Keywords
cardiotocography (MeSH) - electrohysterograph - external tocodynamometer - intrauterine
pressure catheter - uterine contraction (MeSH) - uterine monitoring (MeSH) - patient
preference (MeSH) - user preference
Annually, more than 5 million women give birth in the European Union. Most of them
receive uterine monitoring during labor through the external tocodynamometer (TOCO),
the intrauterine pressure catheter (IUPC), or the electrohysterograph (EHG). These
techniques are compared in several studies that mainly focus on diagnostic values,
interpretability, and labor outcomes.[1]
[2]
[3]
[4]
[5] Only 1 article describes patients' and users' (i.e., healthcare provider) satisfaction
of 2 securing methods (belts), both concerning external TOCO devices.[6] Reports on users' and patients' preferences of all 3 uterine monitoring methods
are still missing, while this topic is becoming more important nowadays.
Each uterine monitoring technique has advantages and limitations from patients' and
users' perspectives. For example, TOCO measures changes of the abdominal wall noninvasively.
It is generally applied by nursing staff and wireless connections are developed. A
problem of this abdominal transducer is signal loss following maternal movements.
With TOCO, a significant period of absent uterine activity monitoring (complete signal
loss in 20 out of 42 minutes of registration) is described.[7] To obtain a continuous registration of good quality, this method requires frequent
repositioning of the transducer and tightening of the abdominal elastic belt. The
alternative external method, EHG, measures uterine electrical activity noninvasively
by abdominal electrodes that can be applied by the nursing staff.[8] Due to the adhesive properties, these electrodes are potentially less-motion-sensitive
than TOCO. For EHG, reduction of the skin impedance with abrasive sandpaper is necessary
for proper data acquisition and the abdominal patch needs to be removed after the
delivery.[9] The current gold standard, IUPC, provides a direct and accurate measurement of the
pressure changes inside the uterine cavity. Therefore, it can only be used, when the
membranes are ruptured.[10] Moreover, severe IUPC related complications have been described, such as placental
or uterine wall perforation.[11] In addition, the invasive IUPC needs to be inserted by experienced obstetricians
or midwives, who might not always be available.
In a separate paper, we described a study with simultaneous recordings of EHG, TOCO,
and IUPC.[5] Apart from the presented test characteristics, we wanted to gain insight into the
patients' and users' preferences and characteristics, as well as they should be considered,
when opting for uterine monitoring techniques. We hypothesize that both patients and
users prefer EHG, since this method is noninvasive and less influenced by maternal
movements.
Materials and Methods
We performed a prospective diagnostic accuracy study in the Máxima Medical Center,
Veldhoven, the Netherlands. Term pregnant women carrying a singleton fetus in cephalic
presentation were included. Once in active labor, eligible women were simultaneously
connected to TOCO, IUPC, and EHG for 2 hours. Per patient we used 3 identical cardiotocography
(CTG) monitors (Avalon FM30, Philips Healthcare, Eindhoven, the Netherlands) to store
each real-time tocogram in the Electronic Patient System (Ezis, Chipsoft, Amsterdam,
the Netherlands).
First, after ultrasound localization of the placenta and during vaginal examination,
a flexible sensor-tipped IUPC (Koala, Clinical Innovations, Murray, Utah, USA) was
inserted in the amniotic cavity. This was done by an experienced physician or midwife,
in presence of 1 of the researchers that checked proper placement after connection.
Second, 1 of the researchers prepared the abdominal skin by abrasive paper to reduce
skin impedance, and positioned the EHG patch (Graphium, Nemo Healthcare, Eindhoven,
the Netherlands). The skin impedance was checked with the impedance meter (SIGGI II,
MedCaT, Klazienaveen, the Netherlands). The preparation was considered adequate, when
values were below 5kΩ. The EHG patch was then connected to the translation module
for data processing (PUREtrace, Nemo Healthcare, Eindhoven, the Netherlands). Third,
TOCO was placed at the uterine fundus and tied up with an elastic belt. For logistic
reasons, TOCO was wirelessly connected to the CTG monitor. The researchers were present
during each measurement, lasting from 30 minutes up to 2 hours, to annotate adjustments
to any of the 3 techniques. TOCO signal quality was checked by the attending nurses
every 30 minutes and the position of the TOCO was adjusted, if necessary. After 2
hours, we removed TOCO and EHG, while IUPC remained in place until the end of the
delivery.
