Transcript Document

Critical Care Ventilation
Technology Perspective
Fran Hegarty
Atoms and Molecules
are connected together.
The connections are
the attraction of molecules
to each other.
Atoms and Molecules
are connected together.
The connections are
the attraction of molecules
to each other.
As molecules get more energy (temperature)
they tend to become less bound by the attraction
between them, and the properties of the matter change.
Molecules have:
Low Energy
Low Temperature.
Molecules held in place by
attraction to each other.
Solid.
Molecules have:
Some Energy
Higher Temperature.
Molecules held in place by
attraction to each other
but have enough energy to move
relative to each other.
Liquid
Molecules have:
Lots of Energy
Higher Temperature.
Molecules no longer held in place
by attraction to each other
but move freely
relative to each other.
Gas
Molecules have:
Lots of Energy
Higher Temperature.
Molecules no longer held in place
by attraction to each other
but move freely
relative to each other.
Gas
Properties of Gases.
Gases.
Volume = Defined Space i.e. 1 Litre.
If it is empty i.e. contains no matter of any kind its called a vacuum.
Gases.
A gas will expand to fill the volume which contains it.
Gases.
A gas will expand to fill the volume which contains it.
As it does so it becomes less dense.
Gases.
1 Litre of Oxygen
(low density)
1 Litre of Oxygen
(high density)
So how do you know how much gas is in a
one litre volume ?
To answer that
we need to know more
about
Gas Pressure.
Gases.
The gas molecules are in constant motion, and so
they regularly hit the walls of the container.
Gases.
The force of the gas molecules hitting the walls
of the container is called the Gas Pressure.
Gases.
The more gas molecules there are, the more often the
walls of the container are hit,
therefore the Gas Pressure is higher.
Gases.
If the temperature (energy) of the gas is increased
the molecules move faster and so hit the walls harder
causing the Gas Pressure to rise also.
Gases.
The effect of the expected variations in room
temperature have very little effect on
medical gas pressure (so we will ignore this effect).
Gases.
The amount of Gas Molecules in a volume is
given by the Volume x Gas pressure.
Volume = 1
Pressure = 1
Volume = 1
Pressure = 2
What would happen if we suddenly doubled
the size of the container ?
Volume = 1
Pressure = 2
What would happen if we suddenly doubled
the size of the container ?
Remember there are the same number of molecules in each.
Volume = 1
Pressure = 2
Volume = 2
Pressure = ?
Gas expands to fill the volume.
Density of gas falls.
Force per unit ares due to gas hitting the walls falls.
Pressure falls.
Volume = 1
Pressure = 2
Volume = 2
Pressure = 1
Volume = 2
Pressure = 1
Volume = 0.5
Pressure = 4
Volume = 1
Pressure = 2
VxP=2
VxP=2
VxP=2
How come we never talk about the pressure when
deciding how much gas is to be delivered to the patient ?
To answer that we need to know more about
Atmospheric Pressure.
Atmosphere is
a gas (Air).
Space
is a vacuum.
Air molecules
hit the surface of
the earth.
Atmospheric Pressure
Pressure of the Air
molecules hitting
the earth.
(or any other surface
in the atmosphere).
14 lbs. per square inch
We are so use to Atmospheric Pressure
that we forget its there.
So, when we say we want to give a patient
“a tidal volume of half a litre of air”
…….we realy mean….
“ a tidal volume of half a litre of air at atmospheric pressure”.
How do you make a gas move or flow.
Gases flow from areas of high pressure,
to areas of low pressure.
What does it all have to do
with the Siemens 300 ?
Patm
Lungs
Patm
Lungs
Patm
Lungs
Patm
Lungs
Patm
Lungs
How we Breath.
Patm = PL
How we Breath.
Patm > PL
How we Breath.
Patm < PL
Boyles Law in action !
Patm
Spontaneous Breathing.
P
Patm
Airway Pressure
0.7 L
FRC
Volume of Air in Lungs
Mechanical Ventilation.
Patm
Bellows
Lungs
Patm
Bellows
Lungs
Patm
Bellows
Lungs
Patm
Bellows
Lungs
Patm
Patm
Patm
Patm
Patm
Ventilator
Bellows
Patient
Lungs
Ventilator
Patient
Bellows
Lungs
Ventilator
Patient
Patm
Bellows
Lungs
Patient
Ventilator
Patm
Bellows
Inspiration
Lungs
Patient
Ventilator
Patm
Bellows
Inspiration
Lungs
Patient
Ventilator
Patm
Bellows
Inspiration
Lungs
Patient
Ventilator
Patm
Bellows
Inspiration
Lungs
Patient
Ventilator
Patm
Bellows
Pause
Lungs
Patm
Bellows
Pause
Lungs
Patm
Expiration
Lungs
Patm
Expiration
Lungs
Patm
Expiration
Lungs
Airway Pressure Waveform
Patm
time.
