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PubMed1994

Molecular dynamics simulation of equine infectious anemia virus Tat protein in water and in 40% trifluoroethanol.

Two molecular dynamics (MD) simulations were performed in order to increase the understanding of the dependence of protein conformation on solvent environment. The protein used for these simulations is the transcriptional activator of the equine infectious anemia virus (EIAV-Tat). The structure of this protein has been determined by nuclear magnetic resonance (NMR) in aqueous solution (Willbold et al., Science 264, 1584 (1994)) and in 40% (v/v) trifluoroethanol (TFE) (Sticht et al., Eur. J. Biochem., submitted) showing considerable differences in the stability of the secondary structure elements. In order to investigate the influence of the solvent MD simulations (300 K: 200 ps) were carried out in water and in a solvent containing 40% (v/v) TFE. In both simulations the structure as determined in 40% TFE by NMR showing three-helices and a tight type II turn, was used as the initial structure. The MD simulations clearly indicate a decreased stability of the secondary structure elements in aqueous environment as made obvious by larger atomic motions and stronger fluctuations in the length of the hydrogen bonds. Complete unfolding of the helices was not observed on a 200 ps timescale. The root mean square deviation (RMSD) values of the backbone atoms after 200 ps simulation compared to the starting structure underline the strong influence of the solvent on the protein stability. This RMSD value is 1.95 A for the simulation in water and 1.29 A for the simulation in TFE/water. This result supports the notion that TFE acts as a secondary structure inducing and stabilizing solvent. The differences apparent from the MD simulations are in good agreement with the data derived from NMR measurements, showing the relevance of MD as a method for estimating conformational and dynamical properties of proteins.

Amino Acid Sequence↗
PubMed2001

Epstein-Barr virus latently infected cells are selectively deleted in simulated-microgravity cultures.

Rotating-wall vessels (RWVs) allow for the cultivation of cells in simulated microgravity. Previously, we showed that the cultivation of lymphoblastoid cells in simulated microgravity results in the suppression of Epstein-Barr virus (EBV) reactivation. To determine if the suppression generated by simulated microgravity could be reversed by changing to static culture conditions, cells were cultured in an RRWV for 5 d, and then switched to static conditions. Following the switch to static conditions, viral reactivation remained suppressed (significantly lower) relative to static control cultures over a 4-d period. Additionally, experiments were conducted to determine if chemical treatment could induce viral reactivation in cells from simulated-microgravity cultures. Cells were cultured in static flask cultures and in simulated microgravity in RWVs for 4-7 d. The cells were then transferred to 50-cm3 tubes, and treated with 3 mM n-butyrate for 48 h, or 18 ng/ml of phorbol ester, viz., 12-0-tetradecanoylphorbol-13 acetate (TPA) for either 2 or 48 h, under static conditions. Although EBV was inducible, the cells from simulated-microgravity cultures treated with n-butyrate displayed significantly lower levels of viral-antigen expression compared with the treated cells from static cultures. Also, incubation with TPA for 2-3 h, but not for 48 h, reactivated EBV in cells from RWV cultures. In contrast, EBV was inducible in cells from static cultures treated for either 2-3 or 48 h with TPA. TPA reactivation of EBV following a 2-3-h period of treatment indicates that the protein kinase C signal-transduction pathway is not impaired in lymphoblastoid cells cultured in simulated microgravity. However, the exposure of B-lymphoblastoid cells from simulated-microgravity cultures to TPA for more than 3-4 h triggered a lytic event (apoptosis or necrosis), which prevented replication of the virus. Thus, EBV-infected cells in simulated microgravity were negatively selected in the absence of any cytotoxic cells.

B-Lymphocytes↗
PubMed2007

[Simulation and aggravation in ENT medical examinations. A prospective study].

