Estimation of volumetric surface soil moisture content using microwave-calibrated soil evaporative efficiency information

ABSTRACT

Soil moisture (SM) is a critical variable in energy and water partitioning at the interface between the land surface and atmosphere. In this study, we provided a robust method to retrieve soil moisture using optimal remotely sensed soil evaporative efficiency (SEE) information. Specifically, SEE was deduced from the triangle space constituted by remotely sensed land surface temperature (LST) and fractional vegetation cover (Fc). Theoretical solutions of the dry and wet boundaries were derived by annual-scale optimization and microwave SM calibration. The two limits of SM were obtained by linear fit function between SEE and microwave-based SM. The proposed method was validated at the Liaoning Province of China in the year 2011 by using MODerate Resolution Imaging Spectroradiometer (MODIS) and Soil Moisture and Ocean Salinity (SMOS) satellite images as input. Results indicated that the new method has not only bypassed the complex parametric scheme in the calculation of boundaries within the LST-Fc feature space but also performed superior in the estimation of soil moisture status at all-sky days. Besides, the optimal method has reproduced the spatial and temporal patterns of soil moisture reasonably well, with a root mean square error of 0.07 m³ m^?3. Therefore, the proposed method can be regarded as a suitable tool to provide accurate and continuous monitoring of soil moisture.     

Calibration of a distributed SWE model using MODIS snow cover maps and in situ measurements

In this letter, we propose the calibration procedure for a Snow Water Equivalent (SWE) forecasting model, using Moderate-Resolution Imaging Spectroradiometer (MODIS) multi-temporal snow cover maps and in situ measurements. The presented study refers to one of the largest artificial lakes in the Western Europe – the Serre-Ponçon reservoir, on the Durance river, in the region of the French Alps. The SWE model, an integral part of the MORDOR (MOdèle à Réservoirs de Détermination Objective du Ruissellement) hydrological model, provides SWE as a function of local precipitation and temperature, as well as of accumulation and melting correction coefficients. The principal motivation for the proposed calibration method comes from the significant model sensitivity with respect to these two coefficients, which, given that they account for the influences of topology and mountain winds, ought to vary spatially. Three different optimization procedures are compared using the set of in situ measurements acquired by the EDF (Eléctricité de france) cosmic-ray snow sensors for 4 out of 36 ground stations in the regions of interest. The appropriate optimization method is selected and the corresponding representative optimal coefficients are derived for these four stations. Further, by combining the selected optimization algorithm and the continuous activation function, we propose a new method for deriving the spatially varying coefficients characterizing the entire region, using multi-temporal MODIS snow cover binary maps. When analysed with respect to the mean square error (MSE) criterion, the SWE model, calibrated in this manner, appears to be significantly more accurate than the original version (using a priori estimated, spatially fixed coefficients). Furthermore, the calibration procedure based on MODIS data is comparable and, for some ground stations, exhibits even better performances than the one based on the in situ measurements.     

Intra-arterial blood gas monitoring system: More accurate values can be obtained

Objective. To compare values measured by a continuous intra-arterial blood gas monitoring system with those measured by conventional blood gas analyzer for the assessment of the clinical performance of a new device for measurement of PaO₂, PaCO₂, and arterial pH.Methods. Forty-six patients undergoing cardiopulmonary bypass were enrolled in this study. All patients had a continuous intra-arterial sensor (PB 3300) placed into the radial artery through a 20-gauge catheter. A total of 319 arterial blood gas and pH values were obtained for comparison with a conventional blood gas analyzer. The measurements were performed every 12 hrs after the initialin vitro calibration of the sensor for each patient.Results. Measurements were made over a range of 12 to 192 hrs. The overall bias and precision determined by the two methods were 4.5 and 17.1 mmHg for PaO₂; 4.5 and 6.2 mmHg for PaCO₂; and 0.009 and 0.035 for pH, respectively. For the range of PO₂ less than 150 mmHg, the bias and precision improved to 4.2 and 9.5 mmHg. The sensor-derived PCO₂ value, PCO₂(IABG), increased significantly more than the conventional blood gas analysis value, PCO₂(ABG), even within 72 hrs (2.8 and 4.1 mmHg). The relationship between the two measurements can be described as: PCO₂(IABG)/PCO₂(ABG) = 1 + 0.0026 ·t where t is the time period of use (in hours). By correcting the PCO₂(IABG) value using this formula, the overall bias and precision of the values measured by two methods decreases to –0.4 and 3.6 mmHg.Conclusions. The PO₂ and pH values derived from an intra-arterial blood gas monitoring system agreed well with the values measured by a conventional blood gas analyzer. However, the PCO₂ value must be corrected due to an increase of drift, especially with extended use for more than 72 hours.     

