Philips Fetal Monitor User manual

Philips Fetal Monitors

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Fetal Monitoring Technology

Application Note

This application note explains how Philips fetal
monitoring technology supports safe and accurate
fetal and maternal monitoring. Four technological
aspects are collected together here:

• Precision Signal Track and Hold

• Cross-Channel Verification

• Fetal Heart Rate Baseline Offset

•Fetal Movement Profile

Precision Signal Track and Hold

This technology allows the monitor to track the fetal
heart rate signal very closely to ensure an accurate
fetal heart rate measurement with almost no gaps.

The signal is monitored with two ultrasound
receiver channels so that two overlapping time
windows can be monitored (ultrasound travelling
time=depth). When the signal is strong in both
windows the optimal monitoring depth is found.
The measurement window stays in this position
while the control window is moved in both
directions to check the strength of the signal at
different depths. When the control window registers
a change in the signal position (due to movement of
the fetus or mother) the measurement window is
moved to the new optimal position. This adaptation
to changing depth happens with each heart beat and
so virtually eliminates gaps in the trace due to lost
signals.

As the signal is so well tracked, the measurement
window around the heart can be made as small as

possible thus reducing the ultrasound energy that
mother and fetus are exposed to.

Ultrasound Crystal Placement for Optimal Geometry

The crystals in the Ultrasound transducer are located
six around the circumference and one in the center.
In this configuration, all lines between crystals are
equidistant. If a line were drawn from crystal to
crystal, a series of equilateral triangles would be
created. This allows the coverage area to be
homogenous, or of equal signal strength throughout.

crystals

A homogenous signal eliminates any "dark spots" in
the beam, which will reduce the number of times the
clinician will need to reposition the transducer. If
there are more than 7 crystals within a transducer
there are no longer equidistant lines between the
crystals and the triangles created are isosceles
triangles. This configuration is unlikely to provide a
homogenous signal, but rather "dark spots" within
the beam.

AD

Correlation to Directly Measured FHR

The signal tracking and the homogenous ultrasound
signal from the 7-crystal transducer both contribute
to a fetal heart rate measured by ultrasound which
correlates very highly to the directly measured fetal

heart rate. The degree of smoothing caused by
autocorrelation signal processing is reduced to a
minimum as seen in the following comparison of
traces.

fetal trace from ultrasound

Cross-Channel Verification

Cross-Channel Verification indicates when the same
heart rate is being recorded by different transducers.

When the maternal heart rate and fetal heart rate are
being monitored, Cross-Channel Verification will
alert you when the values are the same. This may be
an indication that the fetus is deceased and the
transducer is picking up a signal from the maternal
heart or a large blood vessel.

Cross-Channel Verification can compare all fetal and
maternal heart rates and indicates when multiple
channels are picking up the same signal. This means
when monitoring multiples and maternal heart rate
simultaneously Cross-Channel Verification will
compare the values from all fetuses and each of these
values with the maternal heart rate.

This technology helps reduce potential legal liability
associated with continuing to monitor an incorrect
heart rate.

When signal “cross-over” occurs, you are alerted
within approximately 60 seconds to check the traces
and potentially reposition the transducers.

Note: Be aware that

a maternal heart rate trace can

exhibit features that are very similar to those of a
fetal heart rate trace, even including

accelerations

and decelerations. Do not rely solely on trace pattern
features to identify a fetal source.

original DECG trace

Figure 1 CCV symbol prints on the trace when two

channels are recording the same heart beat

Cross-Channel Verification Plus (CCV+) indicator

(Series 50 XMO, not available in the USA and Japan)

To warn you if you accidentally record maternal
SpO

instead of fetal SpO2, (because the sensor is

2

facing the uterine wall instead of the fetus) the
monitor compares the heartrate it derives from
DECG on the Cardio 1/Combi channel, (or from
US on the Cardio 2 channel if DECG is not in use)
with the pulse rate it derives from FSpO

. The

2

CCV+ indicator illuminates and is printed on
the trace if the monitor records a pulse rate from
FSpO

and a heart rate from DECG or ultrasound

2

that do not match for more than one minute.

FHR Baseline Offset

Fetal Movement Profile

When the baselines of multiple FHR traces are very
similar, independent trend interpretation can be
difficult. To alleviate this, you can offset a baseline
by 20 bpm. You can deactivate the offset feature and
return the FHR trace to its original baseline anytime
you wish.

