8/14/2019 Morris Vent Synch
1/38
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
8/14/2019 Morris Vent Synch
2/38
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
8/14/2019 Morris Vent Synch
3/38
How to Assess VentilatorModes
q Exhalation
what is controlled
when does it end
how does it adjust
8/14/2019 Morris Vent Synch
4/38
How to Assess VentilatorModes
q Inhalation
what is controlled
what is targeted
how does it adjust
8/14/2019 Morris Vent Synch
5/38
Simple Pressure System
Pressure 20 cm H2O
Pressure20 cm H2O
8/14/2019 Morris Vent Synch
6/38
Time Constant
q time it takes to get 1/2 way to
equilibrium
q total resistance x total compliance
8/14/2019 Morris Vent Synch
7/38
Increased Compliance
Pressure 20 cm H2O
Pressure
20 cm H2O
8/14/2019 Morris Vent Synch
8/38
Increased Resistance
Pressure 20 cm H2O
Pressure20 cm H2O
Obstruction
8/14/2019 Morris Vent Synch
9/38
Volume 500 ml
Pressure 3500 cm H20
Simple Volume System
Volume 500 ml
8/14/2019 Morris Vent Synch
10/38
Volume 2000 ml
Pressure 3500 cm H20
Pop!
Simple VolumeSystem
8/14/2019 Morris Vent Synch
11/38
Big Secret!
q Ventilator modes are simulations
pressure control
volume control
q Microprocessors control the simulation
8/14/2019 Morris Vent Synch
12/38
Dadmobile
8/14/2019 Morris Vent Synch
13/38
Minivan Tire
8/14/2019 Morris Vent Synch
14/38
High Pressure Pump
8/14/2019 Morris Vent Synch
15/38
Filling the Tire
8/14/2019 Morris Vent Synch
16/38
Tire Pressure
8/14/2019 Morris Vent Synch
17/38
Toy Balloon: deflated
8/14/2019 Morris Vent Synch
18/38
Toy Balloon: inflated
8/14/2019 Morris Vent Synch
19/38
Toy Balloon: popped
8/14/2019 Morris Vent Synch
20/38
Flow Control
8/14/2019 Morris Vent Synch
21/38
Control of Resistor
i h
8/14/2019 Morris Vent Synch
22/38
Pressure 3500 cm H20
High PressureSystem
valve
Pressure 35 cm H20
Tidal volume 500 ml
8/14/2019 Morris Vent Synch
23/38
Volume Control
Deflated Volume Inflated Volume
8/14/2019 Morris Vent Synch
24/38
Pressure Control
Deflated Pressure Inflated Pressure
Wh t t l th
8/14/2019 Morris Vent Synch
25/38
What controls theadjustments?
Volume?
(flow control)
Pressure?
Mi
8/14/2019 Morris Vent Synch
26/38
Pressure 3500 cm H20
MicroprocessorControl
Inhalationvalve(resistor)
solenoid
Microprocessor
exhalevalve
Tidal volume 500 ml
Pressure 35 cm H20
8/14/2019 Morris Vent Synch
27/38
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
8/14/2019 Morris Vent Synch
28/38
How to Assess VentilatorModes
q Inhalation
what is controlled
what is targeted
how does it adjust
8/14/2019 Morris Vent Synch
29/38
Targeting
q How much breath is enough?
8/14/2019 Morris Vent Synch
30/38
Targeting
Control
q Flow
q Pressure
Target
q Time
q Pressure
q Volume
Volumecontrol
8/14/2019 Morris Vent Synch
31/38
Targeting
Control
q Flow
q Pressure
Target
q Time
q Pressure
q Volume
Time-cycledpressure
control
8/14/2019 Morris Vent Synch
32/38
Targeting
Control
q Flow
q Pressure
Target
q Time
q Pressure
q VolumeVolumetargeted
pressure
control
H t A V til t
8/14/2019 Morris Vent Synch
33/38
How to Assess VentilatorModes
q Inhalation
what is controlled
what is targeted
how does it adjust
Patients generate
8/14/2019 Morris Vent Synch
34/38
Patients generatepressures
q Negative pressure
inhalation efforts
q Positive pressure
bucking
8/14/2019 Morris Vent Synch
35/38
Negative pressure:Adjustments
q No adjustment
q Increase in pressure/flow to match
demand
q Decrease in pressure/flow to foster
weaning
8/14/2019 Morris Vent Synch
36/38
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
8/14/2019 Morris Vent Synch
37/38
How to Assess VentilatorModes
q Exhalation
next year
8/14/2019 Morris Vent Synch
38/38
Coming up next...
Reality