Clinical consequences of analytical variance and calculation strategy in oral busulfan pharmacokinetics

BackgroundBusulfan pharmacokinetic (PK) monitoring of the area under the concentration–time curve (AUC) is necessary to minimize adverse events associated with both under- and over-dosing of busulfan during hematopoietic stem cell transplantation (HSCT). Three strategies are frequently used to calculate the AUC including in-house polynomial methods, the trapezoidal method (also called noncompartmental analysis), and the single compartment model with first-order elimination method. We compared these 3 methods, their clinical performance, and the relationship of AUC variance to analytical variance when each of these methods is used.MethodsClinical busulfan PK data was reviewed from 159 patients receiving the first dose of oral busulfan while undergoing HSCT. These data were used as templates to simulate AUC results and actions with varying amounts of analytical precision.ResultsBased on a predefined goal therapeutic target, the method for calculating AUC significantly changed the number of recommended busulfan dose adjustments (p < 0.000001). Overall, the number of dose adjustments would be expected to drop by approximately 10% due to calibration optimization of the busulfan concentration measurement method.ConclusionAnalytical variance and the AUC calculation method play a considerable role in the clinical management of busulfan dosing during HSCT. With better understanding and optimization of the analytical method, the reliability of clinically actionable information from busulfan PK can increase.     

Implantable cardioverter defibrillator electrogram adjudication for device registries: methodology and observations from ALTITUDE

Background: The increasing use of remote monitoring with the associated large retrievable databases provides a unique opportunity to analyze observations on implantable cardioverter‐defibrillator (ICD) therapies. Adjudication of a large number of stored ICD electrograms (EGMs) presents a unique challenge. The ALTITUDE study group was designed to use the LATITUDE remote monitoring system to evaluate ICD patient outcomes across the United States. Methods and Results: Of 81,081 patients on remote monitoring, a random sample of 2,000 patients having 5,279 shock episodes was selected. The ALTITUDE EGM review committee was comprised of seven electrophysiologists from four institutions. An online EGM adjudication system was designed. Episodes were classified as appropriate (70% of shock episodes) or inappropriate ICD therapies (30%). Light's Kappa was used to assess agreement. Interobserver and intraobserver Kappa scores for dual‐chamber ICDs were 0.84 (0.71–0.91) and 0.89 (0.82–0.95), consistent with substantial agreement. Interobserver and intraobserver Kappa scores for single‐chamber ICDs were 0.61 (0.54–0.67) and 0.69 (0.59–0.79). The rhythm categories of “nonsustained arrhythmia” and “polymorphic and monomorphic ventricular tachycardia” resulted in the greatest degree of discordant adjudication between reviewers. Conclusions: This method of adjudication of a large volume of stored EGM data prior to device therapies will allow new observations in regards to device performance and has the potential to improve device programming and design. There was substantial interreviewer agreement for rhythm classification. Agreement was greater for dual‐chamber compared to single‐chamber devices, indicating the atrial lead adds diagnostic value in rhythm interpretation. (PACE 2011; 34:1003–1012)     

A self-determination theory-based self-myofascial release program in older adults with myofascial trigger points in the neck and back: A pilot study

