B to A Mechanical Ventilation good lecture.ppt

mechanical ventilation

1. B to A - Mechanical Ventilation newer
modes,graphics etc. DNB Lect
Dr.Vilas Gundecha (M.D. Med)
Director – ICU
Inlaks & Budhrani Hospital
Pune

2. Introduction
Mechanical ventilation is a useful modality
for patients who are unable to sustain the
level of ventilation necessary to maintain
the gas exchange functions-oxygenation
and carbon dioxide elemination

3. Indications:
 Physiological changes like deterioration of lung parenchyma
 Diseased states like chest trauma
Medical/surgical procedures like post operative recovery
Ventilatory failure or oxygenation failure due to
1. Increased airway resistance
2. Changes in lung compliance
3. Hypoventilation
4. V/Q mismatch
5. Intrapulmonary shunting
6. diffusion defect

4. Key terms
Lung compliance: Is the change in volume per unit
change in pressure
Types:
 Static compliance=Corrected tidal volume
 Plateau pressure-PEEP
Dynamic compliance
 = corrected tidal volume
 Peak inspiratory pressure-PEEP

5. Clinical conditions that decrease
compliance

Type Conditions
Static compliance atelectasis
ARDS
Tension pneumothorax
Obesity
Retained secretions
Dynamic compliance Broncho spasm
Kinking of ET tube
Airway obstruction

6. High compliance – exhalation is often
incomplete due to lack of elastic recoil by
the lungs.
Seen in conditions that increase patients
FRC-

Obstructive lung defect

Airflow obstruction

7. Operating modes
Spontaneous
Positive end expiratory pressure (PEEP)
Continuous positive airway pressure (CPAP)
Bilevel positive airway pressure (BiPAP)
Controlled mandatory ventilation (CMV)
Assist control (AC)
Intermittent mandatory ventilation (IMV)

8. Synchronized intermittent mandatory
ventilation (SIMV)
Mandatory minute ventilation (MMV)
Pressure support ventilation (PSV)
Adaptive support ventilation (ASV)
Proportional assist ventilation (PAV)
Volume assured pressure support (VAPS)

9. Pressure regulated volume control (PRVC)
Pressure control ventilation (PCV)
Airway pressure release ventilation
Inverse ratio ventilation (IRV)
Automatic tube compensation (ATC)

10. Pressure cycled and volume cycled ventilationPressure cycled and volume cycled ventilation
Pressure-cycled modes deliver a fixed pressure at variable volume
Volume-cycled modes deliver a fixed volume at variable pressure
•Volume-cycled modes
•Control
•Assist
•Assist/Control
•Intermittent Mandatory Ventilation (IMV)
•Synchronous Intermittent Mandatory
Ventilation (SIMV)
Pressure-cycled modes
• Pressure Support Ventilation (PSV)
• Pressure Control Ventilation (PCV)
• PEEP
• CPAP
• BiPAP

11. Physiology of PEEP
Reinflates collapsed alveoli and maintains alveolar
inflation during exhalation
PEEP
Decreases alveolar distending pressure
Increases FRC by alveolar recruitment
Improves ventilation
Increases V/Q, improves oxygenation, decreases work of breathing

12. High intrathoracic pressures can cause
decreased venous return and decreased cardiac
output
May produce pulmonary barotrauma
May worsen air-trapping in obstructive
pulmonary disease
Increases intracranial pressure
Alterations of renal functions and water
metabolism
DANGERS

13. CONTROLLED MANDATORY
VENTILATION(CMV)

14. Assist/Control ModeAssist/Control Mode
•Assist Mode
•Pt initiates all breaths, but
ventilator cycles in at initiation to
give a preset tidal volume
•Pt controls rate but always
receives a full machine breath
•Assist/Control Mode
.Mandatory mechanical breath
either triggered by patient
spontaneous inspiratory
efforts(assist)
•Time triggered by a preset
respiratory rate – (control)
•POTENTIAL HAZARD-alveolar
hyperventilation-higher pH and
low PaCO2-respiratory alkalosis
Ventilator delivers a fixed volume

15. Intermittent mandatory ventilationIntermittent mandatory ventilation
•IMV
•Pt receives a set number of
ventilator breaths
•Different from Control: pt can
initiate own (spontaneous)
breaths
•Different from Assist:
spontaneous breaths are not
supported by machine with fixed
T
V
•Ventilator always delivers
breath, even if pt exhaling
•Breath stacking is the
complication.

16. Synchronization window
Time interval just prior to time triggering in
which ventilator is responsive to the
patients spontaneous inspiratory efforts
Varies with ventilator,0.5 is representative

17. ADVANTAGES
Maintains respiratory muscle
strength/avoids muscle atrophy
Reduces ventilation and perfusion
mismatch
Decreases mean airway pressure
 Facilitates weaning

18. Pressure Control Ventilation (PCV)Pressure Control Ventilation (PCV)
Ventilator determines inspiratory time – no patient participation
•Parameters
•Triggered by time
•Limited by pressure
•Affects inspiration only
•Disadvantages
•Requires frequent adjustments
to maintain adequate V
E
•Pt with noncompliant lungs
may require alterations in
inspiratory times to
achieve adequate T
V

19. Vent settings to improve <oxygenation>Vent settings to improve <oxygenation>
•FIO
2
•Simplest maneuver to quickly increase P
a
O
2
•Long-term toxicity at >60%
•Free radical damage
•Inadequate oxygenation despite 100% FiO
2

usually due to pulmonary shunting
•Collapse – Atelectasis
•Pus-filled alveoli – Pneumonia
•Water/Protein – ARDS
•Water – CHF
•Blood - Hemorrhage
PEEP and FiO
2
are adjusted in tandem