Evaluation of patients' preferences was performed by a questionnaire filled out by
the participating women within a few hours postpartum. The survey entailed 3 identical
continuous scale questions for each uterine monitoring technique (IUPC, TOCO, and
EHG) with a 100 mm scale corresponding to “not bothering at all” (0 mm) to “very bothering”
(100 mm) regarding: (1–3) positioning, (4–6) presence during labor, and (7–9) removal.
The actual value of the scale was not visible for the participants, but was calculated
by the researchers afterwards. Additionally, this identical 0 to 100 mm scale was
used to assess: (10) skin preparation for EHG and (11) transducer modifications during
labor for TOCO. The survey entailed 4 multiple choice questions: (12) which of the
3 methods women preferred (EHG, TOCO, IUPC); (13) which factors of both external methods
they considered as being most important (least difficult to position, least discomfort,
least adjustments, least limitation of mobility, or least difficult to remove); (14)
which external method women preferred (scale −50 to +50, corresponding to −50 for
TOCO, 0 for neutral, and +50 for EHG); and (15) which aspects of uterine monitoring
(either internal or external) they considered as being most important (costs, quality,
discomfort, or potential harm). We also asked our participants, whether they experienced
irritation, pain, discomfort, or dislocations with either 1 of the techniques. Finally,
the women had the opportunity to leave other remarks or notes.
After completion of the validation study, EHG was introduced as standard alternative
in our clinic. In case, TOCO was inadequate, EHG was applied by obstetric nurses that
were trained by the main researchers on correct application. To evaluate user satisfaction,
we asked all obstetric nurses that had been working with EHG, to fill out a questionnaire.
This questionnaire entailed 9 continuous scale questions from 1 to 5, regarding their
experiences with EHG: (1) sufficient knowledge of EHG, (2) sufficient competence with
EHG, (3) usefulness of uterine palpation, (4) inconvenience due to performing skin
preparation, (5) frequency of performing uterine palpation, (6) frequency of using
the impedance meter, (7) repeating skin preparation, when the skin impedance is above
5 kΩ, (8) installing EHG without technical problems, (9) the prevalence of local skin
irritation. The 5-point scale corresponded to 1 = “agree” and 5 = “disagree” for questions
1 to 3, to 1 = “very bothering” and 5 = “not bothering” for question 4, and to 1 = “always”
and 5 = “never” for questions 5 to 9.
Furthermore, this user questionnaire entailed 6 additional questions regarding their
experiences with external uterine monitoring techniques: (10) which technique is more
time-consuming (TOCO, EHG, or no difference); (11) method of preference (TOCO, EHG,
or no preference); (12) advantages of EHG (open question); (13) disadvantages of EHG
(open question); (14) recommendation of EHG to colleagues working in another hospital,
(rated from 0 = “not likely” to 10 = “very likely”); (15) frequency of weekly EHG
usage in clinical practice (open question). For every question, there was the opportunity
to write comments.
Statistical Analysis
The sample size of 52 patients was based on a power analysis to validate the sensitivity
of EHG, reported in our previous publication.[5] We used SPSS (Statistical Package for Social Science) 23 statistics (IBM, New York,
USA) for statistical evaluation. Descriptive statistics included frequencies with
percentages and 95% confidence intervals (CI) for categorical data,[12]
[13] mean with standard deviation (SD) for normally distributed continuous variables,
or median with interquartile range (IQR) for nonnormally distributed continuous variables.
Normality was checked visually using histograms, in addition to values for skewness
and kurtosis between −1 and +1. Statistical significance was accepted at a 2-sided
p-value below 0.05.
The results of the continuous scale questions regarding the placement, presence during
labor and removal of the equipment were tested with the Wilcoxon's signed rank test
for paired data, when comparing 2 techniques. The Friedman's test was used, when comparing
all 3 techniques together. The patients' preferences for either 1 of the 3 techniques
were tested by the Chi-squared test. Additionally, the patients' preferences were
compared in subgroups based on obesity and labor analgesia. We hypothesized that patients
without labor analgesia prefer TOCO over EHG and IUPC, because its wireless connection
enables patients' mobility. Obese women might prefer IUPC over the external methods,
as their increased abdominal adipose tissue significantly hampers their pregnancy
and labor surveillance. These subgroup comparisons were tested with the Fisher's Exact
test.
