Pressure Measurement Error Research Articles

Intra-arterial blood pressure measurement: sources of error and solutions.

Intra-arterial blood pressure measurement is the cornerstone of hemodynamic monitoring in intensive care units (ICU). Accuracy of the measurement is dependent on the dynamic response of the measuring system, defined by its natural frequency (fnatural) and damping coefficient (Zdamping). Gardner's plot (1981) has long been the only way to determine the accuracy of the pressure measurement. Specific objectives: (i) estimation of the amplitude of error in pressure measurement through simulations based on real-world data, (ii) a novel method to correct the error. Simulated blood pressure waveforms of various heart rates were passed through simulated measurement systems with varying fnatural and Zdamping. The numerical errors in systolic and diastolic pressures and mean error in the measured pressure were used to generate heat maps for the various recording conditions, in the same plot as that by Gardner (1981). fnatural and Zdamping from 121 patient recordings are plotted on these heat maps to demonstrate the fraction of unacceptable recordings. Performance of a tunable filter to correct the error is demonstrated. In many clinical settings, the measurement of intra-arterial pressure is prone to significant error. The proposed tunable filter is shown to improve the accuracy of intra-arterial pressure recording.

Using web-based training to improve accuracy of blood pressure measurement among health care professionals: Arandomized trial.

Accurate blood pressure measurement is crucial for proper screening, diagnosis, and monitoring of high blood pressure. However, providers are not aware of proper blood pressure measurement skills, do not master all the appropriate skills, or miss key steps in the process, leading to inconsistent or inaccurate readings. Training in blood pressure measurement for most providers is usually limited to a one‐time brief demonstration during professional education coursework. The American Medical Association and the American Heart Association developed a 30‐minute e‐Learning module designed to refresh and improve existing blood pressure measurement knowledge and clinical skills among practicing providers. One hundred seventy‐seven practicing providers, which included medical assistants, nurses, advanced practice providers, and physicians, participated in a multi‐site randomized educational study designed to assess the effect of this e‐Learning module on blood pressure measurement knowledge and skills. Participants were randomized 1:1 to either the intervention or control group. The intervention group followed a pre‐post assessment approach, and the control group followed a test‐retest approach. The initial assessment showed that participants in both the intervention and control groups correctly performed less than half of the 14 skills considered necessary to obtain an accurate blood pressure measurement (mean scores 5.5 and 5.9, respectively). Following the e‐Learning module, the intervention group performed on average of 3.4 more skills correctly vs 1.4 in the control group (P < .01). Our findings reinforce existing evidence that errors in provider blood pressure measurements are highly prevalent and provide novel evidence that refresher training improves measurement accuracy.

Potential impact of systematic and random errors in blood pressure measurement on the prevalence of high office blood pressure in the United States.

The authors examined the proportion of US adults that would have their high blood pressure (BP) status changed if systolic BP (SBP) and diastolic BP (DBP) were measured with systematic bias and/or random error versus following a standardized protocol. Data from the 2017–2018 National Health and Nutrition Examination Survey (NHANES; n = 5176) were analyzed. BP was measured up to three times using a mercury sphygmomanometer by a trained physician following a standardized protocol and averaged. High BP was defined as SBP ≥130 mm Hg or DBP ≥80 mm Hg. Among US adults not taking antihypertensive medication, 32.0% (95%CI: 29.6%,34.4%) had high BP. If SBP and DBP were measured with systematic bias, 5 mm Hg for SBP and 3.5 mm Hg for DBP higher and lower than in NHANES, the proportion with high BP was estimated to be 44.4% (95%CI: 42.6%,46.2%) and 21.9% (95%CI 19.5%,24.4%). Among US adults taking antihypertensive medication, 60.6% (95%CI: 57.2%,63.9%) had high BP. If SBP and DBP were measured 5 and 3.5 mm Hg higher and lower than in NHANES, the proportion with high BP was estimated to be 71.8% (95%CI: 68.3%,75.0%) and 48.4% (95%CI: 44.6%,52.2%), respectively. If BP was measured with random error, with standard deviations of 15 mm Hg for SBP and 7 mm Hg for DBP, 21.4% (95%CI: 19.8%,23.0%) of US adults not taking antihypertensive medication and 20.5% (95%CI: 17.7%,23.3%) taking antihypertensive medication had their high BP status re‐categorized. In conclusions, measuring BP with systematic or random errors may result in the misclassification of high BP for a substantial proportion of US adults.

