Transcript HFOV vs. Conventional Ventilation

HFOV vs.
Conventional
Ventilation
Latoya Robinson
Julie Ordones
Joshua Globke
Matthew Heaton
08/14/06
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Introduction
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We are students attending
Kingwood College researching the
safety and hazardous effects of
High Frequency Oscillatory
Ventilation (HFOV) vs.
Conventional Mechanical
Ventilation (CV) for adult patients
with ARDS.
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Hypothesis
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We predict that adults with ARDS
that are placed on HFOV will have
a lower mortality rate as opposed
to ARDS patients left on CV.
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Background
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High frequency was accidentally
discovered by anesthetist P.
Lunkenheimer in 1973. (5)
In 1980, Bohn also using HFOV
discovered excellent gas exchange
in normal dogs with the use of
oscillatory ventilation.(1)
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Definition: What is HFOV?
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HFOV “employs the delivery of small
tidal volumes ”called Amplitude at
frequencies or Hertz of greater than one
fifty beats per minute; usually equal or
less than the dead space.(3)
Lungs are kept open to a constant
airway pressure via a mean pressure
adjustment system.(3)
HFOV improves gas exchange and V/Q
matching, increases alveolar recruitment,
and enables stable lung inflation by use
of a rapid flow pattern, and constant
airway pressures(3)
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Indications for HFOV
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Severe blunt trauma to the thoracic
cavity
Persistent Pulmonary
Hypertension of the Newborn
Pneumothoracies and Congenital
Diaphragmatic Hernias
Risks of volutrauma and
barotraumas with conventional
ventilator settings that are very
high
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Hazards of HFOV
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Over distension
Tension Pneumothorax
Lung collapse
Difficulty maintaining ET tube
position
Difficulty assessing breath sounds
due to the loud noise from the
HFOV
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Methodology
Population
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In all 3 studies the population was
selected as a pt with ARDS and the
following criteria:
Adult >35 kg
P/F ratio of <200
CXR w/ bilateral pulmonary infiltrates
No atrial hypertension
No Hx of COPD
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Methodology
Equipment Used
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All 3 studies in the HFOV trial used
the Sensormedics 3100B oscillatory
ventilator.
The conventional mechanical
ventilators used in one of the studies
included the Dräger EVITA4,
Lübeck, and the Siemens
Servo300B. The other studies did
not list which vents used.
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Methodology
st
Testing Methods 1 Study
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In the first study, within the CV group, ventilators
were initially set on a time cycled pressure controlled
mode with a respiratory rate to achieve low tidal
volumes up to 60 bpm. The maximum peak pressure
was limited to 40 cmH2O. PEEP was advocated up
to 15cmH2O and an I: E Ratio up to 2:1 could be
used to achieve adequate oxygenation. In order to
minimize the inspiratory pressures, an arterial PH >
7.20 was acceptable regardless of the level of
PaCO2.
Methodology
st
Testing Methods 1 Study
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Patients in the HFOV group of Study 1 were
ventilated with a Sensor Medics 3100 B ventilator
using a high lung volume strategy with continuous
distending pressure at 5 cm H2O higher than mean
airway pressure on CV and then adjusted to
receive the most favorable lung volume. Initially
CDP was increased until an O2 saturation of >95%
was achieved; and not decreased until a FiO2 of <
60% was possible. The frequency was initially set
at 5 Hz with an inspiratory time of .33. Delta P was
adjusted according to PaCO2 and chest wall
vibrations.
Methodology
Testing Methods 2nd Study
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In Study 2, ventilators were initially set on a tidal
volume of 6-10 ml/kg with a RR to maintain a Ph of
>7.15, and an I-time also of .33. Adjustments were
made accordingly, for ventilation, an increase in RR
and Vt, and for oxygenation, an increase in PEEP,
FiO2, and or an increase in inspiratory time. When
weaning adjustments were made they included a
decrease in FiO2 and PEEP and converting to PS
for breathing trials.
