Biomedical subjects

F Foerster

Publications and source records attributed to F Foerster.

22 records · Page 2Linked to original sources

PubMedDate not supplied

Skin evaporative water loss (SE) and skin conductance (SC) under various psychophysiological conditions.

A procedure for measuring tonic and phasic reaction components of skin evaporative water loss (SE) on the basis of a capacitive measurement principle is developed and used in a psychophysiological study employing various stimulus conditions. SE and skin conductance (SC) are registered continuously to obtain comparative data of both biosignals for research concerning the underlying mechanisms of EDA. Results indicate that correlations of some phasic parameters of SC and SE prove to be rather high (up to 0.88), tonic parameters (the levels SCL and SEL), however, show less covariance (0.44). The intersituational discriminative efficiency of SC-parameters appears generally better than those of SE. SCL, as well as SEL, show the highest percentage of person variance. A rather high redundancy of the two biosignals, both taken from neighbouring areas of the right palm, has been found. An unexplicable residual may, however, lend some support to the notion of a partial independence of EDA from sweating.

Adult↗

PubMedDate not supplied

Non-invasive estimations of ventricular ejection time and stroke volume: comparison of impedance cardiography and the Portapres 2.

Stroke volume estimates and left ventricular ejection time (1) derived from calibrated finger pulse pressure recordings (Portapres 2, TNO-BMI, Amsterdam) based on the Model Flow method and (2) derived from impedance cardiography were compared in 20 student subjects. The recordings were made for seven conditions: supine rest, standing, mental arithmetic, ergometer exercise 50 W, motor performance test, reading aloud, and walking. Findings indicated that caution is required in assuming concurrent validity for both methods in tracking haemodynamic changes. Within-subject correlations were low or even negligible. Basic discrepancies were evident regarding the estimation of left ventricular ejection time but obviously more sources of measurement error exist which necessitate further research.

Adult↗

PubMedDate not supplied

Joint amplitude and frequency analysis of tremor activity.

Clinical tremor analysis mostly is used for the measurement of tremor frequency. The analysis is based on short segments of EMG recordings and on clinical ratings of tremor intensity. Accelerometry appears to have some practical advantages. The present study was concerned with the development of a methodology for assessing tremor activity using the three parameters, frequency (Hz), amplitude (g), and occurrence of tremor (in per cent of time). These parameters were derived from joint amplitude frequency analysis of the calibrated accelerometer raw signal and from appropriate decision rules. This methodology was used in connection with 27 patients with Parkinson's disease, to investigate the aforesaid parameters of tremor activity. Postural tremor had a higher occurrence time (right-hand only) and higher frequency (left-hand only) than resting tremor, however, the average amplitudes did not differ. The correlations between right-hand and left-hand measures were higher during postural tremor test. Frequency was not correlated to amplitude or occurrence time, however, moderate correlations did exist between amplitude and occurrence time. In addition to the assessment of tremor activity, multi-channel accelerometry may be used for the detection of posture and motion. Further applications of this methodology, for example, in 24 hr ambulatory monitoring of tremor, are discussed.

Acceleration↗

PubMedDate not supplied

Tremor in Parkinson's disease: 24-hr monitoring with calibrated accelerometry.

Monitoring systems enable the long-term registration of tremor in patients with Parkinson's disease This method is useful in the objective measurement of tremor during the course of treatments. Indeed, the symptoms of tremor as well as the aggravating and attenuating influences can be observed under real-life conditions. The methodology of data recording and analysis, described in previous investigations, was extended to automatically detect body position and certain movement patterns with calibrated 4-channel accelerometry. The main purpose of the present investigation was to apply this refined and extended methodology to patients in a clinical rehabilitation program, and to examine its practability with respect to the results of the treatment and the patients' compliance. The methodology was tested on 30 patients (17 male, 13 female) with Parkinson's disease. The mean age was 64.8 years (s = 8.9). The Hoehn-Yahr index ranged from 1 to 3 (m = 2.3, s = 0.7) and the overall UPDRS scale between 10 and 74 (m = 42.9, s = 18.1). The data recording included: (1) the registration of tremor under standardised conditions of rest and postural tremor test with and without distraction; (2) a standard protocol to obtain reference values for body position and movement; and (3) the 24-hr monitoring. 21 patients could be recorded a second time, on average 18 days after the first recording. Between the two registrations, patients received individually tailored drug treatment supplemented with specific activating physiotherapy, ergotherapy measures, and individual psychotherapeutic counseling. Changes between first and second recording were evident for the three tremor variables, but significant only for the 24-hr ambulatory monitoring. The between and within-subjects correlations of the tremor variables were rather low except the correlations between occurrence and amplitude (between-subjects. 87; within-subjects. 67). Conditions of rest and postural tremor test showed a correlation with corresponding segments of the ambulatory monitoring of about. 50 for the tremor occurrence. The best prediction of the day-time monitoring was made by the tremor tests with distraction, whereas the night segment was best predicted by the standard protocol.

Adult↗