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W S Jordan

Publications and source records attributed to W S Jordan.

At least 19 recordsLinked to original sources
PubMed1992

Microprocessor-based near real-time bedside blood chemistry monitor.

A microprocessor-based instrument which integrates the function of a volumetric infusion pump with a blood chemistry analyzer has been developed. Presently, the instrument is capable of measuring Na+, K+, Ca++ and pH within approximately 40 sec at a frequency of up to every 2 min. The system is set up as an intravenous (IV) infusion pump with the addition of an array of disposable sensors placed at the distal end of the IV set. An isotonic IV solution is used to keep the site patent while also serving as a calibrant for the sensors. The instrument first calibrates the sensors, then withdraws approximately 0.6 ml of blood to come in contact with the sensors. Within approximately 15 sec, it displays the results, flushes the blood back into the patient and resumes normal infusion. There is no blood loss to the patient and no need to handle blood. The system was first validated with known aqueous controls and then used on-line in a variety of animal studies where dynamic fluctuation of electrolytes and pH occurred. Excellent correlation was found with off-line samples tested on conventional STAT analyzers. Some preliminary patient data is also presented.

Animals↗
PubMed1991

Comparison of tidal ventilation and high-frequency jet ventilation before and after cardiopulmonary bypass in dogs using two-dimensional transesophageal echocardiography.

This study compared the use of high-frequency jet ventilation (HFJV) and tidal ventilation (TV) in a group of dogs with induced global myocardial ischemia before and after cardiopulmonary bypass. Transesophageal echocardiography was used to determine whether HFJV with its lower airway pressures could improve cardiac performance. The surgical procedure was separated into four study periods: closed chest before bypass, open chest before bypass, open chest after bypass, and closed chest after bypass. During each of these study periods, the dogs were randomly ventilated with alternate periods of TV and HFJV to maintain the PaCO2 at 34.3 +/- 3.3 mm Hg (mean +/- SEM). Cardiac output, stroke volume, systemic mean blood pressure, left ventricular ejection fraction, left ventricular end-diastolic volume, left ventricular dP/dt, left ventricular stroke work, and expiratory volumetric flows were higher during HFJV, whereas airway pressures and pulmonary vascular resistance were lower. Increases in cardiac output and stroke volume during HFJV were due to a combination of improved left ventricular contractility indicated by increased LV dP/dt and increased left ventricular end-diastolic volume accompanying decreased airway pressures. These data indicate that HFJV with its lower airway pressure is associated with significantly less impairment of cardiovascular function than TV in dogs with induced global myocardial ischemia.

Animals↗
PubMed1991

A system for automatic feedback control of plasma potassium concentration.

A system is described for automatic feedback control of plasma potassium concentration in experimental animals. Plasma potassium was monitored continuously and the signal compared with the desired plasma potassium concentration. The resulting error signal controlled the infusion rates of a concentrated potassium chloride solution (50 or 200 mmol litre-1) and a solution of 50% glucose with insulin 200 u litre-1. Plasma potassium was increased or decreased to the desired concentration at various rates, dictated by the controller constants. Increases were achieved significantly faster than reductions. The system may prove useful for elucidating the fate of infused potassium and for determining the optimum rate of insulin infusion in hyperkalaemia. If adapted for clinical use, it may find applications in the management of various abnormalities of potassium homeostasis.

Animals↗
PubMed1988

Heparinization of samples for plasma ionized calcium measurement.

Maintenance of normal plasma ionized calcium concentration forms part of the management of the critically ill patient; it is, therefore, important to measure accurately plasma ionized calcium. We have compared the ionized calcium concentration of blood samples heparinized with a carefully measured amount of heparin with that of blood samples heparinized in the conventional fashion. The amount of heparin in the deadspace of a syringe was demonstrated to artifactually lower the plasma ionized calcium concentration. Samples for plasma ionized calcium measurement should be heparinized with a measured quantity of heparin, since the conventional technique introduces an unknown and probably excessive quantity of heparin into the syringe deadspace.

Animals↗
PubMed1987

A collaborative report: rhinoviruses--extension of the numbering system from 89 to 100.

To define the number of rhinovirus serotypes, cross neutralization tests and characterization studies were completed on 25 candidate prototype rhinoviruses submitted to a third phase of a collaborative program. Based on the results, 11 distinct prototype strains were designated and the numbering system was extended to include 100 rhinoviruses. In addition, recent evidence indicates that over 90% of rhinoviruses isolated in three areas of the country could be typed with antisera for rhinovirus types 1-89.

