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Biomedical subjects

J M Van de Water

Publications and source records attributed to J M Van de Water.

At least 19 recordsLinked to original sources
PubMed2005

Hemodynamic and pulmonary fluid status in the trauma patient: are we slipping?

Recent reports point to problems in the clinical assessment of the cardiopulmonary system in hemodynamically unstable patients, especially with the decreasing usage of pulmonary artery catheters. Our purpose was to evaluate the hypothesis that clinical judgment alone is inadequate for a reliable estimate of cardiopulmonary status in critically ill patients. Physician assessments (high, normal, or low) of cardiac index (CI) and thoracic fluid content (TFC) were made in 68 acute trauma cases and compared to the results obtained with impedance cardiography (ICG). Physician assessment using clinical judgment alone was correct only 42 per cent and 57 per cent, respectively, for CI and TFC. There was very little difference in heart rate (HR), blood pressure (BP), Glasgow Coma Score (GCS), and the number of injured systems between the incorrect and correct assessments of CI. However, the mean Injury Severity Score (ISS) was markedly higher for the incorrect than the correct CI values (18.8 +/- 9.3 vs 14.2 +/- 9.8, P = 0.0589). Thus, there is a need for an objective measurement of CI and TFC especially in the more severely injured patient. The inaccuracy of the clinical exam strongly suggests the need for a supplemental measurement, which the new and improved ICG monitor could provide.

Adult↗
PubMed1995

An advanced signal processing technique for impedance cardiography.

A new design using the latest technique in signal processing, the time-frequency analysis method, was developed to process impedance cardiography signals. This technique, when used to determine the relevant calculation parameters, was found to be more accurate than conventional methods. It was shown to be advantageous in reducing ventilation artifacts and motion noise, resulting in greater accuracy. Its cardiac output values had a much better correlation coefficient when compared in the clinical setting to the standard thermodilution technique than did the values from conventional impedance cardiography devices.

Cardiography, Impedance↗
PubMed1994

Multicenter trial of a new thoracic electrical bioimpedance device for cardiac output estimation.

OBJECTIVE: To evaluate the capacity of a new thoracic electric bioimpedance system to estimate cardiac output compared with the conventional thermodilution method. DESIGN: Prospective, multicenter study. SETTING: A university-run county hospital, a university-run U.S. Veterans Affairs hospital, and a university-affiliated U.S. military hospital. PATIENTS: A series of 68 critically ill patients whose conditions required pulmonary artery catheter insertion. MEASUREMENTS AND MAIN RESULTS: A total of 842 simultaneous pairs of cardiac output estimations by conventional thermodilution and a new thoracic electric bioimpedance system that uses an improved signal processing technique based on an all-integer-coefficient filtering technology, using a time-frequency distribution that provides a high signal/noise ratio were evaluated. The r value was .86, r2 = .74, and p < .001 by regression analysis; the mean difference between the two methods relative to their average value was 16.6 +/- 12.9 (SD) %; the precision was 1.4 L/min or 0.8 L/min/m2; the bias was -0.013 L/min. The mean difference between successive pairs of thermodilution measurements was 8.6 +/- 0.6 (SD) %, which was about half the difference between simultaneous pairs of measurement by the two methods. The changes in impedance estimations were close to simultaneously measured changes in thermodilution estimates of cardiac output. CONCLUSIONS: The new bioimpedance system satisfactorily estimated cardiac output as measured by the thermodilution technique. The difference between the two estimations is more than made up for by the continuous noninvasive capability of the impedance system.

Adult↗
PubMed1989

An impedance cardiography system: a new design.

An IBM compatible impedance cardiac output monitoring prototype system has been developed for use at the bedside on patients in the ICU, CCU, ER, Cath. Lab, and OR, etc. This impedance cardiographic (ICG) system, whose operation is completely technician-free, provides a continuous display with digital results and four channel color waveforms on an Enhanced Graphics Display screen. The software is written in C language with several special segments in assembly code where speed is essential. In this prototype system, a real-time algorithm was introduced to modify the ensemble averaging technique so that it averages nonperiodic signals such as: ECG, dZ/dT, delta Z, etc. Also, a real-time algorithm was developed to adaptively detect R spikes from conventional ECG signals. A signal preprocessor was developed to process signals digitally before any further work is done. This procedure reduces muscle noise, 60 Hz interference, and ventilatory movement. A special digital filter was designed to cope with the cases in which pacemakers are used. A special algorithm was also developed to further reduce the ventilation artifacts so that a period of apnea is unnecessary during the performance of the measurements. An anatomically specified electrode configuration has been defined enabling precise and reproducible positioning of the electrodes--hopefully leading to electrode standardization. At the present time, this prototype system has been compared with standard hand calculation and correlated with the clinical "gold standard," the Swan-Ganz thermodilution cardiac output. Using 144 sets of data from 10 healthy volunteers, 4 critically ill patients, and 8 healthy exercising volunteers, calculations of cardiac output were made using our system and the standard hand calculation of stroke volume, based upon Kubicek's equation; there was a relatively high and stable correlation: r = 0.93, p less than 0.005 (healthy); r = 0.94, p less than 0.002 (ill), r = 0.95, p less than 0.002 (exercise). From 20 patients at two different hospitals all with Swan-Ganz catheters in their hearts, 65 correlation studies between our system and the standard thermodilution technique were performed; the results were encouraging in terms of accuracy and consistency (r1 = 0.84, p less than 0.01, n = 10 CCU patients), and (r2 = 0.93, p less than 0.01, n = ICU patients). These results along with a growing body of data from other investigators indicate that this noninvasive and technician-free system for measuring cardiac output could have a significant role in patient care.

Cardiography, Impedance↗
PubMed1985

Vascular distensibility and vascular surgery.

The elastic property of an arterial wall decreases considerably with aging and/or with a variety of pathological conditions. The resulting decrease in vascular compliance has a profound physiological effect on arterial perfusion. The objectives of this study were to assess a quantitative measure of peripheral vascular distensibility (D), to apply it in some clinical conditions, and to establish a potential means of predicting success in vascular surgery for limb salvage. A technique described earlier by us for the determination of D based on an accurate measurement of volume change (delta V) with pressure change (delta P) was further analyzed and then tested in four groups: the first two were non-surgical, 18 normal subjects, and 23 hypertensive men paired with 22 normotensive men; the last two were surgical, patients undergoing aortofemoral bypass (AFB) operations for limb salvage (salvaged vs unsalvaged); and patients who underwent below-knee amputations (BKA) for severe arterial insufficiency (healed vs unhealed). The results indicate that D can be used as a reliable assessment of the pathophysiological status of the arterial system in the lower extremity; furthermore, D can be used as a predictor of success in at least two types of vascular procedures: AFB with profundoplasty for limb salvage and BKA for severe arterial insufficiency.

Adult↗
PubMed1980

Which deep breathing device should the postoperative patient use?

A study was undertaken to compare the use of three types of deep-breathing devices in patients undergoing upper-abdominal operations. Seventy-nine patients were divided into three groups, each receiving preoperative bedside testing of pulmonary function and instruction in the use of one of three randomly assigned deep-breathing devices thought to be representative of those currently available (Triflo II, Bartlett-Edwards Incentive Spirometer, or Spirocare). Repeat testing and instruction were provided daily during each of the first five postoperative days. There were few statistically significant differences in pulmonary function, vital signs and white blood cell count, and no difference in length of postoperative stay. No device was uniformly acceptable to patients, and none was used as frequently as recommended. When left at the bedside and only one daily reinforcement of instructions, the three devices showed no clinically important differences.

Adult↗