Philips OBTRNSBV1 User Manual

9Non-Stress Test Timer

The non-stress test (NST) timer shows the elapsed time for the non-stress test. The timer counts up to the time you set for the NST.

Setting NST Autostart/Autostop

You can set the recorder so that it starts automatically (NST Autostart) when the NST timer is started, and stops automatically ( As default,

NST Autostart is On, and NST Autostop is Off.

NST Autostop) when the NST is complete (when the set run time has elapsed).

Viewing the NST Timer

You can configure the timer notification symbol, (the NST label), a progress bar and the elapsed time to be displayed in the top left-hand corner of the screen. By default, the NST timer is not displayed on the screen.

Alternatively, you can view the timer in the

To open the

Either

• Press the

• Access the NST pop-up keys (see “Accessing the NST Setup Pop-up Keys” on page 152), and press the

Timers window:

Timer SmartKey.

Timers key.

Timer Expiry Notification

Timers window.

When the timer expires, the color changes from blue to green, you hear a single tone, and a message appears in the status line on the main screen.

The volume of the tone can be set in Configuration Mode.

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9 Non-Stress Test Timer

Accessing the NST Setup Pop-up Keys

You control and set up the NST timer (for example, start, stop, or clear the timer, and set the run time) using a selection of pop-up keys that you access via any one of three possible routes:

•Via the

Timer SmartKey (Route 1)

Main Setup SmartKey (Route 2)

• Via the NST display area at the top left-hand corner of the screen (Route 3). When you touch the NST display area, the NST pop-up keys become available at the bottom of the screen.

Via the Timer SmartKey (Route 1)

Press the

Timer SmartKey. The Timers window opens, and the pop-up keys for controlling/setting up

the NST timer appear (see “Pop-up Keys for NST Timer Setup” on page 152).

Via the Main Setup SmartKey (Route 2)

1 Enter the Main Setup menu using the SmartKey.

2 Select NST to enter the Setup NST menu. At the same time, the pop-up keys for setting up the NST

timer appear (see “Pop-up Keys for NST Timer Setup” on page 152).

Via the NST Display Area (Route 3)

Select the NST display area at the top left-hand corner of the screen (when so configured). The pop-up keys for controlling/setting up the NST timer become available at the bottom of the screen (see “Pop-

up Keys for NST Timer Setup” on page 152).

Pop-up Keys for NST Timer Setup

Pop-Up Keys Selecting this pop-up key lets you: Comments

Start Start the timer.

Stop Stop the timer, allowing either restarting after a

pause (

Start) or clearing (Clear key).

Setup NST Enter the Setup NST menu. From here you can set

the run time.

This pop-up key is not available with Route 2, as the

Setup NST menu is

already open.

Timer Return to the Timers window. This pop-up key is not available with

Route 1, as the

Timers window is already

open.

Runtime

The run time can be set from 10 to 60 minutes. See the Configuration Guide for details how to set the run time.

Run Time

The run time can be set from 10 to 60 minutes. See the Configuration Guide for details how to set the run time.

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10Non-Stress Test Report

It is generally accepted that a non stress test (NST) allows you to assess fetal well-being. The monitor's NST report process uses fetal ultrasound (but not DECG) heart rate traces and the Maternal Toco trace to generate a printed report when criteria are met and it is an indication of the fetal well-being. The American term Non Stress Test (NST) is used for antepartum testing. The interpretation algorithm and rule set are equivalent to those implemented in OB TraceVue Revision G.xx or IntelliSpace Perinatal Revision H.xx and higher, and are based on the 2008 NICHD guidelines.

An NST report is a diagnostic aid, but it does not replace the clinician’s judgment. The interpretation and the appropriate clinical response remain with the clinician.

A fetus normally produces characteristic heart rate patterns. Average baseline variability and acceleration of the FHR in response to fetal movement are considered reassuring signs. This test does not take into account any form of external fetal stimulation.

For every active ultrasound fetal heart rate measurement, one NST report can reside in the monitor’s memory. The reports are cleared when you discharge a patient and when you start a new NST report.

When the NST Report option is available and the available ultrasound fetal heart rate measurements are displayed on the screen.

The minimum displayed information is:

• NST identification (by FHR number: 1, 2, 3)

• Current NST status (by color: inverse for "not started yet", white for "running", yellow for "stopped", green for "finished")

Setting Up an NST Report

To set up NST Report functionality:

1 Enter the Main Setup menu and select the NST Report.

2 Or select the NST Report SmartKey.

3 Press the Setup pop-up key.

NST Report feature is "on", the NST status for all

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10 Non-Stress Test Report

Set your configuration options.

Select from:

NST Analysis choose from On or Off.

• This switches the report feature on or off. This is linked to the NST timer. Both must be set to

for the NST report to function.

Report Recording choose from:

• –

Manual - press the Record Report pop-up key to trigger a manual request. After Recorder Stop - report is recorded as soon as recorder becomes idle.

–

Immediately - if a realtime recording is running, the monitor pauses it. The recording is

–

continued after the report has been recorded.

Average short term variability (STV) value is documented in [bpm] and [ms] if STV is configured as part of the NST Report. This parameter is not considered as reassuring criteria.

NST Report Status Window

The NST Report window displays a detailed overview of the current NST status for any available ultrasound fetal heart rate measurement. You can see:

• NST Status - whether it is ready, ongoing, or the time and date at which it was stopped, or at which it was finished.

• Elapsed time - the time that has elapsed since the NST began.