Neutralization Tests↗
PubMed1986

Computer applications in intravenous anaesthetic administration.

The place of computerization in intravenous anaesthesia delivery: Although total intravenous anaesthesia may have advantages over inhalational anaesthesia in certain circumstances, it has drawbacks from the point of view of feedback control. The ideal agent is not available, although di-isopropylphenol holds promise. There is an undefinable end-point. Inadequate dosage produces the extremely unpleasant phenomenon of intra-operative awareness. Future developments, it seems, should include the development of suitable intravenous agents and transducers of anaesthetic depth, rather than increasingly complicated control systems. It is extremely unlikely that a computer will replace the anaesthetist in the foreseeable future. The anaesthetist is still required for, amongst other things, specifying the desired depth of anaesthesia and varying it during the operation, and for responding to unforeseen crises. It may be hoped that, by liberating the anaesthetist from those tasks which can be automated, more time can be devoted to patient monitoring and other aspects of anaesthetic care, thereby improving patient safety. There is an undoubted place for computerized delivery of anaesthesia in teaching (particularly teaching pharmacokinetic principles) and in research (for standardization of anaesthetic depth).

Analgesics, Opioid↗
PubMed1983

Uptake of enflurane: a study of the variability between patients.

Variability in the uptake of enflurane has been studied using a computer-controlled "overpressure" induction technique in 23 paediatric patients. The administration of enflurane was feedback-controlled and its uptake measured using a closed anaesthesia delivery system with the end-tidal concentration held constant at 2.0%. The standard deviation in uptake was greater than 28% of the average uptake during the first 60 min of enflurane anaesthesia. The uptake at 60 min ranged from 5.7 to 16.2 ml min-1 m-2. The variability in enflurane uptake between patients was best minimized by normalizing the patient's uptake according to body surface area. Although the average total volume of enflurane calculated according to a model compared well with the average total volume given in our study, the variation in uptake between patients indicated that a single model cannot be used to deliver anaesthesia to a varied patient population. The system described in this paper demonstrates the feasibility of using feedback control of fresh gas delivery for the automatic control of an "overpressure" induction technique.

Adolescent↗
PubMed1983

Monitoring anesthetic vapor concentrations using a piezoelectric detector: evaluation of the Engstrom EMMA.

The Engstrom anesthetic gas analyzer (EMMA) was evaluated to determine the reproducibility, response time, gas interference, water vapor dependence, and sensitivity. The analyzer also was evaluated clinically in 20 children undergoing orthopedic surgery. Difference between the analyzer output and anesthetic gas standard (reproducibility) ranged from 0.013 +/- 0.008 vol % to 0.018 +/- 0.018 vol %. Response times decreased from 710 ms at 5 l X min-1 to 149 ms at 30 l X min-1. Nitrous oxide caused an offset of +0.11 +/- 0.007 vol %. Water vapor caused positive offsets of 0.25 +/- 0.044 vol %, 0.51 +/- 0.027 vol %, and 0.80 +/- 0.037 vol % at 25 degrees C, 30 degrees C, and 34 degrees C, respectively. The analyzer reproducibly measured dry gas concentrations, but compensation had to be made for water vapor when measuring wet gases. The analyzer's usefulness for end-tidal monitoring was questioned because of its slow response time and its sensitivity to water vapor.

Anesthesiology↗
PubMed1983

Differential lung ventilation after unilateral hydrochloric acid aspiration in the dog.

Differential lung ventilation (DLV) may be necessary in the supportive care of patients with severe unilateral or asymmetrical lung disease. The best method for allocating tidal volume between the 2 lungs is unknown. Eighteen mongrel dogs were given a unilateral hydrochloric acid (HCI) aspiration injury. A computer-controlled differential lung ventilation system was used to ventilate 6 dogs with equal volumes in each lung, 6 dogs with equal end-inspiratory pressure in each lung, and 6 dogs with equal end-tidal CO2 fraction in each lung. The computer allocated volume between the 2 lungs by these 3 schemes on a breath-by-breath basis and maintained PaCO2 at 35 torr and total tidal volume at 15 ml/kg. Oxygen tension fell and pulmonary venous admixture increased after aspiration. There were no differences in gas exchange among the groups. Without PEEP, differential partitioning of tidal volume is of little consequence in differential lung ventilation of asymmetrical injuries.