OBJECTIVE: The occurrence and characteristics of simulation and aggravation in audiology still lack detailed scientific research. A reliable and reasonable classification of simulation and aggravation, which could help assess a patient's cooperative behavior, has not been defined. PATIENTS AND METHODOLOGY: All patients who underwent an audiological medical examination were included in this study prospectively. These patients were examined based on a well structured and predetermined sequence of actions. As a result, they were grouped into one of four categories, from category 0 for no simulation or aggravation to category III for severe simulation and aggravation. For category III, reliable and valid thresholds for pure tone audiometry only can be achieved by using objective audiological measurements such as brainstem electric response audiometry. Measured thresholds were then compared with simulated or aggravated thresholds and finally correlated with socio-economic factors. RESULTS: A total of 61 individuals were included in this study. Only 42% (26/61) showed no simulation or aggravation (category 0). In all 10% were grouped in category III. The remaining 48% fell into categories I and II. Statistical evaluation revealed no significant differences in thresholds between categories I, II and III. The tendency to simulation or aggravation increased with patient' age, level of education and the frequency of medical examinations prior to this investigation. CONCLUSION: Simulation and aggravation is a frequent phenomenon (approximately 58% of all audiological examinations). Additional work on defining a unique schema for the classification of simulation and aggravation is necessary. The use of such a schema is highly recommended.

Artifacts↗
PubMed2004

Cranial suture simulator for ultrasound diagnosis of craniosynostosis.

BACKGROUND: In evaluating the effectiveness of ultrasound as a screening tool for craniosynostosis it was discovered that sonologists and sonographers needed more experience scanning and visualizing cranial sutures on ultrasound. OBJECTIVE: To create an ultrasound simulator to train radiologists and technologists to locate and recognize patent and fused cranial sutures in children. MATERIALS AND METHODS: The hypoechoic appearance of patent sutures was simulated by cutting lines into life-sized plastic doll heads and filling them with a commercial hypoechogenic material. Fused hyperechoic sutures were simulated by not cutting into the hard plastic region of a suture. The simulator's teaching value was evaluated on three radiology residents and three fellows. Subjects performed pre-training scans on unknown simulators, received feedback and an opportunity to scan a training simulator, and then performed post-training scans on random unknown simulators. Accuracy was recorded as percentage of correctly demonstrated sutures. RESULTS: The suture simulator reproduces the sonographic appearance of patent and fused cranial sutures. Accuracy of acquisition, interpretation, and overall diagnosis increased from 64 to 91%, 79 to 91%, 61 to 97%, respectively, between pre and post training scans. CONCLUSION: An ultrasound simulator can reproduce the appearance of patent and fused cranial sutures in children and can be used to train radiologists and technologists in the performance of a screening protocol.

Cranial Sutures↗
PubMed1995

Simulation accuracy in radiotherapy for maxillary sinus tumors.

PURPOSE: To evaluate the accuracy and clinical importance of beam positioning during simulation of radiation treatment for tumors in the maxillary sinus. METHODS AND MATERIALS: Five patients were prepared as if they were to be treated for a maxillary sinus tumor. A three-beam computed tomography (CT) scan-based computer plan was made for each patient. The location of the central beam axis of each beam was measured, relative to bony anatomical structures. A simulation was performed using the bony references to position the radiation beams during simulation. After this, the simulation procedure was repeated by the use of a noninvasive external localization frame with a known accuracy and reproducibility within 2 mm margins. RESULTS: When defining the clinical target volume as the known tumor with a 1 cm margin, three out of five patients would suffer a partial geographical miss throughout the entire radiation treatment due to erroneous beam positioning at the simulation stage when using bony structures as a guide for beam positioning. The influence of these errors is analyzed as normal tissue complication and tumor control probabilities. CONCLUSION: When defining a planning target volume, one should consider a margin to correct for possible simulation errors. We advise the use of objective, external (and thus nonanatomical) landmarks as a reference during simulation to reduce this extra margin to a minimum. In case of simulation, using bony structures as a reference, an additional margin should be entered, depending on the simulation accuracy that can be obtained.