20. Vent settings to improve <ventilation>Vent settings to improve <ventilation>
•Respiratory rate
•Max RR at 35 breaths/min
•Efficiency of ventilation decreases
with increasing RR
•Decreased time for alveolar
emptying
•T
V
•Goal of 10 ml/kg
•Risk of volutrauma
•Other means to decrease P
aCO
2
•Reduce muscular activity/seizures
•Minimizing exogenous carb load
•Controlling hypermetabolic states
•Permissive hypercapnea
•Preferable to dangerously high RR
and T
V, as long as pH > 7.15
RR and T
V
are adjusted to maintain V
E
and P
a
CO
2
•I:E ratio (IRV)
•Increasing inspiration time will
increase T
V
, but may lead to
auto-PEEP
•PIP
•Elevated PIP suggests need for
switch from volume-cycled to
pressure-cycled mode
•Maintained at <45cm H
2O to
minimize barotrauma
•Plateau pressures
•Pressure measured at the end
of inspiratory phase
•Maintained at <30-35cm H
2
O to
minimize barotrauma

21. Ventilator Graphics…..

22. Purpose
Graphics are waveforms that reflect the patient-
ventilator system and their interaction.
Purpose of monitoring graphics includes:
•Allows user to interpret, evaluate, and troubleshoot
the ventilator and the patient’s response to ventilator.
•Monitors the patient’s disease status (C and Raw).
•Assesses patient’s response to therapy.
•Monitors ventilator function
•Allows fine tuning of ventilator to decrease WOB,
optimize ventilation, and maximize patient comfort.

23. Measured Parameters….
Flow
Pressure
Time
Calculated Parameters …..
Volume (as an integration of flow)
Compliance
Resistance
Work of Breathing
Auto-PEEP

24. A. Trigger …….
What causes the breath to begin?
B. Limit ……
What regulates gas flow during the breath?
C. Cycle …….
What causes the breath to end?
Basics phase variables…………..
A
B C

25. The Pulmonary graphics display in two
formats………
…………………… Waveforms..!!!
…………………… .Loops ..!!!

26. Most Commonly used
Waveforms and Loops……
1.Pressure vs. Time
2.Flow vs. Time
3.Volume vs. Time
AND
1.Pressure – volume loop
2.Flow – volume loop

27. Waveforms: plot pressure/volume/flow
against time…time is the x axis
Loops: plot pressure/volume/flow against
each other…there is no time component

28. Volume ModesPressure Modes
Types of Waveforms……
P
r
e
s
s
u
r
e
F
lo
w
V
o
lu
m
e
Time

29. Pressure/Time waveform
•In Volume modes,
the shape will be
an exponential rise
or an accelerating
ramp for
mandatory breaths.
In Pressure modes, the
shape will be rectangular
or square.
This means that pressure
remains constant
throughout the breath
cycle.
•In Volume modes, adding an inspiratory pause may improve distribution of ventilation.

30. Pressure/Time waveform
•Air trapping (auto-PEEP)
•Airway Obstruction
•Bronchodilator Response
•Respiratory Mechanics (C/Raw)
•Active Exhalation
•Breath Type (Pressure vs. Volume)
•PIP, Pplat
•CPAP, PEEP
•Asynchrony
•Triggering Effort
Can be used to assess:

31. Pressure/Time waveform

A
B
1
2
Inspiratory pause
= MAP
1 = Peak Inspiratory Pressure (PIP)
2 = Plateau Pressure (Pplat)
A = Airway Resistance (Raw)
B = Alveolar Distending Pressure
• The area under the entire curve represents the mean airway pressure (MAP).

32. Pressure/Time waveform
•The baseline for the pressure waveform increases when PEEP is
added.
•There will be a negative deflection just before the waveform with
patient triggered breaths.
5
15
No patient effort Patient effort
PEEP
+5

33. Pressure/Time wave form
Increased Airway Resistance Decreased Compliance
PIP
Pplat
PIP
Pplat
A. B.
•A-An increase in airway resistance causes the PIP to increase, but Pplat pressure
remains normal.
•B-A decrease in lung compliance causes the entire waveform to increase in size.
The difference between PIP and Pplat remain normal.

34. Pressure/Time waveform
Expiratory hold
Set
PEEP

Auto-
PEEP

+5
+9
Total-
PEEP

+14
Air-Trapping (Auto-PEEP)
•While performing an expiratory hold maneuver, the waveform rises above the baseline.
•The +9 of Aut0-PEEP represents 9 cm H2O pressure caused by air trapped in the lungs.
•Fix by increasing the amount of “set PEEP” to offset the amount of auto-PEEP.
•An acceptable amount of auto-PEEP should be < 5cm H2O

35. Asynchrony
Flow Starvation
•The inspiratory portion of the pressure wave shows a scooping or
“dip”, due to inadequate flow.

36. Volume/Time waveform
The Volume waveform will generally have a “mountain peak”
appearance at the top. It may also have a plateau, or “flattened”
area at the peak of the waveform.
•There will also be a plateau if an inspiratory pause set or inspiratory hold
maneuver is applied to the breath.

37. Volume/Time waveform
•Air trapping (auto-PEEP)
•Leaks
•Tidal Volume
•Active Exhalation
•Asynchrony
Can be used to assess:

38. Volume/Time waveform
Inspiratory Tidal Volume
Exhaled volume returns
to baseline

39. Volume/Time waveform
Air-Trapping or Leak
•If the exhalation side of the waveform doesn’t return to baseline, it
could be from air-trapping or there could be a leak (ETT, vent
circuit, chest tube, etc.)
Loss of volume

40. Flow/Time waveform
In Volume modes, the
shape of the waveform will
be square or rectangular.
This means that flow
remains constant
throughout the breath
cycle.

