No increase in Kidney Injury Molecule-1 and Neutrophil Gelatinase-Associated Lipocalin excretion following intravenous contrast enhanced-CT.

OBJECTIVES: To analyze kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (N-GAL) excretion post-intravenous contrast enhanced-CT (CE-CT) in patients with chronic kidney disease (CKD). METHODS: Patients were enrolled in a trial on hydration regimes to prevent contrast-induced acute kidney injury (CI-AKI). Blood and urine samples were taken at baseline, 4 - 6, and 48 - 96 h post CE-CT. Urinary KIM-1 and N-GAL values were normalized for urinary creatinine levels, presented as medians with 2.5 - 97.5 percentiles. RESULTS: Of the enrolled 511 patients, 10 (2%) were lost to follow-up. CI-AKI occurred in 3.9% of patients (20/501). Median KIM-1 values were 1.2 (0.1 - 7.7) at baseline, 1.3 (0.1 - 8.6) at 4 - 6 h, and 1.3 ng/mg (0.1 - 8.1) at 48 - 96 h post CE-CT (P = 0.39). Median N-GAL values were 41.0 (4.4 - 3,174.4), 48.9 (5.7 - 3,406.1), and 37.8 µg/mg (3.5 - 3,200.4), respectively (P = 0.07). The amount of KIM-1 and N-GAL excretion in follow-up was similar for patients with and without CI-AKI (P-value KIM-1 0.08, P-value N-GAL 0.73). Neither patient characteristics at baseline including severe CKD, medication use, nor contrast dose were associated with increased excretion of KIM-1 or N-GAL during follow-up. CONCLUSION: KIM-1 and N-GAL excretion were unaffected by CE-CT both in patients with and without CI-AKI, suggesting that CI-AKI was not accompanied by tubular injury. KEY POINTS: • KIM-1 and N-GAL excretion were unaffected by intravenous contrast-enhanced CT (CE-CT). • Patient or procedure characteristics were not associated with increased KIM-1 or N-GAL excretion. • Performance of CE-CT in CKD patients is likely to be safe.

Abnormal surface EMG during clinically normal wrist movement in cervical dystonia.

We investigated whether patients with cervical dystonia (CD) have abnormal muscle activation in non-dystonic body parts. Eight healthy controls and eight CD patients performed a flexion-extension movement of the right wrist. Movement execution was recorded by surface electromyography (EMG) from forearm muscles. Although patients had no complaints concerning wrist movement and had no apparent difficulty in executing the task, they demonstrated lower mean EMG amplitude (flexor: 0.32 mV and extensor: 0.61 mV) than controls (flexor: 0.67 mV; P = 0.021 and extensor: 1.18 mV; P = 0.068; borderline significant). Mean extensor muscle contraction was prolonged in patients (1860 ms) compared with controls (1334 ms; P = 0.026). Variation in mean EMG amplitude over movements tended to be higher in patients (flexor: 43% and extensor: 35%) than controls (flexor: 34%; P = 0.072 and extensor: 26%; P = 0.073). These results suggest that CD patients also have abnormal muscle activation in non-dystonic body parts at a subclinical level. This would support the concept that in dystonia, non-dystonic limbs are in a 'pre-dystonic state'.

Electrical impedance tomography to measure pulmonary perfusion: is the reproducibility high enough for clinical practice?

A possible clinical application of electrical impedance tomography (EIT) might be to monitor changes in the pulmonary circulation, provided the reproducibility of the EIT measurement is adequate. The purpose of this study was threefold: the intra- and inter-investigator variability of repeated measurements was investigated. Three different regions of interest (ROI) were analysed to assess the optimal ROI. Twenty-four healthy subjects and six patients were included. The Sheffield applied potential tomograph (DAS-01P, IBEES, Sheffield, UK) was used. Electrodes were attached by investigator A, and duplicate EIT measurements were performed. After detachment and 45 min of rest, the protocol was repeated by another investigator B, and afterwards by the initial investigator A. Three ROIs were analysed: whole circle, 'inner half circle' and contour. The mean difference in impedance changes between observers is presented in arbitrary units (AU) +/- SD. Finally, the influence of age, body composition and sex on the EIT result was examined. For the contour ROI, the mean difference for the intra-investigator situation was -1.44 x 10(-2) +/- 18.45 x 10(-2) AU (-0.7 +/- 9.0%), and was 5.46 x 10(-2) +/- 21.66 x 10(-2) AU (2.7 +/- 10.8%) for the inter-investigator situation. The coefficient of reproducibility of the intra- and inter-investigator reproducibility varied between 0.89 and 0.97 for all ROIs (P < 0.0001). There is a relation between impedance change and age (correlation coefficient r = -0.63, P < 0.01 for contour ROI), and between impedance change and body mass index (BMI) (r = -0.53, P < 0.05). We found a significant difference in mean impedance change between groups of males and females. In conclusion, EIT results are highly reproducible when performed by the same investigator as well as by two different investigators.

