Results
Phase 1: Performance evaluation of the CDXP and Omron M6 Comfort
Of the approached 68 women 34 were willing to participate and met the
inclusion criteria as described above. Participant details of this phase
are shown in Table 3. A total of 33 complete measurements with the CDXP,
Omron M6 Comfort and the aneroid manometer were conducted. 1 Participant
was excluded in the comparison of the CDXP due to the inability to
refrain from moving the arm.
The mean aneroid recruitment SBP
was 113 mmHg (93-147 mmHg), the mean DPB was 73 mmHg (59-99 mmHg). We
did not detect any difference in SBP and DBP between the aneroid meter
and CDXP: -0.7±6.5 mmHg (p=0.38) and 0.4±5.7 mmHg (p=0.55) for SBP and
DBP respectively. The aneroid manometer measured SBP mmHg significantly
higher (1.5±5.8 (p=0.04)) and DBP lower (-2.8±5.8 mmHg
(p<0.01)) as compared to the Omron M6 Comfort. Using an
univariate regression analysis we did not find a difference between
measurements in round 1 and 2 and we could not explain the differences
in blood pressure measurements between the Omron M6 Comfort and the
aneroid manometer by body mass index, gestational age, upper arm or
wrist circumference.
Figure 1 and 2 illustrate Bland-Altman plots of both the CDXP and Omron
M6 Comfort and shows that there is no indication of a systematic
relation between the blood pressure ranges and the performance of the
two devices.
Phase 2: Home CDXP versus office blood pressure measurement
Of the 64 approached women 32 were willing to participate and met the
inclusion criteria as described above. 3 Women accidently measured their
home measurement on a different day as their hospital measurement and
were excluded from statistical analyses. Participant details of this
phase are shown in Table 3.
The mean blood pressure values and the mean differences between
measurements are listed in Table 4. In 7 patients the home blood
pressure measurements were not complete due to technical problems (n=3),
simply forgetting (n=3) and going into labor during the measurements
(n=1). Their available partial data were incorporated in the analysis.
Comparison showed that for both CDXP self-measurements the SBP, but not
the DBP, was significantly lower than the standard office measurement.
The second measurement of the office self-measurement was slightly
significantly lower than the first measurement. This was not observed in
home self-measurement. The found significant differences in office SBP
and home SBP was not correlated with age, amenorrhea duration, BMI
before and during pregnancy, parity, wrist and upper mid arm
circumference, pulse rate and the range of blood pressure (data not
shown).
Evaluation of the home
self-measurements with the CDXP during the day showed that there were
small differences between the first and second home self-measurement at
the different time points in both SBP (maximum of 2.3±4.6 mmHg) and DBP
(maximum of 2.1±3.1 mmHg). Figure 3 shows the mean standard office
measurement and mean first home self-measurements of SBP and DBP over
the different time points. The standard office measurement of SBP was
significantly higher as compared to all time points of the home
self-measurement: morning 6.7±10.5 mmHg, noon 7.6±9.7 mmHg, afternoon
7.6±10.7 mmHg, night 7.2±11.9 mmHg. We did not detect any difference in
DBP between the standard office measurement and the home
self-measurement time points.
Table 5 shows the mean scores to the patients’ experience questionnaire.
Two patients did not fill out the questionnaire and two patients left
one question blank and were therefore excluded from analysis. The mean
SUS-score was 85%, corresponding with an excellent score. Most women
indicated that they managed to follow all the instructions and that they
trusted their measured blood pressure. The vast majority thought that
home monitoring of the blood pressure is a good idea and a good option
for replacement of the standard office measurement. Most women liked the
idea of having less hospital visits due to home monitoring, while only
3% disagreed. Women reported that they rather not miss listening to the
fetal heart. Patients also reported that they liked the idea of home
monitoring of the blood pressure even more if the course of pregnancy
led to extra hospital visits for blood pressure measurement only.