Sensitivity of Piezoresistive Pressure Sensors to Acceleration

The article presents the negative aspects of the influence of static and dynamic acceleration on the accuracy of pressure measurement for a selected type of transmitter. The influence of static accelerations from catalog notes was shown and compared with the tests results for a few selected sensors. The results of research on the influence of dynamic acceleration for various types of its variability for selected converters are presented. Moreover, a method of measurement patented by the authors that uses a complex transducer is shown. The method allows for more accurate measurements on moving objects. The tests were performed based on the proposed method. The obtained results of the influence of acceleration on the classical sensor as well as the construction using the proposed method are shown. The paper presents approximate pressure measurement errors resulting from the influence of acceleration. For example, errors in measuring the speed of an airplane may occur without the proposed method. The last part of the article presents a unique design dedicated to a multi-point pressure measurement system, which uses the presented method of eliminating the influence of accelerations on the pressure measurement.

Design of a low-cost pressure measurement device: validation and testing

Pressure measurement is essential in aerospace engineering. Measuring pressure allows us to understand the aerodynamic characteristics of the model. Consequently, it helps us propose an optimisation model design with high aerodynamic performance and low structure fatigues. However, the pressure measurement device is often complicated and costly. It is a big problem for developing countries to possess the device. This study proposes a simple and effective new pressure measurement device design. The device is sufficiently low cost, but it can provide high accuracy data as a commercial device. A calibration process was presented in a simple wind tunnel. Experiments are then conducted for measuring pressure distribution on NACA 2415 airfoil, and they are compared with the numerical data. The new pressure measurement device shows close results to the numerical data. A significantly low-pressure region is observed near the leading edge of the model. Additionally, when the angle of attack increases, the negative pressure peak increases its magnitude, both in numerical and simulation methods. The pressure measurement errors are less than 10%, and consequently, they can be applied for further study.

Fluidic Considerations of Measuring Intracranial Pressure Using an Open External Ventricular Drain.

Measurement of intracranial pressure (ICP) during cerebrospinal fluid (CSF) drainage with an external ventricular drain (EVD) typically requires stopping the flow during measurement. However, there may be benefits to simultaneous ICP measurement and CSF drainage. Several studies have evaluated whether accurate ICP measurements can be obtained while the EVD is open. They report differing outcomes when it comes to error, and hypothesize several sources of error. This study presents an investigation into the fluidic sources of error for ICP measurement with concurrent drainage in an EVD.Our experiments and analytical model both show that the error in pressure measurement increases linearly with flow rate and is not clinically significant, regardless of drip chamber height. At physiologically relevant flow rates (40 mL/hr) and ICP set points (13.6 - 31.3 cmH2O or 10 - 23 mmHg), our model predicts an underestimation of 0.767 cmH2O (0.56 mmHg) with no observed data point showing error greater than 1.09 cmH2O (0.8 mmHg) in our experiment. We extrapolate our model to predict a realistic worst-case clinical scenario where we expect to see a mean maximum error of 1.06 cmH2O (0.78 mmHg) arising from fluidic effects within the drainage system for the most resistive catheter.Compared to other sources of error in current ICP monitoring, error in pressure measurement due to drainage flow is small and does not prohibit clinical use. However, other effects such as ventricular collapse or catheter obstruction could affect ICP measurement under continuous drainage and are not investigated in this study.

