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Perfusion Distribution (perfusion + distribution)

Distribution by Scientific Domains
Medical Sciences85%

Selected Abstracts

Multiple Inert Gas Elimination Technique For Determining Ventilation/Perfusion Distributions In Rat During Normoxia, Hypoxia And Hyperoxia

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2001
V Alfaro
SUMMARY 1. The use of the multiple inert gas elimination technique (MIGET) in quantifying ventilation/perfusion distributions (V,A/Q,) in small animals, such as the rat, may cause results to be biased due to haemodilution produced by the large volume of liquid infused intravenously. 2. We tested two methods of administering inert gases in rats using the MIGET: (i) standard continuous intravenous administration of inert gases (method A); and (ii) a new method based on the physicochemical properties of each inert gas (method B). This method included acute simultaneous inert gas administration using three pathways: inhalation, intravenous infusion and rectal infusion. Both MIGET methods were applied to obtain data while breathing three different inspiratory fractions of oxygen (FIO2): normoxia, hypoxia and hyperoxia. 3. Inert gas levels obtained from blood or expired air samples were sufficient for chromatographic measurement, at least during a 2 h period. The V,A/Q, distributions reported using both methods were acceptable for all the physiological conditions studied; therefore, the alternative method used here may be useful in further MIGET studies in rats because haemodilution resulting from continuous intravenous infusion of less-soluble gases can be avoided. 4. Normoxic rats showed lower mean values of the V,A/Q, ratio of ventilation distribution and higher mean values of the V,A/Q, ratio of perfusion distribution with the usual method of inert gas administration (method A). These non-significant differences were observed under almost all physiological conditions studied and they could be caused by haemodilution. Nevertheless, the effect of interindividual differences cannot be discarded. An additional effect of the low haematocrit on cardiovascular changes due to low FIO2, such as pulmonary vasoconstriction or increased cardiac output, may explain the lower dispersion of perfusion distributions found in group A during hypoxia. [source]

Altered skin blood perfusion in areas with non blanchable erythema: an explorative study

INTERNATIONAL WOUND JOURNAL, Issue 3 2006
Margareta Lindgren
Abstract Non blanchable erythema, i.e. stage I pressure ulcer, is common in patients in acute and geriatric care and in nursing homes. Research has shown that this type of lesions is prone to develop into more severe pressure ulcers. The peripheral skin blood perfusion is of major importance for the development of pressure ulcers. The aim of this study was to explore the peripheral skin blood perfusion over time, in areas with non blanchable erythema and in corresponding undamaged areas on the opposite side of the body. A total of 19 measurements were performed, over time, using a laser Doppler perfusion imager. The blood flow distribution profiles over areas with non blanchable erythema and undamaged skin were found to be different. As the area of the non blanchable erythema decreased, the blood perfusion distribution profiles gradually became more heterogeneous; an area of high blood perfusion in the centre of the lesions was seen and the perfusion successively decreased closer to the edge. These results indicate that there are differences in blood perfusion between skin areas of non blanchable erythema and undamaged skin. The results also indicate that the visible redness in areas with non blanchable erythema is related to altered blood perfusion. The skin blood perfusion also seems to increase in relation to the size of the non blanchable erythema. [source]

Muscle fractal vascular branching pattern and microvascular perfusion heterogeneity in endurance-trained and untrained men

THE JOURNAL OF PHYSIOLOGY, Issue 2 2003
Kari K. Kalliokoski
Less heterogeneous skeletal muscle perfusion has recently been reported in endurance-trained compared to untrained men at macrovascular level. The causes of this difference in perfusion heterogeneity are unknown as is whether the same difference is observed in microvasculature. We hypothesised that the difference could be caused by changes in muscle vascular branching pattern. Perfusion was measured in resting and exercising muscle in 14 endurance-trained and seven untrained men using [15O]water and positron emission tomography. Fractal dimension (D) of perfusion distribution was calculated as a measure of fractal characteristics of muscle vascular branching pattern. Perfusion heterogeneity in microvascular units (1 mm3 samples) was estimated using the measured heterogeneity in voxels of positron emission tomography (PET) images (relative dispersion, RD =s.d./mean) and corresponding D values. D was similar between the groups (exercising muscle 1.11 ± 0.07 and 1.14 ± 0.06, resting muscle 1.12 ± 0.06 and 1.14 ± 0.03, trained and untrained, respectively). Trained men had lower perfusion (151 ± 44 vs. 218 ± 87 ml min,1 kg,1, P < 0.05) and macrovascular perfusion heterogeneity (relative dispersion 21 ± 5 vs. 25 ± 5 %, P < 0.05) in exercising muscle than untrained men. Furthermore, estimated perfusion heterogeneity in microvascular units in exercising muscle was also lower in trained men (33 ± 7 vs.48 ± 19 %, P < 0.05). These results show that fractal vascular branching pattern is similar in endurance-trained and untrained men but perfusion is less heterogeneous at both the macro- and the microvascular level in endurance-trained men. Thus, changes in fractal branching pattern do not explain the differences in perfusion heterogeneity between endurance-trained and untrained men. [source]

Multiple Inert Gas Elimination Technique For Determining Ventilation/Perfusion Distributions In Rat During Normoxia, Hypoxia And Hyperoxia