• Accelerations - the number of FHR accelerations detected so far.

• Baseline - the average baseline value.

• Variability - the average variability value.

• Short Term Variability - the current short term variability (STV) value.

• Decelerations - the number of FHR decelerations detected so far.

• FHR Availability - current statistical FHR availability value.

• Sinusoidal - the current status of sinusoidal rhythm detection.

For criteria not yet met, a white arrow symbol marks the overall status on the top line, and also appears against every criterion not yet met. A yellow symbol indicates detection of severe or prolonged decelerations.

The pop-up keys let you perform the following actions:

FHR1, FHR2, FHR3 - switch to the window showing the current NST status for the fetal heart rate.

•

Record Report - print the NST Report on paper.

•

Record Trace - record the trace episode that belongs to the current report. Depending on device

• usage, the trace recording might be incomplete.

Setup - open the Setup NST Report window.

•

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Example NST Report

Field Field Content

10 Non-Stress Test Report

Report Title, with FHR label

NST Report for FHR1 on 12 Oct. 2009

and date

Product Information Product DE53102345 G.01.70, OB A.04.24,

Toco DE52401090, FHR1 DE00002345 A.05.26

Patient Information Rogers, Alice

Age: 27

Week 34, Day 5

min

Start time, end time, Elapsed time, configured runtime

Gestational Age:

Time: 11:34 – 12:06

Elapsed time: 32

Run time: 20 min

Overall one-line NST result

NST Criteria*: not met

summary

Title Trace Interpretation Summary

Result Accelerations Accelerations: 2

at: 11:59 12:02

Result: Contractions Contractions: 3

at: 11:57 12:00 12:04

Result: Baseline and Variability

Baseline: 125 bpm (Range: 118-129 bpm)

Variability: 23 bpm (Range: 20-24 bpm)

Statistics: FHR availability FHR available: 95%

Result: Decelerations Decelerations: 1

Result:

Sinusoidal Rhythm detected

at: 11:58

severe

prolonged

Sinusoidal: No

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10 Non-Stress Test Report

Field Field Content

Result: Decelerations before Reporting Period

Guideline/Criteria Information

Events before Reporting Period:

Decelerations: 1

at: 11:38

severe

prolonged

This field is enabled if there were decelerations between the start of NST and the start of the reporting period.

(*) Interpretation criteria based on guideline "NICHD 2008, v01"

User-defined criteria for CTG tracing:

• valid FHR for 90% of reporting period

• baseline heart rate between 120 bpm and 160 bpm

• at least 2 accelerations in 10 min

• not more than 1 decelerations

• moderate baseline variability (6-25 bpm)

Additional criteria:

• no severe or prolonged decelerations

• no sinusoidal pattern in reporting period

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NST Criteria

The patient is monitored for a user-definable period of time (10-60 minutes in steps of 5 minutes). The test is considered reassuring when the following criteria are met:

• The fetal heart rate is valid at least 90% (this is configurable) of the specified time span.

• The FHR features a user-defined minimum number of accelerations.

• The FHR features a user-defined maximum number of tolerated decelerations, and does not include severe or prolonged decelerations, which are never tolerated.

• The average baseline fetal heart rate lies within the user-defined limits for low heart rate and high heart rate over the whole time span.

• The FHR exhibits a moderate variability (user-defined) for the specified time span.

An NST Report is generated when the reassuring criteria are met the first time in the current monitoring phase. When performing NST with twins or triplets, a separate NST Report is generated for each fetus.

After the reassurance criteria have been met, the clinician can print the NST Report and then turn the fetal monitor off, or may continue fetal monitoring and print the report at any time.

10 Non-Stress Test Report

Non-Reassuring Report

If the reassurance criteria are not met when the test has run for 90 minutes, or if you stop anytime during the 90 minute period, then the test is stopped, and a report is generated stating the reassurance criteria have not been met.

Nonreactive NST Test

If a nonreactive test occurs, and you then use acoustic stimulation, you must exercise caution in interpreting the resulting traces, as artificial stimulation is not taken into account when calculating test results.

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10 Non-Stress Test Report

158

11Cross-Channel Verification

(CCV)

The cross-channel verification helps to reduce the possibility of misidentification of the maternal heart rate for the fetal heart rate. It does this by comparing the measured fetal heart rate to the maternal heart rate. If there are multiple fetal rates, they are also compared with each other and the maternal heart rate.

Misidentification of Heart Rates

FHR detection by the monitor may not always indicate that the fetus is alive. Confirm fetal life before monitoring, and continue to confirm that the fetus is the signal source for the recorded fetal heart rate (see “Confirm Fetal Life Before Using the Monitor” on page 10).

To reduce the possibility of mistaking the maternal HR or pulse for FHR, or FHR1 for FHR2 or FHR3, it is recommended that you monitor both maternal HR/pulse and the heart rates of all fetuses (see “Monitoring FHR and FMP Using Ultrasound” on page 165, “Monitoring Twin FHRs” on

page 183, “Monitoring Triple FHRs” on page 191, and “Monitoring Maternal Heart / Pulse Rate” on page 221).

Here are some examples where the maternal HR can be misidentified as the FHR, or one FHR for another FHR (twins/triplets).

When using an ultrasound transducer:

– It is possible to pick up maternal signal sources, such as the maternal heart, aorta, or other

large vessels. Especially if the recorded maternal HR, and any other artifact is over 100 bpm.

– It is possible to pick up the same fetal heart rate simultaneously with multiple transducers.