Humans↗
PubMed2006

Simulation of biological ion channels with technology computer-aided design.

Computer simulations of realistic ion channel structures have always been challenging and a subject of rigorous study. Simulations based on continuum electrostatics have proven to be computationally cheap and reasonably accurate in predicting a channel's behavior. In this paper we discuss the use of a device simulator, SILVACO, to build a solid-state model for KcsA channel and study its steady-state response. SILVACO is a well-established program, typically used by electrical engineers to simulate the process flow and electrical characteristics of solid-state devices. By employing this simulation program, we have presented an alternative computing platform for performing ion channel simulations, besides the known methods of writing codes in programming languages. With the ease of varying the different parameters in the channel's vestibule and the ability of incorporating surface charges, we have shown the wide-ranging possibilities of using a device simulator for ion channel simulations. Our simulated results closely agree with the experimental data, validating our model.

Computer-Aided Design↗
PubMed2006

How to qualify and validate wear simulation devices and methods.

The clinical significance of increased wear can mainly be attributed to impaired aesthetic appearance and/or functional restrictions. Little is known about the systemic effects of swallowed or inhaled worn particles that derive from restorations. As wear measurements in vivo are complicated and time-consuming, wear simulation devices and methods had been developed without, however, systematically looking at the factors that influence important wear parameters. Wear simulation devices shall simulate processes that occur in the oral cavity during mastication, namely force, force profile, contact time, sliding movement, clearance of worn material, etc. Different devices that use different force actuator principles are available. Those with the highest citation frequency in the literature are - in descending order - the Alabama, ACTA, OHSU, Zurich and MTS wear simulators. When following the FDA guidelines on good laboratory practice (GLP) only the expensive MTS wear simulator is a qualified machine to test wear in vitro; the force exerted by the hydraulic actuator is controlled and regulated during all movements of the stylus. All the other simulators lack control and regulation of force development during dynamic loading of the flat specimens. This may be an explanation for the high coefficient of variation of the results in some wear simulators (28-40%) and the poor reproducibility of wear results if dental databases are searched for wear results of specific dental materials (difference of 22-72% for the same material). As most of the machines are not qualifiable, wear methods applying the machine may have a sound concept but cannot be validated. Only with the MTS method have wear parameters and influencing factors been documented and verified. A good compromise with regard to costs, practicability and robustness is the Willytec chewing simulator, which uses weights as force actuator and step motors for vertical and lateral movements. The Ivoclar wear method run on the Willytec machine shows a mean coefficient of variation in vertical wear of 12%. Force measurements have revealed that in the beginning of the stylus/specimen contact phase the force impulse is 3-4 times higher during dynamic loading than during static loading. When correlating material properties to the wear results of 23 composite resins subjected to the Ivoclar method, some parameters could be identified and incorporated into a wear formula to predict wear with the Ivoclar method. A round robin test evaluating the wear of ten dental materials with five wear simulation methods showed that the results were not comparable, as all methods follow different wear testing concepts. All wear methods lack the evidence of their clinical relevance because prospective studies correlating in vitro with long-term in vivo results with identical materials are not available. For direct restorative materials, amalgam seems to be a realistic reference material. For indirect, namely crown and bridge materials, low strength ceramic is appropriate.

Biomechanical Phenomena↗
PubMed2005

Ballistic skin simulant.

