Pressure Support Ventilation – A New Triggered Ventilation Mode for Neonates

-37-2011
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Pressure Support Ventilation –
A New Triggered Ventilation Mode for Neonates
Jean Christophe Rozé
Thomas Krüger

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Important Notice:
Medical knowledge changes constantly as a result of new research
and clinical experience. The authors of this introductory guide has
made every effort to ensure that the information given is completely up
to date, particularly as regards applications and mode of operation.
However, responsibility for all clinical measures must remain with the reader.
Written by:
Prof. Jean Christophe Rozé, MD
Neonatal intensive care unit
Hôpital Mère Enfant
University hospital
Nantes, France 44035
Thoms Krüger
Dräger Medical GmbH
Moislinger Allee 53/55
23542 Lübeck
All rights, in particular those of duplication and distribution, are reserved
by Dräger Medizintechnik GmbH.
No part of this work may be reproduced or stored in any form using
mechanical, electronic or photographic means, without the written
permission of Dräger Medizintechnik GmbH.
ISBN 3-926762-41-1

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Pressure Support Ventilation –
a New Triggered Ventilation Mode for Neonates
Jean Christophe Rozé
Thomas Krüger

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CONTENTS
1.0
Introduction
6
2.0
Pressure Support Ventilation
8
2.1 Definition
8
2.2
Advantages of Pressure Support Ventilation in Adults
10
2.3
Pressure Support Ventilation in Neonates
11
3.0
Triggered Ventilation in Neonates
12
3.1
Consequences of Asynchrony
12
3.2 Preventing
Asynchrony
12
4.0 Trigger
Signals
14
4.1
Principles of Triggering
14
4.1.1 Thoracic Impedance
14
4.1.2 Abdominal Movement
15
4.1.3 Airway Pressure Changes
15
4.1.4 Airway Flow Changes
16
4.1.5 Esophageal Pressure Changes
17
4.2
Specific Problems with Different Trigger Signals
18
4.2.1 Lack of Response
18
4.2.2 Autotriggering
18
4.2.3 Artefact
18
4.2.4 Antiphasic Trigger
19
4.2.5 Delayed Response Time
19
4.3
Technical Comparison of Different Trigger Signals
20
4.4
Clinical Comparison of Different Trigger Signals
21
5.0
Different Ventilation Modes
22
5.1
Untriggered Modes
22
5.2 Triggered
Modes
24
5.3
Pressure Support Ventilation
26
5.3.1 Definition
26
5.3.2 Automatic Leak Adaptation
28
5.3.3 Backup Ventilation
30
5.3.4 Limitations and Contra-Indications
31
5.4
Clinical Studies Comparing Ventilation Modes
34

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04|05
6.0
Benefits of Pressure Support Ventilation
34
6.1
Weaning Newborn Infants from the Ventilator
34
6.1.1 Easy Weaning
34
6.1.2 Difficult Weaning
34
6.2 Weaning
Strategies
36
6.2.1 Selection of Weaning Type
36
6.2.2 Physiological Studies
36
6.2.3 Clinical Studies
38
6.2.4 PSV is better than A/C!
39
6.2.5 PSV with Volume Guarantee
40
7.0
Pressure Support Ventilation in Practice
42
7.1
Ventilator Settings in PSV
42
7.1.1 Selecting the PSV Mode
42
7.1.2 Adjusting Trigger Threshold
43
7.1.3 Adjusting Inspiratory Flow
44
7.1.4 Adjusting Inspiratory Time (Backup TI)
45
7.1.5 Adjusting Initial Pressure Support Level
46
7.1.6 Setting the Backup Rate
46
7.2
Weaning by Pressure Support Ventilation
47
7.3
Monitoring Pressure Support Ventilation
49
7.3.1 Physiological Background
49
7.3.1.1 Chemical Control
49
7.3.1.2 The Respiratory Pump
51
7.3.1.3 Oxygen Consumption, Carbon Dioxide Production and Work of Breathing
51
7.3.1.4 Pulmonary Reflexes
51
7.3.1.5 Pattern of Respiration in Neonates with RDS
52
7.3.2 Monitoring in Practice
53
8.0 Conclusion
56
9.0 Appendix
58
9.1 Case
Reports
58
9.2 Abbreviations
62
10.0 References
64

