Bland-Altman Mean Difference Research Articles

Global Small Bowel Motility: Assessment with Dynamic MR Imaging

To assess the repeatability in human volunteers of software-quantified small bowel motility captured with magnetic resonance (MR) imaging and to test the ability to detect changes in motility induced by pharmacologic agents. The study was approved by the Royal Free Research Ethics Committee, and all subjects gave full written informed consent. Twenty-one healthy volunteers (14 men, seven women; mean age, 28 years) underwent cine MR imaging with a three-dimensional balanced turbo field-echo sequence to capture small bowel motility. Volume blocks (15 cm thick) were acquired every second during a 20-second breath hold. A randomized, blinded, placebo-controlled crossover study of either 0.5 mg neostigmine or saline (n = 11) or 20 mg intravenous butylscopolamine or saline (n = 10) was performed with motility MR imaging at baseline and repeated at a mean of 4 weeks (range, 2-7 weeks). Two readers independently drew regions of interest around the small bowel, and motility was quantified by using a registration algorithm that provided a global motility metric in arbitrary units. Repeatability of the motility measurements at baseline was assessed by using Bland-Altman and within-subject coefficient of variation measures. Changes in mean motility measurements after drug administration were compared with those after placebo administration by using paired t testing. The repeatability between baseline measurements of motility was high; the Bland-Altman mean difference was -0.0025 (range, 0.28-0.4), the 95% limit of agreement was ±0.044 arbitrary units (au), and the within-subject coefficient of variation was 4.9%. Measured motility with neostigmine (mean, 0.39 au) was significantly higher than that with placebo (mean, 0.34 au; P < .001), whereas that with butylscopolamine (mean, 0.13 au) was significantly lower than that with placebo (mean, 0.30 au; P < .001). Quantification of small bowel motility with use of MR imaging in healthy volunteers is repeatable and sensitive to changes induced by means of pharmacologic manipulation. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13130151/-/DC1.

A new method to estimate the amplitude spectrum analysis of ventricular fibrillation during cardiopulmonary resuscitation

AIMSAccurate ventricular fibrillation (VF) waveform analysis usually requires rescuers to discontinue cardiopulmonary resuscitation (CPR). However, prolonged “hands-off” time has a deleterious impact on the outcome. We developed a new filter technique that could clean the CPR artifacts and help preserve the shockability index of VF METHODSWe analyzed corrupted ECGs, which were constructed by randomly adding different scaled CPR artifacts to the VF waveforms. A newly developed algorithm was used to identify the CPR fluctuations. The algorithm contained two steps. First, decomposing the raw data by empirical mode decomposition (EMD) into several intrinsic mode fluctuations (IMFs) and combining the dominant IMFs to reconstruct a new signal. Second, calculating each CPR cycle frequency from the new signal and fitting the new signal to the original corrupted ECG by least square mean (LSM) method to derive the CPR artifacts. The estimated VF waveform was derived by subtraction of the CPR artifacts from the corrupted ECG. We then performed amplitude spectrum analysis (AMSA) for original VF, corrupted ECG and estimated VF. RESULTSA total of 150 OHCA subjects with initial VF rhythm were included for analysis. Ten CPR artifacts signals were used to construct corrupted ECG. Even though the correlations of AMSA between the corrupted ECG vs. the original VF and the estimated VF vs. the original VF are all high (all p<0.001), the values of AMSA were obviously biased in corrupted ECG with wide limits of agreement in Bland–Altman mean-difference plot. ROC analysis of the AMSA in the prediction of defibrillation success showed that the new algorithm could preserve the cut-off AMSA value for CPR artifacts with power ratio to VF from 0 to 6dB. CONCLUSIONThe new algorithm could efficiently filter the CPR-related artifacts of the VF ECG and preserve the shockability index of the original VF waveform.

