Microvascular research
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Microvascular research · Nov 2011
Comparative StudyComparison of laser speckle contrast imaging with laser Doppler for assessing microvascular function.
To compare the inter-day reproducibility of post-occlusive reactive hyperaemia (PORH) and sympathetic vasomotor reflexes assessed by single-point laser Doppler flowmetry (SP-LDF), integrating-probe LDF (IP-LDF) and laser speckle contrast imaging (LSCI), and the spatial variability of PORH assessed by IP-LDF and LSCI. We also evaluated the relationship between IP-LDF and LSCI perfusion values across a broad range of skin blood flows. ⋯ The reproducibility of cutaneous PORH was better when assessed with LSCI compared to SP-LDF and IP-LDF; probably due to measuring larger skin areas (lower inter-site variability). However, when measuring sympathetic vasomotor reflexes on the finger pad, reproducibility was better with SP-LDF and IP-LDF, perhaps due to the high sensitivity of LSCI to changes in skin blood flow at low levels.
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Microvascular research · Nov 2011
The microcirculatory response to compensated hypovolemia in a lower body negative pressure model.
The objective of the present study was to test the hypothesis that controlled, adequately compensated, central hypovolemia in subjects with intact autoregulation would be associated with decreased peripheral microcirculatory diffusion and convection properties and, consequently, decreased tissue oxygen carrying capacity and tissue oxygenation. Furthermore, we evaluated the impact of hypovolemia-induced microcirculatory alterations on resting tissue oxygen consumption. To this end, 24 subjects were subjected to a progressive lower body negative pressure (LBNP) protocol of which 14 reached the end of the protocol. ⋯ We found that application of LBNP resulted in: 1) a significantly decreased microvascular density (PVD) and perfusion (MFI and MFIhetero); 2) a significantly decreased THI and StO2; and 3) an unaltered resting tissue oxygen consumption rate. In conclusion, using SDF imaging in combination with NIRS we showed that controlled, adequately compensated, central hypovolemia in subjects with intact autoregulation is associated with decreased microcirculatory diffusion (PVD) and convection (MFI and MFIhetero) properties and, consequently, decreased tissue oxygen carrying capacity (THI) and tissue oxygenation (StO2). Furthermore, using a VOT we found that resting tissue oxygen consumption was maintained under conditions of adequately compensated central hypovolemia.
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Microvascular research · Nov 2011
Comparative StudyEvaluation of the effects of gender and estradiol treatment on the intestinal microcirculation during experimental sepsis.
Intestinal barrier dysfunction plays an important role in sepsis. Females may tolerate sepsis better than males, which could be due to the relative resistance of the female intestine to gut injury and inflammation when subjected to sepsis. In this study the intestinal microcirculation was investigated in 50 female and 40 male rats divided in to 9 groups of 10 animals. ⋯ We found that there was gender difference mainly in the leukocyte endothelial interaction rather than the functional capillary density (FCD), in which male showed significant increases (P<0.05) both in the leukocyte adhesion and rolling leukocytes in submucosal venules (V1 and V3) in comparison to female rats. (Leukocyte adhesion: V1 107.1 ± 49.2n/mm(2); V3 112.3 ± 68.1n/mm(2)) (Rolling leukocytes:V1 16.2 ± 10.3n/min; V3 8.4 ± 8.2n/min). In addition estradiol replacement in ovariectomized female and male rats induced significant decreases (P<0.05) in the leukocyte adhesion and rolling (V1 and V3) with a significant increase in the muscular FCD in comparison to the corresponding placebo treated groups. (Leukocyte adhesion: V1 60 ± 31 n/mm(2); V3 78.11 ± 37.6n/mm(2)) (Rolling leukocytes: V1 13.4 ± 8.9 n/min; V3 5.8 ± 7.4n/min) (Longitudinal muscular FCD (cm/cm(2)): in ovariectomized female rats 107.1 ± 12.2; in male rats 106.2 ± 15.3) (Circular muscular FCD (cm/cm(2)): in ovariectomized female rats: 84.8 ± 14.2; in male rats: 86.1 ± 15.3). We conclude that gender difference in the leukocyte endothelial interaction could explain the resistance of female intestine to injury, and that estradiol treatment could improve the intestinal microcirculation through its effects on the leukocyte endothelial interaction and the FCD both in male and ovariectomized female rats.
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Microvascular research · Nov 2011
Correlation analysis between prefrontal oxygenation oscillations and cerebral artery hemodynamics in humans.
The objective of this study is to assess the correlation between the prefrontal cerebral oxygenation oscillations measured by near-infrared spectroscopy (NIR) and cerebral artery hemodynamic parameters as measured by transcranial Doppler (TCD). A total of thirty subjects were recruited from the university to participate in this study. The cerebral oxygenation signal and TCD hemodynamic parameters were monitored on separate days. ⋯ Significant negative correlation was found between the cerebral [Hb] and [HbO(2)] oscillations in frequency intervals from I to V and the PI or RI in left external carotid artery (ECA) (p<0.005). Also weak negative correlation was found between the cerebral [Hb] and [HbO(2)] oscillations in frequency intervals III, IV, V and the mean velocity in left middle cerebral artery (MCA) (p<0.05). The results suggested that the cerebral oscillations measured from the frontal lobe were closely related to the pulsatility of ECA and reflect partly the vessel stiffness of MCA.