Effect of electrode locations and respiration in the characterization of myocardial tissue using a transcatheter impedance method

Our objective is to evaluate whether it is possible to characterize the passive electrical properties of myocardial tissue in contact with the electrocatheters used in arrhythmia diagnosis or radio frequency ablation techniques. To characterize the tissue, we propose the use of electrical impedance spectroscopy to measure the impedance between the catheter tip and an external electrode, assuming a three-electrode method. We constructed a 3D finite-element model of the thorax to estimate the impedance as measured in different situations. We defined an area on the anterior wall of the left ventricle in which we simulated three tissue states: healthy, acute ischaemic and scar. We studied the effect of the following parameters on the measured impedance spectrum: the position of the external electrode, the position and orientation of the catheter tip and the overall effect of the subject's respiration. Results show that the highest frequency phase (around 300 kHz) yields the best differentiation of tissue states and that it is less sensitive to respiration than the impedance magnitude. The phase is also less influenced by the catheter tip position (either touching the wall or floating) and the orientation of the catheter inside the left ventricle. The best position for the external electrode is on the chest; this position is less affected by breathing and is more sensitive to tissue changes. One can still distinguish between tissue states if the external electrode is placed on the back, but the effect of respiration is higher.     

Triage in the trauma bay with the focused abdominal sonography for trauma (FAST) examination

Bedside ultrasonography has been applied to the evaluation of blunt trauma patients for over a decade. The Focused Abdominal Sonography for Trauma (FAST) examination has been used to successfully triage blunt trauma patients. Although not traditionally thought to be as useful in penetrating trauma patients, ultrasound can help determine the extent of injury especially of the heart. We present two cases of multiple-stabbing victims who arrived at our Level I trauma center at the same time, when our trauma system was particularly overburdened by multiple consecutive traumas. The FAST examination helped us to accurately determine which of the two patients required operative intervention first, despite that patient's appearance of relative hemodynamic stability in comparison to the other stabbing victim.     

Experience with focused abdominal sonography for trauma (FAST) in 313 pediatric patients

PURPOSE: The use of focused abdominal sonography for trauma (FAST), which detects free fluid in the abdomen and pelvis, for the assessment of blunt abdominal trauma is gaining acceptance worldwide and has been described extensively in the general medical literature. The precise application of this technique in pediatric patients, however, has yet to be established. The aim of this study was to assess the utility of FAST in pediatric trauma patients by comparing the results of this technique with those of CT and explorative laparotomy (ELAP). METHODS: We retrospectively reviewed the medical records and sonographic examinations of pediatric patients who had sustained multiple traumatic injuries for which they were treated at our hospital during a 20-month period. For all patients, FAST had been the initial screening examination for blunt abdominal trauma. We compared the FAST findings, which had been recorded as positive or negative, with the findings on CT or ELAP, which were considered definitive. RESULTS: A total of 313 patients (204 boys and 109 girls) with a mean age of 7.1 years were included in the study. The FAST finding had been negative in 274 patients, of whom 201 had had no clinical signs of abdominal injury and had been managed conservatively without complications. CT had been performed in 109 patients and ELAP in 11. FAST had yielded 3 false-negative and 2 false-positive results. The sensitivity, specificity, and accuracy of FAST were 92.5%, 97.2%, and 95.5%, respectively. CONCLUSIONS: FAST is an effective tool in screening pediatric trauma patients for blunt abdominal trauma.     

Sonographic assessment of changes in thickness of different abdominal fat layers in response to diet in obese women