In Pressure modes,
(PC, PS, PRVC,
VS) the shape of
the waveform will
have a decelerating
ramp flow pattern.
•Some ventilators allow you to select the flow pattern that you want in Volume
Control mode.

41. Flow/Time waveform
•Air trapping (auto-PEEP)
•Airway Obstruction
•Bronchodilator Response
•Active Exhalation
•Breath Type (Pressure vs. Volume)
•Flow Waveform Shape
•Inspiratory Flow
•Asynchrony
•Triggering Effort
Can be used to assess:

42. Flow/Time waveform
Volume Pressure

43. Flow/Time waveform
•The decelerating flow pattern may be preferred over the constant
flow pattern. The same tidal volume is delivered, but with a lower
peak pressure.

44. Flow/Time waveform
Auto-Peep (air trapping)
•If expiratory flow doesn’t return to baseline before the next breath starts,
there’s auto-PEEP (air trapping) present , e.g. emphysema.
Start of next breath
Expiratory flow
doesn’t return to
baseline

45. Flow/Time Scalar
Bronchodilator Response
•To assess response to bronchodilator therapy, you should see an increase in
peak expiratory flow rate.
•The expiratory curve should return to baseline sooner.
Peak Exp. Flow
Improved Peak Exp. Flow
Shorter
E-time
Longer
E-time
Pre-Bronchodilator Post-Bronchodilator

46. Pressure/Volume Loops
Volume is plotted on the y-axis, Pressure on the x-
axis.
Inspiratory curve is upward, Expiratory curve is
downward.
Spontaneous breaths go clockwise and positive
pressure breaths go counterclockwise.
The bottom of the loop will be at the set PEEP level.
It will be at 0 if there’s no PEEP set.
If an imaginary line is drawn down the middle of the
loop, the area to the right represents inspiratory
resistance and the area to the left represents
expiratory resistance.

47. P-V loops……
Lung Overdistention
Airway Obstruction
Bronchodilator Response
Respiratory Mechanics
WOB
Flow Starvation
Leaks
Triggering Effort

48. inspiration
expiration
15
30
5
The loop is almost square in PC/PS because of pressure
limiting (constant) , during the inspiratory part of the loop.
P-V Loop……. Components
V
o
lu
m
e

Pressure
P-V slope
A = Inspiratory
Resistance/
Resistive WOB
B = Exp.
Resistance/
Elastic WOB
Dynamic
Compliance
Pressure mode……
PIP
AB

49. P-V Loop……. Components
V
o
lu
m
e

PIP
V
T
Pressure
A = Inspiratory
Resistance/
Resistive WOB
B = Exp.
Resistance/
Elastic WOB
E
x
p
i r a
t i o
n
I n
s p
i r a
t i o
n
Dynamic
Compliance(Cdyn)
The top part of the P/V loop represents Dynamic compliance (Cdyn).
Cdyn = Δvolume/Δpressure
Volume mode
A
B

50. Spontaneous Breath………
Inspiration
Expiration
0 20 40 602040-60
0.2
0.4
0.6
Pressure
cmH
2
O
V
T
Clockwise
CPAP

51. Assisted Breath…………
Inspiration
Expiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH
2
O
Assisted
Breath
V
T Clockwise to
Counterclockwise
PEEP

52. Controlled Breath…….

Expiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH
2
O
Inspiration
V
T
Anticlockwise
PEEP
P-V loop and PEEP…..

53. P-V Loops….in Airway Resistance
•As resistance increases, the loop will become wider.
•An ↑ in expiratory resistance is more common.
• ↑ inspiratory resistance …….kinked ETT or patient biting.
“ h
y s te
r e
s is ”
e
x p
. r e
s is t a
n
c e
in
s p
. r e
s is t a
n
c e

54. Decreased Compliance……….
V
o
lu
m
e
Pressure Pressure
↓compliance… Loops moves down (angle becomes < 40)…….RDS (HMD)
….moves up (>45) …….. ↑ compliance……. Surfactant therapy

55. Lung Compliance Changing in P-V Loop (pressure
mode)………….
Volume
Preset PIP
V
T

le
v
e
ls
Pressure
RDS…lung
1.With surfactant
2. Emphysematous L
Constant PIP……… variable VT

56. Lung Compliance Changes and
the P-V Loop…. (Volume mode)
Volume
PIP levels
Preset V
T
PressurePressure
↑C C ↓C
Constant VT………. Variable Pressure

57. Air leak…..
•The expiratory portion of the loop doesn’t return to baseline. This indicates a leak.
Inspiration
Expiration

58. Insufficient flow……
V
o
l
u
m
e
Pressure
Normal
Insufficient Flow
Cuspin
g

60. Flow/Volume Loops
Flow is plotted on the y axis and volume on the x axis
Flow volume loops used for ventilator graphics are the same
as ones used for Pulmonary Function Testing, (usually upside
down).
Inspiration is above the horizontal line and expiration is
below.
The shape of the inspiratory curve will match what’s set on
the ventilator.
The shape of the exp flow curve represents passive
exhalation…it’s long and more drawn out in patients with less
recoil.
Can be used to determine the PIF, PEF, and Vt
Looks circular with spontaneous breaths

61. Flow/Volume Loops
•Air trapping
•Airway Obstruction
•Airway Resistance
•Bronchodilator Response
•Insp/Exp Flow
•Flow Starvation
•Leaks
•Water or Secretion accumulation
•Asynchrony
Can be used to assess:

62. Flow-Volume Loop……….
Volume (ml)
Inspiration
Expiration
F
l
o
w

(
L
/
m
i
n
)
PIFR
PEFR
FRC
VT
Pressure Mode

63. F-V loops…. variations

64. Air-leak……….
Volume (ml)
Inspiration
Expiration
F
l
o
w

(
L
/
m
i
n
)
PIFR
PEFR
FRC
VT
Air Leak

65. Volume (ml)
Inspiration
Expiration
F
l
o
w

(
L
/
m
i
n
)
PIFR
PEFR
VT
Air Trapping…….
Does not returnDoes not return
to baselineto baseline

66. Volume (ml)
Inspiration
Expiration
F
l
o
w

(
L
/
m
i
n
)
PIFR
PEFR
FRC
VT
Airway Secretions
……….Water in the Circuit

67. Volume (ml)
Inspiration
Expiration
F
l
o
w

(
L
/
m
i
n
)
PIFR
FRC
VT
↓PEFR
“Scooped out”
pattern
Increased Airway Resistance……

68. Bronchodilator Response….. F-V loop
2
1
1
2
3
3
V
LPS
.
V
T
Normal
AFTER
Bronchospasm Relief
2
1
1
2
3
3
V
.
2
1
1
2
3
3
V
.

69. Air Trapping (auto-PEEP)
Causes:
•Insufficient expiratory time
•Early collapse of unstable alveoli/airways during exhalation
How to Identify it on the graphics
•Pressure wave: while performing an expiratory hold, the waveform
rises above baseline.
•Flow wave: the expiratory flow doesn’t return to baseline before the
next breath begins.
•Volume wave: the expiratory portion doesn’t return to baseline.
•Flow/Volume Loop: the loop doesn’t meet at the baseline
•Pressure/Volume Loop: the loop doesn’t meet at the baseline
How to Fix:
•Give a treatment, adjust I-time, increase flow, add PEEP.

70. Airway Resistance Changes
Causes:
•Bronchospasm
•ETT problems (too small, kinked, obstructed, patient biting)
•High flow rate
•Secretion build-up
•Damp or blocked expiratory valve/filter
•Water in the HME
How to Identify it on the graphics
•Pressure wave: PIP increases, but the plateau stays the same
•Flow wave: it takes longer for the exp side to reach baseline/exp flow rate is
reduced
•Volume wave: it takes longer for the exp curve to reach the baseline
•Pressure/Volume loop: the loop will be wider. Increase Insp. Resistance will
cause it to bulge to the right. Exp resistance, bulges to the left.
•Flow/Volume loop: decreased exp flow with a scoop in the exp curve
How to fix
•Give a treatment, suction patient, drain water, change HME, change ETT, add a
bite block, reduce PF rate, change exp filter.

71. Compliance Changes
Decreased compliance

ARDS

Atelectasis

Abdominal distension

CHF

Consolidation

Fibrosis

Hyperinflation

Pneumothorax

Pleural effusion
How to Identify it on the graphics

Pressure wave: PIP and
plateau both increase

Pressure/Volume loop: lays
more horizontal
•Increased compliance
•Causes
Emphysema
Surfactant Therapy
• How to Identify it on the
graphics
Pressure wave: PIP and plateau
both decrease
Pressure/Volume loop: Stands
more vertical (upright)

72. Leaks
Causes
•Expiratory leak: ETT cuff leak , chest tube leak, BP fistula, NG tube in
trachea
•Inspiratory leak: loose connections, ventilator malfunction, faulty flow
sensor
How to ID it
•Pressure wave: Decreased PIP
•Volume wave: Expiratory side of wave doesn’t return to baseline
•Flow wave: PEF decreased
•Pressure/Volume loop: exp side doesn’t return to the baseline
•Flow/Volume loop: exp side doesn’t return to baseline
How to fix it
•Check possible causes listed above
•Do a leak test and make sure all connections are tight

73. Ventilator management algorithimVentilator management algorithim
Initial intubation
• FiO
2
= 50%
• PEEP = 5

• RR = 12 – 15
• V
T = 8 – 10 ml/kg
S
aO
2 < 90% S
aO
2 > 90%
S
a
O
2
> 90%
•Adjust RR to maintain PaCO
2
=
40
•Reduce FiO
2
< 50% as tolerated
•Reduce PEEP < 8 as tolerated
•Assess criteria for SBT daily
S
aO
2 < 90%
•Increase FiO
2 (keep S
aO
2>90%)
•Increase PEEP to max 20
•Identify possible acute lung
injury
•Identify respiratory failure
causes
Acute lung injury
No injury
Fail SBT
Acute lung injury
•Low T
V
(lung-protective) settings
•Reduce T
V
to 6 ml/kg
•Increase RR up to 35 to keep
pH > 7.2, P
aCO
2 < 50
•Adjust PEEP to keep FiO
2 < 60%
S
a
O
2
< 90% S
a
O
2
> 90%
S
a
O
2
< 90%
•Dx/Tx associated conditions
(PTX, hemothorax,
hydrothorax)
•Consider adjunct measures
(prone positioning, HFOV, IRV)
S
a
O
2
> 90%
•Continue lung-
protective ventilation
until:
•PaO
2
/FiO
2
> 300
•Criteria met for
SBT
Persistently fail SBT
•Consider tracheostomy
•Resume daily SBTs with CPAP
or tracheostomy collar
Pass SBT
Airway stable
Extubate
Intubated > 2 wks
•Consider PSV wean (gradual
reduction of pressure support)
•Consider gradual increases in
SBT duration until endurance
improves
Prolonged ventilator
dependence
Pass SBT
Pass SBT
Airway stable
Modified from Sena et al, ACS Surgery:
Principles and Practice (2005).