Purpose: To examine the effectiveness and adherence to a self-determination theory (SDT)-based self-myofascial release (SMR) program in older adults with myofascial trigger points (MTrPs), and to investigate the factors that influence participant behavioral change while conducting the program in a home setting. Methods: An explanatory mixed-method design was used to evaluate a 12-week SDT-based SMR program, including a 4-week group-based education and practice (EP) phase and an 8-week home-based self-management (SM) phase. Pain intensity on palpation and sensitivity to pain were assessed at baseline and the post EP and post SM phase. Focus group interviews were conducted at the post SM phase. Findings: Fifteen participants completed the study. Pain intensity and sensitivity to pain significantly improved at the post SM phase compared with the baseline. Adherence increased during the SM phase compared with that during the EP phase. Four main themes emerged as factors that influenced participant behavioral change: 1) “awareness of the effectiveness”; 2) “a sense of duty to perform the exercise”; 3) “obedience to expert instruction”; and 4) “lack of friendship.” Conclusions: These results support the effectiveness of an SDT-based SMR program for the treatment of MTrPs and in motivating older adults to participate in the program.     

增强MRI肿瘤-皮下脂肪信号强度比值鉴别椎管内神经鞘瘤与脊膜瘤北大核心CSCD

目的观察定量分析增强MRI所示椎管内神经鞘瘤(IS)和脊膜瘤(SM)肿瘤-皮下脂肪信号强度比值(SIR)鉴别二者的价值。方法回顾性分析76例经病理证实的IS(IS组,n=43)和SM(SM组,n=33)患者的术前MRI,由2名医师(医师1和医师2)分别测量增强T1WI所示肿瘤及皮下脂肪信号强度(SI),并计算其SIR;比较组间SIR异,采用受试者工作特征(ROC)曲线评价SIR鉴别IS与SM的效能,计算相应曲线下面积(AUC)。结果医师1测得IS组及SM组的SIR分别为0.91±0.12和0.62±0.09,医师2分别为0.88±0.12和0.64±0.10,IS组的SIR均高于SM组(Z=-6.825、-6.368,P均<0.01)。ROC曲线显示,医师1及医师2测量的SIR鉴别IS与SM的AUC分别为0.959和0.928;医师1测量SIR的最佳临界值为0.77时,其诊断敏感度为86.05%,特异度为100%;医师2测量SIR的最佳临界值为0.79时,其诊断敏感度为81.40%,特异度为96.97%。结论增强MRI所示IS肿瘤-皮下脂肪SIR高于SM,据此可有效鉴别二者。     

Measurement of Lumbar Lordosis: A Comparison of 2 Alternatives to the Cobb Angle

ObjectiveThe purpose of this study was to compare 2 alternative methods, the radiologic Harrison Posterior Tangent Method (HPTM) and the nonradiologic Spinal Mouse (SM), to the Cobb angle for measuring lumbar lordosis.MethodsSixteen participants with previously existing lateral lumbopelvic radiographs underwent nonradiographic lordosis assessment with a Spinal Mouse. Then 2 investigators analyzed each radiograph twice using the Harrison Posterior Tangent Method and Cobb angle. Correlations were analyzed between HPTM, the Cobb angle, and SM using the Spearman rank correlation coefficient; intraexaminer and interexaminer agreement were analyzed for HPTM and the Cobb angle using intraclass correlation coefficients.ResultsThe HPTM correlated highly with the Cobb angle (Spearman ρ = 0.936, P < .001); SM had moderate to strong correlations with the Cobb angle (ρ = 0.737, P = .002) and HPTM (ρ = 0.707, P = .003). Intraexaminer and interexaminer agreement for the Cobb angle and HPTM were excellent (all intraclass correlation coefficients > 0.90). One participant had slight kyphosis according to HPTM and SM analyses (which consider the entire lumbar region), whereas the Cobb angle, based only on L1 and L5, reported mild lordosis for that participant.ConclusionIn this sample, HPTM measurements showed high correlation with the commonly used Cobb angle, but this method requires more time and effort, and normal values have not been established. The SM may be an alternative when radiographs are inappropriate, but it measures soft tissue contours rather than lordosis itself.     

