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Biomedical subjects

P Svedman

Publications and source records attributed to P Svedman.

35 records · Page 2Linked to original sources
PubMed1989

Staphylococcal wound infection in the pig: Part II. Inoculation, quantification of bacteria, and reproducibility.

Bacteria from full-thickness excision wounds with staphylococcal infection in the pig were cultured quantitatively. The bacterial concentration increased with the size of the inoculum, and after 2 days it had already reached a stable, maximal level of approximately log 8 CFU/g in the tissue. The correlation coefficient was 0.753 in comparing concentrations from superficial and deep biopsy halves and 0.145 from "surface wash" and superficial biopsies. The "within wound" sample distribution was logarithmic. The gain in precision when assessing the mean bacterial concentration from three instead of one biopsy was 45%. The coefficient of variation of between wound and within wound determinations was in the same range (i.e., 7.1-12.5%). Paired observations from a sample population with 7 sites (wounds) were needed to determine a 10% change in the bacterial concentration at a significance level of p less than 0.05, and a similar change could be determined from unpaired observations based on two populations with eleven sites.

Animals↗
PubMed1989

A device for noninvasive assessment of perfusion pressure in the skin of healthy volunteers.

A device allowing pressure to be applied to a local skin site where the skin blood flow is followed using laser Doppler flowmetry is described. The blood flow was studied on the back of the hand in eight volunteers before and during brachial arterial occlusion and while the external pressure was increased step by step. The flowmetry value during arterial occlusion was 0.3 +/- 0.1 AU, and when the external pressure was increased to 120 mm Hg the values were similar (p = .44). The skin perfusion pressure, defined as the least external pressure needed to achieve flow cessation, was found to be 92 +/- 16 mm Hg (range 70-111 mm Hg), and the mean arterial pressure was 90 +/- 9 mm Hg (NS). The skin perfusion value is in agreement with that found by others using other techniques for measuring blood flow and a circumferent cuff for applying pressure.

Adolescent↗
PubMed1988

On expander pressure and skin blood flow during tissue expansion in the pig.

The structural and circulatory dynamics of expanded skin in connection with expander fillings were assessed in pigs following 7, 14, and 21 days of expansion by measuring the pressure of te fluid in the expander (Pexp) and the dermal blood flow. The results differed consistently on thoracic and abdominal sites. It was suggested that the stimulus to expansion be defined as the relative increase in extensible surface area of the expander. When plotting this value against Pexp, as measured at the end of injection, there was a good fit to an exponential curve. The area/Pexp relation was used to assess the connective tissue reaction around the expander; the reaction was most pronounced at 21 days. The decrease in Pexp after injection of fluid to 100 mm Hg showed that the tissue adapted rapidly during the first hour. Blood flow in the skin covering the expander was lower than on adjacent normal skin, and there was no increase during the three weeks of expansion. The decreases in blood flow were moderate even after injection of fluid until Pexp reached 100 mm Hg. It was suggested that the connective tissue capsule might protect the dermis from flow decrease.

Animals↗
PubMed1987

Viability and vascularization of an expanded buttock island flap in the pig.

In 14 of 16 buttock island flaps, half of which had been expanded within their cranial arterial part before elevation, areas of skin necrosis were noted within the caudal random part. The mean area of necrosis on the expanded side did not differ from that on the control side. In vivo angiograms indicated that the circumflex iliac artery was more tortuous and wider on the expanded side than on the control side. The findings suggest that expanding the arterial part of the flaps has no apparent negative effects on the circulation. The concept of expanding skin to be used as a free flap, so that the size of the flap may fulfill demands in special circumstances, is supported.

Angiography↗
PubMed1986

A dressing system providing fluid supply and suction drainage used for continuous or intermittent irrigation.

In this article a dressing system is described that is capable of providing continuous or intermittent wound irrigation. It is based on a felt dressing provided with an adhesive cover and ports for fluid supply and suction drainage. At continuous irrigation (approximate rate, 70 ml/h), a 1-L fluid bag and a siphon about 30 cm in height are used; at intermittent irrigation (approximate rate, 60 ml/min), a 60-ml fluid bag and a suction balloon are used. In an experimental set-up it was shown that the supplied fluid diffused throughout the dressing felt and that the felt was partly saturated both during continuous and after intermittent irrigation, the effect of gravity being counteracted by capillary force and suction. The suction pressure at the drainage port and within the occlusively applied felt showed a linear relationship. The drainage of particles, while relatively impeded at low flow rates, was satisfactory at rates recommended for clinical use. The dressing felt was inert to adherence of bacteria and white blood cells. This dressing system would seem to provide access to the whole wound surface for active therapy through fluid supply and suction drainage.