Static pressure measurement error for wall taps with high Reynolds number turbulent pipe flow

An experimental study on a static pressure measurement errors in wall taps was conducted using a high Reynolds number actual flow facility (Hi-Reff). The bulk Reynolds number ReD examined was up to 1.3 × 107 and tap Reynolds number Ret was up to 8.5 × 104. The behavior of the static pressure measurement error at high Reynolds numbers was clarified experimentally. The static pressure measurement error normalized by wall shear stress increases with Reynolds number and reaches an asymptotic value. Its maximum value is 7.1 at Ret = 8470. The asymptotic value increases with the size of the tap diameter up to 6 mm and then becomes constant for tap diameters exceeding 6 mm. The universal curve reported in previous studies is observed for only a limited range of tap Reynolds numbers of below 700 and of tap diameters below 4 mm.

New technique revives direct deconvolution methods for Wellbore storage removal in pressure transient analysis

Eliminating wellbore storage (WBS) effects inherent in pressure transient data is one of the challenges in well test analysis. The available WBS-removal techniques are either direct or time-consuming approaches. The direct methods are mostly unstable and require accurate data with almost no noise. However, well test data often have noise in both rate and pressure measurements.This work discusses the development of a stable technique to overcome the shortcomings in the available WBS-removal methods. The technique presented here takes advantage of the recently developed stable deconvolution algorithms (e.g. von Schroeter algorithm) to achieve a stable WBS-removal process. The developed approach provides longer WBS-free reservoir response signal (extended over the entire test duration) than the previous methods. In addition, the approach introduced here can remove WBS-effects in noisy data and does not require sandface rate measurements.Different simulated and field examples were used to validate the proposed approach. The examples included data with different levels of rate and pressure measurement errors and covered wide variety of well/reservoir models. The available approaches were implemented to the same examples. A comparison of the results shows the superiority of the approach presented in this paper.

Correction methods for noncontact intraocular pressure measurement in patients with keratoconus and healthy individuals.

The objective of this study was to investigate the usefulness of four different algorithms to correct noncontact intraocular pressure measurement errors in keratoconus patients and normal individuals. Noncorrected intraocular pressure and corrected intraocular pressures were measured in one eye of 34 patients with keratoconus and 34 age- and gender-matched healthy controls using Corvis Scheimpflug Technology. The correlation of noncorrected intraocular pressure and corrected intraocular pressures with age, axial length, corneal shape, thickness, and biomechanics was calculated. Corrected intraocular pressures were compared with noncorrected intraocular pressure using paired t test and Bland-Altman plots (95% limits of agreement). The noncorrected intraocular pressure correlated with corneal thickness and biomechanical parameters in both groups (all p≤0.047), and front and back mean keratometry in the keratoconus group (r=-0.39, p=0.02, and r=0.39, p=0.02, respectively). After adjustment with different intraocular pressure correction algorithms, biomechanically corrected intraocular pressure showed a minimal correlation with corneal features and a nonsignificant difference with noncorrected intraocular pressure in the healthy group (-0.1 ± 1.1 mmHg, p=0.58; 95% limits of agreement: -2.3 to 2.1 mmHg). Measuring intraocular pressure using noncontact tonometry and its corrected forms with a corneal thickness-based simple linear formula in patients with keratoconus is associated with many errors. Using more complex formulas that take into consideration more corneal stiffness parameters in addition to corneal thickness, such as biomechanically corrected intraocular pressure formula, may be more reliable and beneficial in this group of patients.

Temperature and Pressure Composite Measurement System Based on Wireless Passive LC Sensor