NOTE

When an ultrasound transducer is connected to the monitor, but not applied to the patient, the measurement may generate unexpected intermittent FHR readings.

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11 Cross-Channel Verification (CCV)

When Fetal Movement Profile (FMP) is enabled:

The FMP annotations on a fetal trace alone may not always indicate that the fetus is alive. For example, FMP annotations in the absence of fetal life may be a result of:

• Movement of the deceased fetus during or following maternal movement.

• Movement of the deceased fetus during or following manual palpation of fetal position (especially if the pressure applied is too forceful).

• Movement of the ultrasound transducer.

When using a scalp electrode (DECG):

• Electrical impulses from the maternal heart can be transmitted to the fetal monitor through a recently deceased fetus via the spiral scalp electrode, appearing to be a fetal signal source.

Cross-Channel Verification Functionality

The cross-channel verification functionality (CCV) of the fetal monitors compares all monitored heart rates (maternal and fetal), and indicates automatically whether any two channels are picking up the same signal, or monitoring similar values.

If the fetal monitor detects that any channels have the same or similar values, the issued with an INOP tone that can have a configurable delay. In addition, yellow question marks appear next to the numerics on the touchscreen that have the same or similar values. On the recording trace there is also a question mark from the point where recorded traces continuously overlap.

Visual Aids for CCV Detection

Coincidence INOP appears on the screen of the fetal monitor.

Question mark appears on the screen of the fetal monitor next to the numerics that show the same or similar values.

Question mark recorded on the trace from the point where two measured values coincide.

Coincidence INOP is

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11 Cross-Channel Verification (CCV)

Overview of Cross-Channel Comparisons

Measurements from Transducers

Measurement Transducer

FHR (US) From Ultrasound or CL Ultrasound transducer

dFHR (DECG) From a fetal scalp electrode

aFHR (abdom. ECG) From the CL Fetal & Maternal Pod

MP transducer

FHR1 (US)

Pulse (Toco) From Toco MP, or CL Toco

Pulse (SpO

HR (MECG) From MECG electrodes

aHR (abdom. ECG) From the CL Fetal & Maternal Pod

Measurement Comparison Done by the Fetal Monitor for Cross-Channel Verification

) From SpO2 or CL SpO2 Pod

FHR1 (US) FHR2 (US) FHR3 (US) dFHR (DECG)* aFHR* (ECG)

FHR2 (US)

FHR3 (US)

dFHR (DECG)*

aFHR (abdom. ECG)

Pulse (Toco)

Pulse (SpO

HR (MECG)

aHR (abdom. ECG)

)

* dFHR and aFHR always replace one of the fetal channels (1,2, or 3) and cannot be compared to the channel it replaces. If you monitor for example twins with two ultrasound transducers, you see the numerics FHR1 and FHR2 at the monitor. If you decide to replace the ultrasound transducer for FHR2 with a fetal scalp electrode, the dFHR numeric is then shown as dFHR2.

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11 Cross-Channel Verification (CCV)

Coincidence Examples

Coincidence of Maternal Pulse and FHR

When the maternal pulse and FHR are being monitored, and the measured values are very similar or the same, the coincidence question mark is displayed on the monitor’s screen above both of the corresponding numerics (in this case maternal pulse and FHR). Often the signal loss or coincidence happens because the fetal or maternal movement displaced the ultrasound transducer, and a repositioning of the transducer is necessary.

1 Coincidence INOP

2 Coincidence question mark

FHR1

above

3 Coincidence question mark

above pulse from Toco MP

Pulse Delay

pulse rate traces have an averaging calculation of approximately 10 seconds and an overall delay

SpO

of approximately 12 seconds (depending on recorder speed). This differs from a non-averaged beat-tobeat MECG heart rate trace or an ultrasound heart rate trace calculation (having switched to the maternal HR) with no significant delay. Note that Maternal Pulse from Toco has an averaging of 4 seconds and an overall delay of between 6 and 8 seconds.

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11 Cross-Channel Verification (CCV)

The coincidence question mark is also printed on the trace paper next to the corresponding FHR and maternal pulse.

1 Printed coincidence

question mark on trace

2 Fetal heart rate trace from

Ultrasound

3 Maternal pulse trace from

SpO

Coincidence of Twins/Triplets FHRs

When both FHR1 and FHR2 are being monitored, and the measured values are very similar or the same, the coincidence question mark is displayed on the monitor’s screen above both of the corresponding numerics (in this case

FHR1 and FHR2).

1 Coincidence INOP

2 Coincidence question

mark above

3 Coincidence question

mark above

FHR1

FHR2

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11 Cross-Channel Verification (CCV)

The coincidence question mark is also printed on the trace paper next to FHR1 and FHR2.

1 Printed coincidence question mark on

trace

2 FHR1 and FHR2 traces

Recommended Actions for Coincidence INOP

1 Confirm fetal life by palpation of fetal movement or auscultation of fetal heart sounds using a

fetoscope, stethoscope, or Pinard stethoscope.

2 Manual determination of the maternal pulse and comparison with the fetal heart rate sound signals

from the loudspeaker.

3 Reposition the transducer, or ensure that the fetal scalp electrode is placed correctly, until you

receive a clear signal and the monitor is no longer issuing the

4 In case of difficulties deriving a stable maternal pulse reading using the Toco MP or CL Toco

transducer, use SpO measurement from SpO

or the CL SpO2 Pod instead. In case of similar problems with the pulse

, use MECG instead. Reasons to switch the method for deriving a

maternal pulse or heart rate include: motion artifacts, arrhythmia, and individual differences in pulse signal quality on the abdominal skin (via Toco MP).