Frequencies, percentages, and 95%CI regarding users' preferences were calculated.[12]
[13] For calculation of cumulative percentages, score 1 (totally agree) and 2 (agree)
were summed up, or score 4 (disagree) and 5 (totally disagree).
Ethical Approval
The Institutional Review Board of Máxima Medical Center approved the protocol on 15
July 2014 (NL48951.015.14) and the study is registered in the Dutch trial register
(NTR5894), http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5894.
Pregnant women were recruited in Máxima Medical Center (Veldhoven, the Netherlands).
All measurements were performed by 2 researchers (K.M.J.T. and M.W.C.V), after informed
consent was received.
Results
Patients' Preferences
From July 2014 to June 2016, 52 women participated in our study. All questionnaires
were completed within 24 hours postpartum, except for 1 which was filled out within
1 week after the delivery. No questionnaires were lost to follow-up. Six patients
did not fill out all questions regarding “the presence” (4 women) or “the removal”
(2 women) of the 3 uterine monitoring techniques, therefore impeding comparison of
these paired measurements. In addition, 1 woman did not answer the questions regarding
the most important factor of the external methods. The patient characteristics are
presented in [Table 1].
Table 1
Sociodemographic and clinical characteristics of 52 women simultaneously monitored
with the electrohysterograph, external tocodynamometer and intrauterine pressure catheter
|
Characteristic
|
n = 52
|
|
Maternal age (y)
|
31.7 ± 4.3
|
|
Race
|
|
Caucasian
|
48 (92.3%)
|
|
Other
|
4 (7.7%)
|
|
Parity
|
|
Nulliparous
|
29 (55.8%)
|
|
Multiparous
|
23 (44.2%)
|
|
Gestational age (wk + d)
|
39.3 ± 8.1
|
|
Body mass index (BMI, kg/m2)
|
|
Before pregnancy
|
29.2 ± 8.1
|
|
During measurement [a]
|
33.8 ± 7.4
|
|
Start of labor
|
|
Spontaneous onset
|
16 (30.8%)
|
|
Induction of labor
|
36 (69.2%)
|
|
Oxytocin usage
|
|
No
|
14 (26.9%)
|
|
Yes
|
38 (73.1%)
|
|
Labor analgesia
|
|
No analgesia
|
15 (28.9%)
|
|
Epidural analgesia
|
34 (65.4%)
|
|
Remifentanil
|
3 (5.8%)
|
|
Duration measurement (min)
|
104.4 ± 29.1
|
|
Cervical dilatation (cm)
|
|
Start measurement
|
4.0 (3–10)
|
|
Stop measurement
|
8.5 (3–10)
|
|
Mode of delivery
|
|
Spontaneous vaginal delivery
|
36 (69.2%)
|
|
Vacuum delivery
|
7 (13.5%)
|
|
Cesarean section
|
9 (17.3%)
|
Note: Data are mean ± standard deviation, median (range), n, or n (%) unless otherwise specified.
a In 3 women, body mass indices during labor are missing (values of 20, 42 and 48 before
pregnancy).
Of the 52 women, 42 (80.8%; 95% CI; 68.4–89.8%) preferred uterine monitoring by EHG,
9 women (17.3%; 95% CI; 8.8–29.4%) preferred IUPC, and 1 woman (1.9%; 95% CI; 0.1–9.1%)
preferred TOCO. This result was tested as a significant difference ([Table 2]). The subgroup comparisons based on obesity (nonobese or obese) and labor analgesia
(none, epidural analgesia or remifentanil) reported no significant differences regarding
the preferences of the women ([Table 2]). Furthermore, we asked the women to choose between one of the external methods
based on a continuous scale from −50 for TOCO to +50 for EHG. This revealed a strong
preference for EHG, with an average score of 38.7.
Table 2
Patients' preferences regarding uterine monitoring techniques
|
IUPC
|
TOCO
|
EHG
|
Significance
|
|
Overall (n = 52)
|
9 (17.3%)
|
1 (1.9%)
|
42 (80.8%)
|
p = < 0.001[a]
|
|
Maternal obesity
|
|
Nonobese (n = 20)
|
5 (25.0%)
|
0 (0.0%)
|
15 (75.0%)
|
p = 0.452[b]
|
|
Obese (n = 32)
|
4 (12.5%)
|
1 (3.1%)
|
27 (84.4%)
|
|
Labor analgesia
|
|
No (n = 15)
|
1 (6.7%)
|
1 (6.7%)
|
13 (86.6%)
|
p = 0.226 b
|
|
Epidural (n = 34)
|
7 (20.6%)
|
0 (0.0%)
|
27 (79.4%)
|
|
Remifentanil (n = 3)
|
1 (33.3%)
|
0 (0.0%)
|
2 (66.7%)
|
Note: Data are n (%); maternal obesity was defined as a body mass index of ≥ 30 kg/m2 during labor.
a Chi-squared test.
b Fisher's Exact test.