A section of a twins’ tracing is shown above. It shows
the FHR 1 trace before (Line a) and after (Line b)
the baseline offset feature is activated. To indicate
the recording is in the offset mode, a +20 symbol is
repetitively printed at the top of the trace.

Study finds Philips’ FMP saves clinicians’ and patients’

time, costs, and undue concern

Fetal movement is recognized as an important
indication of fetal condition. Consequently,
recordings of fetal movement are increasingly being
obtained as part of routine antepartum screenings in
obstetricians’ offices, clinics and hospitals.

In use in Europe, the United States and Japan since
1991, Philips Fetal Monitors simultaneously assess
fetal heart rate (FHR), fetal gross body movement
via the Fetal Movement Profile (FMP) parameter,
and uterine activity.

Benefits of the FHR-FMP assessment range from:

• helping clinicians determine the baseline heart
rate - especially in difficult-to-interpret traces, to

• predicting and supervising high risk pregnancies
which involve a number of fetal disorders,
including fetal growth retardation (IUGR).

One of the most important benefits of Philips’ FMP
monitoring is its efficiency and cost effectiveness as
an early screening tool.

Clinical trials confirm that the use of Philips Fetal
Monitors in routine antepartum screenings reduces
the number of patients with “suspicious” FHR test
results, thus eliminating their need for additional
expensive, second-level testing at the hospital. For
the patient, this represents significant savings in
time, cost and concern. It also means cost savings for
the health care system.

Fetal Movement and Fetal Heart Rate

The classic evaluation of fetal movement employs
the mother’s own perception. Clinical trials show
that the Philips Fetal Monitors detect on average 40
percent more movement than perceived by the
mother. Not only can they assure both mother and
clinicians of a more accurate level of fetal movement
detection, but the FMP, recorded simultaneously
with the heart rate, helps in the interpretation of the
FHR trace.

Physicians know that heart rate is directly influenced
by the physical activity of the fetus and they can
assign the baseline heart rate more efficiently with
the Fetal Movement Profile recording.

Furthermore, studies confirm that reduced or lack of
fetal gross body movement often precedes the
change in FHR pattern associated with intrauterine
growth retardation (IUGR)

Figure 2 The FMP information provided by the

Philips Fetal Monitors enhances the
clinician’s ability to assign the baseline FHR.
Specifically as shown here (lower trace),
without the assistance of FMP, the baseline
FHR is unclear. With the fetal movement
data (upper trace), the baseline FHR and
accelarations are clearly recognizable.

More Efficient Antepartum Screening

periods are 40 minutes. In 40 to 60 percent of the
tests, acoustic stimulators are used.)

In the 3,500 tests using monitors with FMP, the
“non-reactive” percentage dropped to 3 percent.
After the clinical trials were concluded and the
equipment removed, the reported rate of
“suspicious” nonstress test returned to the higher
level.

Used as a non-invasive tool in nonstress testing,
Philips’ FHR-FMP monitoring employs two of the
five parameters of the Fetal Biophysical Profile
(BPP). This is a second-level testing prescribed for
high-risk pregnancies. These two parameters, along
with the measurement of uterine activity, provide a
more efficient way to assess fetal condition. Clinical
trials have shown a 50 percent reduction in the
number of reported “suspicious” nonstress test
(NST) results.

In a one-year clinical trial conducted at the Women’s
Hospital, University of Southern California School
of Medicine, 3,500 women received antepartum
screening using Philips Series 50 Fetal Monitors.

Normally, 5 to 6 percent of women who undergo the
nonstress FHR test (NST) at Women’s Hospital
present “non-reactive” results; that is, the fetus fails
to show qualifying accelarations of heart rate. (Test

“The fetal Movement Profile is a tool that makes our
testing approach and interpretation better”, states
Dr. Richard H. Paul, Professor of Gynecology at the
University of Southern California School of
Medicine, and Chief of Maternal Fetal Medicine at
the Women’s Hospital. “It has proven to be a great

addition to our antenatal program. Second level
evaluation procedures are expensive and time­consuming for patients and the hospital alike. With
the FMP monitors, we reduced the number of these
advanced evaluations in half!”

Early Detection and Supervision of High-Risk

Pregnancies

Traditionally clinicians have waited until the mother
complains of reduced fetal movement before
initiating further testing such as ultrasound imaging.
However, with routine screening using the Philips
fetal monitors with FMP, fetal movement levels can
be automatically, accurately, and reliably identified.
Patients with FHR-FMP traces indicating little or
no fetal movement can then be referred for fetal BPP
testing, which also assesses fetal tone, fetal breathing
and amniotic fluid volume. This can assist in
identifying potential abnormalities.

