H. H. Ros

Noninvasive continuous blood pressure measurement during anaesthesia: A clinical evaluation of a method commonly used in measuring devices

The objective of the study was assess the utility during anaesthesia of noninvasive continuous blood pressure measurement techniques which use intermittent oscillometric blood pressure measurement for their calibration. The assessment was performed by comparing noninvasive blood pressure with intra-arterial blood pressure. The noninvasive blood pressure measurement device used for evaluation was the NCAT N-500 which uses tonometry for its continuous measurements. Fifteen patients were studied. In 10 patients the intra-arterial blood pressure curve (IBP) was recorded from the radial artery (radial artery group), and in 5 patients it was recorded from the brachial artery (brachial artery group). In all patients the oscillometrically calibrated tonometric blood pressure (OTBP) was recorded from the other arm. To discriminate between calibration dependent measurement error and tonometric measurement error, the OTBP signal was recalibrated against the IBP signal to get the intra-arterial calibrated tonometric pressure curve (ITBP). OTBP-IBP reflected the overall measurement error, ITBP-IBP the error of the tonometric measurement, and OTBP-ITBP the calibration dependent measurement error. According to criteria formulated in the discussion the accuracy and agreement of the ITBP-IBP measurements were clinical acceptable. Accuracy and agreement of OTBP-IBP and of OTBP-ITBP were not clinical acceptable. Correlation of dynamic behavior was lower for OTBP than for ITBP. A significant effect of site difference between calibration measurements and continuous measurements was not found. It is concluded that the approach of continuous noninvasive blood pressure measurement based on the combination of two different measurement methods, in which the continuous method is calibrated by the oscillometric method, lead to clinical unacceptable accuracy and agreement in the patient group studied.

The use of neurophysiologic monitoring during anaesthesia

ConclusionBrain monitoring is necessary, because the brain is the most sensitive organ for hypoxia due to different causes. The EEG is sensitive to changes in cerebral oxygenation. EEG monitoring can be used effectively during general anaesthesia and surgery. In order to make this type of monitoring more specific, a lot of research has to be done into the relation between the EEG and the underlying processes in the brain. State of the art computer technique fulfils the requirements for easy handling and immediate interpretation of the signals without having the training of a neurologist.

Noninvasive Continuous Blood Pressure Measurement with the Cortronic APM 770

Methods for noninvasive and continuous measurement of the arterial bloodpressure combine the advantages of minimal risks for the patient and ease of use. If these methods are reliable and accurate they can in many occasions replace invasive bloodpressure measurements, thus avoiding the possible complications inherent to the invasive technique (1).

Monitor; a Low Cost, Versatile Data Acquisition Program

For research purposes it is often necessary to collect analog data. Until recently it was customary to view this analog data on an oscilloscope, and to store it on an analog tape recorder, thus introducing with the disadvantage of extra noise and a limited dynamic range. Interesting parts of the data could be played back for reviewing and production of a hard copy with a chart recorder. After this the tedious job of working out the collected data started. Time intervals and amplitudes were measured with a ruler and recorded manually on an other piece of paper. From this data graphs were plotted manually and statistics were calculated.

CONTINUOUS PULSE CONTOUR CARDIAC OUTPUT DURING MAJOR ABDOMINAL VASCULAR SURGERY

A new pulse contour method to determine cardiac output continuously in patients on a beat-to-beat basis from an arterial pressure wave has been implemented in a simple, fully automatic computer system. The pulse contour method computes a volume from the systolic area under the arterial pressure curve. This calculation requires a model which relates volume and pressure. The Wesseling method used in our study is based on a transmission line model of the aorta1.