Hydrogels prepared from water solutions containing 10-20 mass% gelatine are generally accepted muscle tissue simulants in terminal ballistic research. They, however, do not have a surface layer which simulates the effect of human skin. The purpose of this research was to find a suitable skin simulant for enhancing the testing fidelity and the credibility of the results with gelatine-based materials when assessing the injury potential of not only high energy bullets, but also especially that of non-penetrating "less lethal" kinetic impact ammunition and relatively low energy ricochet fragments. A skin simulant also permits the simulation and assessment of exit wounds. The mechanical and ballistic properties of human skin and target simulant were established on the basis of results found in the literature. Some errors in these were found. The corrected values are included in this paper for comparison. The target values of the mechanical properties of the skin simulant were the following: threshold velocity v(th)=94+/-4 m/s, tensile strength 18+/-2 N/mm2 and elongation at break 65+/-5%. A selection of synthetic and natural materials was evaluated as skin simulants by analysing their mechanical and ballistic properties. The results were compared to literature values obtained with human cadavers. The tests showed that the best skin simulant of the ones evaluated was semi-finished chrome tanned upholstery "crust" cowhide of 0.9-1.1 mm nominal thickness. Its threshold velocity was 90.7 m/s, tensile strength 20.89+/-4.11 MPa and elongation at break 61+/-9%. These values are the same as the average values of human skin. Of the synthetic materials evaluated, 1mm thick natural rubber can be used on impact side as a threshold velocity filter with some reservations although its theoretical threshold velocity is only 82.9 m/s.

Humans↗
PubMed1999

Defining the transmembrane helix of M2 protein from influenza A by molecular dynamics simulations in a lipid bilayer.

Integral membrane proteins containing at least one transmembrane (TM) alpha-helix are believed to account for between 20% and 30% of most genomes. There are several algorithms that accurately predict the number and position of TM helices within a membrane protein sequence. However, these methods tend to disagree over the beginning and end residues of TM helices, posing problems for subsequent modeling and simulation studies. Molecular dynamics (MD) simulations in an explicit lipid and water environment are used to help define the TM helix of the M2 protein from influenza A virus. Based on a comparison of the results of five different secondary structure prediction algorithms, three different helix lengths (an 18mer, a 26mer, and a 34mer) were simulated. Each simulation system contained 127 POPC molecules plus approximately 3500-4700 waters, giving a total of approximately 18,000-21,000 atoms. Two simulations, each of 2 ns duration, were run for the 18mer and 26mer, and five separate simulations were run for the 34mer, using different starting models generated by restrained in vacuo MD simulations. The total simulation time amounted to 11 ns. Analysis of the time-dependent secondary structure of the TM segments was used to define the regions that adopted a stable alpha-helical conformation throughout the simulation. This analysis indicates a core TM region of approximately 20 residues (from residue 22 to residue 43) that remained in an alpha-helical conformation. Analysis of atomic density profiles suggested that the 18mer helix revealed a local perturbation of the lipid bilayer. Polar side chains on either side of this region form relatively long-lived H-bonds to lipid headgroups and water molecules.

Amino Acid Sequence↗
PubMed2001

Sunscreen standards tested with differently filtered solar simulators.

BACKGROUND: The COLIPA standard for solar simulators permits a range of spectral filtration. Published studies comparing the SPFs of sunscreen formulas show that a range of SPFs is generally expected between laboratories. Specifically, three studies determining the SPFs of sunscreen standards have been performed in a series of laboratories and differences exceeding 50% have been reported. No studies to date have specifically examined potential differences in performance of Standard Sunscreen Test Formulas with varying solar simulator spectra within the permitted range of optical filtration. METHODS: In a paired clinical trial, two SPF standard sunscreen formulas were tested using two solar simulators that complied with the COLIPA standard for solar simulators but were filtered differently. One solar simulator was filtered as supplied by the manufacturer and delivered a high percentage of UVB; the other solar simulator was modified by removing the visible absorbing filter to deliver energy more closely resembling sunlight in the UVA-1 part of the spectrum, with a lower percentage of UVB. RESULTS AND CONCLUSION: The result was that the SPF of each standard sunscreen was almost 50% greater with the unmodified solar simulator than with the modified solar simulator. In vitro evaluation of the sunscreen standards predicted similar differences due to the spectral differences of the solar simulators, which appears to rule out reciprocity failure. However, reciprocity failure of the control MEDs was observed. The total intensity of the modified lamp was approximately 3 times that of the unmodified lamp.

