Ambulatory measurement of body position

Ambulatory monitoring is playing an important role in the clinical and research field. In the modem era, physicians are showing much interest in measuring heart rate, blood pressure and many other physical and cardiac conditions and recording electrocardiogram (ECG, a popular technique for diagnosing heart related disease), while the patient is ambulatory. Heart rate, blood pressure and ECG waveform can change because of body position. In the case of the ECG, the changes caused by body position are can change the ST-T segment and also the QRS amplitude. The heart rate and blood pressure changes when there is a change in position from standing to sitting, sitting to standing, sitting to lying or any of the combinations. The goal of this project was to develop a device that can measure body position using an accelerometer technique and to interface the accelerometer with a handheld computer. A software program was also developed to display and store the position information into a handheld computer. The software program was developed in LabVIEW PDA module environment. To prove the validity and accuracy of the system, a pilot experiment was conducted where the readings from the device at different positions and during normal activities were recorded from five healthy subjects and compared. Data showed that as the subjects changed their posture, the system was able to correctly identify three basic body postures, which are sitting, standing and lying