Intérêt de la quantification automatique de l'activité sur la reproductibilité des variations circadiennes de la pression artérielle

Objective : To determine how much of the variations of blood pressure during a 24 hour period could be accounted for by a change in activity using an accelerometer to detect the physical activity and establish a predictive model. Materials and methods : 18 healthy subjects (mean age 25 ± 2 yrs) were studied during daily life (24 hours) twice one week apart. The systolic and diastolic blood pressure, heart rate (HR), and time of measure were recorded by ambulatory monitoring using Spacelabs (4 mesures per hour). A portable digital memory device was designed for the 24 hours ambulatory monitoring of HR (ECG) and physical activity. This device consists of an ECG Holter (ELA medical model Cinesis with digital memory) and a three piezoresistive type accelerometer sensors (prototype ELA research) able to record physical activity in the 3 space dimension. Results : The data of the first recording were compared to the predicated values from the application of a logarithmic model of activity to the second recording. The model then predicted 53 ± 19 % of the systolic BP values of the test day. The mean individual difference for a given time period of one hour between the measured and the predicted systolic BP from the model was 1.45 ± 3.1 mmHg with a range of [-6.9 : 3,4 mmHg]. The mean individual systolic BP difference for the same given time period of one hour but without predictive model was 1.29 ± 10 mmHg with a range of [-28 ; 43 mmHg]. Conclusion : This study show that 3 D accelerometer is an easy tool to program individual model of ambulatory blood pressure variability. The introduction of this qualitative method seems logical in therapeutic trial.