5 If you cannot hear the fetal heart sounds, and you cannot confirm fetal movement by palpation,

confirm fetal life using obstetric ultrasonography.

Coincidence INOP.

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12Monitoring FHR and FMP

Using Ultrasound

To monitor a single FHR externally, you use an ultrasound transducer attached to a belt around the mother's abdomen. The ultrasound transducer directs a low-energy ultrasound beam towards the fetal heart and detects the reflected signal. Your monitor can also detect fetal movements and print the fetal movement profile ( 25th week of gestation for non-stress testing or routine fetal monitoring.

WARNING

Performing ultrasound imaging or Doppler flow measurements together with ultrasound fetal monitoring may cause false FHR readings, and the trace recording may deteriorate.

FMP) on the trace. Monitoring using ultrasound is recommended from the

Technical Description

Fetal monitors use the ultrasound Doppler method for externally monitoring the fetal heart rate. Using the Doppler method, the transducer (in transmitter mode) sends sound waves into the body which are then reflected by different tissues. These reflections (Doppler echoes) are picked up by the transducer (in listening mode). These Doppler echoes are amplified and sent to the monitor’s speaker through which the fetal heart signal can be heard. In parallel the Doppler echoes are processed through an autocorrelation algorithm to determine the fetal heart rate (FHR). The FHR is displayed on the monitor’s numeric display and on the recorded trace.

Properly representing the fetal heart rate using a device that derives heartbeats from motion is a formidable task and the limitations of the technology will be discussed shortly. Basic fetal cardiac physiology may contribute to difficulties in obtaining a reliable ultrasound signal.

A heart rate pattern of a fetus is capable of extraordinary variation, ranging from a stable pattern with minimal variation while the fetus is “asleep” to robust accelerations of 40-60 bpm above baseline rate over a few seconds, or exaggerated variability when the fetus is active. Decelerations of the rate 60-80 bpm below baseline may develop even more abruptly than the accelerations. Beat-to-beat arrhythmias may further exaggerate the amount of “variability” and can be seen at the bottom of variable decelerations, or in the presence of fetal breathing movements which also tend to lower the fetal heart rate. The recognition of these normal variations in fetal heart rate patterns will greatly assist in the separation of genuine fetal information from the artifact.

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12 Monitoring FHR and FMP Using Ultrasound

Limitations of the Technology

All tissues moving towards or away from the transducer generate Doppler echoes. Therefore, the resulting signal that is provided to the monitor’s speaker, and for further fetal heart signal processing, can contain components of the beating fetal heart wall or valves, fetal movements, fetal breathing or hiccup, maternal movements such as breathing or position changes, and pulsating maternal arteries.

The fetal heart signal processing uses an autocorrelation algorithm to obtain periodic events such as heart beats. If the signal is erratic such as from a fetal arrhythmia, the ultrasound device may have trouble tracking the abrupt changes, and may misrepresent the true FHR pattern. Signals such as those from moving fetal limbs are usually very strong, thereby masking the fetal heart signal. During prolonged movements where the fetal heart signal is masked, the FHR appears blank on the numeric display and as a gap on the recorded trace. Fetal position changes, maternal position changes, or uterine contractions can move the fetal heart partly or fully out of the ultrasound beam resulting in signal loss, or even picking up Doppler echoes from pulsating maternal arteries. In these cases a maternal heart rate or sometimes even a rate resulting from the mixture of fetal and maternal signals may be displayed on the monitor’s numeric display and on the recorded trace.

In contrast to the timely well-defined R-peak of an ECG signal obtained with a fetal scalp electrode, the ultrasound Doppler signal from a fetal heart consists of multiple components from atria (diastole), ventricles (systole), valves, and pulsating arteries. These components vary depending on fetal and transducer position and angle, and are further modulated by factors such as fetal or maternal breathing. These effects may produce what is called “artifact”. Optimal transducer positioning therefore is key to minimizing these effects and thereby minimizing artifact.

Misidentification of Maternal HR as FHR

“Confirm Fetal Life Before Using the Monitor” on page 10 and “Cross-Channel Verification (CCV)” on page 159).

What You Need

• Ultrasound transducer

• Toco MP or CL Toco

•Ultrasound gel

• Transducer belt (and optional butterfly belt clip, if applicable)

MP transducer

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12 Monitoring FHR and FMP Using Ultrasound

Cableless Monitoring - Important Considerations

When using an Avalon CL or Avalon CTS Fetal Transducer system with your monitor, note the following:

Refer to “Cableless Status Indication” on page 95 for general rules regarding the use of cableless transducers from an Avalon CL or Avalon CTS Cableless Fetal Transducer system.

CAUTION

Never use ultrasound transducers connected to more than one fetal monitor on the same patient.

• When using an Avalon CL or Avalon CTS you should be aware that FMP is not recommended when the mother is likely to move, and you should disable Fetal Movement Profile (FMP) on the fetal monitor (

page 170.

• With the Avalon CL Transducer System, you can monitor twins and triplets with cableless transducers. The Avalon CTS System does not have this option.

Fetal Movement Off) if the mother is walking. See also “Fetal Movement Profile” on

The wireless symbol appears next to the measurement label, indicating that the measurement is being made by a cableless transducer.