Hemodialysis (HD) versus peritoneal dialysis (PD): latent overhydration in PD patients?

Data on the difference in fluid status between hemodialysis (HD) and peritoneal dialysis (PD) patients are scarce. Bio-electrical impedance analysis (BIA) is able to detect total body water (TBW) and its distribution in intracellular (ICW) and extracellular water (ECW). Echographic determination of the diameter of the inferior caval vein (VCD) provides information about the intravascular space (IVS). Nineteen PD-patients and 20 HD-patients in stable clinical condition were studied. In HD-patients a significant decrease in VCD, mean arterial pressure (MAP), TBW and ECW was noted due to ultrafiltration. Both ratios of VCD to ICW/ECW and of VCD to ECW/TBW decreased. No significant differences were found in these variables between PD-patients and HD-patients before HD. In both patient groups the measured variables pointed towards overhydration and the increased ratios both of VCD to ICW/ECW and VCD to ECW/TBW towards the storage of surplus of fluid in the intravascular space. It can be concluded that both PD-patients and HD-patients before HD have a surplus of fluid in the extracellular compartment, predominantly stored in the intravascular space.

The effect of profiled hemodialysis on intradialytic hemodynamics when a proper sodium balance is applied.

BACKGROUND: Profiled hemodialysis (HD) has been claimed to ameliorate intradialytic complications such as hypotension. Frequently, these profiles are based on providing the patient with an accumulating sodium load. This increases the risk of interdialytic complications, such as hypertension and increased weight gain. The present study investigated the effect of profiled HD, without an accompanying sodium loading, on intradialytic hemodynamics in stable HD patients. METHODS: In eight stable HD patients a standard hemodialysis (S-HD) was compared to a decreasing Na(+)-profiled hemodialysis (Na-HD), and an ultrafiltration profiled hemodialysis (UF-HD). Care was taken to have the sodium balances similar during these sessions. The patients were monitored non-invasively during dialysis with respect to their cardiac performance by means of electrical impedance cardiography, their variation in blood volume by means of an on-line optical measurement, and their hydration state by means of body impedance analysis. RESULTS: Sodium balance and mean arterial sodium concentrations were similar in the three treatments. Intradialytic hemodynamics during UF-HD were similar to those of S-HD. However, Na-HD improved blood pressure preservation, remarkably without significant blood volume preservation, due to a better stroke volume preservation in the first hour of dialysis. CONCLUSION: Sodium-balanced, Na-profiled HD improves blood pressure preservation in stable HD patients without providing the patients with a sodium load. This effect is due to a better stroke volume preservation early in dialysis, without a significant reduction in blood volume decrease. UF-HD, as mono-therapy, has no beneficial effect on intradialytic hemodynamics in stable patients.

Epoprostenol-induced pulmonary vasodilatation in patients with pulmonary hypertension measured by electrical impedance tomography.

Electrical impedance tomography (EIT) has been proposed as a method to monitor dynamic changes in the pulmonary vascular bed. In this study we examined the validity of EIT in the measurement of pulmonary vasodilatation in eight patients with primary and secondary pulmonary hypertension when given the vasodilating agent epoprostenol (Flolan). Therefore, catheterization of the pulmonary artery was performed in the ICU and the cardiac output was measured by means of the Fick method. The pulmonary vascular resistance (PVR) and mean pulmonary arterial pressure (mPAP) were determined. Epoprostenol was given in increasing doses to test reversibility of pulmonary hypertension. The maximum test dose was 12 ng kg(-1) min(-1). During each step simultaneous EIT (DAS-01 P Portable Data Acquisition System, Sheffield, England) measurements were performed with the 16 electrodes equidistantly positioned in the third intercostal space. The maximal systolic impedance change, relative to end-diastole, deltaZperf, was chosen as a measure of pulmonary perfusion. The impedance change between baseline and highest tolerable epoprostenol concentration was compared with the change in PVR. The mean PVR (dyn s/cm5) decreased from 636 (+/-399) to 366 (+/-242); p < 0.01. DeltaZperf (in arbitrary units) for the whole patient group increased from 901 (+/-295) x 10(-3) to 1082 (+/-472) x 10(-3) (p<0.05). Only one patient showed a reduction in pulmonary artery pressure >20%, which is defined as significant vasodilatation. A strong relationship was found between the impedance changes and the change in PVR and mPAP in the patient with a significant vasodilatation on epoprostenol. From these results we conclude that EIT is a reliable method to measure blood volume changes due to pharmacologically induced vasodilatation in the pulmonary bed.