Bandages↗
PubMed1985

Detecting arterial and venous obstruction in flaps.

Island skin flaps based on the latissimus dorsi muscle were raised in domestic pigs. Flap circulation, maintained only by the vascular pedicle, was monitored by laser Doppler flowmetry, laser photometry, and transcutaneously measured carbon dioxide tension. Both arterial and venous occlusion were accompanied by very low laser Doppler flow values. In laser photometry, the backscattered intensity of light remained unchanged or was slightly increased during arterial occlusion. In response to venous occlusion, however, the light intensity decreased markedly. Transcutaneous carbon dioxide tension increased in both venous and arterial occlusion. When venous outflow pressure was raised incrementally, both the laser Doppler flow value and the total backscattered light intensity fell proportionately. Laser Doppler flowmetry might thus be useful clinically to detect decreased blood flow in transferred flaps, and laser photometry may determine if the decreased flow is related to the arterial or venous side.

Animals↗
PubMed1985

Detecting changes of arterial and venous blood flow in flaps.

Island skin flaps based on the latissimus dorsi muscle were raised in domestic pigs. Simultaneous recordings of laser Doppler flowmetric and laser photometric values were made on the skin in the middle of the flap. Occlusion of either the artery or the vein of the pedicle was accompanied by very low laser Doppler flow values. In laser photometry the total intensity of backscattered light remained unchanged or was sightly increased during arterial occlusion. In response to venous occlusion, however, it decreased markedly. As venous outflow pressure was increased step by step, both the laser Doppler flow value and the laser photometry value fell proportionally; thus, the greater the increase in pressure the lower were the steady state levels of both variables. Stepwise reductions of arterial inflow pressure were followed by proportional decreases in both mean blood volume flow, recorded using electromagnetic flowmetry, and in laser Doppler flowmetric values. However, laser photometric values varied only minimally. Laser Doppler flowmetry thus might be a useful clinical aid in detecting decreased blood flow in transferred flaps, and laser photometry may determine whether the decreased flow is due to arterial or venous causes.

Animals↗
PubMed1985

Laser Doppler flowmetry and laser photometry for monitoring free flaps.

A device based on the laser Doppler perfusion meter, "Periflux", was constructed for continuous post-operative monitoring of the circulation of free flaps. It was evaluated in 17 consecutive clinical free flaps, four of which were beset by circulatory complications. In all 17 cases the device provided reliable and readily accessible information concerning the state of flap blood flow.

Humans↗
PubMed1983

Irrigation treatment of leg ulcers.

Wound healing produced by isotonic saline irrigation via a special dressing was compared with that produced by conventional saline dressings in 12 inpatients with 18 leg ulcers. Patients served as their own controls. Wound cleansing was estimated by fibrin crust disappearance and granulation tissue formation. Both occurred earlier during irrigation. Wound contraction was similar during the two treatments. Wound blood flow, estimated by means of a laser Doppler flowmeter, increased earlier with irrigation.

Adult↗
PubMed1983

Radioactive dextran particles for studying circulation in animals.

Two types of dextran particles, (density 1.12 g X cm-3), ie chelating dextran particles (diameters 15.0 and 52.0 microns) and Sephadex (diameter 49.5 microns) were prepared for use as radioactive microspheres after labelling with 57Co, 58Co or 131I. The labelling efficiency was 96.4% with 57Co or 58Co and 7.8% with 131I. The specific activities were in the range 1 to 60 microCi X mg-1. The dissociation of cobalt label was found to be negligible in vitro, and in vivo 0.4 to 0.7% per h. Most of this activity was rapidly excreted in the urine. 35 days after injection of 15 microns particles they were still entrapped in the lungs and had undergone no microscopic changes and caused no tissue reaction. The findings validate the use of cobalt labelled particles for animal experiments of several hours duration. The dissociation of the iodine label was considerable both in vitro and in vivo limiting the use of the iodine labelled particles to experiments where a single determination of blood flow distribution is sufficient.