PURPOSE: We evaluated the potential application of sonography to monitor alterations in abdominal fat thickness in obese women before and after dieting. METHODS: This study included 40 obese women (mean age, 42.2 +/- 9.4 years; mean body mass index [BMI], 36.0 +/- 5.9 kg/m2) who underwent a 3-month low-calorie diet. Height, weight, waist circumference (WC), and hip circumference (HC) were measured. BMI and waist-to-hip ratio (WHR) were calculated. Abdominal subcutaneous (S) and intra-abdominal preperitoneal (P) fat were measured at their maximum (max) and minimum (min) thickness sites using a 7.5-MHz linear-array probe. Intra-abdominal visceral (V) fat was measured using a 3.5-MHz convex-array probe. Measurements were taken before and after caloric restriction. RESULTS: The mean weight was reduced from 88.6 +/- 17.1 kg to 83.0 +/- 15.9 kg (p < 0.0001). The mean changes in S(min) (r = 0.376, p = 0.017), S(max) (r = 0.508, (p = 0.001), P(min) (r = 0.439, p = 0.005), and V (r = 0.365, p = 0.022) fat thicknesses were positively correlated with change in weight; the change in P(max) fat thickness showed the best and most significant correlation (r = 0.591, p < 0.0001). BMI (r = 0.969, p < 0.0001), WC (r = 0.510, p = 0.001), and HC (r = 0.422, p = 0.007) changes were also positively correlated with weight change, but the WHR change (r = 0.019, p > 0.05) was not. CONCLUSIONS: All the abdominal fat layers, particularly the intra-abdominal P fat, will decrease in response to loss of body fat by dieting. Sonography seems to be useful in monitoring small variations in the thicknesses of abdominal S and intra-abdominal P and V fat.     

Construct validity of the functional independence measure (FIM): questioning the unidimensionality of the scale and the "value" of FIM scores

The Functional Independence Measure (FIM) is one of the most widely used disability and dependence assessment instruments in rehabilitation medicine. As for other similar scales, the expression of results as a unique score raises an important question. Is it legitimate to consider the object being measured (functional independence) as a unidimensional entity? The answer is of major practical importance in justifying the use of the FIM. Having made a critical analysis of the previous validation procedures, the authors then submitted admission FIM items of 127 consecutive patients admitted in a French rehabilitation unit to different multidimensional statistical methods in order to analyse the structure of the FIM. Their findings demonstrate the multidimensional nature of the phenomenon assessed by the scale. This observation raises the question of the relevant use of the FIM total score, currently too widely applied without sufficient precaution, and suggests that preferably subscores should be used.     

Clinical predictors of injuries not identified by focused abdominal sonogram for trauma (FAST) examinations

This study's objective was to identify clinical characteristics of patients with a blunt traumatic injury that increased the risk of peritoneal or pericardial fluid collections and abdominal organ injuries not identified by a bedside focused abdominal sonogram for trauma (FAST) examination. This observational study used a retrospective chart review of a cohort of patients identified through a query of the University of Nebraska Medical Center's trauma registry, a tertiary referral center for portions of Nebraska, Iowa, and Missouri. Adult patients presenting to the Emergency Department (ED) for an evaluation of blunt traumatic injury from September 1996 to December 2002 were eligible if their ED course included admission to the trauma service after completion of a bedside FAST examination (US) and a confirmatory study (Conf) such as an abdominopelvic computed tomography scan or exploratory laparotomy within 12 h of completion of the ED FAST examination. The medical records of those patients with a US+/Conf+ or US-/Conf+ examination were reviewed. Clinical characteristics were recorded on a standard data collection form. Statistically significant predictors of a US-/Conf+ examination were found using a stepwise logistic regression procedure. A query of the trauma registry for the study period revealed 1453 adult individuals with blunt abdominal trauma, with 458 patients meeting the inclusion criteria. The clinical characteristics of the 79 US+/Conf+ examinations were compared to those of the 53 US-/Conf+ examinations. The presence of a radiographically proven pelvic fracture (odds ratio 3.459; 95% confidence interval of 1.308-9.157) and a radiographically or operatively proven renal injury (odds ratio 3.667; 95% confidence interval of 1.013-13.275) were found to be significant predictors. The presence of a pelvic fracture or renal injury in adult victims of blunt abdominal trauma increases the likelihood of a US-/Conf+ examination. Patients with a negative FAST examination and pelvic fracture may benefit from additional radiographic or operative evaluations for occult injuries.     

