ACTIVITY AND POSITION MONITORING DURING AMBULATORY BLOOD PRESSURE AND HEART RATE MONITORING
P. Gosse(1), P. Guillo(2), M.L. Wetzler(3)
(1) Hopital Saint André, Bordeaux, France
(2) Clinique Saint Yves, Rennes, France
(3) Novacor, Rueil-Malmaison, France
Objectives
The main limitation in the interpretation of ambulatory BP monitoring is linked to high BP variability with activity and position changes. The analysis and quantification of such changes is thus an important objective, especially when assessing the effects of antihypertensive drugs.
Methods
We tested a new device (Quatrholter, Novacor France) allowing both BP and continuous ECG monitoring, equipped with a thorax position sensor and a two direction accelerometer fixed on the patient's thigh. These 2 sensors give continuous information on pt's position and on activity of the legs. 24h monitoring during daily routine was performed twice, 7 days apart, in 18 normal volunteers. BP was measured every 15 ¢ during day and night.
Results
The information from the 2 sensors allowed to classify the activity of the patients in 5 groups: Lying asleep, Lying awake, Sitting, Standing immobile, Walking or running (with information on walking speed). BP and HR were significantly influenced by these 5 conditions. The reproducibility of BP and HR measurements between the 2 recordings was analysed according to these 5 conditions. Results for SBP are summarised in table with mean values for the 2 recordings, standard deviation of differences (SDD) and coefficient of correlation (r). As expected, BP and HR measured when asleep or in sitting position were the most reproducible. BP measured when standing immobile or moving is much more variable from a recording to another.
| |
Mean |
SDD |
r |
24h average (mmHg)
Daytime
Night-time
Lying
Sitting
Standing
Lying asleep
Lying awake
Sitting
Standing immobile
Walking |
105.7
109.8
99.1
100.2
110.5
111.8
98.6
104.4
110.5
109.1
116.9 |
4.9
5.3
5.2
61.
4.3
9.5
4.4
9.3
4.3
11.3
9.7 |
0.84
0.85
0.85
0.72
0.93
0.55
0.87
0.67
0.93
0.4
0.66 |
Conclusion
This new device allows a reliable and efficient analysis of the patient's positions and activities during BP and HR monitoring. Analysis of BP and HR according to these information allow to limit the influence of changes in activity on the interpretation of the results.
Abstract: 4C.1
Journal of Hypertension Volume 23, Supplement 2, June 2005, page S135
HAUT DE LA PAGE
Validation
of a two-axis accelerometer for monitoring patient activity during
blood pressure or ECG holter monitoring.
Wetzler ML et al.
OBJECTIVES
The
aim of the study was to evaluate the efficiency of a position/activity
monitoring system based on a dual-axis accelerometer strapped
to the subject's thigh and a position sensor located within a monitor
placed on the subject's belt
METHODS
Twenty-six
subjects wearing two monitors (one accelerometer on each thigh)
were submitted
to
various activities and positions under the control of an observer.
An analysis of each tracing was performed both manually by
a technician and automatically by dedicated software before being
compared with
the information gathered during the study.
RESULTS
The accelerometer
allowed accurate discrimination between the standing versus
the
sitting and lying positions. The sitting and lying positions
were correctly detected by the built-in position sensor provided
the
unit was firmly attached. Walking was adequately detected
by the accelerometer. The activity score was well correlated with
treadmill
speed. Changes in position and activity were detected with
a mean error of less than 3 s.
CONCLUSIONS
The
combination of an
accelerometer
placed on the subject's thigh and a position sensor located
at the subject's waist appeared to be a suitable system for
position/activity monitoring during ambulatory ECG and blood pressure
monitoring.
Wetzler ML et al.: Validation of a two-axis accelerometer for monitoring
patient activity during blood pressure or ECG holter monitoring.
Télécharger l'article au format PDF
2003, Blood
Press Monit., 8:229-35.
