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Biomedical subjects

S Mieke

Publications and source records attributed to S Mieke.

17 recordsLinked to original sources
PubMed1999

Assessment of the performances of three oscillometric blood pressure monitors for neonates using a simulator.

BACKGROUND: The majority of monitors for non-invasive measurement of blood pressure in neonates and infants use the oscillometric method. OBJECTIVE: To use a simulator to investigate the overall system accuracy for three oscillometric blood pressure monitors. The tested devices are DINAMAP 8100 (Critikon), SpaceLabs M90426 (SpaceLabs Medical)and the module HP M 1008B (Hewlett-Packard). METHODS: The blood pressure values obtained by the three devices were compared with those of the invasive reference. A blood pressure simulator was used for testing the performance of the three blood pressure monitors. RESULTS: The Dinamap and SpaceLabs readings are generally in good agreement with the invasive reference. In contrast, the HP M 1008B readings for the diastolic and mean arterial pressures are inaccurate (the mean errors are 21 and 15mmHg, respectively). CONCLUSION: These results contradict our previously published data obtained when a different simulator (Cufflink)was used. These findings are important, because blood pressure values that are too low can result in a different therapeutic approach being applied, for newborn babies have only a small range of mean arterial pressure for the autoregulation of the cerebral blood flow.

Blood Pressure↗
PubMed1998

Blood pressure measurement in epidemiological studies: a comparative analysis of two methods. Data from the EPIC-Potsdam Study. European Prospective Investigation into Cancer and Nutrition.

OBJECTIVE: To investigate the impact of a device replacement in blood pressure measurement in epidemiological studies on comparison and interpretation of epidemiological data by replacing traditional aneroid manometry with automated oscillometric devices. DESIGN: Within the context of a continuing epidemiological study (EPIC-Potsdam Study), blood pressure measurements were performed simultaneously with an aneroid sphygmomanometer and an automated oscillometric device for each subject. We randomly selected 400 men and women from the main study population and one observer performed three consecutive blood pressure measurements for each subject according to a standardized procedure. In total, 10 oscillometric devices of the same type were used. Demographic and anthropometric data for each subject were obtained by trained interviewers. RESULTS: The mean difference between the aneroid and the oscillometric measurements of systolic blood pressure was 0.2 +/- 5.6 mmHg (aneroid value greater, NS), whereas the mean difference in diastolic blood pressure, 0.5 +/- 3.5 mmHg (aneroid value smaller), attained statistical significance (P = 0.0001). Estimates of prevalence for hypertension differed by 0.4% for women, and by 2.9% for men. Associations with the differences between methods were observed with age, blood pressure, lean body mass, upper arm circumference and specific devices without indicating a strong and consistent pattern. CONCLUSIONS: The use of automated oscillometric devices in epidemiological studies introduces a bias of very small magnitude compared with use of the aneroid method. The effect of the change to this automated measurement procedure on prevalence estimates is small but might affect comparability of data. Minor differences in measurement performance between devices of one type might affect population parameters.

Adult↗
PubMed1997

Substitute of simulators for human subjects.

At present the overall accuracy of automated sphygmomanometers is assessed in validation studies performed with human subjects with a wide range of blood pressures. These studies permit test devices to be designated as having acceptable or unacceptable accuracy. The feasibility of performing and the statistical rationale for such validation tests under varying circumstances, such as during exercise, and with various subjects, such as the obese, are limited due to the time and money required. Many studies have inadequate quality controls for the reference blood pressure measurements. Simulators have the potential to improve the validation of automated sphygmomanometers, as long as they are able to replay the human biosignals in all their complexity and variability. The simulator developed by the Physikalisch-Technische Bundesanstalt and described in this paper demonstrates that this is feasible, whereas the commercially available devices do not satisfy these requirements, though they are suitable for assessing quality control and for testing reproducibility for manufacturers.

Journal Article↗
PubMed1996

[Evaluation of the oscillometric blood pressure monitors: Dinamap 1846 and HP M-1008B].

Using the PTB simulator, which emits real signals from patients, we examined the precision of the oscillometric blood pressure measurement with the Dinamap 1846 (Critikon) and the HP M-1008B (Hewlett Packard). For this purpose we simultaneously registered invasive arterial pulsewave, cuff pressure and cuff pressure oscillations of 20 patients from our intensive care unit and stored them in the database of the simulator. The invasive reference blood pressure values were determined following the recommendations given by the Association for the Advancement of Medical Instrumentation. The invasive system showed a cut-off frequency of 35 Hz; the damping constant was 0.21. With 49 record signals from patients we carried out 15 simulated measurements each. From a total of 49 bio-signals from patients the Dinamap 1846 was able to process 41 signals and the HP M-1008B 47 signals. The mean error of the oscillometric blood pressure measurement of the systolic, diastolic and mean arterial pressure amounted to -2.50 mmHg, 3.35 mmHg (P < 0.05) and 1.51 mmHg with the Dinamap 1846 and to -8.5 mmHg (P < 0.001), -5.15 mmHg (P < 0.001) and -5.58 mmHg (P < 0.001) for the HP M-1008B. The 95% confidence limit for the systolic, diastolic and the mean arterial pressure amounts to 56 mmHg, 30 mmHg and 35 mmHg for the Dinamap 1846 and 50 mmHg, 38 mmHg and 35 mmHg for the HP M-1008B. The differences between that two instruments could be caused by the different algorithms for the calculation of blood pressure values and different artefact detection and elimination techniques. The results of the performance tests we achieved with the PTB simulator correspond to the results of other clinical examinations. The American Association for the Advancement of Medical Instrumentation recommends a maximum mean error of 5 +/- 8 mmHg. None of the examined instruments lay within these limits. Due to the systematic and stochastic errors, we think that the Dinamap 1846 (Critikon) and the HP M-1008B (Hewlett Packard) do not achieve performance levels that are adequate for measuring critically ill patients.

