ASV use and algorithmASV use and algorithm

HAMILTON MEDICAL AGSwitzerland

February 2001

ContentsContents

•Introduction

•Clinical use of ASV

•Functional description of ASV

•Scientific basis

IntroductionIntroduction

b) The obvious but difficult solutionRemove as many knobs as possible while still giving the user control over the pertinent parameters

a) Problems with conventional ventilatorsToo many knobs, too many controls, very few guidelines for setting controls

c) Definitions of pertinent parameters V'A To control pH/PaCO2 and WOB PEEP To control FRC and thus PaO2

FiO2 To control PaO2

Tp

Rate

Psup

Pinsp

Ti Te

@

FiO2

PEEPVt

FiO2

PEEP

VA

CMV

SIMV

PCV

PSV

Alveolar Ventilation Oxy.

Conventional

ASV

Introduction (cont.)Introduction (cont.)

Uses of ASVUses of ASV

•As start-up procedure only

•To critique the actual settings

•During weaning with and w/o protocol

•For post-cardiac surgery patients only

•For all patients, including ARDS

•As start-up procedure only

•To critique the actual settings

•During weaning with and w/o protocol

•For post-cardiac surgery patients only

•For all patients, including ARDS

How to use ASV clinically (1)How to use ASV clinically (1)

1) Set Body Wt of patient and high Pressure limit to 45 mbar (will yield Pmax < 35 mbar)

2) Set %MinVol to 100% (except COPD)

3) Set PEEP & FiO2 according to clinical requirements

4) Connect patient

How to use ASV clinically (2)How to use ASV clinically (2)

5) Ventilate for some minutes and assess blood gases and/or WOB (clinically)

6) Adjust %MinVol to meet pH/PaCO2 targets or WOB targets

7) Adjust PEEP and FiO2

8) Review high Pressure limit setting, consider changes only in exceptions

9) Observe Ppeak and fSpont trends

Repeat steps 5-9 until you consider extubation

Set high Pressure limit, Body Wt, %MinVol

Ventilate patient

Check blood gases and clinical statusPlot Pinsp, fTotal, fSpont trend

Set alarms

Consider weaning complete

fSpont and

ABG OK?

Yes

No

Prepare GALILEO

Pinsp< 8 cmH2O

No

Yes

Optimize %MinVol

Consider reducing %MinVol

Practical usePractical use

Optimize %MinVolOptimize %MinVolsee Operator‘s Manual p.D-13 and D-14see Operator‘s Manual p.D-13 and D-14

%MinVol change Remarks

Normal art. blood gases None

High PaCO2 Increase %MinVol Pay attention to

inspiratory pressures

Low PaCO2 Decrease %MinVol Pay attention to Pmean,

CO2 status

High respiratory drive Consider Increase in

%MinVol

Consider sedation,

analgesia, other treatment

Low O2 saturation None Consider PEEP and/or

FiO2 increase

How to monitor the patientHow to monitor the patient

• Target graphics window shows

– ASV target MinVol, Vt, f

– Actually achieved values for MinVol, Vt, f

– Safety limits for Vt and f

– Check feasibility of %MinVol settings

• Trends show

– level of support provided by the ventilator vs. level of patient activity

ASV Target Graphics ASV Target Graphics WindowWindow

How to monitor the patient: How to monitor the patient: Trend and trackTrend and track

Pinsp

fSpont

I I I I I I I

1h 2h 3h 4h

Tp

Rate

Psup

Pinsp

Ti Te

@

FiO2

PEEPVt

FiO2

PEEP

VA

CMV

SIMV

PCV

PSV

Alveolar Ventilation Oxy.

Conventional

ASV

How does ASV work?How does ASV work?

0

500

1000

1500

2000

0 20 40 60

f (b/min)

Vt (

ml)

Input: Minute ventilationInput: Minute ventilation

MinVol (l/min)

V

ASV is a "servant" to achieve a preset ASV is a "servant" to achieve a preset MinVol while respecting boundary MinVol while respecting boundary

conditions.conditions.

"Maintain at least 100% of normal ventilation, take spontaneous breathing into account,

prevent tachypnea,prevent AutoPEEP,

prevent excessive dead space ventilation,fully ventilate in apnea or low drive,

give control to patient in case breathing activityis okay, and do this without exceeding a 35 mbar

plateau pressure."

Command to servantCommand to servant

Functional description of ASVFunctional description of ASVsee also see also

flow chart in ASV brochureflow chart in ASV brochureAppendix D of Operator‘s ManualAppendix D of Operator‘s Manual

ASV User‘s GuideASV User‘s Guide

1) Calculation of minute ventilation

2) Application of lung-protective rules

3) Optimal breath pattern

4) Approach the target

0

500

1000

1500

2000

0 20 40 60

f (b/min)

Vt (

ml)

1. Calculation of MinVol (trivial)1. Calculation of MinVol (trivial)

MinVol (l/min)

0.1 l/min (adults)0.2 l/min (pediatric)

IBWV

IBW: Ideal Body Weight

2. Lung-protective rules 2. Lung-protective rules (boundary conditions)

0

500

1000

1500

2000

0 20 40 60

f (b/min)

Vt (

ml)