1 FHR1

2 Toco p a ramet e r

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12 Monitoring FHR and FMP Using Ultrasound

WARNING

• During ambulant FHR monitoring, the chance of losing the signal or detecting the maternal heart rate is higher than during stationary monitoring. The frequency of the patient's walk may be detected, and mistaken for an FHR signal.

• Check the mother’s pulse periodically during monitoring and compare this with the FHR signal. Beware of mistaking a “doubled” maternal heart rate for FHR. If a fetus is dead, there is a risk that the maternal heart rate is monitored and misinterpreted as the fetal heart rate. Therefore, the simultaneous monitoring of maternal heart rate (preferably, the maternal ECG) and the fetal heart rate is encouraged.

• Do not interpret maternal movements as fetal movements.

• Artifacts: FMP artifacts are generated during fetal heart rate searching by changing the transducer position, therefore the fetal monitors enable the FMP only after detecting a valid heart rate signal for several seconds. FMP is not recommended when the mother is likely to move, and you should disable Fetal Movement Profile (FMP) at the fetal monitor ( walking.

• Gaps in maternal heart rate detection can occur: – if the transducer is not correctly positioned. – due to the pulsation of uterine blood vessels. –if the fetus moves.

Fetal Movement Off) if the mother is

Preparing to Monitor

Prepare for ultrasound monitoring using the list below. The standard procedures in use in your facility determine the sequence of actions.

1 Determine fetal position.

2 Fasten the belt around the patient.

3 Switch on the monitor and the recorder.

4 Connect the transducer to a free socket. The signal quality indicator for the heart rate initially

displays an invalid signal.

5 Apply a thin layer of ultrasound gel to the underside of the transducer.

CAUTION

Using ultrasound gel not approved by Philips may reduce signal quality and may damage the transducer. This type of damage is not covered by warranty.

1 Place the transducer on the abdomen, if possible over the fetal back or below the level of the

umbilicus in a full-term pregnancy of cephalic presentation, or above the level of the umbilicus in a full-term pregnancy of breech presentation. Work the transducer in a circular motion to ensure the gel layer makes good contact.

2 When the transducer is connected correctly and you receive a good signal, the signal quality

indicator should be filled out. If an inadequate signal is produced, the signal quality indicator will indicate a poor signal, and no numeric will appear on the screen.

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12 Monitoring FHR and FMP Using Ultrasound

Adjust the audio volume of the monitor's loudspeaker to a clearly audible level, while moving the

transducer over the abdomen. When you have a good signal, secure the transducer in position below the belt.

WARNING

Periodically compare the mother's pulse with the signal coming from the monitor's loudspeaker to ensure that you are monitoring fetal heart rate. Do not mistake a doubled or elevated maternal HR for FHR.

The ultrasound transducer may warm slightly (less than 1°C/1.8°F above ambient temperature) when applied to the patient. When not applied, the transducer can reach a maximum temperature of 44°C/

112.2°F at an air temperature of 40°C/104°F.

Selecting Fetal Heart Sound

You can listen to the fetal heart sound from one ultrasound transducer at a time. When the fetal heart sound is selected for an FHR channel, you see the audio source symbol next to the FHR numeric label for that channel.

1 FHR1

2 Audio source symbol

To select the audio source for an FHR channel:

1 Enter the Setup FHR1 menu for the channel you want to hear (FHR1 used as an example).

2 Press Select Audio. It may take a few seconds for the audio source symbol to appear.

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12 Monitoring FHR and FMP Using Ultrasound

Changing the Fetal Heart Sound Volume

The FHR volume symbol at the top right of the Fetal Heart Sound Volume window gives you an indication of the current volume. To change the volume:

1 Select the volume symbol. The volume scale pops up.

2 Select the required volume from the volume scale.

1 Fetal Heart Sound Volume

Fetal Movement Profile

The Fetal Movement Profile (FMP) parameter detects fetal movements with an ultrasound transducer connected to the monitor. Only the fetus monitored on the FHR1 channel is monitored for FMP.

Once you have enabled FMP (see “Switching FMP On and Off” on page 171), it is triggered automatically whenever:

• You connect an ultrasound transducer.

• A patient is discharged.

When FMP is enabled, the ultrasound transducer detects most fetal body movements. Eye movements are not detected, and movement of the feet and hands may not be detected. Positioning or repositioning of the transducer is recorded as fetal movement. Maternal movement, excessive fetal breathing, or fetal hiccups may also be recorded as fetal movement (also in case of fetal demise or during the second stage of labor). You can mark these artifacts on the trace paper using either the remote event marker, or the event marker key as described in “Marking an Event” on page 60. FMP should be interpreted with care, or disabled when the patient is ambulating or during the second stage of labor. Ignore these movements when you interpret the FMP. When monitoring twins or triplets, only the fetus monitored on the FHR1 channel is monitored for movement, but be aware that movements recorded for FHR1 may also be caused by movement of the second or third fetus.

The fetal movement profile (FMP) appears as "activity blocks" along the top of the Toco scale, the length of each block showing the duration of the activity.

170

FMP Statistics

FMP statistics are printed every ten minutes.

12 Monitoring FHR and FMP Using Ultrasound

1 FMP enabled

2 FMP started here

A Indication of current fetal movement

B The FMP statistics are presented as two percentage figures:

The first figure shows the percentage of detected fetal movements in the previous ten minutes.

C The second figure shows the percentage of detected fetal movements since the start of

recording.

To mark the start of the FMP statistic, FMP is printed on the paper with an arrow.