Effects of ecological factors on the survival and physiology of Ralstonia solanacearum bv. 2 in irrigation water.

The fate of Ralstonia solanacearum bv. 2, the causative agent of brown rot in potato, in aquatic habitats of temperate climate regions is still poorly understood. In this study, the population dynamics and the physiological response of R. solanacearum bv. 2 were tested in sterile pure water and in agricultural drainage water obtained from waterways near potato cropping fields in The Netherlands. The behaviour of five different biovar 2 isolates in drainage water at 20 degrees C was very similar among strains. One typical isolate with consistent virulence (strain 1609) was selected for further studies. The effects of temperature, light, canal sediment, seawater salts, and the presence of competing microorganisms on the survival of strain 1609 were assessed. Moreover, the impacts of the physiological state of the inoculum and the inoculum density were analyzed. The population dynamics of strain 1609 in sterile pure water were also characterized. In sterile pure water, the fate of R. solanacearum 1609 cells depended strongly on temperature, irrespective of inoculum density or physiological state. At 4 degrees C and 44 degrees C, strain 1609 CFU numbers showed declines, whereas the strain was able to undergo several cell divisions at 12 degrees C, 20 degrees C, and 28 degrees C. At 20 degrees C and 28 degrees C, repeated growth took place when the organism was serially transferred, at low inoculum density, from grown water cultures into fresh water devoid of nutrients. Both at low and high cell densities and regardless of physiological state, R. solanacearum 1609 cells persisted as culturable cells for limited periods of time in drainage water. A major effect of temperature was found, with survival being maximal at 12 degrees C, 20 degrees C, and 28 degrees C. Temperatures of 4 degrees C, 36 degrees C, or 44 degrees C induced accelerated declines of the culturable cell numbers. The drainage water biota had a strong effect on survival at 12 degrees C, 20 degrees C, and 28 degrees C, as the persistence of strain 1609 was significantly enhanced in sterile drainage water systems. Furthermore, there was a negative effect of incident light, in a light:dark regime, on the survival of R. solanacearum 1609 in natural drainage water. Also, levels of seawater salts realistic for drainage water in coastal areas were detrimental to strain survival. Ralstonia solanacearum 1609 showed considerable persistence in canal sediment saturated with drainage water, but died out quickly when this sediment was subjected to drying. Evidence was obtained for the conversion of R. solanacearum 1609 cells to nonculturable cells in water microcosms kept at 4 degrees C, but not in those kept at 20 degrees C. A substantial fraction of the cells found to be nonculturable were still viable, as evidenced by the direct viable count and by staining with the redox dye 5-cyano-2,3-ditolyl tetrazolium chloride. The potential occurrence of viable-but-nonculturable cells in natural waters poses a problem for the detection of R. solanacearum by cultivation-based methods.

Diameter of inferior caval vein and impedance analysis for assessment of hydration status in peritoneal dialysis.

In 19 stable peritoneal dialysis (PD) patients, hydration status was evaluated by measurement of vena cava diameter (VCD) and bioelectrical impedance analysis (BIA) variables: intracellular water (ICW), extracellular water (ECW), and total body water (TBW). We investigated whether BIA can replace VCD. VCD did not correlate with TBW but correlated moderately with ECW/TBW (r = 0.42; 0.025 < p < 0.05) and ICW/ECW (r = -0.47; p < 0.025). Patients with underhydration (n = 4; VCD <8 mm/m2) revealed limits for BIA variables as ICW/ECW (>1.50) and ECW/TBW (<0.40). The same held true for overhydration (n = 5; VCD >11.5 mm/m2): ICW/ECW (<1.50) and ECW/TBW (>0.40). Although the positive predictive value of ICW/ECW and ECW/TBW for both under- and overhydration was only 50% and 54%, respectively, there were no false negative values. Although BIA cannot replace VCD in PD patients, the reverse holds true as well. Combining BIA and VCD may lead to a better estimation of hydration status because both techniques provide complementary information.