74. The physiology and pathophysiology of
mechanical ventilation
In the first mechanism, mechanical ventilation
enhances surfactant release from the pneumocyte
type II into the alveolus, lost into small airways due
to compression of the surfactant film.
The changes in alveolar surfactant may affect the
permeability of the alveolocapillary barrier to small
solutes and proteins ↑pulmonary leak
in respiratory failure and the formation of edema.

75. The physiology and pathophysiology of
mechanical ventilation
Surfactant composition and function can be
impaired by inhibitory factors from protein- rich
pulmonary edema fluid or by the degradation in the
alveolar space due to lipases and proteinases
The second mechanism is that the alveolar
surfactant and the changes that are associated with
mechanical ventilation may result in the conversion
of surface-active, large surfactant aggregates into
nonsurface-active aggregates

76. The physiology and pathophysiology of
mechanical ventilation
Surfactant changes caused by mechanical
ventilation are reversible due to a
metabolically active de novo production of
surfactant.
The barrier function of surfactant may
collapse with mechanical ventilation, and
there may be transmigration of bacteria.
High-peak inspiratory lung volumes
+↓positive end-expiratory pressure (PEEP)
↑proinflammatory mediators from the
lung tissue into the airway.

77. The physiology and pathophysiology of
mechanical ventilation
10 cm H2O of PEEP at comparable peak inspiratory
lung volumes or lowering peak inspiratory lung
volume when ventilating with zero PEEP reduced
these cytokine levels.
Lung, an important causative part of an
inflammation-induced systemic disease state 
MOF,not only a pulmonary disease process.
Alveolar collapse with improper mechanical
ventilation(PEEP VT
↓ ↑
)  activation of SIRS

79. Conclusion and take home
message
Lung recruitment  opening collapsed
lung units by↑transpulmonary pressure
(PA-Ppl).
↓PEEP VT
↑
 continuous expansion and
collapse of alveoli  barotrauma +
volutrauma, surfactant dysfunction and
cytokine release  activation of SIRS
High PEEP ↓cytokine level.
Standard physiologic VT  5 to 7 cc/kg

80. Conclusion and Take home
message
High opening pressure to recruit the lung
and lower pressures (PEEP) to keep the
alveoli open
The ideal pressure is 15~30 cmH2O to
prevent alveolar collapse.
Pressure-control fresh gas from
ventilator, higher pressure, not from
adjacent lung units
Volume control  intrapulmonary
redistribution of gas  Pendelluft effect.
ARDS  multiple atelectasis, % of recruitable
lung varied widely, from negligible to >50%

81. Evidence Base for Newer Modes of
Mechanical Ventilation: Overview
Background for evidence base levelsBackground for evidence base levels

Dual modes of ventilationDual modes of ventilation
Adaptive Support ventilation (ASV)Adaptive Support ventilation (ASV)
 Proportional Assist Ventilation (PAV)Proportional Assist Ventilation (PAV)

Airway Pressure Release Ventilation (APRV)Airway Pressure Release Ventilation (APRV)

82. Evidence Base for Newer Modes of
Mechanical Ventilation: Background
From: Branson & Johanningman, 2004:RC,49:7, 742-760.

83. New Modes of Mechanical
Ventilation: Examples of the first dual modes

Volume Assured Pressure Support (VAPS) Volume Assured Pressure Support (VAPS)
& Pressure Augmentation& Pressure Augmentation

Pressure Regulated Volume Control Pressure Regulated Volume Control
(PRVC) & similar modes(PRVC) & similar modes

Volume Support Ventilation (VS or VSV) Volume Support Ventilation (VS or VSV)
& similar modes& similar modes

84. Pressure vs. Volume Ventilation
(From Branson, R., Bird product literature)

85. Newer Methods of Ventilatory
Support: dual modes

1st generation dual modes: VAPS, Press. 1st generation dual modes: VAPS, Press.
Aug., PRVC & VS Aug., PRVC & VS

Allow variable flow delivery and pressure Allow variable flow delivery and pressure
“targeted” ventilation approach“targeted” ventilation approach

Attempt to deliver a set tidal volume (TV)Attempt to deliver a set tidal volume (TV)

Allow peak airway pressure to vary breath Allow peak airway pressure to vary breath
to breathto breath

86. VAPS: Volume Assured
Pressure Support

Combines volume ventilation & pressure supportCombines volume ventilation & pressure support

(for mech., vol. limited breaths only)(for mech., vol. limited breaths only)

Uses TV, peak flow, and pressure sup./control settingsUses TV, peak flow, and pressure sup./control settings

Targets PS level with Targets PS level with at leastat least set peak flow first set peak flow first

Continues until flow decreases to set peak flow, then:Continues until flow decreases to set peak flow, then:

If TV not delivered, peak flow maintained If TV not delivered, peak flow maintained
until vol. limituntil vol. limit

If TV or more delivered, breath endsIf TV or more delivered, breath ends

87. VAPS: Volume Assured
Pressure Support
 (From Branson, R., Bird product literature)(From Branson, R., Bird product literature)

88. Pressure Regulated Volume
Control (Servo vents.)

Combines volume ventilation & pressure Combines volume ventilation & pressure
controlcontrol

(for mech., time-cycl. breaths only)(for mech., time-cycl. breaths only)

Set TV is “targeted”Set TV is “targeted”