In this article, we proposed a measurement system that can simultaneously measure temperature and pressure. By analyzing several existing measurement methods of the sensor, we determined that the resonance frequency and $S_{11}$ (reflection coefficient) amplitude of the sensor readout system should be measured when the resonance frequency of the sensor up to a hundred megahertz or even gigahertz and when the sensor works in ultrahigh temperature environment. In addition, we designed a simple and accurate sensor readout circuit and an LC temperature–pressure sensor. By analyzing the resonance frequency and the amplitude of $S_{11}$ , temperature and pressure were measured simultaneously with a single LC circuit. Since the analysis of the whole nonlinear system of sensors is complex, we divide the entire nonlinear system into several linear systems superposition. By analyzing the interference between temperature and pressure, we further optimized the measurement method. The relative errors of the temperature measurements in the range of 25 °C–300 °C and 300 °C–1000 °C were only 2.89% and 1.25%, respectively. From 25 °C to 300 °C and 300 °C to 1000 °C, the average relative errors of pressure measurement were only 4.07% and 4.74%, respectively. Besides, the proposed method can also be widely used in the measurement of LC multiparameter sensors.

Digit Preference in Office Blood Pressure Measurements, United States 2015-2019.

Blood pressure (BP) measurement error may lead to under- or overtreatment of hypertension. One common source of error is terminal digit preference, most often a terminal digit of "0." The objective was to evaluate national trends in terminal digit preference in office BP measurements among adults with treated hypertension. Data were from IQVIA's National Disease and Therapeutic Index, a nationally representative, serial cross-sectional survey of office-based physicians. The analysis included office visits from 2015 to 2019 among adults aged ≥18 years receiving antihypertensive treatment. Annual trends were examined in the percent of systolic and diastolic BP measurements ending in zero by patient sex, age, and race/ethnicity, physician specialty, and first or subsequent hypertension treatment visit. From 2015 to 2019, there were ~60 million hypertension treatment visits annually (unweighted N: 5,585-9,085). There was a decrease in the percent of visits with systolic (41.7%-37.7%) or diastolic (42.7%-37.8%) BP recordings ending in zero. Trends were similar by patient characteristics. However, a greater proportion of measurements ended in zero among patients aged ≥80 (vs. 15-59 or 60-79) years, first (vs. subsequent) treatment visits, visits to cardiologists (vs. primary care physicians), and visits with systolic BP ≥140 or diastolic BP ≥90 (vs. <140/90) mm Hg. Despite modest improvement, terminal digit preference remains a common problem in office BP measurement in the United States. Without bias, 10%-20% of measurements are expected to end in zero. Reducing digit preference is a priority for improving BP measurement accuracy and hypertension management.

Upper limb dimensions in adults presenting for elective surgery \u2013 implications for blood pressure measurement

BackgroundArm conicity is associated with non-invasive blood pressure (NIBP) measurement error and may be avoided by using finger cuffs. Predicting arm conicity may help decisions regarding NIBP measurement techniques.MethodsWe obtained upper limb measurements of adults presenting to the Pre-Anesthetic Clinic to determine: the suitability of arm and finger cuff sizes; the best anthropometric predictor of arm conicity based on the right arm slant angle; the incidence of a right arm slant angle < 83 degrees. Right mid-arm circumference (MAC) was compared to recommended cuff sizes and finger circumference compared to available cuffs. Slant angle was calculated from the measurements obtained. Linear regression was used to determine the better predictor of right arm slant angle. Correlation coefficients were calculated and R2 values compared.ResultsFour hundred fifty-four patients participated and 453 had cone-shaped arms. One participant (0.2, 95% CI 0.0–1.2) had a MAC outside the recommended cuff range. Twenty-five participants (5.5, 95% CI 3.6–8.0) had a middle finger circumference greater than the largest ClearSight™ cuff. Body mass index (BMI), weight and right MAC all had low to moderate correlation with right arm slant angle (r = − 0.49, − 0.39, − 0.48, all p < 0.001) and regression revealed R2 values of 0.24, 0.15 and 0.23. Six participants (1.3, 95% CI 0.5–2.9) had a slant angle < 83 degrees.ConclusionCurrent NIBP equipment caters for most patients, based on the traditional measure of MAC. The utility of finger cuffs is limited by cuff size. BMI and right MAC showed the most promise in predicting arm conicity.

Absolute reliability of tongue pressure measurement in young healthy adults and elderly patients with certification of needing long-term care or support.