Determination of stroke volume by means of electrical impedance tomography.

ECG-gated electrical impedance tomography (EIT) is a non-invasive imaging technique, developed to monitor blood volume changes. This study is the first in comparing this non-invasive technique in measuring stroke volume with established techniques. The objective of this study was to validate EIT variables derived from the EIT images with paired obtained stroke volume measurements by thermodilution and MRI. After right cardiac catheterization, EIT measurements were performed in 25 patients. Regression analysis was used to analyse the relation between the EIT results and stroke volume determined by thermodilution. From the regression line an equation was derived to estimate stroke volume (in ml) by EIT. A strong correlation was found between EIT and stroke volume measured by the thermodilution method (r = 0.86). In a group of 11 healthy subjects this equation was validated to MRI. The mean and standard deviation of the difference between EIT and MRI was 0.7 ml and 5.4 ml respectively. These data indicate that EIT is a valid and reproducible method for the assessment of stroke volume.

The impact of equations on calculation of lean body mass by bioelectrical impedance analysis in RDT patients.

Several equations are available to derive lean body mass (LBM) from bioelectrical impedance analysis (BIA). The purpose of this study was to investigate in dialysis patients the impact of the equation used on the outcome of LBM assessment. To avoid dyshydration as a confounder, vena cava diameter measurement was used to assess normohydration in the 21 patients studied. Five equations were compared. In a previously published study to assess total body water using antipyrine as a gold standard, Deurenberg's formula was advocated to be used in the estimation of LBM by BIA. Therefore, this formula was used as a basis for comparison with the other four equations. One equation gave results comparable to those obtained by Deurenberg's formula. Despite high correlations and agreement according to Bland and Altman analysis, the other three equations showed a significant difference with Deurenberg-derived LBM. Thus, the equation used has a major impact on the outcome of LBM estimations.

Prediction of peak oxygen uptake in men using pulmonary and hemodynamic variables during exercise.

PURPOSE: Many attempts have been made to predict peak VO2 from data obtained at rest or submaximal exercise. Predictive submaximal tests using the heart rate (HR) response have limited accuracy. Some tests incorporate submaximal gas exchange data, but a predictive test without gas exchange measurements would be of benefit. Addition of stroke volume and pulmonary function (PF) measurements might increase the predictability of a submaximal exercise test. METHODS: In this study, an incremental exercise test (10 W x min(-1)) was performed in 30 healthy men of various habitual activity levels. Step-wise multiple regression analysis was used to isolate the most important predictor variables of peak VO2 from a set of measurements of PF: lung volumes, diffusion capacity, airway resistance, and maximum inspiratory and expiratory pressures; gas exchange; minute ventilation (V(E)), tidal volume (V(T)), respiratory exchange ratio (RER = carbon dioxide output divided by VO2); and hemodynamics (HR, stroke index (SI) = stroke volume/body surface area, and mean arterial pressure). These measurements were made at rest and during submaximal exercise. RESULTS: Using the set of PF variables (expressed as percentages of predicted), FEV1 explained 30% of the variance of peak VO2. No other PF variables were predictive. After addition of resting hemodynamic data, SI was included in the prediction equation, raising the predictability to 40%. At the 60-W exercise level, 48% of the variance in peak VO2 could be explained by SI and FEV1. At 150 W, the prediction increased to 81%. At this level VCO2/O2 (RER) also entered the prediction equation of peak VO2: 6.44 x FEV1(%) + 13.0 x SI - 1921 x RER + 2380 (SE = 142 mL x min(-1) x m(-2), P < 0.0001). Leaving out the gas exchange variable RER, maximally 64% of the variance in peak VO2 could be explained. CONCLUSION: In conclusion, inclusion of pulmonary function and hemodynamic measurements could improve the prediction accuracy of a submaximal exercise test. The submaximal exercise test should be performed until a level of 150 W is reached. Noninvasive stroke volume measurements by means of EIC have additional value to measurement of HR alone. Finally, measurement of gas exchange significantly improves the predictability of peak VO2.