非等中心锥束CT成像系统标定及三维重建

目的 研究非等中心锥束CT系统(CBCT)几何参数标定及投影图像重排, 提出新的方法以提高参数标定精度及三维(3D)重建质量, 以期突破现有算法要求等中心系统应用环境的限制。方法 针对非等中心CBCT系统建立坐标系, 推导标定模型中特定标志点空间坐标与其在投影图像中平面坐标之间的几何关系, 建立虚拟等中心CBCT系统, 提出面向非等中心CBCT系统的解析+迭代混合标定方法, 对投影图像进行重排, 在此基础上进行3D重建。将标定模型置于非等中心CBCT系统中, 获取各个旋转角度下的投影图像;提取投影图像中特定标志点坐标, 基于这些坐标数据, 采用所提方法计算虚拟等中心CBCT系统几何参数;并求取虚拟等中心锥束投影图像;最后采用FDK算法进行3D重建。结果 与文献[10]算法相比, 所提算法对转轴在成像板上的投影坐标(u^0' 和v^0' )标定精度相当, 而射线源到成像板的垂直距离(D')和射线源到转轴的距离(R')标定精度明显较优。结论 本研究混合标定算法可提高D'和R'的标定精度, 并可突破文献[10]算法等中心系统应用环境的限制。     

Evaluation of a regional oxygen saturation catheter for monitoring SJVO2 in head injured patients

Objectives. Monitoring jugular venous oxygen saturation (SjvO₂) has been useful for the early identification and treatment of cerebral ischemia in patients with severe head injury. However, the catheters that have been used for this purpose have not performed optimally. The purpose of this study was to evaluate the performance of a new regional oxygen saturation catheter for monitoring SjvO₂.Methods. Eighteen regional oxygen saturation catheters, 4-Fr in diameter (Baxter Healthcare Corporation, Edward Critical Care), were used in this study. Each catheter was inserted percutaneously into the dominant jugular vein and the catheter's tip position in the jugular bulb was verified by radiograph. The catheter was calibratedin vitro prior to insertion using the optic calibrator provided by the manufacturer. The catheter was recalibrated every 8 to 12 hours by comparing the oxygen saturation value from the catheter with that measured by a cooximeter in a blood sample drawn through the catheter.Results. In vitro calibration using the optic calibrator was not always successful. Five catheters could not be calibrated. The remaining 13 catheters could all be calibrated, but only 9 provided a value that was within 4% of the oxygen saturation derived from the blond sample. After the firstin vivo calibration, the correlation between the catheter and the blond sample values was improved. A total of 196 comparisons were made. The median, 25th, and 75th quartile differences between the catheter and the blond sample measurement of SjvO₂ were 0.00, −1.15, and 1.25%, respectively. Using longitudinal data regression, the overall slope of the regression between the catheter and blood values was 0.997 (p = 0.001).Conclusions. The new regional oxygen saturation catheter provided reliable measurement of SjvO₂ 83% of the time when the signal quality index was ≤3, and may be useful for continuous monitoring of SjvO₂. This work was supported by NIH grant #PO1-NS26716.     

Age‐dependent biochemical quantities: An approach for calculating reference intervals