We aimed to determine systematic bias and the range of random error in tongue pressure measurements among young healthy adults and elderly patients with certification of requiring long-term care or support, considering sex, and to establish a measurement method. Subjects were 226 adults (88 young healthy adults and 138 elderly patients with certification of requiring long-term care or support). Tongue pressure was measured thrice. Bland-Altman analysis was performed for the first and second trials, and second and third trials. Fixed bias was revealed for the first and second trials among young healthy adults. Systematic bias was not found for the second and third trials. Fixed bias was revealed for the first and second trials among elderly patients, with a proportional bias with a negative slope for the second and third trials. For young healthy adults, the minimal detectable change was 6.0 and 5.4 kPa in males and females, respectively. For elderly patients, the limit of agreement ranged from -5.9 to 8.6 and from -5.4 to 8.8 kPa in males and females, respectively. There was a difference in systematic bias in tongue pressure measurement between young healthy adults and elderly patients with certification of needing long-term care or support. In young healthy adults, the third trial results showed stability, whereas they decreased in elderly patients. In elderly patients, it was suggested that the number of measurements reduced from three to two when a maximum value was adopted. No differences were observed among sexes in either young or elderly patients. Geriatr Gerontol Int 2020; 20: 488-493.

Abstract P333: National Trends in the Quality of Office Blood Pressure Measurements, 2014-2019

Introduction: Clinical practice guidelines emphasize the importance of accurate blood pressure measurement and recording to diagnose and treat hypertension. Trends in terminal digit preference (typically manifest by a terminal digit of ‘0’) have not been examined nationally. The growing use of automated blood pressure devices may have reduced terminal digit preference and improved accuracy over time. Objective: To evaluate trends in terminal digit preference in office blood pressure measurements among adults with hypertension by patient and provider characteristics. Methods: We used IQVIA National Disease and Therapeutic Index (NDTI) data from January 2014 through June 2019. The NDTI is designed to be nationally-representative of all patient visits to office-based physicians and uses a two-stage stratified sampling design to sample ~4,000 physicians per quarter who report information on all patient visits on 2 random workdays. We included all hypertension treatment visits (~60M/year) among adults aged ≥18. We examined trends in the proportion of hypertension treatment visits with recorded systolic (SBP) and diastolic (DBP) blood pressure measurements with a terminal digit ‘0’. The expected percent of blood pressures with ‘0’ is 10% for automated and 20% for manual readings. Results: There was a decrease in the percent of visits with SBP (43.0% to 37.4%) or DBP (44.3% to 38.1%) recordings ending in zero ( Table ). The decrease in percent of SBPs with a terminal zero was similar by patient and provider characteristics, though the percentage of SBPs with a terminal ‘0’ was consistently higher among patients aged ≥60, when SBP ≥140 mmHg, and among cardiologists. Conclusions: Terminal digit preference is common indicating systematic error in blood pressure measurement and recording, despite some improvement over time. This may lead to under- and overtreatment of patients with hypertension. Improving the quality of blood pressure measurement is central to improving hypertension diagnosis and control in clinical practice.

Performance Improvement of the Pressure Ratio and Rotational Speed Calculation of a Centrifugal Compressor Model

In this study, various investigations were performed on the reduction of calculation errors of compressor models which can calculate compressor performance (pressure ratio, rotational speed) at an arbitrary operating point. For this purpose, three compressor models, including the Jensen & Kristensen model and the newly modified model, are presented in this study. By applying these models, the compressor pressure ratio and rotational speed prediction calculation results are compared with four other compressors. From these, we confirmed the performance characteristics of each model and reduced calculation errors near the surge limit, near the choking limit, and in the high speed range, which was a problem in the standard J & K compressor model. Also, the application performance of the compressor model during actual engine operation is presented through an experiment with a 1.4 liter WGT diesel engine. The pressure measurement error had a large effect on the calculation error of the low rotational speed region, and the influence decreased as the rotational speed increased. The calculation error of the compressor rotational speed was less than 10 % when the rotational speed was higher than 33 % of the maximum rotational speed of the compressor, and accuracy was improved as the rotational speed increased.