Adult↗
PubMed2004

Replica-exchange extensions of simulated tempering method.

In this paper we consider combinations of two well-known generalized-ensemble algorithms, namely, simulated tempering and replica-exchange method. We discuss two examples of such combinations. One is the replica-exchange simulated tempering and the other is the simulated tempering replica-exchange method. In the former method, a short replica-exchange simulation is first performed and the simulated tempering weight factor is obtained by the multiple-histogram reweighting techniques. This process of simulated tempering weight factor determination is faster and simpler than that in the usual iterative process. A long simulated tempering production run is then performed with this weight factor. The latter method is a further extension of the former in which a simulated tempering replica-exchange simulation is performed with a small number of replicas. These algorithms are particularly useful for studying frustrated systems with rough energy landscape. We give the formulations of these two methods in detail and demonstrate their effectiveness taking the example of the system of a 17-residue helical peptide.

Journal Article↗
PubMed2006

X-ray diffraction "fingerprinting" of DNA structure in solution for quantitative evaluation of molecular dynamics simulation.

Solution state x-ray diffraction fingerprinting is demonstrated as a method for experimentally assessing the accuracy of molecular dynamics (MD) simulations. Fourier transforms of coordinate data from MD simulations are used to produce reciprocal space "fingerprints" of atomic pair distance correlations that are characteristic of the ensemble and are the direct numerical analogues of experimental solution x-ray diffraction (SXD). SXD experiments and MD simulations were carried out to test the ability of experiment and simulation to resolve sequence-dependent modifications in helix conformation for B-form DNA. SXD experiments demonstrated that solution-state poly(AT) and poly(A)-poly(T) duplex DNA sequences exist in ensembles close to canonical B-form and B'-form structures, respectively. In contrast, MD simulations analyzed in terms of SXD fingerprints are shown to deviate from experiment, most significantly for poly(A)-poly(T) duplex DNA. Compared with experiment, MD simulation shortcomings were found to include both mismatches in simulated conformer structures and number population within the ensembles. This work demonstrates an experimental approach for quantitatively evaluating MD simulations and other coordinate models to simulate biopolymer structure in solution and suggests opportunities to use solution diffraction data as experimental benchmarks for developing supramolecular force fields optimized for a range of in situ applications.

DNA↗
PubMedDate not supplied

Oscillometric blood pressure devices and simulators: measurements of repeatability and differences between models.

PRIMARY OBJECTIVE: To measure the repeatability and pressure pulse envelope of simulators used for testing oscillometric non-invasive blood pressure (NIBP) devices; to study the effect of different envelopes on NIBP devices, and to measure the difference between NIBP devices due to different oscillometric algorithms. METHODS: Three different models of NIBP simulator and 18 different patient monitors with NIBP function were studied. We developed a pressure measurement system (accuracy 0.048?mmHg) to measure the repeatability of simulators. The effect of changing the envelope was measured by using three simulators with one NIBP device. Differences between 18 NIBP devices were measured using one simulator at seven blood pressure settings. MAIN OUTCOMES AND RESULTS: Simulators generate repeatable pressure pulse envelopes (< 0.2 mmHg) but the magnitude and shape depends on the model of simulator. Oscillometric NIBP devices are highly repeatable (< 2 mmHg) when presented with a repeatable pressure pulse envelope, but different devices employ different algorithms and give different results. For a simulated standard blood pressure setting of 120/80 mmHg, estimates of systolic pressure ranged from 112.6 to 126.6 mmHg (sd of 3.0 mmHg), and diastolic pressure ranged from 74.8 to 86.9 mmHg (sd of 3.5 mmHg). CONCLUSIONS: Simulators and NIBP devices are sufficiently repeatable for clinical use, but further systematic clinical studies are required to better characterize the pressure pulse envelope for different patient groups.

Algorithms↗
PubMed2005

Simulators in surgery.