Regional pressure volume curves by electrical impedance tomography in a model of acute lung injury.

OBJECTIVE: A new noninvasive method, electrical impedance tomography (EIT), was used to make pressure-impedance (PI) curves in a lung lavage model of acute lung injury in pigs. The lower inflection point (LIP) and the upper deflection point (UDP) were determined from these curves and from the traditional pressure-volume (PV) curves to determine whether the PI curves resemble the traditional PV curves. Furthermore, regional differences in the mentioned determinants were investigated. DESIGN: Prospective, experimental study. SETTING: Animal research laboratory. INTERVENTIONS: In nine anesthetized pigs, repeated lung lavage was performed until a Pao2 <80 torr was reached. Thereafter, an inspiratory PV curve was made using a constant flow of oxygen. During the intervention, EIT measurements were performed. MEASUREMENTS AND MAIN RESULTS: In this study, the LIP(EIT) was within 2 cm H2O of the LIP(PV). Furthermore, it was possible to visualize regional PI curves by EIT. No significant difference was found between the LIP(PV) (21.3+/-3.0 cm H2O) and the LIP(EIT) of the total lung (21.5+/-3.0 cm H2O) or the anterior parts of the lung (21.5+/-2.9 cm H2O). A significantly higher LIP (29.5+/-4.9 cm H2O) was found in the posterior parts of the lung. A UDP(PV) could be found in three animals only, whereas in all animals a UDP(EIT) could be determined from the anterior part of the lung. CONCLUSIONS: Using EIT, determination of LIP and UDP from the regional PI curves is possible. The obtained information from the regional PI curves may help in understanding alveolar recruitment. The use of this new bedside technique for clinical decision making remains to be examined.

Monitoring of recruitment and derecruitment by electrical impedance tomography in a model of acute lung injury.

OBJECTIVE: To evaluate a noninvasive system for obtaining information about alveolar recruitment and derecruitment in a model of acute lung injury. DESIGN: Prospective experimental study. SETTING: Animal research laboratory. SUBJECTS: Nine anesthetized pigs. INTERVENTIONS: Electrical impedance tomography measurements were performed. Electrical impedance tomography is an imaging technique that can register the ventilation-induced impedance changes in different parts of the lung. In nine anesthetized pigs, repeated lung lavages were performed until a PaO2 of <80 mm Hg was reached. Thereafter, the lungs were recruited according to two different recruitment protocols: the open lung approach and the open lung concept. Five time points for measurements were chosen: healthy (reference), lavage (atelectasis), recruitment, derecruitment, and maintain recruited (final). MEASUREMENTS AND MAIN RESULTS: After lavage, there was a significant increase in the impedance ratio, defined as the ventilation-induced impedance changes of the anterior part of the lung divided by that of the posterior part (from 1.75 +/- 0.63 to 4.51 +/- 2.22; p < .05). The impedance ratio decreased significantly after performing the recruitment protocol (from 4.51 +/- 2.22 to 1.18 +/- 0.51). During both recruitment procedures, a steep increase in baseline impedance change was seen. Furthermore, during derecruitment, a decrease in the slope in baseline impedance change was seen in the posterior part of the lung, whereas the anterior part showed no change. CONCLUSION: Electrical impedance tomography is a technique that can show impedance changes resembling recruitment and derecruitment of alveoli in the anterior and posterior parts of the lung. Therefore, electrical impedance tomography may help in determining the optimal mechanical ventilation in a patient with acute lung injury.

Survival of Ralstonia solanacearum Biovar 2, the Causative Agent of Potato Brown Rot, in Field and Microcosm Soils in Temperate Climates.