Animals↗
PubMed1983

Feedback control of enflurane delivery in dogs--inspired compared to end-tidal control.

A technique was studied for the rapid induction of anesthesia in a closed rebreathing circuit using feedback control of end-tidal enflurane concentration. This technique was compared to anesthetic induction using a constant inspired concentration. In one group of seven dogs, end-tidal enflurane concentration was maintained at 2.0%. Electronic feedback control automatically decreased the inspired concentration from a maximum of 3.7% to 2.1% during a 4-hr period. In the second group of seven dogs, the inspired enflurane concentration was 2.0% throughout the study. There was no statistically significant difference between the two groups with regard to enflurane uptake, heart rate, blood pressure, or cardiac output. Enflurane uptake was higher in the first group only during the first 6 min after induction. The induction technique that used feedback control to automatically adjust the inspired enflurane concentration appeared to have no adverse cardiovascular effects beyond those present during an induction using a constant inspired concentration.

Anesthesia, Inhalation↗
PubMed1982

A microprocessor based feedback controller for mechanical ventilation.

A microcomputer feedback system has been developed which adjusts the inspired minute volume of a ventilator based on the patient's end-tidal CO2 concentration. The feedback controlled ventilator was evaluated in 6 dogs (18-20 kg). Arterial PCO2 was monitored continuously while end-tidal CO2 concentration was controlled by the micro-computer system and the following perturbations introduced: [1] NaHCO3 was infused IV, [2] a pulmonary artery was occluded, [3] one lumen of a double lumen endobronchial tube was occluded, and [4] an air embolism was given. The end-tidal PCO2 controller kept PaCO2 within 1.2 mm Hg of the desired value when CO2 production increased by as much as 44%. Changing the ventilation/perfusion ratios caused differences as large as 22 mm Hg between the arterial and end-tidal PCO2 and the controller was not effective in keeping PaCO2 at the desired level. Closed loop control of ventilation based on end-tidal PCO2 measurements successfully compensated for increases in CO2 production keeping PaCO2 constant. The controller did not, however, keep PaCO2 at the desired level when significant changes occurred in the distribution of blood flow to ventilation.

Animals↗
PubMed1981

In vivo continuous monitoring of ionized calcium in dogs using ion sensitive field effect transistors.

The authors have used calcium ion (Ca++) sensitive field effect transistor (ISFET) probes to monitor in vivo changes in Ca++ activity in the venous blood of dogs in response to infusions of sodium citrate or calcium chloride. During eight experiments, Ca++ activity changes were monitored in response to sodium citrate infusions simulating infusion of 1, 2, or 4 units of citrate preserved blood per 6 min. The ISFET probe recorded decreases in Ca++ activity during all infusions. Periodic serum samples were analyzed off-line using an in vitro ion selective electrode instrument. Analysis of variance showed no statistically significant differences between off-line sample and ISFET Ca++ activities (p greater than 0.05). A second experiment tested the use of the Ca++ ISFET as a control sensor for maintaining a desired Ca++ level. These studies provided a range of Ca++ activity values for comparison of off-line and ISFET values. Infusion rates of sodium citrate or calcium chloride needed to maintain venous Ca++ activity at 1.0 mEq/L or 3.0 mEq/L for periods of 30 min ranged from 440 to less than 1 mg/min during maintenance periods. Observation of hemodynamics during the calcium ion control maneuvers suggests that calcium ion may be used to improve cardiovascular performance during critical care situations that involve cardiovascular instability.

Animals↗
PubMed1979

A method for measurement of oxygen uptake in neonates.

The frequent use of continuous positive airway pressure and positive end-expiratory pressure in newborn infants with pulmonary disease has prevented the use of conventional methods for measuring oxygen uptake (VO2) in intensive-care units. A feed-back replenishment technique for the determination of the oxygen uptake of these newborn infants has been developed. An instrument utilizing this method has been designed and built permitting continuous VO2 monitoring without interfering in the routine ventilatory therapy of the critically ill infant. Theoretical, bench, and animal experiments using room air as an inspired gas indicate instrument accuracies as a percentage of full scale of 2.4, 2.8, and 7.3, respectively. Preliminary trials on infants demonstrate that the instrument functions satisfactorily in the newborn intensive-care unit.

Biomedical Engineering↗