The FMP detection activates after about half a minute of steady heart rate signals (signal indicator halffull, or full) to minimize transducer positioning artifact. You will notice this deliberate delay:

• When a new patient is admitted. A patient discharge restarts the FMP statistics from zero.

• When you connect an ultrasound transducer.

Switching FMP On and Off

You can switch FMP on and off from any FHR channel. For example, to set it from the FHR1 channel:

1 Enter the Setup FHR1 menu.

2 Select Fetal Movement to switch between On and Off.

3 Return to the main screen.

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12 Monitoring FHR and FMP Using Ultrasound

Troubleshooting

Problem Possible Causes Solutions

Erratic trace

Erratic display

Signal quality indicator is continuously poor

Questionable FHR Recording maternal HR by mistake Reposition transducer

FHR not recorded FHR is less than 50 bpm or over 240 bpm If membranes are ruptured, using a fetal scalp

FHR1 Equip Malf or FHR2 Equip Malf or FHR3 Equip Malf INOP displayed. See “Patient Alarms and INOPs” on

FHR1 Signal Loss or FHR2 Signal Loss or FHR3 Signal Loss INOP

displayed.

FHR1 Unplugged or FHR2 Unplugged or FHR3 Unplugged INOP

displayed.

If you suspect the transducer is malfunctioning Test the transducer.

Fetal arrhythmia Consider monitoring FHR using DECG after

Obese patient

Transducer position not optimal Reposition transducer until signal quality

Belt loose Tighten belt

Too much gel Remove excess

Very active fetus -

Insufficient gel Use enough gel to ensure the transducer

Transducer position not optimal Reposition transducer until signal quality

FHR less than 50 bpm (and the FHR is audible)

Recording periodic signals when the transducer is not applied to the patient

Recorded FHR appears to be suspiciously higher, or suspiciously lower, than real FHR. In very rare cases, half- or double-counting of the FHR can occur.

the rupture of membranes.

indicator shows a good signal (at least half-full).

makes good contact with the mother's skin.

indicator shows a good signal (at least half-full).

If membranes are ruptured, using a fetal scalp electrode (FM30 and FM50 only) allows measurement of FHR down to 30 bpm.

Confirm fetal life

Disconnect all NON-USED ultrasound transducers, as continuous, regular mechanical, or electromagnetic influences can result in an artificial trace.

If you have reason to question the validity of the recorded FHR, always verify FHR by independent means (by auscultation, for example). Measure maternal pulse by independent means.

electrode (FM30 and FM50 only) allows measurement of FHR down to 30 bpm.

If FHR is outside of the specified range, verify FHR by independent means.

page 129.

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Testing Ultrasound Transducers

If any of the following tests fail, repeat the test using another transducer. If the second transducer passes the tests, confirming that the first transducer is defective, contact your service personnel.

If the second transducer also fails the tests, contact your service personnel.

12 Monitoring FHR and FMP Using Ultrasound

To test an ultrasound transducer:

1 Switch on the monitor and the

recorder.

2 Connect the transducer to the fetal

monitor.

3 Select the fetal heart sound for this

channel.

4 Increase the loudspeaker volume

to an audible level.

5 Holding the transducer in one

hand, move your other hand repeatedly towards and then away from the surface.

You can test all ultrasound transducers, including the cableless ones, as described above.

Additional Information

Artifact in Fetal Heart Rate Measurement

How to detect it and reduce its occurrence using the Avalon Fetal Monitor

The ultrasound derived FHR measurement technique in Avalon fetal monitors, like all other ultrasound fetal monitors’ FHR measurement techniques, has limitations that can lead to misrepresentation of the fetal heart rate pattern and potential misinterpretation of the fetal condition.

An incorrect interpretation of the trace may lead to either unnecessary interventions, or to failure to detect fetal distress, and the need for intervention. Thus, the on-going evaluation of the recorded trace requires regular confirmation that the trace represents the true FHR. Specific situations requiring such confirmation include the following:

6 Check that a noise is heard from

the loudspeaker.

• After starting a measurement or changing a transducer

• After maternal position changes, for example during pushing with contractions

• When the tracing shows abrupt changes in baseline rate, variability, or pattern (decelerations to accelerations) especially in the second stage of labor

• When the baseline maternal heart rate is within about 15 bpm of the FHR

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12 Monitoring FHR and FMP Using Ultrasound

• When you are unable to determine a baseline rate, and variability occurs between consecutive contractions

There are several ways to verify the source and/or accuracy of the recorded fetal heart rate pattern. These include:

Verification of the FHR with:

• An obstetric stethoscope

• Ultrasound imaging

• A fetal scalp electrode

Verification of the maternal heart rate:

• Using pulse oximetry - for a maternal heart rate pattern displayed simultaneously with the FHR (Cross-Channel Verification (CCV) feature)

• Using Maternal ECG - for a maternal heart rate pattern displayed simultaneously with the FHR (CCV feature)

• Manual determination of the maternal pulse

Whenever possible measure the maternal pulse rate to make use of the monitor’s Cross-Channel Verification (CCV) feature, especially during the second stage of labor, or when the maternal pulse is

elevated over 100 bpm. The Avalon fetal monitor provides a Toco MP or CL Toco for maternal pulse detection and the creation of a maternal heart rate pattern plotted on the same recorder as the FHR pattern. In case of difficulties deriving a stable maternal pulse reading using the

Toco MP or CL Toco+ MP transducer, use SpO2 or MECG instead.