ABSTRACT After outbreaks of potato brown rot in three different fields in the Netherlands, the fate of the brown rot pathogen, Ralstonia solanacearum biovar 2, was monitored in soil by immunofluorescence colony staining (IFC) supported by R. solanacearum division-2 specific polymerase chain reaction. In selected areas of all fields, the R. solanacearum population densities were initially on the order 10(4) to 10(6) per g of topsoil. These population densities then declined progressively over time. In two fields, however, the pathogen persisted for periods of 10 to 12 months. The survival of a selected R. solanacearum biovar 2 isolate, strain 1609, in three soils, a loamy sand and two different silt loam soils, was further studied in soil microcosm experiments. The effects of temperature and soil moisture content were assessed. At 12 or 15 and 20 degrees C, a gradual decline of the population densities was observed in all three soils, from the established 10(5) to 10(6) CFU g(-1) of dry soil to significantly reduced levels, occasionally bordering the limit of detection (10(2) CFU g(-1)of dry soil), in periods of approximately 90 to 210 days. Soil type affected the rate of population decline at 20 degrees C, with the greatest decline occurring in loamy sand soil. In all three soils, the survival of IFC-detectable R. solanacearum 1609 cells at 4 degrees C was severely impaired, reflected in an accelerated decline of CFU counts, to undetectable numbers. Moreover, indications were found for the occurrence of viable but nonculturable strain 1609 cells in the loamy sand as well as in one silt loam soil under these conditions. In addition, a single freezing-thawing cycle caused a significant additional reduction of the culturable R. solanacearum 1609 populations in the three soils, though detectable populations remained. Moderate soil moisture fluctuations of approximately pF 2 did not affect the survival of R. solanacearum 1609 in soil. Severe drought, however, drastically reduced the populations of strain 1609 CFU in all three soils.

Electrical impedance tomography in the assessment of extravascular lung water in noncardiogenic acute respiratory failure.

STUDY OBJECTIVES: To establish the value of electrical impedance tomography (EIT) in assessing pulmonary edema in noncardiogenic acute respiratory failure (ARF), as compared to the thermal dye double indicator dilution technique (TDD). DESIGN: Prospective clinical study. SETTING: ICU of a general hospital. PATIENTS: Fourteen ARF patients. INTERVENTIONS: In order to use the TDD to determine the amount of extravascular lung water (EVLW), a fiberoptic catheter was placed in the femoral artery. MEASUREMENTS AND MAIN RESULTS: Fourteen consecutive ARF patients receiving mechanical ventilation were measured by EIT and TDD. EIT visualizes the impedance changes caused by the ventilation in two-dimensional image planes. An impedance ratio (IR) of the ventilation-induced impedance changes of a posterior and an anterior part of the lungs was used to indicate the amount of EVLW. For the 29 measurements in 14 patients, a significant correlation between EIT and TDD (r = 0. 85; p < 0.001) was found. The EIT reproducibility was good. The diagnostic value of the method was tested by receiver operator characteristic analysis, with 10 mL/kg of EVLW considered as the upper limit of normal. At a cutoff level of the IR of 0.64, the IR had a sensitivity of 93%, a specificity of 87%, and a positive predictive value of 87% for a supranormal amount of EVLW. Follow-up measurements were performed in 11 patients. A significant correlation was found between the changes in EVLW measured with EIT and TDD (r = 0.85; p < 0.005). CONCLUSION: We conclude that EIT is a noninvasive technique for reasonably estimating the amount of EVLW in noncardiogenic ARF.

Sleep complaints and sleep disordered breathing in hemodialysis patients.

BACKGROUND: The objective of the study was to determine the prevalence of sleep complaints and of sleep disordered breathing (SDB) in hemodialysis patients not selected for sleep complaints and to determine the effect of hemodialysis on SDB. The feasibility of home recording of sleep related respiration in these patients was also studied. METHODS: The patients completed a questionnaire and parameters of SDB were examined in the home setting on nights following dialysis and nights following no dialysis with the Edentrace II Recording System. RESULTS: Six (46%) of 13 patients had sleep complaints. Symptoms suggestive for sleep apnea syndrome were found in four (31%) of these 13 patients. In three (75%) of these four patients SDB was found. Sleep related respiration was monitored in 15 patients. Registrations satisfactory for interpretation were obtained in all patients. SDB was observed in five (33%) of these 15 patients. There were no significant differences in parameters of SDB between nights following dialysis and nights following no dialysis. CONCLUSIONS: Home recording of sleep related respiration in hemodialysis patients is feasible. Sleep complaints and SDB are common in these patients. No clinically significant differences in SDB were found between nights following dialysis and nights following no dialysis.

Evaluation of electrical impedance tomography in the measurement of PEEP-induced changes in lung volume.

