| 1. |
|
|
| 2. |
|
|
| 3. |
- Golster, Helena, et al.
(författare)
-
Heterogeneous blood flow response in the foot on dependency, assessed by laser Doppler perfusion imaging
- 1997
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 159:2, s. 101-106
-
Tidskriftsartikel (refereegranskat)abstract
- The exact nature of the decrease in foot skin blood flow seen after a change in posture remains unsettled. This mechanism has previously been examined by non-invasive techniques such as the laser Doppler perfusion monitor (laser Doppler flowmetry). Taking into account the shortcomings of laser Doppler perfusion monitoring when applied to the determination of skin blood flow, which normally shows substantial heterogeneity, we have applied an emerging technology, the laser Doppler perfusion imager (LDPI). This technique provides a more comprehensive picture of the blood flow distribution in the skin, as it maps skin blood flow over a surface area (120×120 mm, 4096 measurement sites). It was used to examine if the reduction in tissue perfusion or the alterations in flow distributions seen after a change in posture (supine to dependency) could be fully explained by an increase in venous pressure (venous stasis of 50 mmHg) or if the data suggest a complementary mechanism.Skin blood flow of the forefoot decreased from 0.60 V (volt) (median) during rest to 0.40 and 0.38 V during venous stasis and dependency, respectively. Although almost identical median values were obtained during stasis and dependency, the flow distributions were different, with a loss of high flow values during venous stasis. Biological zero was 0.24 V.As the LDPI technique readily records skin perfusion during variations in venous stasis and posture, as well as information on flow distribution changes, it appears promising for future application in stimuli-response studies of skin blood flow. The difference in flow distribution seen between increased venous pressure and dependency suggests an additive regulatory mechanism to the veni-vasomotor reflex during a change in posture.
|
|
| 4. |
- Golster, Helena, et al.
(författare)
-
Red Blood Cell Velocity and Volumetric Flow Assessment by Enhanced High-Resolution Laser Doppler Imaging in Separate Vessels of the Hamster Cheek Pouch Microcirculation
- 1999
-
Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 58:1, s. 62-73
-
Tidskriftsartikel (refereegranskat)abstract
- An enhanced high-resolution laser Doppler imager (EHR-LDI), configured to fit the demands of a measurement area containing separate microvessels, was evaluated for perfusion measurements in hamster cheek pouch preparations during ischemia, reperfusion, and pharmacologically induced vasodilation and vasoconstriction. Measurements in separate microvessels where the laser beam was smaller than the vessel diameter were referred to as red blood cell (RBC) velocity estimates, as previously validated in vitro, whereas a relative flow index, RFI (mean RBC velocity/tissue area), was introduced as a volumetric flow measure. Microvessel diameter and RBC velocity changes during ischemia, reperfusion, as well as during vasoconstriction and vasodilation correlated to the data obtained from the microscope. Correspondingly, during the described provocations anticipated volumetric flow changes were registered as changes in the RFI. When data on intravessel RBC velocity profiles are presented they reflect a parabolic flow profile usually seen in this size microvessel. The EHR-LDI appears a promising tool for investigation of the microvasculature, as it almost simultaneously provides information on relative changes of both in vivo RBC velocity and volumetric flow (RFI), although the latter estimate needs to be further refined.
|
|
| 5. |
- Kimme, Peter, et al.
(författare)
-
Cerebral blood flow of the exposed brain surface measured by laser Doppler perfusion imaging
- 1997
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 159:1, s. 15-22
-
Tidskriftsartikel (refereegranskat)abstract
- A novel application of laser Doppler flowmetry (LDF), laser Doppler perfusion imaging (LDPI), was used to study cerebral cortical blood flow (CBFcortex). In contrast to the conventional laser Doppler perfusion monitor, LDPI creates two-dimensional maps of the tissue perfusion in a well defined area of up to 120×120 mm comprising 4096 measurement points. Measurements of CBFcortex were made through an optically transparent polyester film applied to a cranial window preparation in ventilated anaesthetized pigs. Temporal and spatial heterogeneity in CBFcortex were visualized by LDPI during provocations which are known to alter CBF (varying arterial PCO2 or MABP, or infusion of adenosine at constant MABP (concomitant angiotensin administration) or by hyperoxemia). During hypercapnia the recorded CBFcortex increased homogeneously. The adenosine-mediated increase in recorded CBFcortex was concentrated on the lower flow interval, as was the hyperoxemia-caused decline. At decreasing MABP the autoregulatory threshold was found to vary locally within the cortex. The results suggest that LDPI, apart from detecting localized changes in CBFcortex, also visualizes flow changes within different vascular segments. Together with the practical advantages of the system, i.e. not necessitating direct contact with the tissues, this feature makes the technique suitable for studies of CBFcortex distributions.
|
|
| 6. |
|
|
| 7. |
- Lindén, Maria, 1965-, et al.