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2001
V Alfaro
SUMMARY 1. The use of the multiple inert gas elimination technique (MIGET) in quantifying ventilation/perfusion distributions (V,A/Q,) in small animals, such as the rat, may cause results to be biased due to haemodilution produced by the large volume of liquid infused intravenously. 2. We tested two methods of administering inert gases in rats using the MIGET: (i) standard continuous intravenous administration of inert gases (method A); and (ii) a new method based on the physicochemical properties of each inert gas (method B). This method included acute simultaneous inert gas administration using three pathways: inhalation, intravenous infusion and rectal infusion. Both MIGET methods were applied to obtain data while breathing three different inspiratory fractions of oxygen (FIO2): normoxia, hypoxia and hyperoxia. 3. Inert gas levels obtained from blood or expired air samples were sufficient for chromatographic measurement, at least during a 2 h period. The V,A/Q, distributions reported using both methods were acceptable for all the physiological conditions studied; therefore, the alternative method used here may be useful in further MIGET studies in rats because haemodilution resulting from continuous intravenous infusion of less-soluble gases can be avoided. 4. Normoxic rats showed lower mean values of the V,A/Q, ratio of ventilation distribution and higher mean values of the V,A/Q, ratio of perfusion distribution with the usual method of inert gas administration (method A). These non-significant differences were observed under almost all physiological conditions studied and they could be caused by haemodilution. Nevertheless, the effect of interindividual differences cannot be discarded. An additional effect of the low haematocrit on cardiovascular changes due to low FIO2, such as pulmonary vasoconstriction or increased cardiac output, may explain the lower dispersion of perfusion distributions found in group A during hypoxia. [source]

Regional cerebral blood flow during hyperventilation in patients with acute bacterial meningitis

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2000
K. Møller
Mechanical hyperventilation is often instituted in patients with acute bacterial meningitis when increased intracranial pressure is suspected. However, the effect on regional cerebral blood flow (CBF) is unknown. In this study, we measured regional CBF (rCBF) in patients with acute bacterial meningitis before and during short-term hyperventilation. In 17 patients with acute bacterial meningitis, absolute rCBF (in ml/100 g min,1) was measured during baseline ventilation and hyperventilation by single-photon emission computed tomography (SPECT) using intravenous 133Xe bolus injection. Intravenous 99mTc-HMPAO (hexamethylpropyleneamine oxime) was subsequently given during hyperventilation. In 12 healthy volunteers, rCBF was measured by SPECT and 99mTc-HMPAO during spontaneous ventilation. Using standard templates to identify regions of interest (ROIs), we calculated rCBF in percentage of cerebellar (99mTc-HMPAO images) or mean hemispheric (133Xe images) flow for each ROI, the degree of side-to-side asymmetry for each ROI, and the anterior-to-posterior flow ratio. On 133Xe images, absolute rCBF decreased significantly during hyperventilation compared to baseline ventilation in all regions, but the relative rCBF did not change significantly from baseline ventilation (n=14) to hyperventilation (n=12), indicating that the perfusion distribution was unchanged. On 99mTc-HMPAO images (n=12), relative rCBF and the anterior-to-posterior flow ratio were significantly lower in patients than in controls in the frontal and parietal cortex as well as in the basal ganglia. Focal perfusion abnormalities were present in 10 of 12 patients. Regional cerebral blood flow abnormalities are frequent in patients with acute bacterial meningitis. Short-term hyperventilation does not enhance these abnormalities. [source]

Multiple Inert Gas Elimination Technique For Determining Ventilation/Perfusion Distributions In Rat During Normoxia, Hypoxia And Hyperoxia

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2001
V Alfaro
SUMMARY 1. The use of the multiple inert gas elimination technique (MIGET) in quantifying ventilation/perfusion distributions (V,A/Q,) in small animals, such as the rat, may cause results to be biased due to haemodilution produced by the large volume of liquid infused intravenously. 2. We tested two methods of administering inert gases in rats using the MIGET: (i) standard continuous intravenous administration of inert gases (method A); and (ii) a new method based on the physicochemical properties of each inert gas (method B). This method included acute simultaneous inert gas administration using three pathways: inhalation, intravenous infusion and rectal infusion. Both MIGET methods were applied to obtain data while breathing three different inspiratory fractions of oxygen (FIO2): normoxia, hypoxia and hyperoxia. 3. Inert gas levels obtained from blood or expired air samples were sufficient for chromatographic measurement, at least during a 2 h period. The V,A/Q, distributions reported using both methods were acceptable for all the physiological conditions studied; therefore, the alternative method used here may be useful in further MIGET studies in rats because haemodilution resulting from continuous intravenous infusion of less-soluble gases can be avoided. 4. Normoxic rats showed lower mean values of the V,A/Q, ratio of ventilation distribution and higher mean values of the V,A/Q, ratio of perfusion distribution with the usual method of inert gas administration (method A). These non-significant differences were observed under almost all physiological conditions studied and they could be caused by haemodilution. Nevertheless, the effect of interindividual differences cannot be discarded. An additional effect of the low haematocrit on cardiovascular changes due to low FIO2, such as pulmonary vasoconstriction or increased cardiac output, may explain the lower dispersion of perfusion distributions found in group A during hypoxia. [source]