Adult↗
PubMed1996

Which requirements must be met by non-invasive blood pressure measuring devices bearing the CE-mark?

Since 1995. non-invasive blood pressure measuring devices (sphygmomanometers) may bear the CE-mark. This indicates conformity of the device with the provisions of the relevant EC directives. The most important directive for non-invasive sphygmomanometers is the Medical Device Directive, which includes only essential requirements, not specific ones for special devices. The detailed requirements for special devices are laid down in harmonized standards. For non-invasive sphygmomanometers a harmonized European standard (EN 1060) was developed in recent years. It specifies performance as well as safety requirements, especially for accuracy. environmental performance and construction. Since the standard (EN 1060) defines the state of the art on a quite high level, no change to the worse in Member States which had a legal quality management system could be expected, but rather an improvement for all users in the whole EU.

Blood Pressure Determination↗
PubMed1994

[Arterial blood pressure measurement with oscillometric instruments in newborns and infants].

Non-invasive blood pressure measurements by the auscultatory method do not provide reliable, reproducible blood pressure values in many neonates because the Korottkoff sounds are often very difficult to detect. This resulted in the development of many alternative indirect methods. Devices utilizing the Doppler ultrasound technique have not found wide acceptance. Since the introduction of automated oscillometric blood pressure monitors, arterial blood pressure has been increasingly brought into discussion as an indicator of the circulatory state. This is the first study to investigate the similarity and reproducibility of the data obtained with five oscillometric devices for measurement of blood pressure in neonates. MATERIALS AND METHODS. Since investigations on the technical performance are not practical in the clinical setting of a neonatal or pediatric ward, we used two simulators, the CuffLink (Dynatech, Nevada, USA) and a device developed by the PTB (Physikalisch-Technische Bundesanstalt). While the latter uses oscillations originally obtained from neonates, the CuffLink uses artificial and therefore ideal signals for the blood pressure monitors. The signals used for the PTB simulator were obtained from three neonates with an average age of 2 months and a weight of 3.5 kg, 4.4 kg, and 7.8 kg. The following blood pressure monitors were studied: Hoyer/Colin, BP-1001; Datex, Cardiocap II; SpaceLabs, model no. 90426; Hewlett-Packard, NBP M1008A; Critikon, Dinamap 1846. Before the measurements were started, the cuff pressure display of each monitor was checked according to a verification procedure. Although the 4 mmHg margin of error was not exceeded, the results were corrected. RESULTS. The results of the measurements show significant differences between the blood pressure monitors from the various manufacturers, with the differences for the ideal signals of the CuffLink-Simulator being less pronounced than those for the PTB simulator. Direct comparison of results is therefore often impossible. The standard deviation, taken from 20 measurements per monitor and simulation, is below 4 mmHg for both simulators. We can therefore conclude that the reproducibility of data is satisfactory and the emerging trend is reliable. DISCUSSION. The difference between the results of the PTB simulator and the CuffLink are probably due to the method of evaluation and the identification of artifacts of each blood pressure monitor. This is also confirmed by the studies of Mieke et al. The manufacturers should provide devices that display comparative results and improve the algorithms for detection of artefacts, increasing the accuracy of their blood pressure monitors. This could be done with the help of simulators. Considering the pathophysiological characteristics of neonates and infants, the systematic differences between the five monitors have to be regarded as serious.

Blood Pressure Monitors↗
PubMed1993

[Does the photoplethysmographic technique show an improvement in the measurement of the indirect blood pressure in intensive care patients?].