Qualification of New Methods for Measuring In Situ Rheology of Non-Newtonian Fluids in Porous Media.

Pressure drop (ΔP) versus volumetric injection rate (Q) data from linear core floods have typically been used to measure in situ rheology of non-Newtonian fluids in porous media. However, linear flow is characterized by steady-state conditions, in contrast to radial flow where both pressure and shear-forces have non-linear gradients. In this paper, we qualify recently developed methods for measuring in situ rheology in radial flow experiments, and then quantitatively investigate the robustness of these methods against pressure measurement error. Application of the new methods to experimental data also enabled accurate investigation of memory and rate effects during polymer flow through porous media. A radial polymer flow experiment using partially hydrolyzed polyacrylamide (HPAM) was performed on a Bentheimer sandstone disc where pressure ports distributed between a central injector and the perimeter production line enabled a detailed analysis of pressure variation with radial distance. It has been suggested that the observed shear-thinning behavior of HPAM solutions at low flux in porous media could be an experimental artifact due to the use of insufficiently accurate pressure transducers. Consequently, a generic simulation study was conducted where the level of pressure measurement error on in situ polymer rheology was quantitatively investigated. Results clearly demonstrate the robustness of the history match methods to pressure measurement error typical for radial flow experiments, where negligible deviations from the reference rheology was observed. It was not until the error level was increased to five-fold of typical conditions that significant deviation from the reference rheology emerged. Based on results from pore network modelling, Chauveteau (1981) demonstrated that polymer flow in porous media may at some rate be influenced by the prior history. In this paper, polymer memory effects could be evaluated at the Darcy scale by history matching the pressure drop between individual pressure ports and the producer as a function of injection rate (conventional method). Since the number of successive contraction events increases with radial distance, the polymer has a different pre-history at the various pressure ports. Rheology curves obtained from history matching the radial flow experiment were overlapping, which shows that there is no influence of geometry on in-situ rheology for the particular HPAM polymer investigated. In addition, the onset of shear-thickening was independent of volumetric injection rate in radial flow.

Combination of experimental and numerical approaches to determine the main characteristics of skimming flow in stepped spillways

ABSTRACT The traditional approach for the hydrodynamic characterization of the flow down stepped spillways is through physical modeling, which is susceptible to scale effects and has limitations related to experimental apparatus, laboratory space and the spatial discretization of data collection. Computational fluid dynamics (CFD) is an important tool for hydrodynamic analysis because, if used properly, it presents great potential for application in hydraulics. In this work, CFD was used to model the skimming flow down a stepped spillway to investigate the effects of possible pressure measurement errors due to uncertainties in the position of the sensors within the steps. The numerical model was validated through literature velocity profiles and pressure experimental data. The results showed that the best values of water fraction (α) to define free surface are α = 0.30 in the nonaerated region and α = 0.10 in the aerated region. Statistical parameters were calculated using experimental data to estimate extreme pressures. These parameters and the simulation results were used to determine that the extreme maximum and minimum pressures occur, respectively, in the region of 0.81 &lt; x/l &lt; 0.98, in the horizontal faces, and in the region of 0.93 &lt; y/h &lt; 0.98, in the vertical faces.

