1. A ventilator mode describes how the ventilator controls pressure (P), volume (V), and flow within each breath through a primary control variable (V, P, or dual) and how mandatory and spontaneous breaths are sequenced (CMV, IMV, CSV). 2. Control types describe the ventilator's feedback control and include tactical (within breath), strategic (between breaths), and intelligent (between patients) control. 3. Phase variables like trigger, limit, cycle, and baseline determine the beginning, sustaining and ending of each breath phase.

2. 
1. CONTROL
To describe how the ventilator manages

p v and flow delivery within a breath



Sequence of mandatory and spontns brth
to create specific breathing patterns

3. equation
of motion
Pvent
+
Pmus
=
P E+ PR
Pvent
=
pressure
generate
d by the
vent @
Airway
opening
Pmus
=
presure
generate
d by the
vent mus
PE
=
the
elastic
load
PR
=
the
resistive
load

4. To calculate the lung mechanic parameters of
R, C given information about p, v and flow.
2. To predict p, v, flow given values for R & C
1.
“For any mode only one variable can be
controlled at a time” ( p v &flow)
Flow is the derivative of volume as a function of
tme, and volume is the integral of flow

5. A ventilator mode must refer a pre defined pattern of interaction between
The patient and the ventilator
The pattern of interaction is
The breathing
Pattern
Even more specifically
The breathing pattern refers to
The sequence of mandatory and
spontaneous breath

6. Thus a mode
description reduces
a specification of
how the ventilator
controls
P, V, flow within a
breath .
Along with a
description of how
the breaths are
sequenced.

8. 







a. Primary breath-control variable
Volume
Pressure
Dual
b. Breath sequence
Continuous mandatory ventilation (CMV)
Intermittent mandatory ventilation (IMV)
Continuous spontaneous ventilation (CSV)

9. 









a. Tactical control (within breaths)
Set point
Auto-set-point
Servo
b. Strategic control (between breaths)
Adaptive
Optimal
C. Intelligent control (between patients)
Knowledge-based
Artificial neural network

10.  a.
Phase variables
 Trigger
 Limit
 Cycle
 Baseline
 b. Conditional variables
 c. Computational logic

11. a). Primary Breath Control Variable
V, P & Dual Control
b). Breath Sequence
CMV, IMV and CSV

12. 1a. Control variable.
The control variable is the variable that the
ventilator uses as a feedback signal to
control inspiration
(ie, pressure, volume, or flow).

13. The control variable can be identified as follows:
 If the peak inspiratory pressure remains
constant as
 the load experienced by the ventilator changes,
then the control variable is pressure.
If the peak pressure changes as the load
changes but VT remains constant, then the
control variable is volume.
 Volume control implies flow control and vice
versa,


14. „‟ Inspiration starts out as VCV and then
switches to PCV before the end of breath
or vice versa ”

15. CMV
IMV
CSV

17. Volume control implies that the ventilator
determines the
 tidal volume [VT], whereas in a spontaneous
breath the
 patient determines the VT.


18. The key difference now between CMV and
IMV is that
 with CMV the clinical intent is to make every
inspiration a mandatory breath,
 Whereas with IMV the clinical intent is to
partition ventilatory support between
mandatory and spontaneous breaths.


19. CMV is normally considered a method of full
ventilatory support,
 whereas IMV is usually viewed as a method
of partial ventilatory support (eg, for
weaning).
“Thus for classification purposes, if
spontaneous breaths are not allowed
between mandatory breaths, the breath
sequence is CMV; otherwise the sequence is
IMV ”


20. 
Control type is a categorization of the
ventilators feedback control function .

At the most basic level control is focused on
what happens within a breath

Tactical Control – within breath (set point, auto
set point , servo )
Strategic Control – between breaths
( adaptive , optimal )
Intelligent Control – between patients
( knowledge based , artificial neural network)





21. Set point
 The output of the ventilator matches a
constant operator preset input value .
 Mandatory breaths are pressure limited and
time cycled, according to the operator set
values for peak inspiratory pressure and
frequency

Eg : PC-IMV


22. The ventilator Selects which operator
adjusted set points are enforced at the
moment
 Inspiration starts in PCV and switches to
VCV
 Eg ; volume assured pressure support


23. The ventilator output automatically follows a
varying input
 The instantaneous value of pressure is
proportional to the instantaneous volume or
flow generated by the patient .