On a continuous scale from 0 to 100, “application of EHG” was scored as being least
bothering, with significant differences between all 3 methods ([Table 3]). Regarding the “presence during labor”, patients were significantly more bothered
by TOCO than by IUPC or EHG. No significant differences were found between the 3 methods
regarding “removal of equipment”. However, when EHG was only compared with TOCO, we
did find a significant difference in favor of TOCO ([Table 3]). The discomfort due to the skin preparation required for EHG was assessed as minor,
with a median of 6.6 (IQR; 2.0–21.9), although 8 patients (15.4%) did report local
irritation due to skin preparation and/or the abdominal EHG patch. In comparison,
local skin irritation with TOCO was reported by only 3 women (5.8%). Several women
complained about discomfort (23.1%) and dislocations (28.8%) of TOCO, which was not
reported for EHG. For IUPC, 3 women (5.8%) reported dislocations, 2 women (3.8%) experienced
discomfort and 1 woman (1.9%) experienced pain.
Table 3
Assessment of the application, presence and removal of intrauterine pressure catheter
(IUPC), external tocodynamometer (TOCO) and electrohysterograph (EHG)
|
|
IUPC
|
TOCO
|
EHG
|
Significance
|
Significance
|
|
Application
(n = 52)
|
30.6 (8.0–53.1)
30.6 (8.0–53.1)
–
|
10.0 (2.1–27.6)
–
10.0 (2.1–27.6)
|
–
2.1 (0.0–5.2)
2.1 (0.0–5.2)
|
p < 0.001[a]
p < 0.001[a]
p < 0.001[a]
|
p < 0.001[b]
|
|
Presence
(n = 48)
|
8.3 (1.0–47.0)
8.3 (1.0–47.0)
–
|
42.0 (10.8–58.7)
–
42.0 (10.8–58.7)
|
–
2.1 (0.0–6.5)
2.1 (0.0–6.5)
|
p = 0.004[a]
p < 0.001[a]
p < 0.001[a]
|
p < 0.001[b]
|
|
Removal
(n = 50)
|
5.2 (1.0–15.0)
5.2 (1.0–15.0)
–
|
3.1 (0.0–9.0)
–
3.1 (0.0–9.0)
|
–
10.0 (2.1–22.9)
10.0 (2.1–22.9)
|
p = 0.052[a]
p = 0.583[a]
p = 0.011[a]
|
p = 0.188[b]
|
Note: Data are median with (interquartile ranges); the continuous scale ranged from 0
to 100, corresponding to “not bothering at all” to “very bothering.”
a Wilcoxon's signed rank test.
b Friedman's test.
Considering uterine monitoring in general (internal and external), “least likely to
harm” was reported as most important factor by 51.9% of the women, “best quality”
by 25.0% and “least discomfort” by 23.1%. Furthermore, when considering the characteristics
of the external methods (n = 51), 60.8% of the participants considered “least discomfort” as an important factor
for external uterine monitoring, followed by “least limitation of mobility” with 27.5%,
“least difficult to position” with 5.9% and “least adjustments” with 5.9%.
Users' Preferences
In April 2017, all obstetric nurses that had been working with EHG (57 nurses, 100%)
completed the questionnaire concerning user satisfaction. Of them, 23 nurses (40.4%;
95% CI; 28.2–53.4%) chose EHG as preferred external method, compared with 20 nurses
(35.1%; 95% CI; 23.6–48.1%) choosing TOCO. Furthermore, 14 nurses (24.6%; 95% CI;
14.7–36.9%) had no preference or replied that their preference was subject to situation
and patient.
Regarding their experiences with EHG on a 5-point scale, 67.3% of nurses reported
that they had sufficient knowledge about EHG (mean 2.1 ± 1.3) and 73.7% of all nurses
considered themselves as competent in the use of EHG (mean 2.2 ± 1.0). Most nurses
also confirmed that they palpate the uterus to ensure optimal localization of EHG
(subdivided into helpfulness 87.3% [mean 1.6 ± 1.0] and frequency 86.8% [mean 1.6 ± 1.0]).
