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Biomedical subjects

S Chase

Publications and source records attributed to S Chase.

At least 37 records · Page 2Linked to original sources
PubMed1991

Treatment of vasospasm with a 480-nm pulsed-dye laser.

Laser energy at a wavelength of 480 nm was applied in 1-microseconds pulses of 3 to 10 mJ to two models of vasospasm. Rabbit common carotid arteries (CCA's) were constricted chronically by the application of human blood within a silicone sheath. Peak vasospasm developed 24 to 48 hours later, and persisted for up to 6 days. Endovascular laser treatment was delivered to 40 CCA's via a 200-microns diameter silica quartz fiber introduced through the femoral artery. The CCA caliber increased from 60% of the pre-vasospasm control diameter to a minimum post-laser diameter of 83% of control. No instances of laser-induced perforation or of arterial thrombosis were observed for up to 60 days after treatment. Prophylactic laser application to nine normal vessels was able to attenuate the development of vasospasm if blood was applied immediately thereafter (88% vs. 59% of control diameter, p less than 0.02), but not if blood was applied 7 days later. Studies in 16 normal CCA's established that there was a considerable margin between the laser energy required to induce dilatation and that which caused perforation, providing that the fiber remained relatively central within the artery. Morphological examination demonstrated focal loss of endothelial cells immediately after laser application, followed approximately 7 days later by the development of areas of intimal hyperplasia. Only minimal changes were observed in the medial or adventitial layers. In a second study, the basilar artery of seven dogs was constricted chronically by two intracisternal injections of autologous blood 3 days apart. Five dogs received endovascular laser treatment 7 or 10 days after the first injection, when basilar artery diameter was reduced to a mean of 61% and 77% of control, respectively. Immediately following treatment, basilar artery diameter increased to 104% and 102% of resting diameter, respectively. Both untreated and laser-treated arteries were smaller than the control diameter at 30 days (80% and 82%, respectively), but in each group the vasodilatory response to hypercapnia was preserved. These findings indicate that 1-microsecond laser pulses are well tolerated by systemic and cerebral arteries in two different animal models, and suggest that the 480-nm pulsed-dye laser may have an application for the treatment or prophylaxis of cerebral vasospasm.

Animals↗
PubMed1985

Tube esophagostomy. A new technique in the management of long-term swallowing disorders.

Surgeons whose patients require long-term management of nutritional intake must usually choose from among nasogastric tube feedings, hyperalimentation by intravenous route, and/or gastrostomy. Cervical esophagostomy has been a useful but not widely employed alternative. The advantages of cervical esophagostomy over other modalities include the avoidance of laparotomy, absence of a nasogastric tube, and lack of the complications of a long-term indwelling intravenous catheter. The disadvantages of standard esophagostomy include the need to wear a tube to keep the fistula open, leakage, and skin irritation. Dobie et al presented a skin flap esophagostomy technique in 1978. We report a variation of this concept that has resulted in no salivary leakage and that allows the patient to dispense a tube between feedings. It provides a directional stoma in which the internal orifice is considerably inferior to the external one, resulting in continence and thus preventing substantial leakage.

Deglutition Disorders↗
PubMed1983

Intensity perception. XII. Effect of presentation probability on absolute identification.

Identification experiments using 13 tone-pulse stimuli (1000 Hz, 500 ms) spaced by equal decibel increments from 42 to 90 dB SPL were conducted under three conditions: all intensities equally likely (denoted Q), the middle intensity presented on roughly 1/3 of the trials (M), and each of the extreme intensities presented on roughly 1/5 of the trials (E). Experiments were performed both with and without feedback, and results were analyzed in terms of sensitivity and bias. Similar results were obtained with and without feedback: listeners generally shifted biases in the M and E conditions relative to the Q condition to increase percent-correct scores, but there were only minor changes in sensitivity from condition to condition. However, sensitivities were generally higher and biases more optimal when feedback was available. The results on sensitivity are consistent with those associated with payoff variation [Lippmann et al., J. Acoust. Soc. Am. 59, 129-134 (1976)], but are inconsistent with those reported for presentation probability variation in tone frequency identification [Cuddy et al., J. Exp. Psychol. 100, 218-220 (1973)]. In an auxilliary experiment concerned with tone frequency identification, results consistent with those obtained for intensity, but inconsistent with those reported by Cuddy et al., were obtained.

Feedback↗
PubMed1982

Treatment of tardive dyskinesia with propranolol.

A double-blind, intensive case design was used to study the effect of propranolol on tardive dyskinesia. No short-term improvement was observed, but two of the four subjects responded to long-term propranolol use. Properties of propranolol other than acute beta blockade are suggested as possible mechanisms of action.

Adult↗
PubMed1981

The inpatient psychiatric unit as a system.

A university-affiliated psychiatric inpatient unit in a private general hospital is an organization which serves many purposes. However, the primary purpose is quite evident: to provide various psychiatric therapies to patients with diverse psychopathologies. This becomes extremely complicated if the unit attempts an eclectic approach. Thus, the unit must consider: (1) psychopathological frameworks such as genetic, sociocultural, psychoanalytic, behavioral, and biochemical etiologies; (2) therapeutic interventions such as individual, group, and family therapy; insight-oriented, supportive, and behavioral psychotherapy; milieu therapy; and psychopharmacological treatment; (3) the various philosophies, attitudes, and skills of the multidisciplinary team of psychiatrists, psychologists, nurses, aides, social workers, activities therapists, expressive therapists, and administrative support personnel. General systems theory and general living systems models may further the conceptualization and understanding of the inpatient unit. This, in turn, may improve patient treatment. For the inpatient psychiatric unit, we describe the 19 critical subsystems of general living systems theory, with special emphasis on the decider subsystem.

Hospital Bed Capacity, 300 to 499↗
PubMed1981

Decision making in an interdisciplinary team.

Decision making in an interdisciplinary team occurs at the interface between groups with varied backgrounds, orientations, interests, and goals. Most interdisciplinary teams attempt to identify the complex set of variables influencing their decisions and then utilize this knowledge to maximize efficiency in health care delivery. Models of information and decision analysis developed by general systems theory are suggested as a method for advancing the understanding of where, when, and how decisions are made by the interdisciplinary team. A university-affiliated psychiatric service in a private general hospital is studied. Here the following forces meet, complement, compete, and collide: the community, university, hospital administration, private practitioners, insurance companies, consultation and liaison psychiatrists, university staff psychiatrists and residents, nurses, aides, social workers, activities personnel, patients and their families, the patient group, the ward milieu. Considering these factors, we describe: (1) the flow of information and feedback loops into, within, and out of the psychiatric service; (2) the location of decision nodes; (3) decision-making echelons. The general systems theory concepts utilized in this analysis are proposed as pragmatic tools for improving interdisciplinary team function.

Decision Making↗
PubMed1968

Discriminative control of "attention".

Three pigeons were trained to discriminate between two tones differing in frequency in the presence of light of one color (A), and not to discriminate between the tones in the presence of light of another color (B). Generalization functions that were determined in the presence of light A showed control of behavior by the frequency of the tone; those determined in the presence of light B did not.

Animals↗