The overall r2 value of .67 indicates that TIC might be useful for trend analysis of different groups of patients. However, for diagnostic interpretation, a r2 value of .53 might not meet the required accuracy of the study. Great care should be taken when TIC is applied to the cardiac patient. However, because the applied reference method was of significant influence, differences between TIC and the reference method are incorrectly attributed to errors in TIC alone.

TIC might be useful for trend analysis of different groups of patients. However, since the reference method was of significant influence, differences between TIC and the reference method are incorrectly attributed to TIC alone.

A method for measuring the susceptibility of a patient to develop decubitus ulcers is described and initially evaluated. It is based on an indirect, noninvasive measurement of the transient regional blood flow response after a test pressure load which simulates the external stimulus for pressure-sore formation. This method was developed to determine the individual risk of a patient and to study the subfactors which contribute to the susceptibility. This would also offer the possibility of evaluating the effect of preventive treatment aimed at reducing the susceptibility. The method was found to discriminate between preselected elderly patients at risk on the one hand, and non-risk patients and healthy young adults on the other hand. No differences in blood flow responses were found between the non-risk elderly patients and the healthy young adults. This suggests that age per se is not a factor in the formation of pressure sores. In the risk group the recovery time after pressure relief was found to be three times as long as the duration of the pressure exercise. This indicates that the recovery time after pressure exercise may be as important as the period of pressure exercise in deducing the risk of developing decubitus ulcers.

The paper describes a new transducer for detection of fetal movements and sounds from the maternal abdominal wall. This transducer is based on an inductive principle. The compliance of the transducer should match the compliance of the maternal abdominal wall in order to detect the very weak acoustic signal caused by individual fetal breathing movements. The contact area of the transducer is supported on a membrane, the tension of which can be adjusted so as to match the compliances of tissue and transducer. The goal of this paper is to investigate detection of fetal movements in order to monitor fetal condition and motility. The more specialized field of investigating fetal heart rate variability by studying the relationship between fetal breathing movements and fetal heart rate may become of more interest in the future. The inductive phonometer (INPHO) shows a flat (+/- 1.5 dB) frequency response between 0.2 and 200 Hz which is not affected by the compliance adjustment. Some in vivo measurements have been performed. The transducer signal is stored on a 20MB hard disk of an Olivetti M24 Personal Computer (PC) simultaneously with a control signal indicating the presence of breathing movements. Ultrasound imaging is exclusively used for verification of breathing movements. The images are stored on videotape simultaneously with control signals from the PC for synchronization of data and image. Substantial digital filtering is necessary to discriminate between actual breathing movements and other fetal activities. It is shown that optimal adjustment of the transducer's compliance to that of the maternal abdominal wall is possible and that individual breathing movements can indeed be measured.

The validity of a one- and a two-cylinder model, underlying thoracic impedance cardiography (TIC), was investigated by studying the length dependence of the impedance parameters Z0, (dZ/dt)min, and stroke volume (SV). It can be shown that, within a one-cylinder model, all parameters are directly proportional to the length, whereas, if the volume conduction of the thorax and the neck are modeled separately, Z0 and (dZ/dt)min are expected to be linear dependent and SV will be nonlinear upon the length. The expectations were compared to results from in vivo measurements. Two electrode arrays were studied, in which the caudal recording electrode position was varied; SV was calculated using Kubicek's equation. Except for small distances, the results showed a nearly linear relation between the parameters and the length. Regression analysis of the linear part revealed statistically significant intercepts (p < 0.05). Neither the intercept nor the nonlinear part can be explained by a one-cylinder model, whereas a model consisting of two cylinders serially connected describes the experimental results accurately. Thus SV estimation based on a one-cylinder model is biased due to the invalid one-cylinder model. Corrections for the Kubicek-equation need to be developed in future research using this two-cylinder model.