Only 13.2% of nurses reported to use the impedance meter to check the impedance after
skin preparation (mean 4.4 ± 1.2). However, the nurses that do use the impedance meter
also repeat skin preparation, when the impedance appeared to be too high (mean 1.5 ± 0.7).
Most nurses (71.7%) reported no problems with application of this EHG system (mean
2.1 ± 0.8). EHG was considered most time-consuming by 60.4% of nurses, compared with
22.6% that found TOCO more time-consuming, the remaining 17.0% was neutral. The users'
questionnaire revealed indifferent results regarding the inconvenience of skin preparation
(mean 3.4 ± 1.2) and local irritation due to EHG (mean of 3.3 ± 1.0), whereas in the
open answers 35.1% of the nurses observed skin redness and 19.3% skin irritation.
The most reported advantage of EHG was a more constant and reliable registration,
which especially holds in case of obesity and with changing maternal position (64.9%
of the respondents). In addition, 24.6% of the nurses considered the improved patient
satisfaction to be an advantage. The main disadvantage, reported by 54.4% of the nurses,
was a decreased mobility of patients by cables of EHG. The fact that this EHG method
cannot be used in bath or shower was reported as a disadvantage by 28.1% of the nurses.
Finally, the users would recommend this EHG method to colleagues with a score of 6.3 ± 2.0
out of 10.
Discussion
This is the first study evaluating patients' and users' preferences of 3 uterine monitoring
techniques; the internal IUPC, which is the current gold standard though not routinely
used, the external TOCO, which is the method of first choice,[14]
[15]
[16] and external EHG that was only recently validated for contraction monitoring.[5] Patients strongly preferred EHG over TOCO and IUPC. EHG is considered as the most
comfortable method regarding both placement and presence during labor. On the contrary,
preferences of healthcare providers were ambiguous.
A strength of the evaluation on patients' preferences is the unique situation: all
patients received all 3 methods, so they are most eligible to evaluate their preferences.
Another strength of our study is that we had little missing data. Almost all women
filled out the questionnaires directly postpartum or within a few hours, which resulted
in a complete database. We also had a high response rate to evaluate users' preferences
as every obstetric nurse completed the questionnaire.
One limitation of this study was that there were no validated questionnaires available
to evaluate neither patients' nor users' preferences on uterine monitoring techniques,
so we developed customized questionnaires for this purpose. Another limitation might
be that we collected the patients' questionnaire this short after a life-event, which
could influence the outcomes. However, we expect that the mutual comparison is minimally
affected, since the comparison includes all 3 methods applied to the same woman at
the same time. Finally, both patients and users were aware that EHG was the newly
introduced technique, which may have caused bias.
Safety
One of the main principles in medicine is “primum non nocere”, i.e first do no harm.[17] Our results underline this statement as most women preferred the aspect “least likely
to harm” above comfort, quality and costs.
On the one hand, noninvasive external monitoring methods are therefore preferred above
invasive methods to monitor the uterine activity pattern.
Extra membranous placement of IUPC is not uncommon (reported incidence is 23–38%)
and potential risks following improper IUPC placement include perforation of the placenta,
the uterus, or fetal blood vessels.[11]
[18] However, a Cochrane review reported no major complications in 977 women being exposed
to IUPC.[1] Therefore, IUPC-related complications are rare, yet can be very severe.
On the other hand, inadequate external uterine monitoring could also be considered
as unsafe for mother and child. The widely used TOCO is noninvasive but has a low
reported sensitivity: from 46 to 74% thereby missing a significant number of contractions.[19]
[20] EHG has a significant higher reported sensitivity: from 86 to 98%.[3]
[4]
[5]
[19]
[20]
[21] Inadequate uterine monitoring can result in fetal distress and cesarean delivery
due to insufficient relaxation time to reoxygenate the placental tissue in case of
(missed) hypertonia or hyper stimulation of the uterus.[22]
[23] Especially during induction or augmentation of labor, the uterine activity pattern
should be closely monitored to improve the safety of not only mother and child,[16] but also of the obstetrical caregiver, as oxytocin is often involved in obstetric
litigation.[24]
Comfort
Of the external methods, patients preferred the technique with the “least discomfort”
(60.8%) during labor above mobility, adjustments, positioning, and removing. TOCO
required frequent adjustments during labor, such as repositioning of the transducer
and tightening of the elastic belt, resulting in discomfort reported by 23.1% of our
participants. Patients also reported to be least bothered by the presence of EHG during
labor compared with TOCO and IUPC. However, a potential discomfort of EHG could be
temporarily skin reactions following skin preparation and/or the abdominal patch,
which has been reported by 15.4% of patients. Another issue concerning comfort is
for the equipment to be waterproof, in case patients prefer having a bath or shower
during labor. The studied EHG method was not waterproof, and IUPC catheters were also
not suitable for use in water. The telemetry variant of TOCO could be used in both
shower and bath, and is therefore most suitable for these patients. When waterproof
EHG methods will be available, patients' comfort could be further improved.