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PRESSURE SUPPORT VENTILATION |
INTRODUCTION
1.0 Introduction
Pressure Support Ventilation (PSV), a well known and widely accepted mode
of respiratory support in adults has numerous publications, which describe
application and benefits in this field of ventilation.
Pressure Support Ventilation although available in a few neonatal/pediatric
ventilators is seldom used due to technical limitations despite the wide use
of triggered ventilation modes such as SIMV or A/C in neonatology.
A specifically adapted neonatal Pressure Support Ventilation is now available
with the Babylog 8000plus. This booklet sets out recommendations and
descriptions, which refer to the Babylog 8000plus with software 5.0. The
offered unique benefits for the use of PSV in neonates facilitate the
application and improve the effectiveness of this new respiratory support.
Nevertheless the first part of this booklet discusses theory of triggered
ventilation in general and describes all the different ventilation modes. As
well, an overview of the numerous publications in the field of triggered
ventilation is given. The second part of this booklet focuses then on Pressure
Support Ventilation as a further step in the evolution of neonatal triggered
ventilation modes. PSV can be used during the acute phase of respiratory
distress syndrome as well as during weaning, preferably in neonates who
show high oxygen cost of breathing. The benefits, indications, limitations,
ventilation strategies and control are described to help clinicians better
understand and apply this new respiratory support. Moreover, the use of
Pressure Support Ventilation in combination with the new mode Volume
Guarantee is discussed.

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06|07
The outlined strategies are based on publications and the first hand personal
experience gained with this new mode. Nevertheless, due to the constant
change in medical knowledge some of the descriptions may require revision
in the future.
We hope that this booklet will help promote the use of Pressure Support
Ventilation, based on the evidence so far there is the potential for many
promising advances in the management of respiratory support of the
critically ill neonate.

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PRESSURE SUPPORT VENTILATION |
PRESSURE SUPPORT VENTILATION
2.0 Pressure Support Ventilation
2.1 DEFINITION
Pressure Support Ventilation is a pressure limited ventilatory mode in
which each breath is patient-triggered and supported. [1] It provides
breath-by-breath ventilatory support by means of a positive pressure
wave synchronized with the inspiratory effort of the patient, both
patient-initiated and patient-terminated. Thus, during a cycle of
Pressure Support Ventilation four phases can be distinguished which
constitute the working principles of PSV [1]:
– Recognition of the beginning of inspiration
– Pressurization
– Recognition of the end of inspiration
– Expiration

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08|09
Paw pressurisation
expiration
phase 2
phase 4
Pinsp
PEEP
t
Peak flow
Flow
15% of peak flow
t
Onset of
End of
inspiration
inspiration
-22593-2010
phase 1
phase 3
D
Figure 1:
Pressure and airway flow signals during a PSV breath, showing the four phases: Recognition of
the beginning of inspiration, pressurisation, recognition of the end of inspiration and expiration.

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PRESSURE SUPPORT VENTILATION |
PRESSURE SUPPORT VENTILATION
2.2 ADVANTAGES OF PRESSURE SUPPORT VENTIL ATION IN ADULTS [1]
In adult ventilation Pressure Support Ventilation is world wide the mostly
used ventilation mode for weaning patients off the ventilator. Many studies
have been performed to evaluate Pressure Support Ventilation in adult
critical care. The main advantages [1] observed during these studies were:
– Better synchrony between patient and ventilator
– Increased patient comfort
– Reduced need for sedation
– Decrease in work of breathing
– Decrease in oxygen cost of breathing
– Shorter duration of weaning process (observed only in few studies) [2]
– Endurance oriented training of respiratory muscles [47]
– Deepening of weak shallow spontaneous breathing
2.3 PRESSURE SUPPORT VENTIL ATION IN NEONATES
During conventional ventilation neonates are ventilated with continuous
flow, pressure limited, time cycled ventilators. The introduction of triggered

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