热致相分离法制备聚羟基丁酸酯-羟基戊酸酯纳米纤维支架及其表征

背景:由微生物合成的聚羟基丁酸酯-羟基戊酸酯(polyhydroxybutyrate-hydroxyvalerate,PHBV)是聚羟基脂肪酸酯的一种,具有良好的生物相容性和机械强度。目的:探讨热致相分离法制备PHBV纳米纤维支架的方法及结晶行为。方法:采用扫描电镜、广角X射线衍射、红外光谱和差示扫描量热分析分析基质的结构。结果与结论:凝胶温度对纳米纤维的结晶和热性质有很大的影响。当凝胶温度较高时,PHBV纳米纤维的结晶度和晶粒尺寸随着凝胶温度的降低而减小,而且随着凝胶温度的降低,其结晶的有序性增加。说明温度对PHBV支架形貌和结构的影响可能对PHBV支架的性质-包括生物降解性和对细胞活性的生物应答反应有一定的积极意义。     

Determination of the minimal clinically important difference in the FIM instrument in patients with stroke

OBJECTIVE: To define the minimal clinically important difference (MCID) for the FIM instrument in patients poststroke. DESIGN: Prospective case series discharged over a 9-month period. SETTING: Long-term acute care hospital. PARTICIPANTS: Patients with stroke (N=113). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Admission, discharge, and change scores were calculated for the total FIM, motor FIM, and cognitive FIM. Assessments of clinical change were rated at discharge on a 15-point (-7 to +7) Likert scale by attending physicians, with MCID defined at a cutoff score of 3. The FIM change scores associated with MCID were identified from receiver operating characteristic curves. Bayesian analysis was used to determine the probability of individual patients achieving MCID. RESULTS: FIM change scores associated with MCID were 22, 17, and 3 for the total FIM, motor FIM, and cognitive FIM, respectively. The accuracy of the MCID was greater when subjects were categorized based on admission FIM scores than when considering the sample as a whole. Larger FIM change scores were related to MCID in subjects with lower admission FIM scores. CONCLUSIONS: These findings will assist in the interpretation of FIM change scores relative to physicians' assessments of important clinical change.     

An inter-rater reliability study of the Functional Assessment Measure (FIM + FAM)

There is an increasing demand for measures of outcome to evaluate the effects of rehabilitation interventions for brain injury from clinicians, research workers and healthcare providers and purchasers. The Functional Assessment Measure (FIM + FAM), an expanded derivative of the Functional Independence Measure (FIM), is designed specifically for this purpose for this patient group. This study examined the inter-rater reliability of the FIM + FAM between two independent raters, a physician and a nurse, the subjects being 30 in-patients in a neurological rehabilitation unit. The results show that the inter-rater reliability was good (kappa values 0·50 to 0·95) for all but one of the 30 items rated on the FIM + FAM. The exception (with a kappa value of 0·35) was ‘adjustment to limits’. Higher agreement was found for rating of physical activities than for cognitive, communication and behavioural items.     

Comparison of changes in abdominal muscle thickness between standing and crook lying during active abdominal hollowing using ultrasound imaging

To determine if transversus abdominis (TrA) demonstrates a greater increase in thickness on lower abdominal hollowing (LAH) in standing compared to crook lying.Muscle thickness measurements of TrA, addition of internal obliques (IO) and external obliques (EO) were measured using ultrasound imaging at rest and during LAH on 28 healthy controls (14 female, 14 male) in crook lying and standing.TrA demonstrated greater thickness changes on LAH in standing (+0.88 mm ± 0.12 mm). IO and EO demonstrated greater thickness changes on LAH in crook lying (+0.59 mm ± 0.08 mm and ?0.87 mm ± 0.12 mm, respectively). These differences were all significant (p < 0.001). Increased resting thickness was noted in standing in TrA (20.7%), IO (10.3%) and EO (1.2%). This increase was only significantly different between TrA and EO (P = 0.004).TrA showed significantly greater increases in thickness on LAH in standing compared to crook lying, and with greater specificity in relation to IO and maybe EO. If muscle thickness can be an indicator of muscle function or activity, then this suggests that TrA rehabilitation should be facilitated in positions of greater function, such as standing.     

First-in-Man (FIM) clinical trials post-TeGenero: a review of the impact of the TeGenero trial on the design, conduct, and ethics of FIM trials

A recent first time in man (FIM) trial of an "immuno modulator" compound (TGN1412) resulted in unprecedented toxicity. Since this occurred in 2006 a widely publicized scientific debate, as well as a controversy in the lay community has examined the principle of design and content of the study as well as the concept of FIM studies.This paper reviews the controversy, analyzes the problems of the TGN1412 trial and FIM trials in general and the reaction of the lay and scientific communities. Difficulties in these high risk trials is highlighted and possible design and execution procedural improvements are recommended. Consideration is given to the ethical debate regarding participation of normal, healthy research volunteers in FIM studies. The role of monetary incentive(s) is discussed as well as the opposition of many participants in this debate on financial compensation of volunteers for the assumption of risk and the need to adopt a no-fault scheme that fairly compensates injured trial participants.FIM studies are critical for the development of new therapeutic agents. Improving trial design and execution and fairly compensating volunteers will facilitate these studies, enhance equity and thus provide an ethical basis for continuing FIM studies that may pose a serious risk to participants, a risk that society needs taken for the development of needed therapeutic agents.     