Inspiration
Airway Pressure Waveform
Patm
time.
Inspiration
Gas flows into
patients lungs.
Airway Pressure Waveform
Patm
time.
End of
Inspiration
As lung expands
the pressure falls
Airway Pressure Waveform
Patm
time.
Pause
Airway Pressure Waveform
Patm
time.
Start of
Expiration.
Airway Pressure Waveform
Patm
time.
End of
Expiration.
Gas flows out of
patients lungs.
Airway Pressure Waveform
Patm
time.
Volume of Air in Lungs
0.7 L
FRC
Airway Pressure Waveform
Patm
time.
Volume of Air in Lungs
0.7 L
FRC
Airway Pressure Waveform
Patm
time.
Volume of Air in Lungs
0.7 L
FRC
time.
Airway Flow Waveform
Into Lungs
time.
Out of Lungs
Airway Pressure Waveform
Patm
Airway Flow Waveform
Into Lungs
time.
Out of Lungs
What is a
Ventilator ?
What is a
Ventilator ?
Lets make one from scratch.
Key Components:
Inspiration and Expiration Limbs and Expiration Valve.
Bellows
Lungs
Bellows
Lungs
Bellows
Lungs
Modes of Ventilation.
Different ways of controlling gas flow
into and out of the patients lungs.
Flow
Pressure
Volume
Lung Response
Computer
User Interface
Display
&
Alarms
Gas Volume
Gas Pressure
Gas Flow
Timing
Gas Volume
Gas Pressure
Gas Flow
Timing
Volume Controlled
Who is in charge ?
How do you determine the waveshape?
Bellows
Lungs
Volume Controlled Ventilation.
Define Tidal Volume
Define Breath Waveshape (timing)
Resultant Airway Pressure is
a function of gas flow into and out of
lung (lung condition important)
Ventilator works out the Gas Flow
on inspiration (expiration is lung
dependent).
Gap
Expiration
Pause
Inspiration
V
Time.
I
E
Respiration Waveform (Volume v Time).
Pressure Controlled
Who is in charge ?
How do you determine the waveshape?
Bellows
Lungs
Pressure Controlled Ventilation.
Resultant Volume delivered is
a function of gas flow into and out of
lung (lung condition important)
Define Target Airway Pressure
Define Breath Waveshape (timing)
Ventilator works out the Gas Flow
to achieve and maintain
the Target Pressure.
All modes are just different ways of controlling the flow
of gas into the patients lungs.
CMV
Ventilator
Controlled
Volume
Pressure
Pressure Regulated Volume Controlled
Who is in charge ?
How do you determine the waveshape?
Bellows
Lungs
Pressure Regulated Volume Controlled
Bellows
Lungs
Pressure Regulated Volume Controlled
Bellows
Lungs
Pressure Regulated Volume Controlled Ventilation.
Machine takes a guess at the pressure
Required to deliver this breath.
Define Breath Waveshape (timing)
Ventilator works out the Gas Flow
to achieve and maintain
the Target Pressure.
Define the target volume
Pressure Regulated Volume Controlled Ventilation.
Machine takes a guess at the pressure
Required to deliver this breath.
Define Breath Waveshape (timing)
Ventilator works out the Gas Flow
to achieve and maintain
the Target Pressure.
Define the target volume
Pressure Regulated Volume Controlled Ventilation.
Machine takes a guess at the pressure
Required to deliver this breath.
Define Breath Waveshape (timing)
Ventilator works out the Gas Flow
to achieve and maintain
the Target Pressure.
Define the target volume
Pressure Regulated Volume Controlled Ventilation.
Machine takes a guess at the pressure
Required to deliver this breath.
Define Breath Waveshape (timing)
Ventilator works out the Gas Flow
to achieve and maintain
the Target Pressure.
Define the target volume
Mode 2. Volume Controlled (Flow-Time Regulated) Ventilation.
Patient is completely paralysed - makes no effort
V
Time.
P
Pressure Controlled Ventilation.
Patient is completely paralysed - makes no effort
V
Time.
P
Volume Controlled (Pressure Regulated) CMV.
Patient is completely paralysed - makes no effort
V
Insp. Time.
P
Time.
Pressure Regulated Volume Controlled.
1st Breath – Test Breath
(Volume Controlled)
2nd Breath – PRVC Breath
Vti
Time.