Objective. A parametric method is often preferred when calculating reference intervals for biochemical quantities, as non‐parametric methods are less efficient and require more observations/study subjects. Parametric methods are complicated, however, because of three commonly encountered features. First, biochemical quantities seldom display a Gaussian distribution, and there must either be a transformation procedure to obtain such a distribution or a more complex distribution has to be used. Second, biochemical quantities are often dependent on a continuous covariate, exemplified by rising serum concentrations of MUC1 (episialin, CA15.3) with increasing age. Third, outliers often exert substantial influence on parametric estimations and therefore need to be excluded before calculations are made. Material and methods. The International Federation of Clinical Chemistry (IFCC) currently recommends that confidence intervals be calculated for the reference centiles obtained. However, common statistical packages allowing for the adjustment of a continuous covariate do not make this calculation. Results. In the method described in the current study, Tukey's fence is used to eliminate outliers and two‐stage transformations (modulus‐exponential‐normal) in order to render Gaussian distributions. Fractional polynomials are employed to model functions for mean and standard deviations dependent on a covariate, and the model is selected by maximum likelihood. Confidence intervals are calculated for the fitted centiles by combining parameter estimation and sampling uncertainties. Finally, the elimination of outliers was made dependent on covariates by reiteration. Conclusions. Though a good knowledge of statistical theory is needed when performing the analysis, the current method is rewarding because the results are of practical use in patient care.     

Partial CO2 rebreathing indirect Fick technique for non-invasive measurement of cardiac output

Objective.Evaluation in animals of a non-invasive and continuous cardiac output monitoring system based on partial carbon-dioxide (CO₂) rebreathing indirect Fick technique. Methods.We have developed a non-invasive cardiac output (NICO) monitoring system, based on the partial rebreathing method. The partial rebreathing technique employs a differential form of the Fick equation for calculating cardiac output (Q_T) using non-invasive measurements. Changes in CO₂ elimination (ΔVCO₂) and partial pressure of end-tidal CO₂ (Δ PETCO₂) in response to a brief period of partial rebreathing are used to measure pulmonary capillary blood flow (Q_PCBF). A non-invasive estimate of anatomic and intrapulmonary shunt fraction (Q_S/Q_T), based on oxygen saturation from pulse oximetry (SpO₂) and inspired oxygen concentration (FIO₂), is added to compute total cardiac output [Q_T=Q_PCBF/(1−Q_S/Q_T)]. The performance of the NICO was compared with iced 5% dextrose bolus thermodilution cardiac output (TDco) measurements in 6 dogs. Cardiac output was varied using dobutamine, and halothane, and by clamping of the inferior vena cava. Two hundred and forty-six (n = 246) paired measurements of TDco and NICO over a range of cardiac outputs (TDco range = 0.60–8.87 l/min) were compared using Bland-Altman analysis and weighted correlation coefficient. Results.The Bland–Altman technique yielded a NICO precision of ± 0.70 l/min (13.8%) with a mean bias of −0.07 l/min (−1.4%) compared to TDco. The weighted correlation coefficient between TDco and NICO values was: r= 0.93 (n= 246). Conclusion.The partial CO₂ rebreathing technique for measurement of cardiac output is non-invasive, automated, and based on the well accepted Fick principle. The limits of agreement between NICO and TDco is within the recommended value for NICO to be a clinically acceptable method for cardiac output measurement. The results of this canine study show that NICO performed as well, and in some cases better, than other currently available non-invasive cardiac output techniques over a wide range of cardiac outputs. This revised version was published online in July 2006 with corrections to the Cover Date.     

A New Calibration Method that Compensates for the Effects of O2 and N2 on Infrared CO2 Analysers

Objective. This study evaluates a method for calibrating mainstream CO₂ analysers in which CO₂ partial pressure (P _CO2) is calculated as a function of the outputs of CO₂ and O₂ analysers. Methods. Three mass flow controllers were used to generate 25 different reference mixtures of O₂, N₂ and CO₂. Reference gas mixtures were combinations of P _CO2 = 2, 4, 6, 8, 10 kPa and O₂ partial pressure (P _O2) = 10, 20, 40, 60, 80 kPa (balance N₂). CO₂ and O₂ analyser data were fitted by a calibration equation which took into account the effects of oxygen partial pressure and nonlinearity of the CO₂ analyser. The calibration coefficients were tested in a separate validation data set with a variety of combinations of CO₂ and O₂. Results. Our new calibration method yields a standard deviation of CO₂ measurement error that is significantly lower than a CO₂-only calibration method in the validation data set (0.54% versus 2.72%, P < 0.05). P _CO2 measurement errors produced by the single gas calibration equation are significantly correlated with P _O2 in both the calibration (R = −0.9906, P < 0.05) and validation data sets (R = −0.9642, P < 0.05), but the errors given by our new calibration equation are independent of P _O2 (R = −0.0364, NS, and R = −0.0305, NS, for calibration and validation data sets respectively). Calibration with only CO₂ cannot eliminate the error related to the collision broadening effect of O₂, which in our CO₂ analyser is approximately a 1% underestimation of P _CO2 for every 10 kPa (75 mmHg) increase in P _O2. Conclusions. This study shows that non-dispersive infrared CO₂ analyser readings can be substantially affected by background oxygen. This effect can be corrected for by calibrating the CO₂ analyser with gases containing known proportions of both CO₂ and O₂.     