Eg; PAV & ATC

24. One ventilator set point is automatically
adjusted to achieve another set point as the
patient condition changes .
 Mandatory breaths are pressure limited , and
the pressure limit is automatically adjusted
between breaths to achieve the preset tidal
volume

Eg ; PRVC


25. One ventilator set point is automatically
adjusted to optimize another set point according
to some model of system behavior, whose
output can be maximized or minimized
dynamically.
 Each breath is pressure limited , and the
pressure limit is automatically adjusted between
breaths ( using ventilator mechanics
measurements ) to minimize WOB
 Eg ; adaptive support ventilation


26.  Set
points are automatically adjusted
according to a rule based expert system.
 pressure support level for spontaneous
breath is automatically adjusted to
maintain appropriate breathing frequency,
TV, ETCO2, depending on the type of
patient .

Eg : smart care

27. 




Auto adjusted set points by artificial neural
network.
The relation b/w inputs & outputs determined by
weighting factors at neural nodes that change
with learning.
The network inputs are the current ventilator
settings and partial pressure of ABG and PH
Network outputs are the most appropriate
ventilator settings projected to maintain blood
gases within an acceptable range
Eg ; experimental

28. Tactical Control
Operator
Ventilator
Patient
Stategic Control
Operator
Model
Ventilator
Patient
Intelligent Control
Ventilator
Model
Patient

29. 
PHASE VARIABLES
a. Phase variables
Trigger
Limit
Cycle
Baseline
b. Conditional variables
c. Computational logic

30. T - Trigger
L - Limit
C - Cycle
B - Baseline
Time

31. The phase variable begins, sustains, and ends
each of the four phases of a breath .
The four phases are ;
1. Change from exhalation to inhalation
2. inspiration
3. Change from inspiration to expiration
4. Exhalation

32. The mechanism the ventilator uses to end
exhalation and begin inspiration is the
triggering mechanism .
 Time trigger ; the ventilator can trigger itself,
 the rate of breathing is controlled by the
ventilator .
 So this mode sometimes is called controlled
ventilation

38. A limit variable is the maximum value a variable
( p, v, v; t) can attain .
1. Pressure limiting; allows pressure to rise to a
certain value but not exceed it .
To prevent excessive pressure from entering
the patients lungs , the operator set a control
sometimes labeled a high pressure limit.
when the vent reaches the high p limit excess
pressure will vented through a spring loaded
pressure release or valve.


39. A volume limited breath is controlled by an
electronically operated valve that measures
the flow passing through during a specific
interval .
 The volume may be set by the operator, or
the ventilator may have a bag, or piston
cylinder that contains a fixed volume .


42. Baseline variable is the parameter that
generally controlled during exhalation .
 Although either V or flow could serve as a
baseline variable , P is the most practical
choice and is used by all modern ventilators.
 The pressure level from which a ventilator
breath begins is called the baseline pressure
 It can be zero , which is also called (ZEEP)
or (PEEP).


43. 5
PA
0
Time

44. Any unique combination of breathing
pattern, control type, and operational
algorithms is technically a mode.
It can be described in terms of “if then”
statements
 Eg ; if spontaneous minute ventilation falls
below a preset threshold , then deliver
enough mandatory breaths to raise MV
above the threshold .

45. Description of the relationship between the inputs,
feedback signals, and outputs, adding detail about
how the mode operates that does not given in the
other components of mode specification.
Eg ; ASV mode of Hamilton Galileo uses WOB as the
performance function , and it is related to lung
mechanics, alveolar ventilation , dead space volume
And breathing frequency. As lung mechanics change,
the ventilator finds the optimum frequency ( to
minimize wob) and then sets the VT to meet the MV
requirement .(Smartcare
mode on dragger)

46. Large Insp effort
No inspiratory effort
Small inspiratory effort
Reduced
pressure
indicates patient
effort during
inspirations
Machine Triggered
Pt-triggered
Set Tidal
Volume

47. Large Insp effort
No inspiratory effort
Reduced
pressure
Machine Triggered
Volume
Target
Volume overshoot
Set Tidal
Volume

48. 
A machine that produces breathing patterns
that mimic the humans normally breathe at
rates and tidal volumes our bodies produces
during the normal activities.