MP transducer

When either of these parameters is utilized, the monitor will automatically and continuously perform a CCV of the maternal heart rate pattern against the FHR pattern displayed on the monitor. If the patterns and rates are similar, the CCV provides an alarm that both rates are probably from the same source (i.e., they both represent the maternal heart rate pattern and the fetus is not being monitored). Repositioning the ultrasound transducer will usually correct this, but it may be necessary to apply a fetal scalp electrode. Advising the mother to temporarily cease pushing during contractions may help to more rapidly resolve any uncertainty in this situation.

Doubling: The autocorrelation algorithm can display a doubled fetal or maternal heart rate if the duration of diastole and systole are similar to each other, and if the heart rate is below 120 bpm. Doubling, usually brief, is accompanied by an abrupt switch of the trace to double the baseline value.

Halving: With fetal tachycardia (above 180 bpm) and some interference from breathing or maternal arteries the autocorrelation algorithm may only recognize every second beat resulting in a halved rate for a limited time. If the actual FHR is above the maximum limit of the monitor (240 bpm), the algorithm will also half-count. Halving is accompanied by an abrupt switch of the trace to exactly half the prior baseline value. This switch may simulate an FHR deceleration and be referred to by clinicians as a “false deceleration.”

Switching to maternal heart rate (also referred to as "Maternal Insertion"): The fetal heart can move partly or fully out of the ultrasound beam and the autocorrelation algorithm may then pick up and display the maternal heart rate. Depending on the signal mix in the ultrasound signal, switching to the maternal heart rate may mimic several conditions with the potential for erroneous interpretation and response as follows:

• The switch to the maternal heart rate may simulate an FHR deceleration (i.e., a decrease of the fetal heart rate, and be referred to by clinicians as a “false deceleration”).

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12 Monitoring FHR and FMP Using Ultrasound

• The maternal heart rate may simulate a normal fetal heart rate pattern (i.e., it may mask an FHR deceleration or fetal demise).

Especially during pushing with contractions in the second stage of labor, the maternal heart rate may increase to the point where it may equal or exceed the fetal rate. Here the maternal trace may mimic a normal fetal trace while the fetus may be having decelerations or fetal demise has occurred. This change from fetal to maternal heart rate pattern may not be at all obvious unless CCV is used and represents the most dangerous pitfall of all the artifacts because fetal distress may go unrecognized.

• The maternal heart rate may simulate an FHR acceleration, which is an increase of the fetal heart rate.

During expulsive efforts, the maternal heart rate normally accelerates and may be at or above the normal FHR range.

• The FHR may display gradual appearing decelerations. Generally, the “false decelerations” described above are abrupt. Rarely, combinations of “noisy/erratic signal” associated with changes in maternal and/or fetal rate or movement will produce more gradual appearing “false decelerations” but these are usually short-lived with an abrupt return to an obviously stable FHR baseline.

“Noisy/Erratic” signals: With mixed or weak signals the tracing may reveal very brief episodes of erratic recorded traces. These represent the autocorrelation algorithm finding brief sequences of apparent and persistent heartbeats amidst a mixed or weak signal. These erratic recorded traces are commonplace, especially in association with fetal or maternal movement. During prolonged periods

of such noisy/erratic signals, the fetus is not being adequately monitored.

Drop out: With mixed or weak signals there may be no heart rate tracing at all. These episodes reflect

that if the algorithm does not find an apparent and persistent heartbeat amidst a mixed or weak signal, it will not print a heart rate on the tracing. Brief episodes of drop out are commonplace, especially in association with fetal or maternal movement. During prolonged periods of drop out, the fetus is

not being adequately monitored.

Multiple Fetuses

With multiple fetuses, the potential to experience these artifacts is increased. Positioning of the transducer is even more critical. Ultrasound scanning should be used to help with positioning of individual transducers. See also “Monitoring Twin FHRs” on page 183 and “Monitoring Triple FHRs”

on page 191.

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12 Monitoring FHR and FMP Using Ultrasound

Obtaining a Good Heart Signal

To successfully position the ultrasound transducer, first determine the fetal position using palpation. Position the transducer over the strongest audible fetal heart sound from the monitor’s speaker and wait at least six seconds after each transducer adjustment to verify a good signal quality displayed on the Signal Quality Indicator and a consistent FHR numeric display. Having determined the position that provides a strong fetal signal, fix the transducer on the abdomen with the belt.

If the quality of the signal or the appearance of the heart rate trace from the ultrasound transducer is questionable, the transducer should be repositioned as described above. Alternatively, the use of an ultrasound scanner will greatly facilitate the determination of the optimal site for the ultrasound heart rate transducer. Factors during the second stage of labor that may influence the quality of the FHR tracing obtained with ultrasound include:

• Uterine contractions

• Changing contour of the maternal abdomen

• Maternal body movement - positioning

• Maternal expulsive efforts - pushing

• Maternal tachycardia/accelerations with contractions

• Fetal decelerations, Fetal tachycardia

• Delayed return of the fetal heart rate from a deceleration

• Descent of the fetus in the birth canal

• Rotation of the fetus in the birth canal

In some cases during the second stage of labor, a good and reliable ultrasound FHR signal may not be obtainable, and the use of a fetal scalp electrode must be considered (fetal ECG).