Indices to quantify changes in intracranial and cerebral perfusion pressure by assessing agreement between hourly and semi-continuous recordings

Objectives Little published data exists on whether nurse-recorded end-hour values of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are representative of continuous monitoring during the hour. There is also no standard method of quantifying the observed perturbations in cerebral hemodynamics. This study compared the level of agreement between end-hour values and computer downloaded observations of ICP and CPP at 15-min intervals. We also developed the intracranial hypertension index and the cerebral hypoperfusion index to quantify perturbations in cerebral hemodynamics. Each of these indices relates the number of abnormal observations to the total number of observations taken.Methods Prospective, non-interventional study.Results The bias and precision between the two methods for ICP and CPP were –0.002±2.6 mmHg and –1.1±6.2 mmHg, respectively. A strong correlation existed between the hourly mean calculated from the 15-min and the end-hour values for both ICP (r²=0.95, p<0.0001) and CPP (r²=0.78, p<0.001). The intracranial hypertension index was 40% from the 15-min measurements and 41% from the hourly observations (p= NS). The cerebral hypoperfusion indices were 13.4% and 13.1% with the 15-min and end-hour values, respectively (p= NS).Conclusions The end-hour values of ICP and CPP are as accurate as more frequent measurements during the hour and are adequate for purposes of epidemiological research and medico-legal audit. The intracranial hypertension and cerebral hypoperfusion indices may be useful in describing cerebral hemodynamics for future interventional studies and for assessing quality in the delivery of neuro-critical care.     

Evaluation of a regional oxygen saturation catheter for monitoring SJVO2 in head injured patients

Objectives. Monitoring jugular venous oxygen saturation (SjvO₂) has been useful for the early identification and treatment of cerebral ischemia in patients with severe head injury. However, the catheters that have been used for this purpose have not performed optimally. The purpose of this study was to evaluate the performance of a new regional oxygen saturation catheter for monitoring SjvO₂.Methods. Eighteen regional oxygen saturation catheters, 4-Fr in diameter (Baxter Healthcare Corporation, Edward Critical Care), were used in this study. Each catheter was inserted percutaneously into the dominant jugular vein and the catheter's tip position in the jugular bulb was verified by radiograph. The catheter was calibratedin vitro prior to insertion using the optic calibrator provided by the manufacturer. The catheter was recalibrated every 8 to 12 hours by comparing the oxygen saturation value from the catheter with that measured by a cooximeter in a blood sample drawn through the catheter.Results. In vitro calibration using the optic calibrator was not always successful. Five catheters could not be calibrated. The remaining 13 catheters could all be calibrated, but only 9 provided a value that was within 4% of the oxygen saturation derived from the blond sample. After the firstin vivo calibration, the correlation between the catheter and the blond sample values was improved. A total of 196 comparisons were made. The median, 25th, and 75th quartile differences between the catheter and the blond sample measurement of SjvO₂ were 0.00, –1.15, and 1.25%, respectively. Using longitudinal data regression, the overall slope of the regression between the catheter and blood values was 0.997 (p = 0.001).Conclusions. The new regional oxygen saturation catheter provided reliable measurement of SjvO₂ 83% of the time when the signal quality index was 3, and may be useful for continuous monitoring of SjvO₂.This work was supported by NIH grant #PO1-NS26716.     