Ventilator estimates vol./press. relationship Ventilator estimates vol./press. relationship
each breatheach breath

Ventilator adjusts level of pressure control Ventilator adjusts level of pressure control
breath by breathbreath by breath

89. Pressure Regulated Volume
Control (Servo vents, example)

First breath = 5-10 cm H2O above PEEPFirst breath = 5-10 cm H2O above PEEP

V/P relationship V/P relationship measuredmeasured

Next 3 breaths, pressure increased to 75% Next 3 breaths, pressure increased to 75%
needed for set TVneeded for set TV

Then up to +/- 3 cm H2O changes per Then up to +/- 3 cm H2O changes per
breathbreath

Time ends inspirationTime ends inspiration

90. Pressure Regulated Volume
Control (Siemens Servo 300)

From Siemens prod. literatureFrom Siemens prod. literature

91. Pressure Regulated Volume
Control - Considerations

Assist-control modeAssist-control mode

Like PC, flow varies automatically to Like PC, flow varies automatically to
varying patient demands varying patient demands

Constant press. during each breath - Constant press. during each breath -
variable press. from breath to breathvariable press. from breath to breath

Time is cycling method; delivered TV can Time is cycling method; delivered TV can
vary from setvary from set

92. First dual modes: VAPS, Press. Aug.
vs. PRVC & VS

VAPS VAPS (& Press. (& Press.
Augmentation)Augmentation)

Use the set TV as a Use the set TV as a
minimumminimum

Normal cycling Normal cycling
occurs at or above occurs at or above
the set TVthe set TV

Mechanics not Mechanics not
measuredmeasured

PRVC PRVC (& Vol. Support)(& Vol. Support)

Use the set TV as the Use the set TV as the
“target” for each breath“target” for each breath

Normal cycling may Normal cycling may
stop insp. below stop insp. below oror
above set TVabove set TV

Pressure used based on Pressure used based on
mechanics measurements mechanics measurements

93. First dual modes: VAPS, Press. Aug.
vs. PRVC & VS

Peak airway pressure can reach high levels:Peak airway pressure can reach high levels:
Set appropriate high pressure limitsSet appropriate high pressure limits

No settings for No settings for maximummaximum tidal volume tidal volume

94. Newer Ventilator Dual Modes:

AutoFlow:AutoFlow:Drager Drager
ventilators Evita 4, ventilators Evita 4,
Evita 2 duraEvita 2 dura

Adaptive Support Adaptive Support
Ventilation (ASV): Ventilation (ASV):
Hamilton GalileoHamilton Galileo

95. Newer Ventilator Dual Modes:
Drager vent’s AutoFlow

First breath uses set TV First breath uses set TV
& I-time& I-time

Pplateau measuredPplateau measured

Pplateau then usedPplateau then used

V/P measured each V/P measured each
breathbreath

Press. changed if Press. changed if
needed (+/- 3)needed (+/- 3)

Then similar to PRVCThen similar to PRVC
From Drager & Mosby’s R. C. Equip., 6th ed. 1999.

96. Newer Ventilator Dual Modes:
Drager vent’s AutoFlow

Allows spont. breathing:Allows spont. breathing:

expiration expiration andand

inspirationinspiration

Exp. efforts at peak insp. Exp. efforts at peak insp.
pressure open exh. pressure open exh.
valve; Ppeak maintainedvalve; Ppeak maintained

Active exhalation valve Active exhalation valve
is a key featureis a key feature
From Drager & Mosby’s R. C. Equip., 6th ed. 1999.

97. Newer Ventilator Dual Modes:
Drager vent’s AutoFlow

Allows spont. breathing:Allows spont. breathing:

expiration expiration andand

inspirationinspiration
From Drager

98. Newer Ventilator Dual Modes:
Drager vent’s AutoFlow - Considerations

Dual mode similar to PRVCDual mode similar to PRVC

Targets vol., applies variable press. based on Targets vol., applies variable press. based on
mechanics measurementsmechanics measurements

Allows highly variable inspiratory flows Allows highly variable inspiratory flows

Time ends mandatory breathsTime ends mandatory breaths

Adds ability to freely exhale during mandatory Adds ability to freely exhale during mandatory
inspiration (maintains pressure)inspiration (maintains pressure)

Adds high TV alarm & limitAdds high TV alarm & limit

Can be used in CMV, SIMV and MMVCan be used in CMV, SIMV and MMV

99. Newer Ventilator Dual Modes:
Hamilton Galileo’s ASV (adapt. sup. vent.)

Clinician enters pt. data & % supportClinician enters pt. data & % support

Vent. calculates needed min. vol. & best Vent. calculates needed min. vol. & best
rate/TV to produces rate/TV to produces least work.least work.

Targeted TV’s given as press. control or Targeted TV’s given as press. control or
press. support breathspress. support breaths

Breath is: PC if time triggered, PS if pt. Breath is: PC if time triggered, PS if pt.
triggeredtriggered

100. Newer Ventilator Dual Modes:
Hamilton Galileo’s ASV (adapt. sup. vent.)

Vent. measures & analyzes data & mechanics each Vent. measures & analyzes data & mechanics each
breath for:breath for:

compliancecompliance

resistanceresistance

inspiratory & expiratory time constantsinspiratory & expiratory time constants

actual I-time, E-time, total f & min. vol. actual I-time, E-time, total f & min. vol.

pressurespressures
Press. adjusts in +/- 2 cm HPress. adjusts in +/- 2 cm H
22O to achieve TVO to achieve TV

101. Newer Ventilator Dual Modes:
Hamilton Galileo’s ASV - Considerations

Mandatory breaths = PC, pt. triggered = PSMandatory breaths = PC, pt. triggered = PS

both at same targeted TV and calculated both at same targeted TV and calculated
press.press.