STUDY OBJECTIVES: A new noninvasive practical technique called electrical impedance tomography (EIT) was examined for the measurement of alveolar recruitment. DESIGN: Prospective clinical study. SETTING: ICU of a general hospital. PATIENTS: Acute respiratory failure (ARF) patients. MEASUREMENTS: The ventilation-induced impedance changes (VICs) of the nondependent and the dependent part of the lung were determined by EIT as a measure of tidal volume distribution. By the use of an impedance ratio (IR), defined as the VIC of the nondependent part of the lung divided by the VIC of the dependent part of the lung, the ventilation performances in both parts of the lung were compared to each other. RESULTS: Between patients, the VIC of the nondependent part of the lung was significantly lower in the patients with a level of positive end-expiratory pressure (PEEP) of > 10 cm H2O than in patients with a PEEP of < 5 cm H2O (p < 0.05). A significantly lower IR (-/+ SD) was found in the group with PEEP of > 10 cm H2O than in the group with PEEP between 0 and 5 cm H2O (1.28+/-0.58 vs 2.99+/-1.24, respectively; p < 0.01). In individual patients, the VIC of the whole lung increased when the PEEP level was increased. The VICs of the nondependent part of the lung and of the dependent part of the lung showed significant increases at a PEEP of 10 cm H2O compared to a PEEP of 0 cm H2O (p < 0.05). Also the IR decreased in individual patients when the PEEP was increased; a significant decrease was found at 10 cm H2O compared to 0 cm H2O (1.67+/-1.24 vs 2.23+/-1.47, respectively; p < 0.05). CONCLUSIONS: The decrease in IR indicates an increase in VIC in the dependent part of the lung above the nondependent part of the lung. The increase in VIC can be regarded as an increase in lung volume, implying alveolar recruitment in the dependent part of the lung. The same results also have been shown in earlier reports by CT scan. Since EIT is far more practical than CT scanning and also is a bedside method, EIT might help in the adjustment of ventilator settings in ARF patients.

Noninvasive measurement of cardiac output: two methods compared in patients with mitral regurgitation.

In search for the origin of the less reliable cardiac output (CO) estimations by means of electrical impedance cardiography (EIC), the authors hypothesized that cardiac valve pathology might be one of the reasons. Twenty-six patients were examined by means of echo Doppler (ED) and EIC. The cardiac valve status was obtained by means of echocardiography and color Doppler flow, while CO was obtained by means of both methods. Seventeen patients had no valve pathology (nVP) while nine patients had mild to moderate mitral regurgitation (MVR). The overall correlation between the calculation of CO by means of the two methods was good (r = 0.85, p < 0.001, mean difference and standard deviation: 0.20+/-0.74 L/min), while there was no significant difference between the paired values. After division into an nVP and an MVR population, the results showed an even closer agreement between the CO values in the nVP population (r = 0.88, p < 0.001, mean difference and standard deviation: 0.15+/-0.68 L/min). Furthermore, significant differences were found in the first derivative of the impedance (dZ/dt) signals of these groups. Although the agreement between ED and EIC was slightly lower in the MVR population, EIC reliably estimated CO, even in case of MVR. The impedance signal itself gave an indication for the existence of MVR.

Non-invasive evaluation of left ventricular function by means of impedance cardiography.

BACKGROUND: Simple, accurate, continuous non-invasive cardiac monitoring during the peri- and postoperative periods for patients at risk of cardiac failure would be very useful. Electrical impedance cardiography (EIC) has been proposed as an accurate method for non-invasive measurement of cardiac function. However, in recent years the accuracy of EIC in stroke volume (SV) measurement has been questioned and this prevented global acceptance of the method. Beside SV, EIC is capable of measuring several other left ventricular contractility indices, which are measured directly from the impedance signal. The aim of this study was to compare these variables with the echocardiographically derived left ventricular wall motion score (WMS) as the reference method. METHODS: In a group of eight coronary artery disease patients we performed a pharmacologically (dobutamine) induced stress test. Echocardiographic and impedance cardiographic recordings were performed simultaneously during four levels of dobutamine infusion. WMS was derived from the simultaneously displayed four-stage echocardiographic image. RESULTS: Analysis of variance showed that the majority of indices changed significantly during the test. Direct correlation with the wall motion score gave very satisfactory results over all stages with the RZ time (r = 0.75, P < 0.001) and Heather index (r = -0.78, P < 0.001). Other correlations were substantially lower. CONCLUSION: The Heather index has to be preferred as indicator of the left ventricular performance. Since EIC is capable of giving continuous information of the left ventricular performance, it might be a valuable method for peri- and postoperative monitoring.