Airway
Pressure
Plateaux Pressure from Volume
Controlled breath used as the
starting point for the PRVC breaths.
Time.
Pressure Regulated Volume Controlled.
Vti
Breath A.
Inspiratory Pressure insufficient
to deliver the required Vti.
Breath B.
Inspiratory Pressure now sufficient
to deliver the required Vti.
Set / Required
Tidal Volume
Time.
Airway
Pressure
Computer detects the volume
Is short and increases the inspiratory
Pressure on the next breath by 3 cmH20
Time.
Pressure Regulated Volume Controlled.
Vti
Breath B.
Inspiratory Pressure now sufficient
to deliver the required Vti.
Breath C.
If something goes wrong and vent
tries to deliver a high pressure breath the
Airway alarm will sound.
Set / Required
Tidal Volume
Time.
Set Upper
Inspiratory
Pressure Alarm Limit
Airway
Pressure
Time.
Volume Controlled (Pressure Regulated) CMV.
Patient is completely paralysed - makes no effort
V
Time.
P
All modes are just different ways of controlling the flow
of gas into the patients lungs.
Ventilator
Controlled
Volume
PRVC
Pressure
All modes are just different ways of controlling the flow
of gas into the patients lungs.
CMV
Ventilator
Controlled
Volume
Pressure
Assisted
Ventilation
Pressure Support.
Patient effort controls the rate (need to set the Trigger Sensitivity).
P
Trigger
Pressure Support.
Patient effort controls the rate (need to set the Trigger Sensitivity).
Ventilator does not deliver a volume…………….
It delivers a flow of gas until the patient airway reaches a
defined pressure (need to define this new pressure level).
P
Pressure Support above PEEP
Trigger
Pressure Support.
V
F
P
Pressure Support above PEEP
Trigger
Volume Support.
V
P
Pressure Support above PEEP
Volume Support.
V
P
Pressure Support above PEEP
All modes are just different ways of controlling the flow
of gas into the patients lungs.
Volume
Pressure
CMV
SIMV
Ventilator
Controlled
Mix
Assisted
Ventilation
CMV Volume Controlled (Revision)
Breath Period = 60/CMV Rate
Waveform determined by flow controls
Volume set by tidal volume
V
2 Sec
CMV Rate
Insp. Rise Time %.
Pause Time %
Insp. Time %
CMV Volume Controlled (Revision)
Breath Period = 60/CMV Rate
Waveform determined by flow controls
Volume set by tidal volume
V
VC
2 Sec
CMV Rate
Insp. Rise Time %.
Pause Time %
Insp. Time %
SIMV Volume Controlled
N.B. The repetition rate is set by a new
control the SIMV Rate.
SIMV Rate
V
CMV Rate
Insp. Rise Time %.
Pause Time %
Insp. Time %
SIMV Volume Controlled
SIMV Rate = 6
Time = 60/6 = 10
Therefore the next VC breath is in ten seconds.
SIMV Rate
V
CMV Rate
Insp. Rise Time %.
Pause Time %
Insp. Time %
SIMV Volume Controlled - Pressure Support
V
SIMV Volume Controlled - Pressure Support
V
SIMV Volume Controlled - Pressure Support
V
SIMV Volume Controlled - Pressure Support
V
SIMV Volume Controlled - Pressure Support
V
SIMV Volume Controlled - Pressure Support
V
SIMV Volume Controlled - Pressure Support
V
All modes are just different ways of controlling the flow
of gas into the patients lungs.
Ventilator
Controlled
Volume
VC
Mix
Assisted
Ventilation
SIMV
(VC&PS)
VS
SIMV
(PC&PS)
PS
PRVC
Pressure
PC
Auto Mode
CMV
SIMV
Assist
Modes
Control Mode
Assist Mode
CMV
SIMV
SIMV
Predominantly
Mandatory
with some
Assisted
Predominantly
Assisted
with some
Mandatory
Assist
Modes
Control Mode
Assist Mode
CMV
SIMV
SIMV
Predominantly
Mandatory
with some
Assisted
Predominantly
Assisted
with some
Mandatory
Assist
Modes
Control Mode
Assist Mode
Perfusion Side.
Arterial Blood Gas
Venous Blood Gas
Invivo Oximetry
O2 CO2 Bicarb
pH
RSO2 SvO2 SpO2
HB
Pulmonary Arterial Pressure
Pulmonary Venous Pressure
Swann
Gantz
Catheterisation
Thermodilution
Cardiac Output
Ventilation Side
Volumes and Timing
Spirometry
Respiratory
Mechanics
How the Volume changes with Pressure
Airway Pressures
Gas Composition
Manometry
Real Time Gas Monitoring