102. ASV: Principle mode of ventilation
Pinsp
PEEP
no patient activity:
* machine triggered
+ time cycled
patient is active:
* patient triggered
+ flow cycled
Flow I
Flow E
* *
+ +
From Hamilton Medical

103. Newer Ventilator Dual Modes:
Hamilton Galileo’s ASV - Considerations

If pt.’s f > “set” by vent., mode is PSIf pt.’s f > “set” by vent., mode is PS

If pt.’s f < “set” by vent., mode is PC-SIMV/PSIf pt.’s f < “set” by vent., mode is PC-SIMV/PS

If patient is apneic, all breaths are PCIf patient is apneic, all breaths are PC

Mandatory breaths = PC, pt. triggered = PSMandatory breaths = PC, pt. triggered = PS

both at same targeted TV and calculated press.both at same targeted TV and calculated press.

104. Newer Ventilator Dual Modes:
Hamilton Galileo’s ASV: Considerations

Using “least work” as a criteria:Using “least work” as a criteria:

calculation for needed rate may change,calculation for needed rate may change,

therefore calculated TV may change, andtherefore calculated TV may change, and

therefore calculated pressure needed for TV therefore calculated pressure needed for TV
may changemay change

Both max. & min. TV limits are usedBoth max. & min. TV limits are used

As patient improves,”support” is decreasedAs patient improves,”support” is decreased

pressure can be reduced to PEEP + 5 cm H2Opressure can be reduced to PEEP + 5 cm H2O

105. Newer Ventilator Dual Modes:
Summary:

Combined methods of press. & volume Combined methods of press. & volume
ventilation ventilation maymay replace standard volume replace standard volume
ventilation.ventilation.

Prudent use of high pressure limits (and Prudent use of high pressure limits (and
volume limits if available) and careful volume limits if available) and careful
monitoring can decrease disadvantages of monitoring can decrease disadvantages of
combined modes.combined modes.

106. Newer Ventilator Dual Modes:
Evidence:

VAPS:VAPS:

No randomized controlled trials (RCT)No randomized controlled trials (RCT)

2 observational studies, 1 bench study 2 observational studies, 1 bench study
with test lungwith test lung

Lower level outcomes:Lower level outcomes:

Reduced workReduced work

Evid. levels III, B & level V, CEvid. levels III, B & level V, C

107. Newer Ventilator Dual Modes:
Evidence:

PRVC/VS PRVC/VS (also referred to as “adaptive PC”)(also referred to as “adaptive PC”)::

2 small randomized controlled trials (RCT): post-op pts, 2 small randomized controlled trials (RCT): post-op pts,
no survival benefit, no diff or slightly shorter vent time, no survival benefit, no diff or slightly shorter vent time,
less interventions & blood gasesless interventions & blood gases

3 other randomized cross-over observational studies, & 5 3 other randomized cross-over observational studies, & 5
other cross-over short term obs. studies: safe, small other cross-over short term obs. studies: safe, small
differences in lower PIP, some shorter to extubationdifferences in lower PIP, some shorter to extubation

Lower level outcomes:Lower level outcomes:

Small RCT trials: II, grade B evidenceSmall RCT trials: II, grade B evidence

Small cross-over studies III, grade CSmall cross-over studies III, grade C

108. Newer Ventilator Dual Modes:
Evidence:

ASV:ASV:

2 small randomized controlled trials (RCT): no survival 2 small randomized controlled trials (RCT): no survival
benefit, sub-group (10 infants) shorter vent time, less benefit, sub-group (10 infants) shorter vent time, less
BPD; adult study showed only less PIP in PRVCBPD; adult study showed only less PIP in PRVC

3 other cross-over observational studies, lower PIP, (better 3 other cross-over observational studies, lower PIP, (better
gas exchange in animal study only)gas exchange in animal study only)

Lower level outcomes:Lower level outcomes:

Small RCT trials: II, grade B evidenceSmall RCT trials: II, grade B evidence

Small cross-over studies III for humans, V for animal Small cross-over studies III for humans, V for animal
study, all grade Cstudy, all grade C

109. New Modes of Mechanical
Ventilation: Bi-level ventilation methods

Ventilation methods that allow spontaneous Ventilation methods that allow spontaneous
breathing at two airway pressures:breathing at two airway pressures:

BiPAP (Drager E-4 & E-2 dura)BiPAP (Drager E-4 & E-2 dura)

BiLevel (NPB 840)BiLevel (NPB 840)

APRV (NPB 840, Drager E-4 & E-2 dura)APRV (NPB 840, Drager E-4 & E-2 dura)

Pressure targeted strategy & spont. Breathing Pressure targeted strategy & spont. Breathing

can fit lung protective criteriacan fit lung protective criteria

110. Spontaneous Breaths
P
T
Spontaneous Breaths
BiLevel Ventilation: NPB 840BiLevel Ventilation: NPB 840

Uses two levels of pressure for two time periodsUses two levels of pressure for two time periods

Mandatory breaths at the higher pressure are time Mandatory breaths at the higher pressure are time
cycledcycled

Spontaneous breaths can be pressure supportedSpontaneous breaths can be pressure supported
From PB product lit.

111. P
T
Synchronized Transitions
PEEP
HIGH
PEEP
LOW
T
LOW
T
HIGH
Synchronized Transitions
BiLevel Ventilation: NPB 840BiLevel Ventilation: NPB 840

Uses 2 pressure levels for 2 time periodsUses 2 pressure levels for 2 time periods
PEEPPEEP
lowlow & PEEP & PEEP
highhigh, T, T
highhigh and T and T
low low

Patient triggering & cycling can change phasesPatient triggering & cycling can change phases
From PB product lit.

