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Biomedical subjects

G Thorne

Publications and source records attributed to G Thorne.

10 recordsLinked to original sources
PubMed2002

Tracheal trauma from percutaneous tracheostomy using the Griggs method.

In a safety evaluation study, relative force and distance measurements during percutaneous tracheostomy were recorded using specially monitored Griggs guidewire dilating tracheostomy forceps on 12 cadavers scheduled to undergo postmortem examination the same day. All measurements were recorded in millivolts and were converted to force and distance via appropriate calibration tables. Markedly more force was required for tracheal destruction than for therapeutic tracheal dilation (87.7 N +/- 19 N vs. 31.6 N +/- 17.1 N, p <0.001). Also relatively less force was required for therapeutic tracheal dilation than for dilation of the pretracheal tissues (44.4 N +/- 17.1 N vs. 31.6 N +/- 17.1 N, p <0.05). These results suggest that the Griggs tracheostomy forceps have a reasonable margin of safety in that tracheal destruction is unlikely to occur inadvertently during therapeutic dilation. Second, the dilation of pretracheal tissues can act as useful guide in knowing how much force to apply in a therapeutic dilation.

Dilatation↗
PubMed2002

Effect of thoracic epidural anaesthesia on colonic blood flow.

BACKGROUND: The effect of thoracic epidural block on splanchnic blood flow is unclear. It remains to be resolved if sympathetic block, increases or decreases regional splanchnic blood flow and whether regional splanchnic flow becomes dependent on cardiac output or perfusion pressure. A clear understanding of the regional haemodynamic consequences of an epidural block may modify practice with respect to epidural anaesthesia. METHODS: Fifteen patients, who underwent anterior resection for rectal cancer, had invasive intraoperative monitoring of arterial pressure, central venous pressure, cardiac output, inferior mesenteric artery flow (Doppler flow probe), and colonic serosal red cell flux (laser Doppler probe), while an epidural block was established with local anaesthetic. In three consecutive time periods, arterial pressure was first allowed to fall (to a mean arterial pressure of 60 mm Hg), then treated with colloid fluid resuscitation and finally by vasopressors until the pre-epidural arterial pressure had been restored. RESULTS: On induction of epidural block, there was a reduction in mean colonic serosal red cell flux to 65% and inferior mesenteric artery flow to 80% (mean) of pre-epidural levels. There was a strong association between mean arterial pressure and both measured inferior mesenteric artery blood flow (P < 0.004) and colonic serosal red cell flux (P < 0.0001). Changes in cardiac output were poorly associated with either inferior mesenteric artery blood flow (P = 0.638) or colonic serosal red cell flux (P = 0.265). Inferior mesenteric artery blood flow and colonic serosal red cell flux were restored to pre-epidural levels after arterial pressure had been improved with a vasopressor. CONCLUSION: Once intraoperative epidural block has been established, colonic serosal red cell flux and inferior mesenteric artery flow are more closely associated with changes in mean arterial pressure than changes in cardiac output. The measured reduction in colonic flow does not respond to an increase in cardiac output with fluid resuscitation, but requires the use of a vasopressor to increase arterial pressure, before colonic blood flow is improved.

Aged↗
PubMed2000

Effects of hypoxia on isometric force, intracellular Ca(2+), pH, and energetics in porcine coronary artery.

When exposed to hypoxic conditions, coronary arteries dilate, which is an important protective response. Although vessel sensitivity to oxygen is well documented, the mechanisms are not known with certainty. To further characterize the mechanisms of oxygen sensing in the coronary artery, we tested the major classes of hypotheses by measuring the effects of hypoxia on energetics, [Ca(2+)](i), K(+) channel function, and pH(i). Hypoxia relaxes porcine coronary arteries stimulated with either KCl or U46619. The extent of relaxation is dependent on both the degree and kind of stimulation. [Ca(2+)](i) was measured in endothelium-denuded arteries using fura 2-AM and ratiometric fluorescent techniques. At lower stimulus levels, hypoxia decreased both force and [Ca(2+)](i). Inhibitor studies suggest that K(Ca) and K(ATP) channels are not involved in the hypoxic relaxation, whereas K(V) channels may play a minor role, if any. Despite the hypoxia-mediated decrease in force, [Ca(2+)](i) was unchanged or increased at high levels of stimulation. Despite a marked increase in lactate content, pH(i) (measured with the ratiometric fluorescent dye BCECF) was also little affected by hypoxia. Measurement of the phosphagen and metabolite profile of freeze-clamped arteries with analytical isotachophoresis indicated that hypoxia increased lactate content by 4-fold and decreased phosphocreatine to 60% of control. However, neither ATP nor P(i) was affected by hypoxia. Interestingly, additional stimulation under hypoxia increased force but not ATP utilization, as estimated from measurements of anaerobic lactate production. Thus, surprisingly, the economy of force maintenance is increased under hypoxia. In porcine coronary artery, both Ca(2+)-dependent and, importantly, Ca(2+)-independent mechanisms are involved in hypoxic vasodilatation. For the latter, mechanisms involving either ATP, [Ca(2+)](i), pH(i), or P(i) cannot be invoked. This novel oxygen sensing mechanism involves a decreased Ca(2+) sensitivity.

