Biomedizinische Technik. Biomedical engineering
-
Currently, metabolic changes in ICU patients in critical states are determined mainly by indirect laboratory parameters (e.g. blood lactate). Microdialysis is a new means of performing metabolic monitoring that permits organ-specific objectification on the basis of interstitial fluid samples. ⋯ The interstitial concentrations of lactate and glycerol rose significantly under endotoxaemia and showed an earlier increase than blood lactate levels. Microdialysis is simple to apply, appears to be a suitable means of obtaining important information about cellular metabolic changes in different tissues of the critically ill patient, and can detect subtle changes that laboratory parameters can identify only later and incompletely.
-
Using a dual channel near infrared (NIR) in vivo optical spectroscopy (INVOS) system (INVOS 3100A, Somanetics Corp. Troy, MI, USA) we investigated the relationship between jugular venous oxygen saturation (SjvO2) and regional cerebral oxygen saturation (rSO2) in 30 infants and children (mean age 4.5 years) with congenital heart disease undergoing cardiac catheterisation. The NIRS-SomaSensor (emitter and dual receiver probe) was applied at a standardised right fronto-temporal location (over the right frontal cortex) on the infant's head and covered with an adhesive flexible bandage. ⋯ No significant correlation was observed between rSO2 values and arterial blood saturation or pulse oximetry. The quantitative correlation between rSO2 (haemoglobin oxygenation in a small hemi-elliptical area of the brain) and reference SjvO2 measurement (method for monitoring global cerebral oxygenation) suggests that NIRS measurement with subtraction algorithm should identify predominantly intracranial saturation in the pediatric age group, and will tend to reflect global oxygenation under physiological conditions. Transcranial oximetry using dual receiving channel NIRS offers a noninvasive, real-time, reliable and practicable means of monitoring cerebral haemoglobin oxygenation changes infants and children with cyanotic and noncyanotic congenital heart disease.
-
The measurement of individual respiratory parameters in the vicinity of the lungs remains an unresolved problem in the areas of anesthesia and intensive care medicine. New technologies such as fibreoptic technology, which meet the extreme demands of medical sensor applications, and their innovative potential as a basis for the development of marketable products, appear promising. This is illustrated by the fundamental principles developed for a sensor-armed tracheal tube for on-line monitoring of ventilated patients.
-
Mimicking the physiological characteristics of the circulatory system, pulsatile bloodflow has also been introduced into extracorporeal perfusion to avoid known postoperative complications. In a mathematical consideration of the situation bloodflow is seen as a function of time F(t) for approximately constant vessel diameter over a given time. The kinetic energy of a column of blood produced by the heart-lung machine is transmitted directly to the arterial circulation via the aorta. ⋯ The energy increase within a cycle should not exceed 150 joules. To optimize the mode of functioning of the heart-lung machine, we introduced the "energy-equivalent pressure" (EEP). Adaptation of the EEP to the physiological conditions required a basic flow of 60% at a pulse rate of 60/min and a pulse duration of 35% within the pulsatile flow interval.
-
Comparative Study
Transcranial optical spectroscopy--A comparison of the TOS 96 and INVOS 3100 cerebral oximeters.
We evaluated two user-friendly, commercially available transcranial cerebral oximeters (TOS 96, Tostec, Tokyo, Japan and INVOS 3100, Somanetics, Troy, USA) for use in adults. We compared the absolute values (%) of regional cerebral oxygen saturation (rSO2) from 108 measurements in 54 healthy volunteers (31 women, mean age 35.8 +/- 16.3 years and 23 men, mean age 35.4 +/- 9.2 years). ⋯ Significant differences (p < 0.01) were found between females and males with the INVOS equipment. The study shows that anatomical (thickness of the skull) and technical (calibration) aspects have to be taken into consideration when interpreting absolute rSO2 values.