Methodology
Testing Methods 2nd Study
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In Study 2, the initial settings for the HFOV were
RR- 5 Hz, mPaw – CV + 5, and an I time of
33%.Once deemed appropriate a patient was
changed to conventional ventilation once the FiO2
was reduced to less than .50 and mPaw was
weaned to 24 cm H2O with an SaO2 of 88% or
greater. For transition, the conventional ventilator
was set in pressure-control mode with an adjusted
PIP to achieve a delivered Vt of 6-10 ml/kg of actual
body weight, PEEP of 10 cm H2O, and an
Inspiratory time of 50%. Adjustments were similar
to those made in conventional ventilation.
Methodology
Testing Methods 3rd Study
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In study 3 during the HFOV trial, the initial settings
used were as follows; FIO2 of 1.0, continuous
distending pressure (CDP) 5 cmH2O above the last
measured mean airway pressure on conventional
ventilation, inspiratory time at 33% of total
respiratory cycle; oscillatory frequency at 5 Hz; bias
flow at 30 l/min; oscillatory amplitude (P) scaled
relative to entry PaCO2.
Discussion:
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Limitations for all three of our
studies included small populations,
concurrent studies, and not listing
the brands of conventional
ventilators.
Statistics: Conventional Ventilators
Raw Data
Total number of Subjects: 139
60
50
21
40
study 1
study 2
study 3
30
20
22
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MAP
O2 I
CO2
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Statistics: Mean Data CV
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Mean MAP= 21 cmH2O
Mean O2 Index= 21
Mean CO2= 50 torr
SD MAP= 21.3 cmH2O
SD O2 Index= 4.5
SD CO2= 7.0 torr
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Statistics: Raw Data HFOV
Total number of Subjects: 154
60
50
40
study 1
study 2
study 3
30
20
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MAP
O2 I
CO2
Statistics: Mean Data HFOV
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Mean MAP= 22 cmH2O
Mean O2 Index= 25
Mean CO2= 51 torr
SD MAP= 22 cmH2O
SD O2 Index= 4.9
SD CO2= 7.11 torr
Conclusions
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In studies 1 & 2, MAP, O2 Index, and CO2 were very
similar. We found that the mean MAP in the CV
groups were less than that of the HFOV group. Also,
the mean O2 Index was less in the CV group than in
the HFOV group. The CO2 mean values correlated
in both groups. In the HFOV group, in study 1:43%
(16/37) died, in study 2: 37% (28/75) died, we were
not able to obtain the mortality rates in the 3rd study.
In the CV group for study 1: 30% (8/24) died, and in
study 2: 52% (38/73) died.
Conclusion
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Overall we discovered that HFOV
is an effective option for treating
ARDS patients because it actively
recruits alveoli while keeping MAP
airway pressures to a minimal. It
was evident from our studies that
HFOV is most effective in reducing
the mortality rate when started at
the earliest possible time.
References
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Study 1
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1. Bryan, A. C. & Cox, P. N. (1999). History of
high frequency oscillation. Schweiz Med
Wochenschr, 129, 1613-6
2. High Frequency Oscillatory Ventilation. (n
.d.) Retrieved July 10, 2006 from http://
www.kfshrc.edu.sa/rcs/html/hfov.html
3. Higginson, R., RN BN (Sept. 2002). High
Frequency Oscillatory Ventilation. CHEST
Medicine Online retrieved July 10 2006, from
http://www.priory.com/cmol/hfov.htm
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References
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Study 2
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Derdak, S. (Nov. 2001). High frequency
oscillatory ventilation: clinical management
strategies for adult patients. Retrieved July 20,
2006, from
http://www.viasyshealthcare.com/smc/Reference/
Critical_Care/CCRs/CCR-Derdak.pdf
References
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Study 3
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Matthias David1, Norbert Weiler2 ,
Wolfgang Heinrichs1, Markus Neumann1,
Thilo Joost1, Klaus Markstaller1 and
Balthasar Eberle1
(1) Department of Anesthesiology, Johannes
Gutenberg University, Langenbeckstrasse 1,
Mainz, Germany
(2) Department of Anesthesiology and Intensive
Care Medicine, Christian Albrecht University,
Schwanenweg 21, 24105 Kiel, Germany
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