In the present report we investigated whether oscillometric and plethysmographic arterial blood pressure measurement techniques yielded different results compared to invasive blood pressure measurements in 18 mechanically ventilated and 14 spontaneously breathing patients. METHODS. Blood pressure was recorded simultaneously with plethysmographic, oscillometric, and invasive systems (FINAPRES 2300, HP 78352A, and 78534A, respectively). Invasive measurements were obtained in the radial artery. Short tubing was chosen in order to avoid transmission errors. The finger cuff of the FINAPRES 2300 was placed on the ipsilateral middle phalanx of the middle finger. The cuff of the oscillometric system was located on the contralateral arm. Differences in arterial blood pressure had been excluded. RESULTS. Histograms of the differences in the various pressure measurements, linear regression, and correlation coefficients were determined for quantitative comparison. The two non-invasive measurement devices (FINAPRES 2300, HP 78352A) yielded similar results in spontaneously breathing patients. In ventilated patients the reliability of oscillometric measurements was worse than that of the photoplethysmographic, especially for diastolic and mean arterial blood pressure values (Table 1, Figs. 2-4). DISCUSSION. The reasons for the differences between invasive and non-invasive measurement techniques are most likely due to problems with cuff handling for the plethysmographic device and the principles of oscillometric measurement. Both methods have to be optimised in hardware and software. However, the photoplethysmographic results showed an improvement in blood pressure measurement in ventilated patients. Due to the remaining deviations between the non-invasive and invasive measurements, especially in critically ill patients in the intensive care unit, direct measurement cannot be replaced by either of the non-invasive methods.

Adult↗
PubMed1993

[The reliability of the measurement of non-invasive oscillometric blood pressure instruments].

METHODS: The performance of five oscillometric blood pressure monitors was tested by means of a simulator. The oscillometric signals of two healthy patients were replayed. These signals were superimposed by sinusoidal artefacts with increasing amplitude, to examine the influence of artefacts on the accuracy of the measurement. Each measurement was repeated 15 times. RESULTS: The artefacts taken for this examination did affect the scattering of each single measurement rather than the mean value of the repeated measurements. The results did get worse with decreasing signal-to-artefact ratio. However, some monitors are able to handle these artefacts better than others. CONCLUSION: It is obvious that the implemented software for the artefact treatment and the determination of blood pressure values differs from manufacturer to manufacturer. Some devices were able to separate relevant signals from artefacts better than others. The most critical point of the oscillometric method is the correct determination of the maximum amplitude of the oscillations, because it directly influences the accuracy of the displayed blood pressure values. The availability of a simulator to test automated sphygmomanometers has shown to be a good tool to examine the performance of these devices.

Artifacts↗
PubMed1987

Decrease of caffeine elimination in man during co-administration of 4-quinolones.

The single dose pharmacokinetics of caffeine (220-230 mg per dose) were investigated in 12 healthy male volunteers before and during treatment with ofloxacin (200 mg bd), ciprofloxacin (250 mg bd) and enoxacin (400 mg bd) with a cross-over study design. None of the parameters: mean elimination half-life (T1/2el), Cmax, total body clearance (Cltot) and the volume of distribution (aVd) of caffeine were noticeably altered by administration of ofloxacin. Striking changes were observed, however, after administration of enoxacin: the T1/2el was prolonged by as much as 260%, the Cmax increased by 41%; the aVd was reduced by 20% and Cltot by 78% (mean values). Treatment with ciprofloxacin led to a prolongation of T1/2el by 15%, to a decrease of aVd by 25% and to a 33% decrease of Cltot. The results of this intra-individual comparison of caffeine pharmacokinetic data demonstrate that treatment with ciprofloxacin and enoxacin may have a significant inhibitory effect on caffeine elimination.

Adult↗
PubMed1987

Interaction between quinolones and caffeine.

The effects of multiple doses of ofloxacin 200 mg, ciprofloxacin 250 mg or enoxacin 400 mg (all twice daily) on the pharmacokinetic properties of single doses of caffeine (220 to 230 mg) were investigated in 12 healthy volunteers. Intraindividual comparisons showed that ciprofloxacin and enoxacin significantly inhibited the elimination of caffeine. Ofloxacin, however, did not affect any of the measured pharmacokinetic properties of caffeine. Thus, caffeine should be avoided in patients with liver disorders, cardiac arrhythmias, latent epilepsy or in intensive care while undergoing treatment with enoxacin or ciprofloxacin.

Adult↗
PubMedDate not supplied

An arm phantom: a digital simulation system for testing sphygmomanometers.

An arm phantom for testing non-invasive blood pressure measuring instruments under reproducible and real conditions has been developed. Signal records, recorded on patients and validated by a reference method, are played into the instruments to be tested using a combination of an electro-pneumatic and an electro-acoustic converter. For each of 90 patients a database contains records of at least three different kinds of signal: cuff pressure oscillations, Korotkoff sounds (except in neonates) and cuff pressure. As the inflation and deflation rate varies between different sphygmomanometers the control and synchronization of the signal output are ensured as a function of the instantaneous cuff pressure, measured continuously by the system. A segmented output procedure synchronizes the data flow during the test procedure. The records of blood pressure signals are separated in different signal groups, containing only one pressure oscillation and Korotkoff sound respectively, whereas the instantaneous cuff pressure determines the signal group to be selected. Suitable interfaces to the sphygmomanometers under test consist of two specifically developed signal converters, an electro-pneumatic converter and an electro-acoustic converter. The system generates both cuff pressure oscillations and Korotkoff sounds from real data earlier recorded on human subjects. It allows any inflation and deflation rate of the cuff pressure to be applied, considers the variability of the pulse rate occurring in the same data record and finally it allows the superposition of artefacts. The arm phantom can replace clinical trials. The possibility of testing the limits of the performance of sphygmomanometers has been considerably extended.

Arm↗