathing Sequence

Volume ControlContinuous Mandatory Ventilation

Intermittent Mandatory Ventilation

Pressure ControlContinuous Mandatory Ventilation

Intermittent Mandatory Ventilation

Continuous Spontaneous Ventilation

Dual ControlContinuous Mandatory Ventilation

Intermittent Mandatory Ventilation

Continuous Spontaneous Ventilation


Potential Confusion

  • All mandatory breaths are assisted

  • Spontaneous breaths may be assisted or not


Definition of “Assisted Breath”

  • Assisted (ventilator does work on patient)

    • Airway pressure rises above baseline during inspiration (or falls below baseline during expiration).

  • Un-Assisted

    • Airway pressure stays constant during inspiration or expiration.

  • Loaded (patient does work on ventilator)

    • Airway pressure falls below baseline during inspiration and rises above baseline during expiration.


Assisted Spontaneous Breaths

  • Pressure Support

    • patient triggered, pressure limited, flow cycled

    • patient controls timing and size of breath

  • Automatic Tube Compensation

    • patient triggered, pressure proportional to flow2, flow cycled

    • active on inspiration and expiration

    • patient controls timing and size of breath


Characteristics of a Mode

  • Breathing Pattern

    • Control variable

    • Breath sequence

  • Control Type

    • Setpoint, auto-setpoint, servo, adaptive, optimal

  • Specific Control Strategy

    • Phase variables

    • Operational logic


Control Types

  • Setpoint

    • user sets pressure, volume, flow, limit

  • Auto-Setpoint

    • ventilator chooses limit variable

  • Servo

    • ventilator delivers pressure in proportion to patient’s inspiratory flow

  • Adaptive

    • ventilator chooses pressure setpoint to achieve operator selected volume setpoint

  • Optimal

    • ventilator chooses both volume and pressure setpoints


Evolution of Ventilator Control Types

Tactical Control (within-breaths)

  • setpoint (PC-IMV)

  • auto-setpoint (Pmax)

  • servo (Automatic Tube Compensation)

operator-selected, static setpoints

Strategic Control (between breaths)

  • adaptive (CMV+AutoFlow)

  • optimal (ASV)

ventilator-selected, dynamic setpoints

static model

Intelligent Control (between patients)

  • knowledge based

  • artificial neural network

ventilator-selected, dynamic setpoints

dynamic model

ability to learn from experience


CMV

CMV + ASSIST

CMV + AUTOFLOW

CMV + PRESS LIMIT

SIMV

SIMV + PRESS SUPPT

SIMV + AUTOFLOW

SIMV + PRESS SUPPT + AUTOFLOW + ATC

PCV

PCV + AUTOFLOW

MMV

MMV + PRESS SUPPT

MMV + AUTOFLOW

APRV

CPAP

CPAP + PRESS SUPPT

Ventilator Mode Options


VOLUME

CONTROL

VC-CMV

VC-IMV

Ventilator Mode Options

PRESSURE

CONTROL

  • PC-CMV

  • PC-IMV

  • PC-CSV

DUAL

CONTROL

  • DC-CMV

  • DC-IMV


Selecting the Best Mode (benefit/cost)

  • Benefits

    • Clinical

      • maintenance of stable gas exchange

      • reduced work of breathing

      • optimum patient-machine synchrony

    • Technical

      • learnability (easy to understand)

      • efficiency (minimum setup and maintenance)

      • low error rate (inappropriate settings)


Selecting the Best Mode (benefit/cost)

  • Costs

    • Clinical

      • adverse reactions (lung stretch damage)

      • associated complications (blood loss)

    • Technical

      • cost to patient (length of stay)

      • cost to hospital (clinician interventions)


VOLUME

CONTROL

VC-CMV

VC-IMV

Ventilator Mode Options

PRESSURE

CONTROL

  • PC-CMV

  • PC-IMV

  • PC-CSV

DUAL

CONTROL

  • DC-CMV

  • DC-IMV


DC-CMV

DC-IMV

DC-IMV + PRESS SUPPT

DC-IMV + ATC (automatic tube compensation)

DC-IMV + MMV (mandatory minute ventilation)

DC-IMV + PRESS SUPPT + ATC

DC-IMV + PRESS SUPPT + MMV

DC-IMV + MMV + ATC

Dual Control Options


Benefit

Cost

Mode

Clinical

Technical

Clinical

Technical

DC-CMV

-Stable tidal volume with each breath

-Least work of breathing because all breaths are equally supported

-Nearly optimum synchrony

-Easy to understand and monitor

-Fewest breath parameters to adjust during weaning or increasing support

-More stable intracranial pressure

-Requires fewer adjustments and perhaps fewer blood gases

-Fewer adjustments may lead to lower LOS and less operator time


Benefit

Cost

Mode

Clinical

Technical

Clinical

Technical

DC-IMV

-Stable volume for mandatory breaths only

-Increased WOB for spontaneous breaths

-Easy to understand and monitor

-Necessary to select correct frequency

-Less stable intracranial pressure

-Less stable minute ventilation

-May require more ABGs

-Weaning means “dumbing down” the ventilator

-More adjustments may lead to longer LOS and operator time


Benefit

Cost

Mode

Clinical

Technical

Clinical

Technical

DC-IMV + anything

-Stable mandatory breaths only

-Variable WOB for spontaneos breaths depending on options and settings

-Difficult to understand and monitor

-Necessary to correctly balance many settings

-Decreased operator efficiency

-Less stable intracranial pressure

-Less stable minute ventilation

-May require more ABGs

-Weaning means “dumbing down” the ventilator

-More adjustments may lead to longer LOS and operator time


DC-CMV

Tidal volume

infrequent

PEEP

FiO2

Weaning

automatic

Ventilator Management Requirements

PC-IMV + Press Support

  • Peak inspiratory pressure

    • frequent

  • PEEP

  • Frequency

  • Pressure support level (?)

  • FiO2

  • Weaning

    • manual

    • may be ineffective with PS


DC-CMV

Tidal volume

infrequent

PEEP

FiO2

Weaning

automatic

Ventilator Management

DC-IMV + Press Support

  • Tidal volume

    • infrequent

  • PEEP

  • Frequency

  • Pressure support level (?)

  • FiO2

  • Weaning

    • mandatory breaths automatic

    • spontaneous breaths manual

    • more manual as rate decreases


Thought For The Day

“In some ways we are as confused as ever, but we believe we are confused on a higher level and about more important things.”

A.R. Feinstein, MD


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