Mobility
Next to comfort, our participants considered mobility as an important factor during
labor. Research has also shown that walking and upright positions positively influence
the progress of labor.[25]
With IUPC, mobility is seriously hampered as these women are confined to bed because
the catheter can fall out, when they walk around. Eight out of 9 (88.9%) women that
chose IUPC as their preferred method, had labor analgesia and were thus being confined
to bed already. Both external methods (EHG and TOCO) can provide more mobility than
IUPC. Cables for both EHG and TOCO are long enough to walk around the bed but mobility
is still compromised. Therefore, wireless connections are preferred to further improve
mobility. TOCO can be wireless (although not all hospitals have the availability of
wireless systems), while most real-time EHG systems do not (yet) provide wireless
connections. On the contrary, EHG can enhance mobility during labor compared with
TOCO due to the adhesive properties of the contact electrodes, which are less sensitive
to position.
Time-Efficiency
Novel techniques used at the labor ward should not only be preferred by patients,
but should also be user-friendly. The results of our user questionnaire revealed ambiguous
results, regarding their preference for EHG (40.4%) or TOCO (35.1%). Less experienced
nurses found the use of EHG more time-consuming than TOCO. Especially, the impedance
meter was considered as difficult to use and a time-consuming step to integrate in
clinical practice. However, Euliano et al suggested that the usage of EHG could reduce
nursing time.[19] Our more experienced nurses also recognized the time-saving aspect of EHG as it
needs to be applied only once per patient, due to its adhesive properties. Thus, while
initiating the measurement might be more time-consuming, this could be compensated
by reduced interference time during the measurement. In contrast, TOCO needs to be
repositioned several times during labor, especially after maternal movements. To assess
this hypothesis, we annotated all adjustments during the measurements. We checked
signal quality every 30 minutes during the 2-hour registration period: on average,
TOCO needed to be repositioned twice due to signal loss. Within the same time frame,
EHG required 1 adjustment on average such as calibration or reset baseline (zero)
on the CTG monitor. IUPC required less adjustments (on average 0.5 per 2-hour registration),
including resetting baseline, flushing and repositioning of the catheter. In 3 cases
the IUPC was expulsed and in 2 of these cases a new catheter had to be inserted.
Another important factor considering time-efficiency is, whether the method can be
applied throughout the different stages of labor (term/preterm labor, first/second
stage, with/without ruptured membranes). The IUPC can only be inserted, when membranes
are ruptured, which is not always the situation during the early stage of labor or
during preterm labor. During second stage of labor the IUPC catheter can be pushed
out. On the contrary, both EHG and TOCO do not require ruptured membranes. These techniques
can already be applied in the early beginning of (preterm) labor and they stay positioned
throughout labor and delivery. For women, this will be more convenient and for nurses
this could improve workflow. Another factor that could influence time-efficiency is
interpretability of uterine monitoring techniques. The adhesive properties of EHG
enable a more continuous CTG registration of good quality that could be less time-consuming
during labor. Previous studies have also shown that EHG registrations have a higher
interpretability and are easier to interpret than TOCO.[4]
[19]
[26]
Individualized Choice of Monitoring Method
Most of above described factors depend on type of patient and situation. Therefore,
these factors should be considered, when choosing a suitable method for uterine monitoring.
Patients that benefit most from registration with EHG, TOCO, or IUPC could be selected.
An overview of these method-specific characteristics is presented in [Table 4].