ADSORPTION OF BENZENE, ACETONE AND CARBON TETRACHLORIDE VAPORS ON MICROPOROUS CARBON ADSORBENT FAS-3

In this paper, the study of the adsorption of organic matter vapors (benzene, carbon tetrachloride, acetone) on the microporous carbon adsorbent FAS-3 in the region of pressures from 0.1 PA to 0.1 MPa and temperatures from 293 to 313 K was conducted, which showed sufficiently high adsorption characteristics of the used adsorbent in comparison with traditional absorbers. Microporous carbon adsorbent FAS-3 is quite new and still not fully understood. The purpose of this study was to determine the parameters of the adsorbent FAS-3, as well as the study of the processes of vapor adsorption of various organic substances on it. The microporous carbon adsorbent FAS-3, obtained on the basis of furfural, was used in the work. Obtaining spherical granules of the adsorbent FAS-3 was carried out in the result of liquid molding of a copolymer of furfural and epoxy resin on the basis of a fundamentally new process of combining the stages of blending monomer, molding the mixture in spherical product of the cured pellets. The activation of spherical grains of FAS-3 was carried out in a rotary kiln by a mixture of water vapor and carbon dioxide at a temperature of 850-900°C to burning that was consistent with the development of porosity in the adsorbent. The equilibrium values of vapor adsorption of substances on FAS-3 were measured on the gravimetric vacuum unit developed in the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences. Regeneration of the adsorbent was carried out for 6 h at a temperature of 623 K to a pressure of 0.1 Pa. The maximum absolute measurement error was ± 0.01 mmol / g with 95% confidence. Measurement of vapor pressure of organic substances within 0.13 Pa-0.13 MPa was carried out by absolute pressure gauges M10, M1000, developed and manufactured in the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences. The pressure measurement error by the manometer M10 in the range of 0.13 to 1330 Pa was ±0.066 Pa, and the manometer M1000 in the range from 13 Pa to 130 kPa was ±4.0 Pa.

Optimisation of the RGA location in the evaluation of NEG coating pumping properties

Non-evaporable getter (NEG) coatings are widely used in vacuum chambers of particle accelerators. Vacuum solutions group at STFC Daresbury Laboratory is continuously developing and optimising the NEG coatings are for various applications and vacuum chamber geometries. The pumping properties of the NEG coatings are characterised by sticking probability and pumping capacity. Initial sticking probability of the NEG coated tube can be measured by gas injection at one end of the tube and partial pressure measurements at either sides, P1 and P2 respectively. This requires the NEG coating facility to be modelled with the Test Particle Monte-Carlo (TPMC) method to obtain the pressure ratio R = P1/P2 as a function of sticking probability, R(α), for each type and geometry of the with each of the NEG coated tubes. The purpose of TPMC modelling reported in this paper was to find R(α) for the NEG coating evaluation facility with a sample in a form of the 0.5-m long NEG coated tubes with inner diameters of 5, 7, 9 and 38 mm. Furthermore, the effect of RGA2 location was also studied. It has been demonstrated that the RGA2 location could significantly (from a few percent up to a factor 3.1) affect the pressure ratio R(α). The effect of pressure measurement errors on calculated sticking probability was studied for ΔR/R = 10, 20 and 50%. The sticking probability accuracy varies: Δα/α = 0.04–0.5 for ΔR/R = 10%, Δα/α = 0.07–0.8 for ΔR/R = 20% and Δα/α = 0.23–2.0 for ΔR/R = 50%.

Monitoring data quality for telehealth systems in the presence of missing data

BackgroundAll-in-one station-based health monitoring devices are implemented in elder homes in Hong Kong to support the monitoring of vital signs of the elderly. During a pilot study, it was discovered that the systolic blood pressure was incorrectly measured during multiple weeks. A real-time solution was needed to identify future data quality issues as soon as possible. MethodsControl charts are an effective tool for real-time monitoring and signaling issues (changes) in data. In this study, as in other healthcare applications, many observations are missing. Few methods are available for monitoring data with missing observations. A data quality monitoring method is developed to signal issues with the accuracy of the collected data quickly. This method has the ability to deal with missing observations. A Hotelling's T-squared control chart is selected as the basis for our proposed method. FindingsThe proposed method is retrospectively validated on a case study with a known measurement error in the systolic blood pressure measurements. The method is able to adequately detect this data quality problem. The proposed method was integrated into a personalized telehealth monitoring system and prospectively implemented in a second case study. It was found that the proposed scheme supports the control of data quality. ConclusionsData quality is an important issue and control charts are useful for real-time monitoring of data quality. However, these charts must be adjusted to account for missing data that often occur in healthcare context.