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S Schall

Publications and source records attributed to S Schall.

9 recordsLinked to original sources
PubMed1996

A PC-based ultrasonic data acquisition system for computer-aided prosthetic socket design.

A PC-based ultrasound data acquisition system has been developed which uses compound scanning techniques to image a residual limb in a water tank. From the received ultrasonic eco data, the system produces cross-sectional images and reconstructs a three-dimensional (3-D) model of the limb. A commercial software for computer-aided prosthetic socket design was modified so that it can display both the external shape and cross-sectional image of the limb and allow the prosthetist to perform socket design with the help of a visualization of the limb's internal structure. The image resolution and measurement accuracy of the system were tested using a wire phantom and a contrast tissue mimicking phantom, respectively. Preliminary results from amputee patients are presented and the sources of measurement error are discussed.

Computer-Aided Design↗
PubMed1991

Population pharmacokinetics of intravenous indomethacin in neonates with symptomatic patent ductus arteriosus.

The population pharmacokinetics of intravenous indomethacin were investigated with 665 indomethacin serum concentrations from 83 neonates (mean +/- SD: gestational age, 28.8 +/- 2.5 weeks; postnatal age, 5.7 +/- 4.7 days; birth weight, 1.13 +/- 0.40 kg) receiving indomethacin for symptomatic patent ductus arteriosus. A one-compartment open model was used for pharmacokinetic analysis. Hypotheses were tested to determine which developmental and demographic data influenced clearance (CL) and volume of distribution (V(area)). In the final regression equation CL and V(area) were modeled as a function of body weight and postnatal age (PNA) from 0 to 20 days. Final estimates were as follows: CL (ml/hr) = 2.63.weight (kg) + 0.244.PNA (days) and V(area) (L) = 0.28.weight (kg) + 0.0041.PNA (days). The coefficients of variation for interindividual variability in CL and V(area) were 77% and 28%, respectively. Intraindividual variability was 19%. These mean population parameter estimates should prove useful in designing dosage regimens to achieve desired indomethacin concentrations for neonates from 0 to 20 days of age with symptomatic patent ductus arteriosus.

Birth Weight↗
PubMed1991

Indomethacin pharmacokinetics in neonates: the value of volume of distribution as a marker of permanent patent ductus arteriosus closure.

Indomethacin (INDO) pharmacokinetics were examined in 18 neonates on 19 occasions, before and after patent ductus arteriosus (PDA) closure. Patients received INDO as an initial dose of 0.25 mg/kg intravenously, and INDO serum concentrations were measured 2 and 8 h after the dose. Subsequent doses were individualized based on clinical response, toxicity, and INDO pharmacokinetics. PDA status was confirmed echocardiographically at the start and end of therapy. INDO pharmacokinetic parameters varied from dose-to-dose within the same patient, and wide interpatient variability was also observed. Pre- and post-PDA closure, only INDO volume of distribution differed significantly (p less than 0.001) with mean values of 0.36 (+/- 0.06) L/kg and 0.26 (+/- 0.08) L/kg. The reason for this occurrence remains unclear. However, a new application for pharmacokinetics as a probe of physiology is demonstrated.

Biomarkers↗
PubMed1990

Indomethacin for patent ductus arteriosus closure. Application of serum concentrations and pharmacodynamics to improve response.

Indomethacin dosing for patent ductus arteriosus closure has been standardized despite wide interpatient variability in indomethacin pharmacokinetics. We compared a novel indomethacin dosing approach using individual pharmacokinetic and pharmacodynamic information (group A) with a control group from our institution (group B) and a level 3 university-based intensive care nursery (group C) who were dosed using current dosing guidelines. Permanent patent ductus arteriosus closure was achieved in 27 of 28 (96.4%) group A patients, 10 of 16 (62.5%) group B patients, and 7 of 13 (52.8%) group C patients. Success rates were significantly higher in group A than Groups B and C (P less than .02). Renal toxicity was the only toxicity reported in any group. The major manifestations of renal toxicity, ie, urine output below 1 mL/kg/h or increased serum creatinine by greater than or equal to 0.5 mg/dL, occurred in none of the group A patients but in seven (43.8%) group B and eight (61.5%) group C patients. Renal toxicity was significantly greater in groups B and C than group A (P less than .02). A pharmacodynamic concentration versus response curve was developed and proved predictive of patent ductus arteriosus closure rates in previous studies where indomethacin concentration versus response data were available. Serum concentration monitoring is a valuable adjunct to indomethacin therapy for patent ductus arteriosus closure, especially when a pharmacodynamic approach is used.

Algorithms↗
PubMed1977

Echocardiographic and hemodynamic relationships of ejection sounds.

The physiologic correlates of ejection sounds have been studied by simultaneous phonocardiograms, echocardiograms and high fidelity pressure tracings. Ejection sounds associated with semilunar valve stenosis or hypertension of the systemic or pulmonary circulation occur at the moment of complete opening of the aortic or pulmonary valve recorded echocardiographically. The start of opening of these valves occurs at the onset of the pressure rise in the corresponding great vessel and completion of valve opening always occurs on the pressure upstroke. The ejection sound in the presence of stenotic valves occurs with checking of the opening motion of the thickened valve cusps. Although the hypertensive ejection sounds also occur at the precise moment of full opening of the valve it remains to be seen whether this relationship is causal or coincidental.

Aorta↗