Table 4
Advantages and limitations of currently available uterine monitoring techniques
|
Technical characteristics:
|
Intrauterine pressure catheter (IUPC)
|
External tocodynamometer (TOCO)
|
Electrohysterograph (EHG)
|
|
Used technique
|
Sensor-tipped or transducer catheters measuring changes of the intrauterine pressure
|
Gauge transducer measuring shape changes of the abdominal wall
|
Abdominal electrodes measuring the electrical activity of the uterine muscle
|
|
Value of the measurement
|
Millimeters of mercury
|
Relative TOCO units
|
MicroVolts
|
|
Internal or external
|
Internal
|
External
|
External
|
|
Invasiveness
|
Invasive
|
Noninvasive
|
Noninvasive
|
|
Application of technique
|
During vaginal examination
|
Abdominal positioning
|
Abdominal positioning
|
|
Placed by
|
Only physicians or midwives
|
Any obstetrical caregiver
|
Any obstetrical caregiver
|
|
Reusability
|
Disposable
|
Reusable
|
Disposable
|
|
Wired or wireless
|
Wired, direct connection is essential
|
Some hospitals have a wireless TOCO (telemetry)
|
Most do not (yet) provide wireless connection
|
|
Potential risks or side-effects
|
Moderate, < 1:1,000, rare though severe complications (placental/uterine perforation)
|
Very low, skin reactions due to the transducer or elastic band around the abdomen
|
Low, skin reactions due to skin preparation or the abdominal electrodes
|
|
Diagnostic values:
|
Intrauterine pressure catheter
|
External tocodynamometer
|
Electrohysterograph
|
|
Accuracy of method
|
Very high
|
Moderate
|
High
|
|
Sensitivity contraction detection
|
> 95%
|
46–74%[a]
|
86–98%[a]
|
|
Sensitivity in obese women[a]
|
> 95%
|
46–51%[a]
|
82–97%[a]
|
|
Performance influenced by second stage of labor
|
Low, the catheter can be expulsed
|
Low, sensitivity might increase as pushing improves the uterine contact
|
Moderate, potentially more technical artifacts due to pushing
|
|
Users' and patients' preferences
|
Intrauterine pressure catheter
|
External tocodynamometer
|
Electrohysterograph
|
|
Difficulty positioning
|
Moderate, ultrasound for placental localization and vaginal examination
|
Very low, can be easily placed and adjusted throughout labor
|
Low, adequate skin preparation is necessary
|
|
Users' preference
|
x
|
35%
|
40%
|
|
Application
|
Moderate, score 31
|
Low, score 10
|
Very low, score 2
|
|
Presence during labor
|
Low, score 8
|
Moderate, score 42
|
Very low, score 2
|
|
Removal
|
Very low, score 5
|
Very low, score 3
|
Low, score 10
|
|
Patients' preference
|
17%
|
2%
|
81%
|
Note: Scale: very low, low, moderate, high, very high; 0–100: 0 = not bothering, 100 = very
bothering x; not assessed.
a Source references are[3]
[5]
[19]
[20]
[21]
Implementation
The nurses of our hospital have been working with EHG for a couple of years now. As
they were the first to work with this real-time method worldwide, they are the so-called
“early adopters” in the “technology adoption life cycle” of the innovation theory
described by Rogers.[27] As for many innovations, there is still a chasm to be crossed. We expect that wide
implementation of this technology may take some time. Experience needs to grow and
investment in training is important. All future users should be trained on key aspects
of EHG. Correct patch localization is important for proper interface with the myometrium
and adequate skin preparation with abrasive sandpaper is essential for an accurate
EHG signal. However, abrading too firm might evoke dermatologic reactions. Therefore,
an impedance meter is useful to check impedances and guide users in preparation and
application. As this step is considered time-consuming, it would be interesting to
implement direct feedback on the EHG monitor with respect to skin impedance. Finally,
for a successful implementation, it is essential that obstetricians will be trained
in interpretation of EHG signals as well.
Conclusion and Future Perspectives
Conclusion and Future Perspectives
Current uterine monitoring techniques have some disadvantages. EHG is therefore being
evaluated as a promising new method that is both safe and reliable. Patients prefer
EHG over TOCO and IUPC, although the opinion of healthcare providers is inconclusive.
For future designs of EHG devices, we would recommend a waterproof and wireless system,
enabling a more continuous and mobile monitoring. Integrating an impedance meter is
also advised. These adjustments could further improve patients' and users' satisfaction,
which is necessary for successful implementation in clinic. The effect of EHG application
on obstetric and perinatal outcome and related cost-effectiveness should be further
evaluated.
