Biomedical subjects

S Farr

Publications and source records attributed to S Farr.

5 recordsLinked to original sources

PubMed1988

Comparison of computer and non-computer-assisted technologies in noninvasive cardiac imaging.

We compared gated magnetic resonance imaging (MRI) and dynamic computed tomography (DCT) with two-dimensional cardiac ultrasound (ECHO) to assess differences in diagnostic information. Magnetic resonance imaging was performed in 41 patients; ECHO in 36, and DCT in 28 patients with various pathologic conditions. We measured the left and right ventricular (LV, RV) long and short axes (LA, SA), LV free wall and septal thickness (WT, ST) at end systole (ES) and end diastole (ED) on the apical four-chamber view (ECHO) or appropriate transaxial slice (MRI, DCT) on a subset of 14 patients. Paired-sample analysis of these three techniques, in this preliminary data, yields statistically different results as follows: LV SA: MRI versus ECHO at ED and ES (P less than 0.001 and 0.005); WT: MR versus ECHO at ES (P less than 0.002); CT versus ECHO at ED and ES (P less than 0.05 and 0.01); ST: MRI versus ECHO at ED and ES (P less than 0.001), and CT versus ECHO at ES (P less than 0.05). Thus, CT and MRI yield similar quantitative data, but both differ in varying degree from ECHO measurements. Differential accuracies and utilities of these techniques warrant further careful investigation.

Echocardiography↗

PubMed1987

Gonadal hormones and conspecific marking in male rats.

Urine deposited by a rat on a conspecific was quantified with injections of sodium fluorescein, a substance that changes the color of urine. The hypothesis examined in experiment 1 was that marking the environment and a conspecific would be similarly androgen-sensitive behaviors during each of three stages--before castration, after castration, and with restorative therapy with testosterone propionate. Findings were that castration reduced both forms of marking, and testosterone therapy to castrated males restored environmental marking in a dose-response fashion. However, the findings for social marking were more complex; for example, a physiological 200-micrograms testosterone dosage to castrated males was unable to elevate conspecific marking over the rates of marking by castrates without testosterone replacement. In experiment 2 the ontogeny conspecific marking in juvenile males was examined in relation to the pubertal surge of androgens. Results suggested that juvenile male marking of an adult male decreased despite a pubertal increase of androgens. Conclusions were that testicular hormones influenced both forms of marking but were less important in the social setting. Moreover, conspecific marking is not simply an extension of marking the environment.

Age Factors↗

PubMed1985

Abrupt withdrawal of atenolol in patients with severe angina. Comparison with the effects of treatment.

The effects of abrupt withdrawal of atenolol, a long acting cardioselective beta blocker, were studied in 20 patients with severe stable angina pectoris admitted to hospital for coronary arteriography. During the 144 hour postwithdrawal period no serious coronary events occurred. Mean and maximal daily heart rates rose steadily for at least 120 hours. No important arrhythmias were noted on ambulatory electrocardiographic monitoring. Treadmill exercise testing at 120 hours showed little reduction in the times to angina, ST depression, and maximal exercise when compared with those recorded at 24 hours. This deterioration was small when contrasted with the improvements in these indices produced by atenolol treatment in a similar group of patients not admitted to hospital. No change in catecholamine concentrations or acceleration of the heart rate response to exercise occurred after atenolol withdrawal, suggesting that rebound adrenergic stimulation or hypersensitivity was absent or insignificant. Catastrophic coronary events after beta blockade withdrawal (the beta blockade withdrawal syndrome) have occurred almost exclusively in patients taking propranolol, many of whom had unstable angina at the time of withdrawal. This study showed that in patients with stable angina, even when severe, the abrupt withdrawal of atenolol can be expected to result in only minor clinical consequences. The risk to any patient of so called rebound events after withdrawal of beta blockade seems to be related to both the clinical setting and the agent being used.

Adult↗

PubMed1985

Conservation of oxygen supply using a reservoir nasal cannula in hypoxemic patients at rest and during exercise.

A reservoir nasal cannula which stores oxygen during exhalation and delivers it as a bolus during inhalation has been reported to conserve oxygen delivery in patients with chronic obstructive pulmonary disease (COPD) at rest. We compared the effects upon arterial oxygen saturation (SaO2) of the reservoir cannula and a standard nasal cannula in hypoxemic obstructed and restricted patients at rest and during exercise. The SaO2 was monitored by ear oximeter. While at rest, 13 obstructed and four restricted patients breathed oxygen from the reservoir cannula at 0.5, 1.0, 1.5, and 2.0 L/min and from a standard cannula at 0.5, 1.0, 2.0, 3.0, and 4.0 L/min. Mean SaO2 was significantly higher with the reservoir cannula compared to the standard cannula at 1.0 and 2.0 L/min (p less than 0.0006) and tended to be higher at 0.5 L/min (p less than 0.1). Seven obstructed patients walked on a level treadmill at 0.75 mph while breathing oxygen at 0.5 and 1.5 L/min from the reservoir cannula and at 1.0 and 3.0 L/min from the standard cannula. The SaO2 during exercise with the reservoir cannula was comparable to that with the standard cannula at approximately half of the oxygen flow rate. The ratio of the oxygen flow rate of the standard to the reservoir cannula to produce 90 percent saturation was estimated and found to be 2.5 +/- 0.8 (mean +/- SD) for patients at rest and 2.9 +/- 1.8 during exercise. We conclude that in hypoxemic patients at rest and during exercise, the reservoir cannula uses less than half the oxygen of a standard cannula to produce similar improvement in SaO2 and thus has advantages of a reduced cost of ambulatory therapy with low-flow oxygen and a longer time permitted away from a stationary source of oxygen.

Carbon Dioxide↗

PubMed1984

Expectancy and dual-task interference.

This research deals with the relationship between expectancy and attention. In two experiments, expectancy concerning the modality of a probe stimulus was manipulated. In Experiment 1, the frequencies of probes in auditory and visual modalities were varied. In Experiment 2, a cue prior to each trial indicated the relative probabilities of the two types of probes. In both experiments, expectancy effects were observed in a single-task condition during which the subject's only task was to respond to the probes and in a dual-task condition in which probes were inserted in the study phase of a pattern recognition task. If maintaining an expectancy requires attention, then diverting attention from the probe task to the pattern recognition task should have attentuated the effects of expectancy. In fact, the pattern recognition task did not alter frequency effects but did significantly reduce cueing effects. We conclude that expectancy as determined by frequency results from automatic activation, whereas expectancy as determined by cueing involves attention.

Attention↗