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Biomedical subjects

R R Mitchell

Publications and source records attributed to R R Mitchell.

17 recordsLinked to original sources
PubMed2001

Health effects following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

Permanent approval of shot composed of tungsten-iron and tungsten-polymer for waterfowl hunting by the U.S. Fish and Wildlife Service was pending the results of the present study that examined the health and reproductive effects of the two shot types on mallards (Anas platyrhynchos) over a 150-day period. We collected data pertaining to the effects of tungsten-iron and tungsten-polymer shot on mortality, body weight, organ weight, tissue pathology, and shot erosion. Thirty-two bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) were dosed orally with eight #4 lead shot (positive control) on day 0 of the study. All lead-dosed ducks died by day 25, whereas no ducks died in the other treatment groups. Significant liver hemosiderosis was present in all control and tungsten-iron-dosed males, in five of eight control and three of eight tungsten-iron-dosed females, and in one tungsten-polymer-dosed male examined. The rate of shot erosion was highest for tungsten-polymer shot (99%), followed by tungsten-iron (72%), and steel (55%) shot. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not have deleterious health effects during the 150-day trial based on mortality, body weights, organ weights, and histology of the liver and kidneys.

Alloys↗
PubMed2001

Hematological effects and metal residue concentrations following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

The U.S. Fish and Wildlife Service required a chronic dosing study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult game-farm mallards (Anas platyrhynchos) prior to granting permanent approval of the shot for waterfowl hunting. Herein, we present the effects of tungsten-iron and tungsten-polymer shot on various hematologic parameters and metal residue concentrations in the femur, liver, kidneys, and gonads. Thirty-two-bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150 day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) received eight #4 lead shot (positive control) on day 0 of the study. Lead-dosed mallards had significantly decreased hematocrit, hemoglobin concentration, and whole-blood delta aminolevulinic acid dehydratase activity on day 7, as well as significant changes in a number of plasma chemistry parameters compared to ducks in the control, tungsten-iron, or tungsten-polymer groups. Mallards dosed with tungsten-iron or tungsten-polymer shot had occasional significant differences in hematocrit and plasma chemistry values when compared to control mallards over the 150 day period, but these changes were not considered to be indicative of deleterious effects. Low concentrations of tungsten were detected in gonad and kidney samples from males and females and in liver samples from females dosed with tungsten-polymer shot. Tungsten was also detected in femur samples from tungsten-polymer-dosed mallards. Higher concentrations of tungsten were detected in femur, liver, kidney, and gonad samples from tungsten-iron-dosed ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not cause adverse hematological effects during the 150 day trial. Concentrations of tungsten in the femur, liver, kidneys, and gonads were generally higher in tungsten-iron-dosed ducks when compared to tungsten-polymer-dosed ducks.

Animals↗
PubMed2001

Reproductive effects and duckling survivability following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

Tungsten-iron and tungsten-polymer shot were given conditional approval for waterfowl hunting by the U.S. Fish and Wildlife Service based partly on the results of a 30-day acute toxicity trial utilizing mallards (Anas platyrhynchos). Final approval of the two tungsten-containing shot was contingent on the results of a 150-day study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult mallards. Reproductive data are presented in this paper. Sixteen male and 16 female adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). Reproductive performance was assessed during the last 90 days (day 61 to day 150) of the trial. There were no significant differences in egg production and fertility and hatchability of eggs from tungsten-iron- and tungsten-polymer-dosed ducks compared to control ducks. There was no evidence of differences in percent survivability and body weight of ducklings from tungsten-iron and tungsten-polymer mallards compared to ducklings from control ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards during the 150 day trial did not adversely affect reproduction or their offspring.

Animals↗
PubMed2000

Comparison of postmortem techniques for the detection of Mycobacterium bovis in white-tailed deer (Odocoileus virginianus).

A retrospective study of various diagnostic postmortem techniques used in a 4-year surveillance program for detection of Mycobacterium bovis infection in wild white-tailed deer (Odocoileus virginianus) was conducted. The tests evaluated were routine histopathology, acid-fast staining, detection of acid-fast bacilli in culture, and an M. tuberculosis group-specific genetic probe applied to pure cultures. Each of these techniques were compared with a reference or "gold standard" of mycobacterial culture and identification. Histopathology, the most rapid form of testing for M. bovis infection in white-tailed deer samples, had a sensitivity of 98% and a specificity of 87%, resulting in a positive predictive value of 94%. The detection of acid-fast bacilli by staining was less sensitive than histopathology (90%), but its higher specificity (97%) resulted in a positive predictive value of 99%. The detection of acid-fast bacilli on culture was both highly specific (93%) and sensitive (100%). The group-specific genetic probe had the highest sensitivity and specificity and produced results in complete agreement with those of mycobacterial culture, suggesting that this technique could be used as the new "gold standard" for this particular wildlife tuberculosis surveillance program.

Animals↗
PubMed1988

A deep breath method for noninvasive estimation of cardiopulmonary parameters.

A specific ventilation pattern incorporating a single deep breath is used to demonstrate the possibility of estimating six cardiopulmonary parameters by measuring respiratory flow and expired oxygen and carbon dioxide concentrations at the mouth. Equations are derived from both alternating and continuous ventilation models of gas exchange which allow the six parameter estimates to be computed. The results indicate that pulmonary capillary blood flow, functional residual capacity, equivalent lung volume, mixed venous PO2 and PCO2, and pulmonary tissue plus capillary blood volume can be estimated in subjects with normal gas exchange. The use of a mechanical ventilator to provide a uniform ventilation pattern before and after the ventilator induced deep breath is the key to the methods simplicity. This allowed parameter estimates to be obtained which could then be analyzed for accuracy and precision. The feasibility of estimating these parameters, demonstrated by the present study, suggests that a recursive least squares estimation procedure could be used to recover the time variation of each parameter during exercise stress testing of subjects with normal or nearly normal gas exchange.

Blood Volume↗
PubMed1986

ICU monitoring of ventilation distribution.

The oxygen washin method has been shown to be a practical way to measure functional residual capacity (FRC) in the intensive care unit. The ventilator oxygen concentration is increased and measurements of respiratory flow and oxygen concentration at the mouth are made with the patient monitoring system. No additional personnel, bedside equipment or ventilator attachments are required. A feasibility study was performed to determine if this method could be used to estimate a continuous distribution of ventilation with respect to ventilation to volume ratio VA/V. Due to gas mixing in the ventilator, the inspired oxygen fraction does not increase instantaneously to its new value. An equation was derived which models the lung as 50 discrete compartments and accounts for the transient change in mean inspired oxygen fraction. A digital computer simulation demonstrated good distribution recovery for one and two mode ventilation distributions. Continuous distributions were computed for four post cardiac surgery patients at four levels of positive end expiratory pressure (PEEP). In these patients a linear increase in the amount of ventilation in the normal VA/V range occurred with increasing PEEP, i.e., slow and fast spaces tended to move centrally toward a more normal VA/V range. At zero PEEP 26% of the ventilation occurred in the normal range and this increased to 49% at 15 PEEP. Dead space fraction was poorly estimated and spurious modes occurred in the high VA/V range.

Cardiac Surgical Procedures↗
PubMed1982

Oxygen wash-in method for monitoring functional residual capacity.

Atelectasis, pulmonary edema, fibrosis, pneumothorax, and mucous plug airway obstruction all result in reduced lung volume. The oxygen (O2) wash-in method provides a way to monitor routinely the functional residual capacity (FRC) in the ICU without disconnecting the patient from the ventilator and without additional personnel or instrumentation. This method is a modification of an open-circuit nitrogen (N2) wash-out procedure and requires a computer-based respiratory monitoring system with a fast response O2 analyzer and respiratory flowmeter. FRC is computed after a 20% or greater change in the ventilator FIO2 setting. The accuracy and reproducibility of the method were evaluated using artificial lungs, normal subjects, and postcardiac surgery patients. FRC estimates by O2 wash-in and helium dilution were highly correlated, with r = 0.97 and a regression slope and zero intercept of 1.06 and -0.13, respectively. The FRC difference between 23 repeated trials in 18 postcardiac surgery patients was 70 +/- 160 ml (mean +/- SD).