Assessment of the unilateral pulmonary function by means of electrical impedance tomography using a reduced electrode set

The usefulness of electrical impedance tomography (EIT) to assess ventilation-related phenomena in the thorax has already been demonstrated, especially in controlled environments. We focus on our developments in the assessment of the unilateral pulmonary function (UPF) in real clinical environments. The impact of the reduction of the number of electrodes used is analysed theoretically and experimentally with different approaches. Sixteen-electrode EIT measurements were performed on a group of lung cancer patients (19 M, 2 F, ages 25-77 years). Results are compared with those obtained from ventilation scintigraphy. Eight-electrode measurements were synthesized from the 16-electrode ones. The Bland and Altman analysis indicates an agreement of about +/- 1 percent points in the estimation of UPF. On five of these patients real 8-electrode measurements were performed, obtaining differences from 0.2 percent to 6 percent points. It is concluded that reducing the number of electrodes does not adversely affect the assessment of UPF, but there is a reproducibility issue affecting all the techniques which needs further study.     

Interobserver reliability of the "Functional Independence Measure" (FIM) in patients with craniocerebral injuries

This study was conducted to examine the inter-rater reliability of the "Functional Independence Measure" (FIM). The FIM is an assessment to determine the functional independence of patients with disabilities. It consists of eighteen items to assess activities of daily living. The degree of independence is measured by a seven point ordinal scale. The inter-rater reliability was examined by a convenience sample of 128 assessments with the FIM. Fifteen nurses assessed thirty patients with brain injuries in a centre for rehabilitation. The design was correlational. The degree of agreement between the assessments was calculated by Cohen's Kappa coefficients. The Kappa coefficients of the assessments were between kappa = 0.56 and kappa = 0.78; the median of the Kappa coefficients is kappa = 0.65. This indicates a moderate to high inter-rater reliability of the FIM when used by nurses for the assessment of patients with head injuries.     

Determination of Cole parameters in multiple frequency bioelectrical impedance analysis using only the measurement of impedances

Conventional bioimpedance spectrometers measure resistance and reactance over a range of frequencies and, by application of a mathematical model for an equivalent circuit (the Cole model), estimate resistance at zero and infinite frequencies. Fitting of the experimental data to the model is accomplished by iterative, nonlinear curve fitting. An alternative fitting method is described that uses only the magnitude of the measured impedances at four selected frequencies. The two methods showed excellent agreement when compared using data obtained both from measurements of equivalent circuits and of humans. These results suggest that operational equivalence to a technically complex, frequency-scanning, phase-sensitive BIS analyser could be achieved from a simple four-frequency, impedance-only analyser.     

Influence of electrode impedance changes on the common-mode rejection ratio in bioimpedance measurements

Bioelectrical impedance in vivo measurements suffer from many potential sources of error due to the patient-instrument interface. The total common-mode rejection ratio (CMRR(T)) was investigated experimentally for three measurement channel circuit versions, including electrode-skin impedance imbalance. The first version was of the 'classical' type. The second one makes use of a differential filter at the input of the instrumentation amplifier. The third circuit was a frequency-converting structure, where the signal was demodulated before being amplified. The differential demodulator was based on synchronous sampling using floating capacitors. The experiments were accomplished with simulated imbalance of the real and imaginary parts of electrode-skin impedances. To reduce unwanted common-mode voltage, a differential accurately balanced current source was used. Considering an application in impedance cardiography, the experiments were carried out at a single frequency of 40 kHz. The results showed the advantage of the circuits using frequency conversion and differential input filter, rendering at least 15 dB higher CMRR(T). The most significant reduction of CMRR(T) resulted from imbalance of the capacitance component of voltage-sensing electrode impedances. The third circuit showed an unexpected behaviour of CMRR(T) improvement with higher imbalance of the electrode-skin impedance resistance component.