DD

AA

CC

BB

5 test breaths

10*Vd10*Vd

5 b/min5 b/min 20/RCexp20/RCexp

2*Vd2*Vd

3. Optimal breath pattern 3. Optimal breath pattern

0

500

1000

1500

2000

0 20 40 60

f bpm

Vt m

l

1+2a*RCexp*(MV-V‘D)/VD -1f-target =

a*RCexp

0

500

1000

1500

2000

0 20 40 60

f bpm

Vt m

l

5 test breaths

4. Adjust Pinsp & fSIMV to meet target4. Adjust Pinsp & fSIMV to meet target

0

500

1000

1500

2000

0 20 40 60

f bpm

Vt m

l

2. Lung-protective rules

1. Calculate MinVol (trivial)

4. Approach the target

3. Optimal breath pattern

Repeat 2,3,4 breath-by-breath

Summary of functionsSummary of functions

Scientific basisScientific basis

Choice of breathing pattern

Role of RCexp

Machine- or patient-triggered Dead space ventilation

Effects of PSL

Scientific basis (1)Scientific basis (1)

Choice of breathing pattern

Role of RCexp

Dead space ventilationMachine- or patient-triggered

Effects of PSL

FSIMPVFSIMPV

Fully Synchronized Intermittent Mandatory Pressure Ventilation (FSIMPV)

Fully Synchronized Intermittent Mandatory Pressure Ventilation (FSIMPV)

Machine- or patient-triggered Machine- or patient-triggered ventilationventilation

• Machine- and/or patient-triggered.

• Gas delivery is pressure-controlled for both the mandatory and the spontaneous breaths. Pressure levels are identical.

• Mandatory breaths are time-cycled if they were NOT triggered by the patient, spontaneous breaths are flow-cycled.

Control settings are: inspiratory pressure, respiratory rate, I:E ratio, pressure ramp, and expiratory trigger sensitivity. Other controls include

FiO2 and PEEP/CPAP.

"FSIMPVFSIMPV"

"FSIMPVFSIMPV"

Pinsp

PEEP

No patient activity:

* Machine-triggered+ Time-cycled

Patient is active:

* Patient-triggered+ Flow-cycled

Flow I

Flow E * *

+ +

"FSIMPVFSIMPV"

Ti To adjust I:E

f To adjust the rate

Pinsp To adjust Vt and fspont

PEEP To control FRCFiO2 To control PaO2

Scientific basis (2)Scientific basis (2)

Choice of breathing pattern

Role of RCexp

Dead space ventilationMachine- or patient-triggered

Effects of PSL

FSIMPVFSIMPV

Flow-volume loopFlow-volume loop

Flow, volume, and pressure tracings: Dynamic hyperinflationFlow, volume, and pressure tracings: Dynamic hyperinflation

-750-500-250

0250500750

V'a

w (

ml/s

)

0 1 2 3 4 5 6 7 8 9 10 11

-1000

100200300400500600700

Vol

(m

l)

0 1 2 3 4 5 6 7 8 9 10 11

05

101520253035

Paw

(cm

H2O

)

0 1 2 3 4 5 6 7 8 9 10 11

Time (s)

-100

0

100

200

300

400

500

600V

ol

(ml)

-1200 -800 -400 0 400 800

V'aw (ml/s)

I

E

Expiratory time constantExpiratory time constantExpiratory time constantExpiratory time constant

Scientific basis (3)Scientific basis (3)

Choice of breathing pattern

Role of RCexp

Dead space ventilationMachine- or patient-triggered

Effects of PSL

FSIMPVFSIMPV

Flow-volume loopFlow-volume loop

Minimal WOB (Otis)Minimal WOB (Otis)

Scientific basis (4)Scientific basis (4)

Choice of breathing pattern

Role of RCexp

Dead space ventilationMachine- or patient-triggered

Effects of PSL

FSIMPVFSIMPV

Flow-volume loopFlow-volume loop

Minimal WOB (Otis)Minimal WOB (Otis)

Radford 2.2 ml/kgRadford 2.2 ml/kg

0

50

100

150

200

250

0 50 100 150 200 250

Height (cm)

Vd

(m

l)

Vd (Hart)Vd - female (Radford)Vd - male (Radford)

Dead space guesstimationDead space guesstimation

Scientific basis (5)Scientific basis (5)

Choice of breathing pattern

Role of RCexp

Dead space ventilationMachine- or patient-triggered

Effects of PSL

FSIMPVFSIMPV

Flow-volume loopFlow-volume loop

Minimal WOB (Otis)Minimal WOB (Otis)

Radford 2.2 ml/kgRadford 2.2 ml/kg

Vt and fVt and f

Effect of PS level in spontaneous breathingEffect of PS level in spontaneous breathing

Borchard et.al. 1991, Anesthesiology 75:739-745

0

100

200

300

400

500

600

PS 0 PS 4 PS 8 PS 12

ml

0

5

10

15

20

25

30

/min Vt

f

0

100

200

300

400

500

600

700

BPS-5 BPS BPS+5 BPS+10

ml

0

5

10

15

20

25

30

35

/min Vt

f

Effect of PS level in spontaneous breathingEffect of PS level in spontaneous breathing

G.Iotti et.al. 1995 Int Care Med 21:406-413

Scientific basis: SummaryScientific basis: Summary

Choice of breathing pattern

Role of RCexp

Dead space ventilationMachine- or patient-triggered

Effects of PSL

FSIMPVFSIMPV

Flow-volume loopFlow-volume loop

Minimal WOB (Otis)Minimal WOB (Otis)

Radford 2.2 ml/kgRadford 2.2 ml/kg

Vt and fVt and f

•ASV works in passive and in active patients

•ASV promotes weaning from minute one

•ASV employs lung-protective strategies to minimize complications from AutoPEEP and thus barotrauma

•ASV prevents tachypnea, apnea, excessive dead space ventilation, and excessive breaths

•ASV adapts continuously to the needs of the patient

BenefitsBenefits

When technology is masterWhen technology is masterwe shall reach disasterwe shall reach disaster

fasterfasterPiet Hein