Global Small Bowel Motility: Assessment with Dynamic MR Imaging

To assess the repeatability in human volunteers of software-quantified small bowel motility captured with magnetic resonance (MR) imaging and to test the ability to detect changes in motility induced by pharmacologic agents. The study was approved by the Royal Free Research Ethics Committee, and all subjects gave full written informed consent. Twenty-one healthy volunteers (14 men, seven women; mean age, 28 years) underwent cine MR imaging with a three-dimensional balanced turbo field-echo sequence to capture small bowel motility. Volume blocks (15 cm thick) were acquired every second during a 20-second breath hold. A randomized, blinded, placebo-controlled crossover study of either 0.5 mg neostigmine or saline (n = 11) or 20 mg intravenous butylscopolamine or saline (n = 10) was performed with motility MR imaging at baseline and repeated at a mean of 4 weeks (range, 2-7 weeks). Two readers independently drew regions of interest around the small bowel, and motility was quantified by using a registration algorithm that provided a global motility metric in arbitrary units. Repeatability of the motility measurements at baseline was assessed by using Bland-Altman and within-subject coefficient of variation measures. Changes in mean motility measurements after drug administration were compared with those after placebo administration by using paired t testing. The repeatability between baseline measurements of motility was high; the Bland-Altman mean difference was -0.0025 (range, 0.28-0.4), the 95% limit of agreement was ±0.044 arbitrary units (au), and the within-subject coefficient of variation was 4.9%. Measured motility with neostigmine (mean, 0.39 au) was significantly higher than that with placebo (mean, 0.34 au; P < .001), whereas that with butylscopolamine (mean, 0.13 au) was significantly lower than that with placebo (mean, 0.30 au; P < .001). Quantification of small bowel motility with use of MR imaging in healthy volunteers is repeatable and sensitive to changes induced by means of pharmacologic manipulation. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13130151/-/DC1.

Prospective Comparison of Valve Regurgitation Quantitation by Cardiac Magnetic Resonance Imaging and Transthoracic Echocardiography

Both transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) imaging allow quantification of chronic aortic regurgitation (AR) and mitral regurgitation (MR). We hypothesized that CMR measurement of regurgitant volume (RVol) is more reproducible than TTE. TTE and CMR performed on the same day in 57 prospectively enrolled adults (31 with AR, 26 with MR) were measured by 2 independent physicians. TTE RVol(AR) was calculated as Doppler left ventricular outflow minus inflow stroke volume. RVol(MR) was calculated by both the proximal isovelocity surface area method and Doppler volume flow at 2 sites. CMR RVol(AR) was calculated by phase-contrast velocity mapping at the aortic sinuses and RVol(MR) as total left ventricular minus forward stroke volume. Intraobserver and interobserver variabilities were similar. For AR, the Bland-Altman mean interobserver difference in RVol was -0.7 mL (95% confidence interval [CI], -5 to 4) for CMR and -9 mL (95% CI, -53 to -36) for TTE. The Pearson correlation was higher (P=0.001) between CMR (0.99) than TTE readers (0.89). For MR, the Bland-Altman mean difference in RVol between observers was -4 mL (95% CI, -21 to 13) for CMR compared with 0.7 mL (95% CI, -30 to 32) for the proximal isovelocity surface area and -10 mL (95% CI, -76 to 56) for TTE volume flow at 2 sites. Correlation was similar for CMR (0.94) versus TTE readers (0.90 for the proximal isovelocity surface area). Compared with TTE, CMR has lower intraobserver and interobserver variabilities for RVol(AR), suggesting CMR may be superior for serial measurements. Although RVol(MR) is similar by TTE and CMR, variability in measured RVol by both approaches suggests that caution is needed in clinical practice.

Prediction of RBC aggregability and deformability by whole body bioimpedance measurements analyzed according to Hanai's mixture conductivity theory

Bioelectrical impedancemetry (BIA) has been used to evaluate hemorheological parameters in vitro, and whole body impedance measurements are also correlated to some hemorheologic factors, due to their close relationship with determinants of electric properties of blood. In previous studies, we have determined a set of predictive equations for hematocrit, whole blood viscosity and plasma viscosity in both sedentary and trained individuals. Recent developments of the interpretation of BIA analysis based on Hanai's mixture conductivity theory allows a more interpretative analysis of the relationships between these electric measurements and body composition. Impedance can be analyzed in terms of resistance and resistivity of the whole body and even more, assuming some simplifications, resistance R and resistivity ρ of total body water (TBW), extracellular water (ECW) and intracellular water (ICW). In this study we thus investigated relationships between blood rheology and these calculations of R and ρ in a sample of 83 subjects (age: 9-64 yr; BMI: 17-44 kg/m(2)). BIA was performed with a multifrequency bioelectrical impedancemeter using low intensity at the following frequencies: 1, 5, 10, 50 and 100 kHz. Viscometric measurements were done with a falling ball viscometer. Hematocrit was measured with microcentrifuge. We found a new prediction of Quemada's viscometric index of RBC rigidity "k" which was positively correlated to the resistance of ECW (R(e)) and even more if it was related to this volume: k = 0.005809 R(e)/ECW + 1.1784 (r = 0.487; Bland-Altman mean difference: 0.0124; range: -0.00481 to 0.00296). A new finding was that red blood cells (RBC) aggregability, that in the previous studies was not related to whole body impedance, despite its in vitro measurability with such measurements, was correlated to extracellular resistance and resistivity. The Myrenne index "M" was negatively correlated to the resistivity of the extracellular fluid ρe and is predicted by: M = -27.4755 ρ(e) + 1121.57029 (r = 0.463; Bland-Altman mean difference: 0.00194; range: -0.842 to 0.842). Furthermore, the SEFAM index "S(10)" is correlated to the ρe and is predicted by S(10) = -59.38579 (ρ(e)-40) + 63.083 (r = 0.761; Bland-Altman mean difference: 0.000722; range: -1.77 to 1.77). Therefore, a more in-depth analysis of electric properties of the body provides a closer approach of RBC rheology, although, of course, most remains to be understood in this intriguing domain.

Informatics Infrastructure for Syndrome Surveillance, Decision Support, Reporting, and Modeling of Critical Illness

To develop and validate an informatics infrastructure for syndrome surveillance, decision support, reporting, and modeling of critical illness. Using open-schema data feeds imported from electronic medical records (EMRs), we developed a near-real-time relational database (Multidisciplinary Epidemiology and Translational Research in Intensive Care Data Mart). Imported data domains included physiologic monitoring, medication orders, laboratory and radiologic investigations, and physician and nursing notes. Open database connectivity supported the use of Boolean combinations of data that allowed authorized users to develop syndrome surveillance, decision support, and reporting (data "sniffers") routines. Random samples of database entries in each category were validated against corresponding independent manual reviews. The Multidisciplinary Epidemiology and Translational Research in Intensive Care Data Mart accommodates, on average, 15,000 admissions to the intensive care unit (ICU) per year and 200,000 vital records per day. Agreement between database entries and manual EMR audits was high for sex, mortality, and use of mechanical ventilation (kappa, 1.0 for all) and for age and laboratory and monitored data (Bland-Altman mean difference +/- SD, 1(0) for all). Agreement was lower for interpreted or calculated variables, such as specific syndrome diagnoses (kappa, 0.5 for acute lung injury), duration of ICU stay (mean difference +/- SD, 0.43+/-0.2), or duration of mechanical ventilation (mean difference +/- SD, 0.2+/-0.9). Extraction of essential ICU data from a hospital EMR into an open, integrative database facilitates process control, reporting, syndrome surveillance, decision support, and outcome research in the ICU.

The Reliability of Measures of Muscle Performance and Physical Function In Younger and Older Men

PURPOSE: Skeletal muscle wasting is a consequence of advancing age (termed sarcopenia) that causes impairments in strength, limitations in function and ultimately loss of independence. To aid in the design of efficacy trials for new therapies for sarcopenia we sought to determine the reliability of key outcome measures of muscle strength and physical function. METHODS: Standardized protocols for assessment of lower and upper body strength and function were performed in younger men (YM), older men (OM) and older men with mobility limitations (OM+ML). The reliability of the selected measures was determined by examining the agreement between trial 1 and trial 2 using two methods: intra-class correlation (ICC) analysis and the Bland Altman (BA) method. RESULTS: Leg press and chest press 1RM measures exhibited excellent test-retest reliability in YM (n = 30), OM (n = 31) and OM+ML (n = 39) (ICCs = 0.946-0.994). Across subjects, the BA mean difference between trial 1 and trial 2 was an improvement of 21.1 and 1.1N for leg press and chest press, respectively. These measures identified significant differences in strength between the groups (ANOVAs, p 0.940, bias was similar and the tests better discriminated between the 3 groups (e.g., stair climb time: YM = 3.55 ± 0.13, OM = 5.14 ± 0.25, OM + ML = 8.00 ± 0.68 sec; p < 0.001). Examination of upper extremity function by a lift and lower measure also demonstrated high agreement (ICCs = 0.925-0.947) and minimal bias (1.4-2.9 more shelves) in each of the groups and revealed significant differences between them (ANOVA = 0.001). CONCLUSIONS: These measures of skeletal muscle strength and physical function are reliable and discriminate between YM, OM and OM + ML. These data will aid in the design of clinical trials to determine the efficacy of novel function promoting therapies. This work was supported by NIH grants U01AG01436906 and R01HD047722 to SB. NKL was in part supported by NIH grant K01AG031154.