Ambulatory impedance cardiography in hypertension: a validation study
Judith A McFetridge-Durdle1, Faye S Routledge, Monica J E Parry
1Dalhousie University, School of Nursing, Halifax, Nova Scotia, Canada. judith.mcfetridge@dal.ca
Insights
The Ambulatory Impedance Monitor (AIM) effectively detects hemodynamic changes during postural shifts in hypertensive patients. This technology offers valid and reliable cardiac function estimates for managing hypertension.
Area of Science:
- Cardiovascular physiology
- Biomedical engineering
- Hypertension management
Background:
- Knowledge of hemodynamics improves hypertension management.
- Impedance Cardiography (ICG) provides hemodynamic data but captures only fixed characteristics.
- Ambulatory technology advancements led to the Ambulatory Impedance Monitor (AIM) for continuous hemodynamic monitoring.
Purpose of the Study:
- To evaluate the sensitivity of the AIM in detecting hemodynamic changes associated with postural shifts in hypertensive individuals.
- To assess the validity and reliability of AIM-derived cardiac function estimates.
Main Methods:
- A repeated measures cross-over design was employed.
- Seventeen hypertensive participants underwent sitting and standing hemodynamic measurements.
- Measurements were taken using both the AIM-BpTRU (office use) and AIM-Spacelabs (ambulatory monitoring) systems.
Main Results:
- Both AIM systems detected significant postural changes in heart rate, stroke volume, left ventricular ejection time, systemic vascular resistance, and diastolic blood pressure.
- Cardiac function measures from both systems were highly correlated and not significantly different.
- p-values: HR (p=0.03), SV (p=0.002), LVET (p<0.001), SVR (p=0.03), DBP (p<0.001).
Conclusions:
- The AIM demonstrates sensitivity to hemodynamic alterations during postural changes in hypertension.
- AIM provides valid and reliable estimates of cardiac function in hypertensive patients.
- This supports the use of AIM for improved hypertension management through continuous hemodynamic monitoring.
Abstract:
The management of hypertension is improved by knowledge of the hemodynamics underlying blood pressure. Impedance Cardiography (ICG) provides data on a range of hemodynamic variables that affect blood pressure. However, ICG captures only fixed descriptions of hemodynamic characteristics. Improvements in ambulatory technology have led to the development of the Ambulatory Impedance Monitor (AIM) which records hemodynamic data during the activities of daily living. The purpose of this study was to evaluate the sensitivity of the AIM to detect hemodynamic changes associated with postural shift in persons with hypertension. Using a repeated measures cross-over design, sitting and standing hemodynamic measures were taken in seventeen persons with hypertension while wearing the AIM-BpTRU system designed for standard office use and the AIM-Spacelabs system designed for ambulatory monitoring. Both AIM-blood pressure monitoring systems detected significant changes from sitting to standing posture in heart rate (p=0.03), stroke volume (p=0.002), left ventricular ejection time (p<0.001), systemic vascular resistance (p=0.03) and diastolic blood pressure (p<0.001). Additionally, both systems generated measures of cardiac function that were positively correlated (p<0.001) and not significantly different (p>0.05). Our findings support previous work and demonstrate that the AIM provides valid and reliable estimates of cardiac function in persons with hypertension.
Related Concept Videos
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Pre-Procedural Guidelines for Assessing Blood Pressure
Assessment of blood pressure in brachial artery(two-step method)
Special considerations while measuring blood pressure
Monitoring Both Arms:
Monitoring BP in both arms during the initial assessment is advisable, as the systolic value may differ by five to ten mm Hg between arms. For subsequent BP assessments, use the arm with the higher reading.
Assessment of blood pressure in brachial artery(one-step method)
Prepare for the Procedure:
Assessing Blood pressure using a doppler ultrasound
Pre-Procedural Guidelines for Doppler Ultrasound Blood Pressure Assessment:
Preparation of Equipment:

