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Biomedical subjects

R G Knapp

Publications and source records attributed to R G Knapp.

28 records · Page 2Linked to original sources
PubMed1986

Quantitative analysis of adenosine: statistical comparison of radioimmunoassay and gas chromatography-mass spectrometry-selected ion monitoring methods.

A new method for quantitating adenosine concentration by capillary gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM) has been developed and used as a reference method for evaluating a newly developed radioimmunoassay (RIA) for adenosine. Details of the GC-MS-SIM method are presented, along with the comparative results and uncertainties of both methods. General considerations in the statistical analysis of method comparison data are discussed with particular reference to studies using quantitative mass spectrometry as the standard method; the adenosine methods are used as specific examples in this discussion. Simultaneous estimation of the y-intercept and slope of the least squares regression line relating the results of the two methods using the 95% joint confidence ellipse demonstrated the absence of either constant or proportional error between the two methods. The relatively small uncertainty in the GC-MS-SIM measurements had no significant effect on the linear regression. Random error between the two methods was detected, and was estimated by the coefficient of variation in the RIA data as ten percent of the RIA value.

Adenosine↗
PubMed1985

A more appropriate statistical method for analyzing mortality data in shock research.

Much of biological research deals with analysis of survival times such as time until death of an organism, length of survival of a skin graft, time of remission of an illness, or time until relief of a particular symptom. When analyzing data that consists of time until occurrence of an event, the commonly used parametric t-tests for comparing mean survival times of treatment groups is inappropriate when 1) the survival times do not follow the bell-shaped Gaussian (normal) distribution and/or 2) when some of the organisms are still "alive" (censored) at termination of the study period. As an alternative to the t-test, a relatively simple-to-use statistical procedure for comparing survival times of two groups is described. This procedure was developed to deal specifically with data consisting of survival times and to take into account the presence of censored observations.

Animals↗
PubMed1985

Ibuprofen, methylprednisolone, and gentamicin as conjoint therapy in septic shock.

Septic shock is associated with increased metabolism of arachidonic acid to thromboxane A2 (TxA2) and prostacyclin (PGI2). The effects of ibuprofen, methylprednisolone-sodium succinate, and gentamicin alone, or in combination on survival time and, TxA2 and PGI2 production in rats in a LD100 fecal peritonitis shock model were assessed. Plasma levels of TxA2 and PGI2 were measured by radioimmunoassay of their stable metabolites immunoreactive (i) TxB2 and i6-keto-PGF1 alpha, respectively. Drugs were given 30 min before induction of fecal peritonitis. Survival times in hours were as follows: fecal peritonitis = 10.5 +/- 0.4 (n = 50); ibuprofen (15 mg/kg) = 16.1 +/- 0.8 (n = 8); methylprednisolone-sodium succinate (40 mg/kg) = 17.1 +/- 0.7 (n = 22); methylprednisolone-sodium succinate (80 mg/kg) = 46.1 +/- 10.4 (n = 25) with 8% long-term survivors (survival greater than 7 days); gentamicin (4 mg/kg) = 23.8 +/- 4.4 (n = 16); methylprednisolone-sodium succinate (40 mg/kg) + ibuprofen = 20.3 +/- 1.8 (n = 6); gentamicin + methylprednisolone-sodium succinate = 31.0 +/- 1.6 (n = 11); gentamicin + ibuprofen = 28.5 + 2.3 (n = 12); gentamicin + methylprednisolone-sodium succinate (40 mg/kg) + ibuprofen = 46.9 +/- 5.4 (n = 8). Treatment with the combination of gentamicin + ibuprofen + methylprednisolone-sodium succinate (80 mg/kg) resulted in a mean survival time of 116 +/- 13.9 h with 26% long-term survivors. Methylprednisolone-sodium succinate (40 mg/kg) reduced (P less than 0.05) plasma iTxB2 from 995 +/- 78 (n = 16) to 714 +/- 48 (n = 18) pg/ml and i6-keto-PGF1 alpha from 4,090 +/- 334 (n = 12) to 2,009 +/- 119 (n = 17) pg/ml, 4 h post-FP. Methylprednisolone-sodium succinate (80 mg/kg) produced no further decrease in either iTxB2 or i6-keto-PGF1 alpha. Ibuprofen reduced the fecal peritonitis-induced iTxB2 and i6-keto-PGF1 alpha synthesis to nondetectable levels (less than 200 pg/ml). The latter results demonstrate that methylprednisolone-sodium succinate is less effective than ibuprofen in inhibiting arachidonic acid metabolism and suggest other salutary actions. These composite observations provide evidence that conjoint therapy with steroidal and nonsteroidal anti-inflammatory agents, and antibiotics in septic shock may be beneficial.

