Search PubMed⌕ Search

Biomedical subjects

S A Carter

Publications and source records attributed to S A Carter.

At least 55 records · Page 3Linked to original sources
PubMed1984

Collapse and viscoelasticity of diseased human arteries.

A laboratory study of the hydrostatic collapse of diseased tibial arteries demonstrated hysteresis in the pressure-flow behaviour which resembled that seen in the stress-strain relations of the arterial tissue. The pressures at which the vessels collapsed were found to be considerably lower than expected on the basis of theoretical elastic models. Also, the pressures at which the vessels reopened were consistently lower than the pressures at which they collapsed. These findings were explained on the basis of viscoelasticity. The difference between collapse and opening pressure may provide insight into the mechanical properties of vessels, and a clue to errors in non-invasive measurements of blood pressure which depend upon collapse of arteries.

Aged↗
PubMed1983

A mobile internal medicine clinic.

The Denver Veterans Administration Medical Center (DVAMC) established a mobile internal medicine clinic (MediVAn) to provide access to primary care for veterans living more than fifty miles from the center and to study the costs of such an outreach program. A fully equipped van staffed by an internist visited four Colorado cities weekly for scheduled appointments. In the first two years of operation there were 4,655 visits by 766 veterans with a mean age of 56 years, with 3.9 diagnoses, and receiving 3.0 medicines. The cost per MediVAn visit was $68, compared with $67 per outpatient visit at DVAMC. We conclude that a mobile medical clinic is a convenient method of delivering primary care over distances and is comparable in cost to outpatient hospital visits.

Colorado↗
PubMed1981

Arterial auscultation in peripheral vascular disease.

Bruits between epigastrium and popliteal fossae were found in 63% of 309 patients with arterial obstruction and in 7% of 149 patients without obstruction. In the former group, ankle systolic pressure at rest was abnormal in 85% of limbs with bruits, indicating a hemodynamic abnormality. In the majority of limbs with bruits and normal pressures at rest, an abnormal pressure response to exercise suggests that auscultation is useful in detection of even milder arterial lesions. Auscultation, after exercise and during compression of arterial branches distal to the bruits, may unmark stenotic lesions that do not produce audible bruits at rest and may localize bruit-producing lesions. This study indicates that peripheral auscultation is a valuable technique for assessing the arterial system in individual patients and for screening population groups.

Arterial Occlusive Diseases↗
PubMed1981

The effect of age on the unfolding of elastin lamellae and collagen fibers with stretch in human carotid arteries.

We measured folding of elastin lamellae and collagen fibers in human carotid arteries and correlated the results with the elastic properties of the vessels. Specimens cut into circumferential strips were stretched to various degrees, fixed, and stained for elastin and collagen. Folding was measured on photographic projections. Elastin lamellae unfolded quickly with initial stretch. In old vessels they did not straighten as much as in the young suggesting that the content of the interlamellar space may interfere with the unfolding. Collagen fibers straightened more during stretch in stiffer older vessels than in the young, already at low degrees of stretch. Young's modulus at extension of 5% appeared to correlate with unfolding of elastin lamellae in young extensible vessels. The modulus correlated significantly with unfolding of collagen fibers at extensions of 15% and greater, and the slope of the regression of the modulus on folding increased with stretch. Our findings provide for the first time morphologic evidence for the role of elastin lamellae in the determination of the elastic properties at low extensions, for the importance of collagen fibers in increasing stiffness with further stretch, and for the relationship between increased stiffness with age and the earlier recruitment of the collagen fibers.

Adolescent↗
PubMed1981

Finger systolic pressures and skin temperatures in severe Raynaud's syndrome: the relationship to healing of skin lesions and the use of oral phenoxybenzamine.

Systolic pressures and skin temperatures were studied in 23 patients with severe Raynaud's syndrome who were given oral phenoxybenzamine. There was a relationship between the measurements and the severity of the disease. Statistically significant correlation was found between the measurements and the time for healing of skin lesions. The chances of early healing are high when digital systolic pressure exceeds 55 mm Hg, the branchial-finger pressure difference is less than 50mm Hg, and the maximal difference among fingers less than 30 mm Hg. Early healing is also likely when finger temperature of 10 degree C or more above room temperature is achieved during "reflex" heating and the difference in temperature among fingers is less than 4 degree C. Therefore, the measurements are of value in the determination of prognosis. Rest pain, local tenderness, trophic skin changes, and vasospastic phenomena improved in the majority of patients soon after beginning treatment with phenoxybenzamine. Some side effects, usually minor, were common but with doses not exceeding 50 mg used in this study they were usually not trouble-some and the drug was tolerated well. Phenoxybenzamine is a valuable drug in the treatment of patients with severe vasospastic disease.

Administration, Oral↗
PubMed1978

Voluntary increase in finger temperature in man in a cooling environment.

To test whether man can increase voluntarily skin temperature in a cool environment, 14 subjects (age 15--51) were studied. They came once or twice a week for five to eight sessions of 1 h. The room temperature of various sessions varied from 21.2 to 15.6 degrees C. Temperatures of six fingers were recorded using thermocouples. During trials to increase temperature, subjects were shown a dial indicating temperature of an index finger and were instructed to try to warm their hands. The trials were begun when skin temperatures were stable or were falling, indicating that vasoconstriction was occurring. They were preceded and followed by a rest period. The differences between changes in temperature during the trials and the rest periods were significant for the group of 14 subjects (p less than 0.01). In 10 subjects with individually significant results, differences between the trial and rest periods averaged 5.0 degrees C for 'the best' and 3.9 degrees C for 'the worst' finger. The maximum temperatures during the trials averaged 30.9 +/- 1.0 degrees C (mean +/- SE) in 'the best' finger. During later sessions, subjects were able to increase temperatures without seeing the dial. The results indicate that humans are able to increase voluntarily cutaneous finger blood flow in a cool environment.

Adolescent↗
PubMed1978

Effect of age, cardiovascular disease, and vasomotor changes on transmission of arterial pressure waves through the lower extremities.

Pressure waves were recorded by indwelling needles in the femoral and foot arteries. At the foot the systolic and pulse pressures were greater and the dicrotic wave more prominent. These changes during transmission increased during vasoconstriction and decreased during vasodilatation. The ratio of the distal to femoral pulse pressure (amplification) increasing from 1.13 +/- 0.05 during body heating to 1.47 +/- 0.06 during body cooling (P less than 0.01), and from 1.14 +/- 0.10 during infusion of trimethaphan to 1.42 +/- 0.02 during cooling (P less than 0.05). Amplification was also significantly greater following inhalation of amyl nitrite and during and after Valsalva maneuver. Greater pulse pressure at the foot paralleled greater amplitude of individual harmonics. Phase velocities decreased with increasing frequency and tended to level off at a value similar to the foot-to-foot pulse wave velocity. The findings are consistent with peripheral reflections of the waves which increase during vasoconstriction. In the absence of procedures that elicit vasoconstriction or vasodilatation, amplification averaged 1.35 +/- 0.03 in control subjects less than 35 years of age and 1.24 +/- 0.06 in older subjects (P less than 0.05). Amplification also did not differ significantly between control subjects and patients with hypertension or ischemic heart disease. In the absence of pronounced vasodilatation or encroachment on the lumen by atherosclerotic plaques, systolic and pulse pressures at the foot should be higher than in proximal pulses. These findings provide a firm basis for interpreting measurements of distal systolic pressures by using blood pressure cuffs when examining patients with occlusive arterial disease in the extremities.

Adolescent↗