Cardiac Surgical Procedures↗
PubMed1982

The need for closed-loop therapy.

The need for closed-loop control of blood pressure in acute hypertension after cardiac surgery was evaluated by estimating the amount of nurse-time required to adjust the infusion rate of sodium nitroprusside. The evaluation consisted of a nationwide telephone survey of head nurses in postsurgical ICUs at 9 institutions performing cardiac surgery. By nurse estimate, the average time spent adjusting the nitroprusside infusion rate was 26% of the time the patients were being infused. When calculated from a hierarchical list of questions, the average nitroprusside adjustment time was 16%. Assuming that a closed-loop controller would be accepted in these ICUs, they would be used 40% of the time that the nurse and patient are on a 1-to-1 basis. It was concluded that a technically acceptable control design exists for clinical use, that at the present time there is a need for such a controller, and that the controller would be accepted by the clinical staff.

Computers↗
PubMed1981

Influence of hematocrit and temperature on solubility of acetylene and dimethyl ether.

Estimation of pulmonary capillary blood flow (Qc) and tissue volume (Vt) by rebreathing acetylene (Ac) and dimethyl ether (DME) is dependent on the blood-gas partition coefficient (lambda) of these gases. We investigated the effects of hematocrit (Hct) and temperature on lambda. Human and canine blood was equilibrated at different Hct for 40 min at 37.5 degrees C with 1% Ac and 1% DME in air. Gas concentration in the headspace was measured by gas chromatography. lambda Ac increased with increasing Hct, suggesting a slight lipid affinity, whereas lambda DME decreased with increasing Hct, displaying the known blood-water content dependence. The influence of temperature on lambda in the range of 32--47 degrees C was investigated also. lambda Ac and lambda DME decreased as the temperature was raised, in accordance with the Gibbs-Helm-holtz equation. Empirical equations were derived to relate lambda to to Hct and temperature.

Acetylene↗
PubMed1979

Platelet turnover studies associated with left ventricular assist device (LVAD) implantation.

Calves given LVADs have been studied to determine changes in platelet turnover induced by the device and modified by time and anticoagulants. Passivation with time occurs but is surprisingly incomplete even one month later and despite coumadin, aspirin and dipyridamole. Without these drugs, enhanced platelet turnover and local thrombus formation on the device is exaggerated. Sequential platelet turnover studies may be useful to quantitate, monitor and/or predict thromboembolic events.

Animals↗
PubMed1979

Incorporating the gas analyzer response time in gas exchange computations.

A simple method for including the gas analyzer response time in the breath-by-breath computation of gas exchange rates is described. The method uses a difference equation form of a model for the gas analyzer in the computation of oxygen uptake and carbon dioxide production and avoids a numerical differentiation required to correct the gas fraction wave forms. The effect of not accounting for analyzer response time is shown to be a 20% underestimation in gas exchange rate. The present method accurately measures gas exchange rate, is relatively insensitive to measurement errors in the analyzer time constant, and does not significantly increase the computation time.

Carbon Dioxide↗
PubMedDate not supplied

Managing the data from respiratory measurements.

Clinical decisionmaking depends upon properly interpreting the significance of physiological and other clinical data. Our experience, summarized in six case studies, suggests that no one variable is sufficient for making clinical decisions. Rather, different parameters are relevant in different situations. This article summarizes two techniques for improving the effectiveness of clinical decisionmaking in the ICU using quantitative physiological monitoring data. First, mathematical modeling has been used for measuring the volume of gas in the lungs of patients receiving mechanical ventilation. The technique analyzes the transient response to oxygen change; thus it is suitable for routine use in the ICU. Second, symbolic processing has been used for interpreting the clinical significance of measured data. This symbolic processing is used for recognizing artifact in measured data, determining expected physiological meaning of measured data in different clinical situations, identifying physiological status, and identifying therapy that may be appropriate for meeting therapeutic goals or correcting physiological problems in patients in the intensive care unit.

Aged↗