The introduction of minimally invasive surgery has demonstrated the need for training surgical skills outside the operating room using animal models or simulators. As laparoscopic surgery involves displaying images on a screen, virtual reality simulation of the surgical tasks is feasible. Different types of simulators have become available. The existing trainers can be divided into three groups: mechanical, hybrid, and virtual reality. This article aims at giving an overview of the different simulators available and the potential of simulators in the education of surgeons with focus on virtual reality simulators. All simulators aim at training psychomotoric skills and some simulators also allow training in decision-making and anatomical orientation. In the future virtual reality simulators may become a tool for training and validation of surgical skills and monitoring the training progress.

Journal Article↗
PubMed2005

In vitro estimations of in vivo jet nebulizer efficiency using actual and simulated tidal breathing patterns.

In vivo aerosol delivery efficiency was estimated in vitro for two jet nebulizers using a breath monitor (Breathe!; Pari GmbH, Germany) and breath simulator (COMPAS; Pari GmbH) to reproduce subject tidal breathing patterns. The AeroEclipse (Trudell Medical International, Canada), a breath-actuated nebulizer, and the LC Star (Pari GmbH), a breath-enhanced nebulizer, were filled with levalbuterol HCl solution (Sepracor, USA) and operated with compressed O(2) at 8 lpm. Tidal breathing patterns of 20 adult subjects were digitally recorded with the Breathe! Breath Monitor. Subjects then breathed tidally from each nebulizer separately for 1 minute and to nebulizer dryness. Levalbuterol aerosol collected on filters placed between the nebulizer and mouth was chemically assayed to determine the inspired mass (IM), wasted mass (WM) and total emitted mass (TM). Measurements were repeated using the COMPAS Breath Simulator to simulate each subject's tidal breathing pattern. IM, WM, and TM measurements using actual versus simulated tidal breathing were highly comparable for each nebulizer, except the IM (p < 0.05) from LC Star measured at nebulizer dryness. Breath simulation was an inaccurate tool for estimating the time to nebulizer dryness as simulated measurements to nebulizer dryness took significantly longer than measurements preformed with actual tidal breathing (p < 0.001). While breath simulation provides an accurate in vitro tool for estimating in vivo aerosol delivery, it should not completely replace in vivo measurements until inherent limitations in simulator operation can be overcome to provide a more clinically realistic simulation.

Administration, Inhalation↗
PubMed1991

Designing a neural network simulator--the MENS modelling environment for network systems: I.

During recent years, the field of neural network research has increasingly attracted the interest of workers from a large number of different disciplines. Current research topics include aspects as different as detailed simulations in brain physiology, predictions of protein structure in biochemistry, database organization in computer science, or various technical applications. The common scheme behind these different approaches is the use of distributed networks of simple computational elements that communicate with each other by means of weighted links. Computer simulations of neural networks require an appropriate software environment. Due to the computational similarities of many classes of such networks, simulation software can be structured into modular components that, to a large degree, are independent of specific applications. The aim of this and the following paper is to discuss some of the design considerations concerning software for neural network simulations. The aspects presented are interesting for both the development of new simulation software and the efficient use and modification of existing programs. Therefore, the general user as well as the software designer may hopefully benefit from this material. This paper briefly introduces some of the basic principles of neural networks. After a short discussion of different approaches to software design, two simple example applications are presented in order to demonstrate a conceptual framework common to many network simulations. The transfer of these considerations to the design of simulation software is then shown by example of the MENS network simulator developed in the Max-Planck-Institute for Brain Research. The paper gives a general introduction to the layout of data structures and different software components. Using the two introductory examples some aspects of network analysis are demonstrated. The following paper then considers further details of the design of a neural network simulator with respect to performance, implementation, and testing.

Animals↗
PubMedDate not supplied

Simulating forest productivity and surface-atmosphere carbon exchange in the BOREAS study region.

