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Biomedical subjects

J R Jordan

Publications and source records attributed to J R Jordan.

23 records · Page 2Linked to original sources
PubMedDate not supplied

A shunt-excited inductive power link.

An alternative derivation of the separation-insensitive property of series-excited self-oscillating inductive power transfer circuits is presented. This analysis is based on network theory and does not include the explicit determination of frequency as a step in the derivation. The separation-insensitivity principle is extended to shunt-excited links which exhibit a theoretical voltage transfer function of unity while the coupling factor exceeds the reciprocal of the secondary quality factor. This requires the inclusion of a series resistor in the primary resonator's capacitive arm. Series RC elements are replaced by parallel forms in both the primary and secondary; this provides a more convenient output impedance level without the need for another transformer. A demonstration circuit is described and tested. It is found that separation-insensitivity occurs while the coupling factor exceeds the reciprocal of the loaded secondary quality factor. Somewhat inferior response is obtained from a simpler circuit having no added resistances in the primary.

Electronics, Medical↗
PubMedDate not supplied

Frequency and causes of discrepancy between Kt/V and creatinine clearance.

UNLABELLED: This study examines the frequency of discrepancy between Kt/V urea and creatinine clearance (Ccr) measurements in patients on peritoneal dialysis (PD) and the reasons for this discrepancy. DESIGN: Nonrandomized, retrospective data analysis. SETTING: Single PD unit of a university teaching hospital. PATIENTS: All adult patients receiving PD at our center from January 1995 to December 1996. METHODS: Actual (a) and desired (d) body weight (BW) were used to calculate urea volume of distribution (V) and body surface area (BSA). Patients were divided into four groups based upon their total small solute clearances (Kt/V and Ccr, normalized by actual weight) and three additional groups based upon actual/desired (a/d) body weight ratio. An additional analysis was performed for the subset of anuric patients. Data collected for all patients included the following: total Kt, total Ccr, 4-hour dialysate/ plasma (D/P) creatinine, serum albumin concentration, duration of PD, actual body weight, age, and height. RESULTS: Twenty-three percent of the clearance measurements in our study were discrepant, defined as having values for either Kt/V or Ccr (but not both) above the accepted targets of Kt/V > or = 2.0/wk and Ccr > or = 60 L/wk/ 1.73 m2. Patients with both values above target are more likely to have higher residual renal function. Patients who are significantly less than BWd and patients on PD for a longer time are more likely to have adequate Kt/V but not Ccr. Furthermore, patients who are less than 90% or greater than 110% of BWd have markedly different values for Kt/V and Ccr when BWa versus BWd values are used. CONCLUSIONS: Kt/V and Ccr values are frequently discrepant; a number of factors affect these two measurements to varying degrees, including weight, degree of residual renal function, and duration of PD.

Adult↗
PubMedDate not supplied

24-hour dialysate collection for determination of peritoneal membrane transport characteristics: longitudinal follow-up data for the dialysis adequacy and transport test (DATT).

OBJECTIVE: To determine the ability of the dialysis adequacy and transport test (DATT) to monitor changes in peritoneal transport characteristics over time. SETTING: University-based peritoneal dialysis program. PATIENTS: One hundred patients on continuous ambulatory peritoneal dialysis who underwent 226 simultaneous DATTs and peritoneal equilibration tests (PET). METHODS: Retrospective analysis of DATT and PET data. RESULTS: The mean 24-hour dialysate-to-plasma creatinine (cr) concentration ratio (D/P cr) from the DATT was 0.70 +/- 0.10, and the mean four-hour D/P cr from the PET was 0.68 +/- 0.10. The correlation coefficient between the four-hour and 24-hour D/P cr was 0.81, and the standard error of estimate was 0.065. The mean (+/- SD) difference between the four-hour and 24-hour D/P cr was 0.023 +/- 0.061. Fifty-eight patients had two or more sequential DATTs and PETs. For these 94 sets of sequential DATTs and PETs, the mean (+/- SD) difference between the change in the four-hour D/P cr and the change in the 24-hour D/P cr was 0.020 +/- 0.024, and the standard error of estimate was 0.064. In 17 patients a change in dwell volume from 2.0 L to 2.5 L occurred between the first and second measures of peritoneal membrane transport characteristics. The mean (+/- SD) difference between the change in the four-hour D/P cr and the change in the 24-hour D/P cr was 0.036 +/- 0.055, and the standard error of estimate was 0.087. CONCLUSION: The DATT can be used to monitor for changes in peritoneal transport over time. It should not be used in patients receiving cycler therapy or in patients whose dwell times and dextrose concentrations vary markedly from day to day.

Biological Transport↗
PubMedDate not supplied

An elevated ratio of measured to predicted creatinine production in CAPD patients is not a sensitive predictor of noncompliance with the dialysis prescription.

OBJECTIVE: To determine the effect a period of "intentional noncompliance" in stable continuous ambulatory peritoneal dialysis (CAPD) patients has on the ratio of measured to predicted creatinine generation. DESIGN: Prospective study that compares baseline to noncompliant periods in individual CAPD patients. PATIENTS: Nine chronic, stable CAPD patients. STUDY DESIGN: At baseline, measured creatinine production and adequacy parameters (KT/V, creatinine clearance, lean body mass, and protein equivalent of nitrogen appearance) were calculated from 24-hour collections of dialysate and urine while patients were performing their routine dialysis prescriptions. After three days of intentional noncompliance (one less exchange/day) the patients repeated their 24-hour collections, again performing their routine number of exchanges. Measured creatinine production and adequacy parameters were again calculated. Predicted creatinine production for each patient was calculated from standard equations. All parameters at baseline were compared to corresponding parameters after intentional noncompliance. RESULTS: In all patients, except one where there was no change, there was a statistically significant increase in not only the ratio of measured to predicted creatinine production but also all other parameters. CONCLUSION: As suspected by previous investigators, this study suggests that one cause of an elevated ratio of measured to predicted creatinine production may be a recent period of noncompliance with the patient's dialysis prescription. However, these data suggest that an isolated ratio of measured to predicted creatinine generation is not a sensitive predictor of noncompliance with the peritoneal dialysis prescription.

Adult↗