Applying terrestrial lidar for evaluation and calibration of airborne lidar-derived shrub biomass estimates in Arctic tundra

Monitoring of climate-driven expansion of low-stature shrubs in Arctic tundra can be improved through application of high-resolution remote sensing. However, the destructive nature of harvest sampling that is usually performed for validation of these data is resource intensive and can limit future comparisons by destroying benchmark measurements. We compared aboveground shrub biomass estimates derived from terrestrial laser scanning (TLS) and airborne laser scanning (ALS) with the goal of determining whether TLS data can be used to accurately calibrate ALS estimates of shrub biomass in Arctic tundra. We used a leave-one-out cross-validation calibration of canopy volume against harvested shrub biomass to establish predictive relationships between TLS canopy volume and harvested shrub biomass, and between ALS canopy volume and TLS-derived shrub biomass estimates. TLS produced more accurate predictions of shrub biomass (R² = 0.78; root mean square deviation [RMSD] = 102 g) than did ALS, but the accuracy of ALS-derived shrub biomass predictions was the same whether they were calibrated directly against harvest biomass or against TLS-derived estimates of biomass (R² = 0.62; RMSD = 140 g). Our results suggest that once the initial TLS-harvest relationship is known, TLS can provide valid ground reference data for calibration of ALS-derived estimates of shrub biomass without the need for additional destructive harvest.     

Comparing medication adherence using a smartphone application and electronic monitoring among patients with acute coronary syndrome

AimThe purpose of this study was to determine the extent of agreement between adherence measures obtained using two technological interventions, electronic monitoring (EM) and a smartphone application (App).BackgroundClinicians, patients, and researchers depend on valid measurements of medication adherence to inform the delivery of preemptive care when needed. Technology is routinely used for monitoring medication adherence in both clinical practice and research, yet there is a dearth of research comparing novel App based approaches to traditional approaches used for assessing medication adherence.MethodsAdherence rates were captured on both the EM and the App for 3697 daily observations from 44 participants with acute coronary syndrome over 90 days immediately following discharge from acute care. For EM, adherence was measured using EM equipped pill bottles. For the App, adherence was measured by having participants upload daily photos to the App prior to taking their daily aspirin. Agreement was assessed using a Bland-Altman analysis.ResultsThe mean adherence rate was higher on the App, 92%, than the EM, 78% (p < 0.001). The mean difference in adherence rates between these methods was 14% (95% Confidence Interval: −23%, −5%).ConclusionsThese findings illustrate a lack of agreement between technological interventions used for measuring adherence in cardiovascular patient populations, with higher adherence rates observed with the App compared to EM. These findings are salient given the increased reliance on telehealth due to the ongoing COVID-19 pandemic.     

Reliability of Continuous Pulse Contour Cardiac Output Measurement during Hemodynamic Instability

Objective Arterial pulse contour analysis is gaining widespread acceptance as a monitor of continuous cardiac output (CO). While this type of CO measurement is thought to provide acceptable continuous measurements, only a few studies have tested its accuracy and repeatability under unstable hemodynamic conditions. We compared continuous CO measurement using the pulse contour method (PCCO) before and after calibration with intermittent transpulmonary thermodilution cardiac output (TpCO). Method We compared the two methods of CO measurements in 15 Landrace pigs weighing 20–25 kg in an experimental model of sepsis. Nine pigs were given an infusion of E. coli lipopolysacchride (LPS), and six pigs acted as controls. PCCO values before and after calibration (PCCO₁ and PCCO₂ respectively) were registered, and their errors relative to TpCO measurements were compared. Results The mean coefficient of variation for repeated PCCO measurements was 6.85% for the control group, and 13.99% for the endotoxin group. The range of TpCO was 1.01–3.15 L/min. In the control group the bias ±2SD was 0.11 ± 0.53 L/min (TpCO vs PCCO₁) and −0.02 ± 0.38 L/min (TpCO vs PCCO₂). In the endotoxin group, the agreement was poor between TpCO and PCCO₁, 0.08 ± 1.02 L/min. This improved after calibration (TpCO vs PCCO₂) to 0.01 ± 0.31 L/min. Conclusions In hemodynamically stable pigs, both pre- and post-calibration PCCO measurements agreed well with the intermittent transpulmonary thermodilution technique. However, during hemodynamic instability, and pre-calibration PCCO values had wide limits of agreement compared with TpCO. This was reflected by larger coefficients of variation for PCCO in hemodynamic instability. The error of PCCO measurement improved markedly after calibration, with bias and limits of agreement within clinically acceptable limits. Johansson A, Chew M. Reliability of continuous pulse contour cardiac output measurement during hemodynamic instability.     