112. PEEP
High
+ PS
P
PEEP
L
PEEP
H
Pressure Support
BiLevel Ventilation: NPB 840BiLevel Ventilation: NPB 840

Pressure support may be applied at both pressures Pressure support may be applied at both pressures
during a spont. breathduring a spont. breath
If PS is set higher than PEEPIf PS is set higher than PEEP
HH, the PS pressure is , the PS pressure is
applied to a spontaneous effort at upper pressureapplied to a spontaneous effort at upper pressure
From PB product lit.

113. Spontaneous Breaths
P
Pressure Support
T
BiLevel Ventilation: NPB 840BiLevel Ventilation: NPB 840
If PS is set lower than PEEPIf PS is set lower than PEEP
HH, PS is , PS is
applied to patient efforts at the lower applied to patient efforts at the lower
pressure, PEEPpressure, PEEP
LL
From PB product lit.

114. APRV (Drager ventilators)

Airway Pressure Release VentilationAirway Pressure Release Ventilation

Like BiPAP/BiLevel but time at the lower Like BiPAP/BiLevel but time at the lower
pressure (“release time”) is usually short, pressure (“release time”) is usually short,
1-1.5 seconds1-1.5 seconds

Spontaneous breathing still allowed Spontaneous breathing still allowed
throughout low & high pressuresthroughout low & high pressures

115. APRV (Drager ventilators)

Airway Pressure Release VentilationAirway Pressure Release Ventilation
From Mosby’s R. C. Equip. 6th ed. 1999.

116. Newer Methods of Ventilatory
Support: Proportional Assist Ventilation

PAV - currently on PB 840 in US PAV - currently on PB 840 in US
prototype/research ventilators, Drager Evita 4 prototype/research ventilators, Drager Evita 4
& Respironics BiPAP Vision& Respironics BiPAP Vision

Allows free flow based on patient effortAllows free flow based on patient effort

““Targets” portion of patient’s Targets” portion of patient’s workwork during during
“spontaneous” breaths“spontaneous” breaths

Automatically adjusts flow, volume and Automatically adjusts flow, volume and
pressure needed each breathpressure needed each breath

117. Methods of Ventilatory Support: PAV
continued

““Vol. assist %” reduces work of elastanceVol. assist %” reduces work of elastance

““Flow assist%” reduces work of resistance'sFlow assist%” reduces work of resistance's

Pressure adjusts during each breath to Pressure adjusts during each breath to
control work levelcontrol work level

Increased patient effort causes increased Increased patient effort causes increased
applied pressure (and flow & volume)applied pressure (and flow & volume)

118. Methods of Ventilatory Support: PAV
continued
From Younes, M: Ch.15, in Tobin, MJ From Younes, M: Ch.15, in Tobin, MJ Prin. & Pract. Of Mech. Vent.Prin. & Pract. Of Mech. Vent. 1994 McGaw- 1994 McGaw-
Hill, Inc.Hill, Inc.

119. Methods of Ventilatory Support: PAV
continued

Other controls useful for PAV:Other controls useful for PAV:

High pressure limitHigh pressure limit

High volume limitHigh volume limit

Back-up ventilation modeBack-up ventilation mode

Typical alarms etc.Typical alarms etc.

120. Methods of Ventilatory Support: PAV
- Considerations

Consistent level of support per breathConsistent level of support per breath

Patient controls breathing patternPatient controls breathing pattern

Patient triggered modePatient triggered mode

(Unless back-up mode present)(Unless back-up mode present)

Reduced support with Auto-PEEPReduced support with Auto-PEEP

Cannot compensate for leaks (prototypes)Cannot compensate for leaks (prototypes)

121. Methods of Ventilatory Support: PAV
-Evidence

Huge number of studies since 1992.Huge number of studies since 1992.

BUT, almost no large RCTs. Most were small, BUT, almost no large RCTs. Most were small,
short term observational comparing PAV to short term observational comparing PAV to
pressure support.pressure support.

Largest trial in NIPPV for ARF: showed no Largest trial in NIPPV for ARF: showed no
difference for intubation, stay, mortality. Better difference for intubation, stay, mortality. Better
comfort for PAVcomfort for PAV

Most all other trials rated level III, grades or C.Most all other trials rated level III, grades or C.

122. New Modes of Mechanical
Ventilation: Other neat stuff

123. New Modes of Mechanical
Ventilation: Other neat stuff

Automatic tube Automatic tube
compensation: compensation:
Drager Evita 4Drager Evita 4
From Drager prod. lit.

124. New modes of mechanical
ventilation in neonates
“Neurally Adjusted Ventilatory Assist
(NAVA)”

125. NAVA concept

126. Measuring of electric diaphragm activity

127. NAVA principle
Sinderby et al Nature Med 1999
Ppeak (Pest) in NAVA =
= NAVA Level x (Edi peak – Edi min) + PEEP

128. NAVA - Synchrony
APPLY

129. Edi Catheter positioning procedure
Position and Edi signal

130. Edi curve

131. Estimated Ppeak (Pest) in NAVA =
= NAVA Level x (Edi peak – Edi min) + PEEP

132. NAVA-intubated
-Weaning of ventilator rather than acute phase
-Severe BPD (late stage)
NAVA-extubated
-Possible adaption to non invasive ventilation
therapy such as Nasal IPPV (IMV).
Possible application of NAVA in NICU

133. Trouble Shooting