A process-based, general ecosystem model (BIOME-BGC) was used to simulate daily gross primary production, maintenance and heterotrophic respiration, net primary production and net ecosystem carbon exchange of boreal aspen, jack pine and black spruce stands. Model simulations of daily net carbon exchange of the ecosystem (NEE) explained 51.7% (SE = 1.32 g C m(-2) day(-1)) of the variance in daily NEE derived from stand eddy flux measurements of CO(2) during 1994. Differences between measured and simulated results were attributed to several factors including difficulties associated with measuring nighttime CO(2) fluxes and model assumptions of site homogeneity. However, comparisons between simulations and field data improved markedly at coarser time-scales. Model simulations explained 66.1% (SE = 0.97 g C m(-2) day(-1)) of the variance in measured NEE when 5-day means of daily results were compared. Annual simulations of aboveground net primary production ranged from 0.6-2.4 Mg C ha(-1) year(-1) and were concurrent with results derived from tree increment core measurements and allometric equations. Model simulations showed that all of the sites were net sinks (0.1-4.1 Mg C ha(-1) year(-1)) of atmospheric carbon for 1994. Older conifer stands showed narrow margins between uptake of carbon by net photosynthesis and carbon release through respiration. Younger stands were more productive than older stands, primarily because of lower maintenance respiration costs. However, all sites appeared to be less productive than temperate forests. Productivity simulations were strongly linked to stand morphology and site conditions. Old jack pine and aspen stands showed decreased productivity in response to simulated low soil water contents near the end of the 1994 growing season. Compared with the aspen stand, the jack pine stand appeared better adapted to conserve soil water through lower daily evapotranspiration losses but also exhibited a narrower margin between daily net photosynthesis and respiration. Stands subjected to water stress during the growing season may exist on the edge between being annual sources or sinks for atmospheric carbon.

Journal Article↗
PubMedDate not supplied

A simulation-based evaluation of nine oscillometric blood pressure monitors for self-measurement.

OBJECTIVE: To evaluate the performance of nine self-measurement oscillometric blood pressure monitors using a simulator. METHODS: For each monitor, simulation data from 48 sets of simulated waveforms with four simulations for each set were used for analysis. The waveforms represent a wide range of blood pressure. The monitor-simulator blood pressure differences were analyzed according to the 1992 Association for the Advancement of Medical Instrumentation (AAMI) and 1993 British Hypertension Society (BHS) protocols, except that corrections were made to take into account simulation variability. One-way analysis of variance was used to compare the differences for various combinations of monitors. The monitors' heart rate readings were compared with the rated accuracy. RESULTS: First, the mean blood pressure differences in general vary from monitor to monitor, the absolute mean differences ranging from 1.2 to 18.2mmHg. This can be partly explained by the likely use of different blood pressure determination criteria. Second, the Omron HEM-711 and HEM-712C gave about the same mean difference for systolic pressure and for diastolic pressure, suggesting that the two monitors may be using the same or approximately the same set of determination criteria. Third, the quantitative assessments for some of the monitors, for systolic or diastolic pressure or both, satisfy the clinical-use accuracy criteria of the AAMI or BHS protocol or both. These assessments alone cannot, however, be used to conclude whether or not any of the monitors fulfils the accuracy requirements of either protocol. Fourth, the corrected standard deviations of the differences range from 1.5 to 16.6mmHg, most of them being substantially less than the 8mmHg limit stipulated in the AAMI protocol. The different standard deviations suggest a varying robustness of the signal-processing methods used by the monitors. Fifth, for 7 out of the 9 monitors, more than 94% of the heart rate readings fall within +/-5% of their reference readings. CONCLUSIONS: The nine monitors in general performed differently with respect to the simulator. The results cannot be used fully to reflect the monitors' performance on human subjects because they were not based on clinical evaluation. Studies that lead to a more realistic simulation of oscillometric blood pressure are needed. Protocols integrating both clinical and simulation-based evaluations need to be developed.

Analysis of Variance↗