Animals↗
PubMed1999

Perceived discomfort in running: scale development and theoretical considerations.

The aim of this study was to develop a discomfort questionnaire to elicit the feelings and thoughts of people engaged in running activities. Ten runners who completed a particularly demanding 9-km run were asked to express their feelings and thoughts during the run they had just completed. These responses were recorded and later used as the first pool of items (k = 36). The questionnaire was then given to 171 runners in different distance races throughout the 1995 competitive season. These responses were analysed using exploratory factor analytic techniques and Rasch probabilistic analysis, as well as traditional reliability and validity procedures. The final version of the questionnaire consisted of 32 items divided into eight correlated subscales: proprioceptive symptoms, leg symptoms, respiratory difficulties, disorientation, dryness and heat, task completion thoughts, mental toughness, and head or stomach symptoms. These eight categories can be collapsed into three global categories suggested by researchers of pain: sensory-discriminative, motivational-affective and cognitive-evaluative. Rasch analysis suggested that the motivational-affective and cognitive-evaluative dimensions (i.e. the psychological) are the most experienced (i.e. rated highest). The eight subscales have ecological validity and were found to alter with the demands of different running distances.

Adolescent↗
PubMed1999

Development of a system to record cardiac output continuously in the newborn.

Intermittent recordings of Doppler flow velocity and cardiac output are of value during intensive care of the sick newborn infant but result in repeated disturbance of the child. We describe a new device for making continuous precordial recordings of Doppler flow velocity from the pulmonary artery in healthy resting newborn infants. Optimal probe siting was evaluated in six babies, and signals were found to be best when the pulmonary artery was insonated from the mid left parasternum. Continuous recordings were made in 13 other babies. Pulmonary artery velocities and, by calculation, cardiac output were measured continuously over periods ranging from 24 to 60 min. Median right ventricular output ranged widely from 148 to 246 mL x kg(-1) x min(-1). In contrast, for individual babies, the values were remarkably stable: the interquartile ranges varied from 13.2 to 29.9 mL x kg(-1) x min(-1). The simultaneous display of signal power allowed independent assessment of artifactual changes in cardiac output. This technique is feasible in healthy term infants and now requires evaluation in the intensive care setting where it may provide useful information concerning trends and short-term variability in right ventricular output.

Cardiac Output↗
PubMed1986

Perception of texture by vision and touch: multidimensionality and intersensory integration.

A series of six experiments offers converging evidence that there is no fixed dominance hierarchy for the perception of textured patterns, and in doing so, highlights the importance of recognizing the multidimensionality of texture perception. The relative bias between vision and touch was reversed or considerably altered using both discrepancy and nondiscrepancy paradigms. This shift was achieved merely by directing observers to judge different dimensions of the same textured surface. Experiments 1, 4, and 5 showed relatively strong emphasis on visual as opposed to tactual cues regarding the spatial density of raised dot patterns. In contrast, Experiments 2, 3, and 6 demonstrated considerably greater emphasis on the tactual as opposed to visual cues when observers were instructed to judge the roughness of the same surfaces. The results of the experiments were discussed in terms of a modality appropriateness interpretation of intersensory bias. A weighted averaging model appeared to describe the nature of the intersensory integration process for both spatial density and roughness perception.

Adolescent↗
PubMed1978

Pyoderma gangrenosum. Abnormal monocyte function corrected in vitro with hydrocortisone.

A 34-year-old man with chronic active hepatitis and pyoderma gangrenosum demonstrated abnormalities in neutrophil and monocyte function. Monocytes from this man had diminished chemotaxis and bacterial phagocytosis. These functions were significantly improved in vitro after one hour of incubation of monocytes with 10(-5) hydrocortisone. Neutrophil function was nornal for bactericidal activity and phagocytosis, but neutrophil chemotaxis was diminished. A plasma inhibitor was not found to explain these phagocyte alterations.

Adult↗
PubMed1976

Vesicular pemphigoid.

Seven patients had a chronic eruption of small vesicles that was initially considered to be atypical dermatitis herpetiformis. Histopathologic studies disclosed a subepidermal bulla that was compatible with either bullous pemphigoid or dermatitis herpetiformis. Immunofluorescence studies demonstrated deposition of IgG or C3, Or both, at the basement-membrane zone (BMZ) in six of seven patients. In four patients, circulating BMZ antibodies were detected also. We belive that these cases represent a vesicular form of bullous pemphigoid.

Adult↗