Biomedical subjects
Publications and source records attributed to V Fidler.
A mixed model is proposed for the two-period change-over clinical trial with binary responses. Tests for the treatment effect are derived under several versions of this model. This approach reveals the relative merits of tests previously described in the literature and leads to a new test for the carry-over effect.
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The rehardening properties of four saliva substitutes on artificially softened human enamel have been investigated by microhardness measurements. The saliva substitutes were all based on the same formula, containing calcium, phosphate and fluoride as the main electrolytes, and mucin or carboxymethylcellulose as the main macromolecules. It has been shown that a rehardening potential exists in the saliva substitutes when calcium and phosphate are present. Omitting F- greatly reduces the rehardening potential. The rehardening is better in case of the CMC-containing saliva than in that containing mucin.
Phase image analysis of blood pool scintigrams was performed in 6 patients with Wolff-Parkinson-White (WPW) syndrome to determine the relationship of phase changes and abnormalities of atrioventricular conduction. The site of preexcitation was located by invasive endocardial mapping. The phase advance generally correlated with the electrophysiologically determined location of the accessory pathway. Factors which increase or decrease the amount of preexcitation also increased or decreased the advance of mean phase angles. Phase imaging is a useful noninvasive means for tentative location of accessory pathways in WPW syndrome.
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The myocardial infarct size was assessed on the basis of serial analyses of serum creatine phosphokinase (CPK) in 70 patients with first transmural myocardial infarction. Clinical symptoms of heart failure (Killip II-III) were found in patients with infarcts larger than 50 CPK-g-equ; in patients with lung oedema the infarct size averaged 104.2 CPK-g-equ. Patients without clinical and roentgenological evidence of left heart failure (Killip I) had infarct sizes always lesser than 50 CPK-g-equ, averaging 31.7 CPK-g-equ. Precordial mapping of the QRS complex in patients with anterior wall infarction revealed a significant correlation (r = 0.916) between the sum of voltages of Q waves on a 30-lead map recorded 24 hours after hospitalization and the enzymically assessed infarct size. Exact skiagraphic and auscultatory examinations of the heart and lungs, together with precordial mapping of the QRS complex, in patients with anterior wall infarct allow a relatively accurate quantification of the infarct size for prognostic classification of the patients.
In the course of pregnancy, whole blood viscosity (WBV) decreases, plasma viscosity (PV) increases and uteroplacental resistance to blood flow falls. According to the Hagen-Poiseuille law, viscosity influences resistance to blood flow. To investigate the contribution of these haemorheological changes to the decrease in resistance to blood flow in the uteroplacental circulation, a serial study was performed. Using blood viscosimetry and pulsed Doppler ultrasound recordings of the uterine arteries, 21 women with normal pregnancies were studied every 8 weeks from 12 weeks onwards. Statistical analysis revealed no significant relationship between WBV, PV and pulsatility index of the uterine arteries. It is concluded that the changes in blood viscosities are of minor influence on resistance to blood flow in the uteroplacental circulation throughout normal pregnancy. The vascular changes e.g. the considerable increase of the diameter of the spiral arteries have a much greater impact on resistance to blood flow.
The aim was to evaluate the effect of two toothpicks and two dental flosses on demineralized enamel and dentine and on plaque composition, using an in situ model with simulated approximal spaces within dentures. Fifteen subjects with full dentures were recruited and 14 completed the study. It consisted of two crossover periods, the first comparing a birch toothpick with AmF and a birch toothpick with NaF, and the second comparing a dental floss with AmF + NaF and a dental floss without F. Between these four periods, there was a control period without any approximal cleaning. In small, rectangular sample holders, one enamel and one dentine specimen were embedded, forming a triangular, approximal-like space. Two sample holders were mounted in the premolar-molar region of the upper or lower dentures. The subjects used the toothpicks or dental flosses 3 times/day for 4 weeks. The results showed that all toothpicks and dental flosses inhibited further demineralization compared to the control period (p < 0.001). The dental flosses were somewhat more effective in this respect than the toothpicks, especially in dentine. There were relatively small numerical differences between AmF and NaF toothpicks, but in favour of NaF regarding mineral gain (p < 0.05). The fluoridated floss gave somewhat less lesion depth in dentine than the non-fluoridated floss (p < 0.01). Toothpicks and flosses resulted in lower counts of microorganisms in plaque compared to the control period (p < 0.001); the AmF toothpick gave a more pronounced reduction than the NaF toothpick (p < 0.001).
The purpose of this study was to develop a model that predicts the outcome of supervised exercise for intermittent claudication. The authors present an example of the use of autoregressive logistic regression for modeling observed longitudinal data. Data were collected from 329 participants in a six-month exercise program. The levels of the polytomous outcome variable correspond to states they defined in a Markov decision model comparing treatment strategies for intermittent claudication. Autoregressive logistic regression can be used to fit multistate transition models to observed longitudinal data with standard statistical software. The technique allows exploration of alternative assumptions about the dependence in the outcome series and provides transition probabilities for different covariate patterns. Of the alternatives examined, a Markov model including two preceding responses, time, age, ankle brachial index, and duration of disease best described the data.
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