Continuous cardiac index monitoring: A prospective observational study of agreement between a pulmonary artery catheter and a calibrated minimally invasive technique

IntroductionContinuous cardiac index (CCI) monitoring can provide information to assist in hemodynamic support. However, pulmonary artery catheters (PAC) pose logistic challenges in acute care settings. We hypothesized that CCI measured with a calibrated minimally invasive technique (LiDCO/PulseCO, UK) would have good agreement with the PAC.MethodsWe performed a prospective observational study in post-operative cardiac surgery patients. All patients had a PAC with CCI monitoring capability. We connected the LiDCO apparatus to a radial artery line and performed a one-time calibration with a lithium dilution indicator. In order to test the least invasive method possible, we used a peripheral intravenous (IV) line for indicator delivery rather than the conventional central line technique. We recorded paired PAC/LiDCO-PulseCO CCI measurements every minute for 3 h. We blinded investigators and clinicians to minimally invasive data with an opaque shield over the monitor. We assessed agreement with Bland-Altman analysis.ResultsWe obtained 1485 paired measurements in 8 subjects. The mean CI was 2.9 L/min/m². By Bland-Altman plot, PAC and LiDCO measurements showed minimal bias (?0.01), but the 95% limits of agreement (±2SD) of ± 1.3 L/min/m² were relatively wide with respect to the mean.ConclusionsThis calibrated minimally invasive (i.e. radial arterial line and peripheral IV) technique demonstrated low bias compared with CCI measured by PAC. However, the relatively wide confidence limits indicate that differences in the two measurements could still be clinically significant.     

Multiple calibrator measurements improve accuracy and stability estimates of automated assays

Objectives The effects of combining multiple calibrations on assay accuracy (bias) and measurement of calibration stability were investigated for total triiodothyronine (TT3), vitamin B12 and luteinizing hormone (LH) using Beckman Coulter’s Access 2 analyzer. Methods Three calibration procedures (CC1, CC2 and CC3) combined 12, 34 and 56 calibrator measurements over 1, 2, and 3 days. Bias was calculated between target values and average measured value over 3 consecutive days after calibration. Using regression analysis of calibrator measurements versus measurement date, calibration stability was determined as the maximum number of days before a calibrator measurement exceeded 5% tolerance limits. Results Competitive assays (TT3, vitamin B12) had positive time regression slopes, while sandwich assay (LH) had a negative slope. Bias values for TT3 were??2.49%, 1.49%, and??0.50% using CC1, CC2 and CC3 respectively, with calibrator stability of 32, 20, and 30 days. Bias values for vitamin B12 were 2.44%, 0.91%, and??0.50%, with calibrator stability of 4, 9, and 12 days. Bias values for LH were 2.26%, 1.44% and??0.29% with calibrator stability of >43, 39 and 36 days. Measured stability was more consistent across calibration procedures using percent change rather than difference from target: 26 days for TT3, 12 days for B12 and 31 days for LH. Conclusions Averaging over multiple calibrations produced smaller bias, consistent with improved accuracy. Time regression slopes in percent change were unaffected by number of calibration measurements but calibrator stability measured from the target value was highly affected by the calibrator value at time zero.