Morris Vent Synch

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    Newer Modes of

    Mechanical VentilationTimothy A. Morris, M.D.

    Division of Pulmonary and Critical Care Medicine

    Medical Director, Respiratory Care

    University of California, San Diego

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    How to Assess VentilatorModes

    q Inhalation

    what is controlled during the breath

    what is targeted (how much is enough?)

    how does it adjust to changes

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    How to Assess VentilatorModes

    q Exhalation

    what is controlled

    when does it end

    how does it adjust

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    How to Assess VentilatorModes

    q Inhalation

    what is controlled

    what is targeted

    how does it adjust

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    Simple Pressure System

    Pressure 20 cm H2O

    Pressure20 cm H2O

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    Time Constant

    q time it takes to get 1/2 way to

    equilibrium

    q total resistance x total compliance

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    Increased Compliance

    Pressure 20 cm H2O

    Pressure

    20 cm H2O

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    Increased Resistance

    Pressure 20 cm H2O

    Pressure20 cm H2O

    Obstruction

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    Volume 500 ml

    Pressure 3500 cm H20

    Simple Volume System

    Volume 500 ml

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    Volume 2000 ml

    Pressure 3500 cm H20

    Pop!

    Simple VolumeSystem

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    Big Secret!

    q Ventilator modes are simulations

    pressure control

    volume control

    q Microprocessors control the simulation

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    Dadmobile

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    Minivan Tire

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    High Pressure Pump

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    Filling the Tire

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    Tire Pressure

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    Toy Balloon: deflated

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    Toy Balloon: inflated

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    Toy Balloon: popped

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    Flow Control

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    Control of Resistor

    i h

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    Pressure 3500 cm H20

    High PressureSystem

    valve

    Pressure 35 cm H20

    Tidal volume 500 ml

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    Volume Control

    Deflated Volume Inflated Volume

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    Pressure Control

    Deflated Pressure Inflated Pressure

    Wh t t l th

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    What controls theadjustments?

    Volume?

    (flow control)

    Pressure?

    Mi

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    Pressure 3500 cm H20

    MicroprocessorControl

    Inhalationvalve(resistor)

    solenoid

    Microprocessor

    exhalevalve

    Tidal volume 500 ml

    Pressure 35 cm H20

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    Quality of the control

    q hardware:

    how frequently is the flow/pressure

    measured how rapidly are adjustments made

    how are adjustments made

    q software timing and patterns of control

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    How to Assess VentilatorModes

    q Inhalation

    what is controlled

    what is targeted

    how does it adjust

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    Targeting

    q How much breath is enough?

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    Targeting

    Control

    q Flow

    q Pressure

    Target

    q Time

    q Pressure

    q Volume

    Volumecontrol

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    Targeting

    Control

    q Flow

    q Pressure

    Target

    q Time

    q Pressure

    q Volume

    Time-cycledpressure

    control

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    Targeting

    Control

    q Flow

    q Pressure

    Target

    q Time

    q Pressure

    q VolumeVolumetargeted

    pressure

    control

    H t A V til t

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    How to Assess VentilatorModes

    q Inhalation

    what is controlled

    what is targeted

    how does it adjust

    Patients generate

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    Patients generatepressures

    q Negative pressure

    inhalation efforts

    q Positive pressure

    bucking

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    Negative pressure:Adjustments

    q No adjustment

    q Increase in pressure/flow to match

    demand

    q Decrease in pressure/flow to foster

    weaning

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    Positive pressure:Adjustments

    q No adjustment

    q End inhalation, open exhalatory

    valve

    q Adjust inspiratory and expiratory

    valves to maintain control

    H t A V til t

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    How to Assess VentilatorModes

    q Exhalation

    next year

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