With the FHR-FMP test, clinicians can screen
patients for conditions associated with reduced
movement, one of which is intra-uterine growth
retardation (IUGR). Studies show that as many as
50 percent of pregnancies with fetuses below the
10th percentile in weight (considered growth
retarded) go undetected by normal clinical
examination.

Once IUGR is suspected, supervision of the
pregnancy is intensified. FMP fetal monitors can
play an important role in establishing movement
trends during the important growth weeks of
gestation. (IUGR may be associated with
hypertension, antepartum hemorrhage, diabetes,
heavy smoking, chromosomal anomalies and many
other factors.)

At University Women’s clinic in Homburg/Saar,
Germany, Drs W Schmidt and J Gnirs validated the
accuracy of Philips’ FMP parameter. Using a Series
50 fetal monitor, they tracked the test results of 217
patients with normal or pathologic (below the 25th
percentile in fetal weight) pregnancies between 28
and 42 weeks gestation. Comparing them with the
results of independently taken sonographic studies,
they found a 90 percent correlation.

Presented on the following pages are the traces of
one of their patients between gestation weeks 30 and

33. The traces show a steady reduction of

movement, leading to a diagnosis of IUGR.
Sonographical biometry verified the slowing of fetal
growth, showing the fetus’ size falling below the
normal range for its gestation age, beginning in week

22. The baby was delivered by cesarean and required

intensive care.

IUGR Case Study

The following is a case study of a patient monitored
by a Series 50 Fetal Monitor with FMP. Fetal
movement “blocks” and “block clusters” are
automatically recorded on the traces (see highlighted
areas). In weeks 30 to 33, each successive FHR trace
shows a reduction of fetal movement. This fetus was
diagnosed as IUGR. The sonographical biometry
chart verifies the slowing of fetal growth and how
the size of this fetus falls below the normal range for
its gestational age beginning in the 22nd week.

Figure 3 Special thanks to Prof.Dr. W Schmidt and

Dr. J. Gnirs of the University Hospital,
Department of OB/GYN, Homburg/Saar,
Germany for sharing these original traces
with us.

Key to German FHR-FMP Traces

UNTERE NORM = Lower than the Normal Value

OLIGOHYDRAMNION = Oligohydramnios

SECTIO CESAREA = Cesarean Section

SSW = Week of Gestation

TOKOGRAMM = Uterine Activity

UNAUFAELLIG = Normal or Inconspicuous

VERLEGUNG NICU = Transfer to NICU

WEIBL. = Female

5.PERZ = 5. PERC

A.ARC (Arteria Arcuata) = Arcuate Artery

ANYDRAMNION = Anydramnios

AORTA Fet. = Fetal Aorta

FW = Amniotic Fluid Volume

A.UMB. (Arteria Umbilicalis) = Umbilical Artery

BEL = Breech Presentation

DROHENDE i.u. ASPHYXIE = Fetal Compromise

FET. BEWEGUNGSPROFIL = Fetal Movement
Profile

FHF = FHR

FLOW = Doppler Flow Velocity Analysis

University Women’s

Hospital

Bi-parietal
Diameter

GENETIK = Genetic Diagnosis

INZISUR = Endiastolic Notch

KCTG = FHR with Fetal Movement Profile
parameter

NACH 18 TAGEN EXTUBIERT = Extubation
after 18 days

Breech presentation

transverse abdominal diameter

Gestation

Summary

The fetal Movement Profile, a parameter provided
by Philips in fetal monitors, has been accepted as an
important additional tool for assessing fetal
wellbeing.

Together with the other features described in this
Application Note: Precision Signal Track and Hold,
Cross-Channel Verification and Baseline Offset,
FMP represents a significant contribution to safety
and accuracy in fetal and maternal monitoring.

Date

ultrasound velocity

Philips Medical Systems is part of
Royal Philips Electronics

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© 2002-2005 Koninklijke Philips Electronics N.V.
All rights reserved.

Philips Medizin Systeme Boeblingen GmbH
reserves the right to make changes in specifications or to
discontinue any product at any time without notice or
obligation and will not be liable for any consequences
resulting from the use of this publication.

Published July 2005
4522 962 05621