(författare)
-
Evaluation of Enhanced High-Resolution Laser Doppler Imaging in an in Vitro Tube Model with the Aim of Assessing Blood Flow in Separate Microvessels
- 1998
-
Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 56:3, s. 261-270
-
Tidskriftsartikel (refereegranskat)abstract
- An enhanced high-resolution laser Doppler imaging (EHR-LDI) technique intended for visualization of separate microvessels was evaluated by use ofin vitroflow models. In EHR-LDI, a laser beam focused to a half-power diameter less than 40 μm successively scans the tissue under study in steps of 25 μm. Spatial blood flow variations within microvascular structures of 1.5 × 1.5 mm are rendered by 64 × 64 measurement sites. Individual microvessel diameters could be estimated and an average difference of 11 μm compared to microscopic measurements was obtained. For the flow algorithm used, the LDI output signal was found to scale linearly with average velocity (0–3.5 mm/s) when a plastic tube of inner diameter 175 μm was perfused with human blood (correlation coefficient 0.99). The LDI output signal was further found insensitive to hematocrit variations in the range 16–44%. Due to the limited laser light penetration in blood, a reduction in the LDI output signal was observed as the inner tube diameters were successively changed from 280 to 1400 μm.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
- Zdolsek, Hans Joachim, et al.
(författare)
-
Non-invasive assessment of intercompartmental fluid shifts in burn victims
- 1998
-
Ingår i: Burns. - 0305-4179 .- 1879-1409. ; 24:3, s. 233-240
-
Tidskriftsartikel (refereegranskat)abstract
- Two non-invasive methods (the bioimpedance technique, BIA, and the impression method, IM) were studied, to find out whether they are sensitive enough to detect and chronicle the development of the oedema and fluid resuscitation effects (Parkland formula) that occur secondary to a major burn. Ten patients with a total burned body surface area (TBSA) of more than 10% were included in this prospective study. Total body water (TBW), as measured by the resistance (BIA) or F(0) variable (IM), reached a maximum on day 2. The tissue fluid translocation (INT) variable (IM) followed a different course, increasing slowly to reach a maximum on day 6, when it was 40% higher than the 12 h value. TBW and the interstitial translocatable fluid were still increased 1 week post-burn. The non-invasive measurements of TBW (resistance by BIA and F(0) by IM) reflected the anticipated changes in TBW. The phase angle (BIA) indicative of cellular membrane effects of burn and sepsis had its lowest values at day 1.5, and stayed significantly low until day 4. Interestingly, the phase angle was lowest in the two cases that died subsequently. The different time course of the INT value (IM), which reflected the translocatable interstitial fluid volume in skin, may be the result of resuscitation fluid remaining in this compartment, due to the excess sodium content together with a possible change in tissue compliance secondary to the early total water peak on day 2.
|
|
| 12. |
- Zdolsek, Hans Joachim, 1960-, et al.
(författare)
-
The effect of hypermetabolism induced by burn trauma on the ethanol-oxidizing capacity of the liver
- 1999
-
Ingår i: Critical Care Medicine. - 0090-3493 .- 1530-0293. ; 27:12, s. 2622-2625
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: To study the rate of elimination of ethanol after a major burn trauma.Design: Prospective, controlled study.Setting: National burns unit in a Swedish university hospital.Patients and Subjects: Eight consecutive patients suffering from 18%-72% total burned surface area and nine healthy male control subjects.Interventions: The patients received ethanol, 0.35-0.60 g/kg body weight intravenously, during 1 hr. This was repeated daily during the first week postburn. The control subjects received the same amount of ethanol once.Measurements and Main Results: Blood samples were drawn at 20- to 30-min intervals during 5 hrs after the start of the infusion. Serum ethanol was determined by headspace gas chromatography. The rate of elimination of ethanol was calculated from the concentration time profile. In the control subjects, the median elimination rate was 0.074 g/kg/hr (range, 0.059-0.083 g/kg/hr). In the patients, it was already 0.138 g/kg/hr (range, 0.111-0.201 g/kg/hr) on the first day; this increased even further over the following 6 days, reaching 0.183 g/kg/hr (range, 0.150-0.218 g/kg/hr) on the seventh day.Conclusions: Ethanol elimination is augmented postburn. A more effective reoxidation of reduced nicotinamide adenine dinucleotide seems the most likely explanation for the increased rate of ethanol elimination in these hypermetabolic trauma patients. This finding suggests that the oxidative capacity of the liver may be assessed by studying the rate of ethanol elimination in burn victims.
|
|