Heart Rate Sound

The heart rate sound emitted by the device is a representation of movement that, in most cases, permits accurate auscultation of the FHR corresponding to the FHR displayed on the monitor and rate pattern depicted on the trace recording. On occasion, the user may hear an FHR that differs from the FHR display and the recorded trace. This may occur in situations where the fetal heart moves partly out of the transducer ultrasound beam. In these cases, the user may hear the FHR emitted from the monitor’s speaker, even though another periodic signal (usually the maternal heart rate) has become stronger. The autocorrelation algorithm will display the stronger maternal heart rate, despite the persistence of a weaker fetal signal. These occurrences are usually very brief and, if persistent, can be addressed by repositioning the transducer.

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Signal Quality Indicator

The signal quality on the Avalon fetal monitor is indicated by a triangle on the touchscreen that is displayed in one of three ways:

12 Monitoring FHR and FMP Using Ultrasound

1 Completely filled triangle, indicating good signal

quality (good/full).

2 Half-filled triangle, indicating limited signal quality.

This condition may indicate a weak or ambiguous signal. If this status persists, reposition the transducer (acceptable/medium).

3 Empty triangle, indicating insufficient signal

quality. No FHR is displayed on the monitor’s numeric display or the recorded trace. If this status persists, reposition the transducer (poor/no signal).

Examples of Artifacts

When monitoring the maternal ECG, a beat-to-beat maternal heart rate trace is printed alongside the FHR recorded trace. When monitoring the maternal SpO

heart rate trace is printed.

Following are recorded trace examples of complaints received regarding inaccurate output from the Avalon monitors. Scaling is 3 cm/min and 30 bpm/cm.

Double-Counting

Baseline Rate 120

Baseline Variability Moderate

Accelerations Present

Decelerations Not apparent

derived pulse rate, a filtered and averaged

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Double-Counting

Contractions Excessive, coupling, hypertonus

Artifact Double-Counting

Comment Reassuring tracing. The excessive uterine activity should prompt discontinuation of any

oxytocic agent.

Remediation The true fetal rate can be confirmed by auscultation or by fetal scalp electrode.

Half-Counting

Baseline Rate 120

Baseline Variability Moderate

Accelerations Present

Decelerations Not apparent

Contractions Minimal

Artifact Half-counting, noise, drop out

Comment Reassuring tracing. The half-count at 4-5 minutes into the tracing may simulate a fetal

deceleration, but the abruptness and the lack of any compensatory changes when the normal rate returns suggests that this is half-counting. Insertion of the maternal heart rate (see below) may produce a similar pattern. Note also very brief episodes of half-counting, maternal insertion, and signal dropout.

Remediation Auscultation or the application of a direct scalp electrode, if feasible, will reveal the true

fetal heart rate.

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12 Monitoring FHR and FMP Using Ultrasound

Maternal-Switching (Maternal Insertion)

Baseline Rate 170 - Tachycardia

Baseline Variability Moderate

Accelerations Unable to determine

Decelerations Absent

Contractions Absent

Artifact Maternal insertion, noise

Comment The fetus has an elevated baseline rate of about 170 bpm with minimal to moderate

variability. The ability to assess fetal status is limited because about half of the tracing displays the maternal heart rate.

Remediation The application of a maternal transducer (ECG or pulse oximeter) will likely resolve any

possible confusion with the tracing. Repositioning the transducer may produce a more reliable tracing. Consideration must also be given to applying a fetal scalp electrode.

Noisy/Erratic Signal and Dropout

Baseline Rate 140

Baseline Variability Moderate

Accelerations Present

Decelerations Absent

Contractions Minimal

Artifact Noisy signal, drop-out

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Noisy/Erratic Signal and Dropout

Comment Reassuring tracing. Note that there is episodic drop out of the signal with discontinuity of the

fetal tracing.

Remediation Either improving the position of the transducer or the application of a fetal scalp electrode

will reduce the amount of artifact in the tracing.

Selection of Literature References on Artifacts

___________________________________________________________

Mosby's Pocket Guide to Fetal Monitoring: A Multidisciplinary Approach (Nursing Pocket Guides) 8th Edition (May 2016).

Lisa A. Miller, David A. Miller, Rebecca L. Cypher

Elsevier Ltd, Oxford. 2017, ISBN 978-0-323-40157-9

___________________________________________________________

Signal ambiguity resulting in unexpected outcome with external fetal heart rate monitoring

By Duncan R. Neilson Jr, MD; Roger K. Freeman, MD; Shelora Mangan, RNC, MSN, CNS

American Journal of Obstetrics & Gynecology, June 2008

___________________________________________________________

Antepartal and Intrapartal Fetal Monitoring, 3rd Edition (2007)

By Michelle L. Murray, PhD, RNC

Springer Publishing Company, ISBN 0-8261-3262-6

Page 2, Table 2: Limitations of Continuous EFM

Item 15: “The US may detect maternal aortic wall movement and the maternal HR will be printed. A failure to recognize the lack of an FHR may delay appropriate management.”

Page 38, “Solving Equipment Problems”, Table 3: The Ultrasound Transducer

___________________________________________________________

JOGC (Journal of Obstetrics and Gynecology Canada)

Volume 29, Number 9, September 2007

Chapter 2: Intrapartum Surveillance

Page S35: “Methods of Electronic Fetal Monitoring”

“… Among its disadvantages are the need for readjustment with maternal or fetal movements and the following: the transducer may record the maternal pulse, it may be difficult to obtain a clear tracing in obese women or those with polyhydramnios, artifact may be recorded, and there may be doubling or halving of the fetal heart rate when it is outside of the normal range.”

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