Animals↗
PubMed1983

Laser Doppler flowmetry and transcutaneously measured carbon dioxide tension for observing changes of skin blood flow in fingers.

Laser Doppler flowmetry (LDF) and transcutaneous carbon dioxide tension measurements (PtcCO2) were performed on fingers of healthy volunteers subjected to a sequence of hydrostatic and thermal stimuli. LDF response using an unheated probe agreed well with measurements made with Xenon133 clearance and strain gauge plethysmography in a previous work. The PtcCO2 results, however, were found not in any way to reflect changes in skin blood flow.

Adult↗
PubMed1983

The influence of venous and arterial occlusion on capillary blood flow and transcutaneous oxygen tension in fingers.

We have previously reported a lack of correlation between the reactions of finger skin capillary blood cell velocity (CBV) and transcutaneous oxygen tension (pTcO2) to different hydrostatic pressures. In the present study the influence of different venous and arterial pressures on nailfold CBV and pTcO2 of the dorsum of the middle phalanx was investigated. In six subjects venous occlusion (50 mm Hg) was performed with the hand at heart level and 40 cm above heart level. At heart level venous occlusion caused a marked reduction in CBV from 0.59 to 0.02 mm/s (p less than 0.01) while pTcO2 was not significantly affected. When the hand was raised 40 cm above heart level CBV remained unchanged but pTcO2 fell from 58.8 to 41.8 mm Hg (p less than 0.001). Venous occlusion in this position caused a decrease in CBV and a further decrease in pTcO2. In another 5 subjects arterial occlusions of varying duration (0.5, 1, 2, 6, 15 min) were performed at the finger base. As judged by the CBV, reactive hyperemia (RH) was always present when duration of occlusion was one minute or more. Post-occlusive pTcO2 was significantly increased compared to baseline pTcO2 (p less than 0.05) only after the 15 min occlusion. Thus, there is a marked difference in the responses of CBV and pTcO2 to variations in venous and arterial pressures. The lack of response of pTcO2 to manoeuvers that result in autoregulatory adjustment of CBV probably reflects the local heating of the probe which causes maximal vasodilation in the underlying skin.

Adult↗
PubMed1982

On the relation between transcutaneous oxygen tension and skin blood flow.

Transcutaneous oxygen tension (pTcO2) varies with pAO2, circulatory parameters, skin metabolism and oxygen diffusion. The necessity to heat the skin beneath the electrode to allow transcutaneous oxygen diffusion limits the use of pTcO2 in the study of skin blood flow. The oxygen measured probably emanates from the capillaries of the superficial dermis. A large number of arteriovenous shunts in the skin may modify the pTcO2 response. The heat-dilated vessels beneath the electrode behave passively in most circumstances. Differences in local blood temperature with secondary shifts in the release of oxygen from oxyhemoglobin may affect pTcO2 at high and low flow rates respectively. pTcO2 may vary with the perfusion pressure and possibly also with the resistance of the blood vessels outside the area heated by the electrode, but only at low flow rates.

Blood Pressure↗
PubMed1982

The influence of hydrostatic pressure and contralateral cooling on capillary blood cell velocity and transcutaneous oxygen tension in fingers.

Measurement of transcutaneous oxygen tension (pTcO2) has become a rather widely used technique. The relation of pTcO2 to skin microcirculatory parameters is, however, unclear. Capillary blood cell velocity (CBV) was compared with transcutaneous oxygen tension (pTcO2) of the finger in seven volunteers on change of hydrostatic pressure and contralateral cooling. On increase in hydrostatic pressure and also with contralateral cooling CBV decreased, while pTcO2 remained unchanged. This finding can be explained by a heat-induced local vasodilation under the pTcO2 probe in spite of a general increase in vasomotor tone. During decreasing perfusion pressure CBV was unchanged, while pTcO2 fell. This shows that with reduction in driving pressure skin pO2 is lowered. Teh absence of a decrease in CBV under these circumstances may be explained by a closure of the arteriovenous shunts, with diversion of blood into the superficial nutritional capillaries. It is suggested that CBV is related to changes in skin vasomotor tone. The pTcO2 findings indicate that the skin vasculature under the isothermally heated (44 degrees C) sensor is dilated and does not respond to vasoconstrictor stimuli.

Adult↗