6-Ketoprostaglandin F1 alpha↗
PubMed1983

Analytic procedures for evaluating health care. Statistical control charts.

The concern for quality of health care motivates evaluation programs designed to monitor the health care system, patient outcome, and provider expertise. An array of audit methods and instruments for evaluating professional and institutional performance has been developed. Although evaluation is viewed by many as the basis for accountability and improvement of health care, few are aware that most existing evaluation programs are really data-collecting systems. Very little if any, analysis of the data is done with the objective of optimizing the system. The "sampling with intervention" procedures often used to monitor the health care delivery system are primarily directed toward the individual patient while the system and provider continue to operate in the established mode. This article outlines analytic procedures for interpreting evaluation data generated by quality control and audit systems. Five common univariate statistical quality control charts are described.

Data Collection↗
PubMed1983

Monitoring simultaneously two or more indices of health care. Multivariate quality control procedures.

Often the data collected in a health care evaluation program consist of a number of indices, each of which represents a different component of a health care process. The question, "Is the health care process in control," to be answered effectively, must be answered in terms of the effect of the several indices considered jointly rather than in terms of each variable considered separately. This article describes the nature of the problem of monitoring jointly several indices of health care and presents two quality control methods, the control ellipse and Hotelling's T2, which are applicable to the multivariable setting. The discussion focuses on the case of monitoring simultaneously two related indices of health care, and extension of the two techniques to more than two indices is discussed briefly.

Factor Analysis, Statistical↗
PubMed1982

Effect of low carrier gas flows (50% oxygen/50% nitrous oxide) on inspired oxygen tension in anesthetized dogs.

Low carrier gas flows of 50% oxygen/50% nitrous oxide were evaluated with regard to their effect on inspired oxygen (PIO2) and carbon dioxide (PICO2) tension during maintenance inhalational anesthesia in dogs, using a circle-system anesthetic machine. A total flow rate of 15 ml/min/kg was associated with a PIO2 of 230 +/- 25 mm of Hg and a PICO2 of 0.4 +/- 0.4 mm of Hg after 4 hours of methoxyflurane anesthesia. End-tidal carbon dioxide, minute volume ventilation, and ventilation frequency did not change during the 4 hours. Lower total flow rates were associated with collapse of the reservoir bag, or a PIO2 less than 200 mm of Hg, or both.

Anesthesia, Inhalation↗
PubMedDate not supplied

Serum cholesterol--risk factor for coronary disease mortality in younger and older blacks and whites. The Charleston Heart Study, 1960-1988.

Serum total cholesterol (> or = 6.7 mmol/L) measured in 1960 in the Charleston Heart Study cohort was found to be a risk for mortality from coronary heart disease during the period of 1960 to 1988 in white men (relative risk [RR] 1.5; 95% confidence interval [CI]: 1.1, 2.2), white women (RR 1.7; 95% CI: 1.1, 2.7), and black women (RR 1.6; 95% CI: .9, 2.9) after age, systolic blood pressure, smoking status, education level, obesity, and diabetes were considered. For black men, the relative risk was .96 (95% CI, .39, 2.39). Only among white women was the relative risk (RR 2.4; 95% CI, 1.2, 4.5) increased among those in the older ages (55 to 74) in 1960. The evidence for cholesterol as a risk factor for coronary disease mortality in black men is inconclusive and requires further study.

Adult↗