Influence Of Vessel Diameter Research Articles

Influence of vessel diameter on the efficacy of distal protection devices during saphenous vein graft intervention

We sought to determine the influence of vessel diameter on the efficacy of distal protection devices during saphenous vein graft intervention. From the Filterwire EX Randomized Evaluation trial, in which patients who underwent saphenous vein graft stenting were randomized to distal protection with the GuardWire or FilterWire EX, outcomes in 572 patients were examined in vessel size tertiles. The 30-day composite incidence of major adverse cardiac events (MACEs) increased with vessel size and was 6.9%, 9.7%, and 14.9% in the smallest, middle, and largest tertiles, respectively (p = 0.04). MACE rates were relatively vessel size independent for the GuardWire but increased steadily with vessel size with the FilterWire EX. In the smallest tertile, MACEs were reduced by 71% with the FilterWire EX compared with the GuardWire (p = 0.05), with the devices showing similar event rates in the other tertiles.

Hypoxia, Metabolic Inhibition, and Isolated Rat Mesenteric Tone: Influence of Arterial Diameter

The present study examined and compared the effects of severe hypoxia (induced by either substitution of O2 in the gassing medium with N2 or by addition of the O2 scavenger sodium dithionite) and metabolic inhibition (induced by addition of sodium cyanide) on the tone of isolated rat mesenteric resistance vessels. The influence of vessel diameter and the endothelium on responses to these maneuvers was investigated. Hypoxia (due to both substitution of O2 with N2 and by addition of 2 mM sodium dithionite) caused near maximal relaxation of all tissues studied. Addition of 10 mM dithionite, however, produced a significantly smaller response. Two mM cyanide also relaxed mesenteric arteries. In small vessels a near maximal relaxation to cyanide was observed, however, in larger vessels the relaxation to metabolic inhibition was significantly less than that observed to hypoxia. Increasing the concentration of cyanide had no further effect on responses. All responses were found to be endothelium-independent. Thus, as the effects of hypoxia and cyanide are not always similar, care must be taken when extrapolating the effects of metabolic inhibition to those of hypoxia. The results of this study suggest that, in large mesenteric vessels at least, an “O2 sensing step,” in addition to effects of metabolism, may be involved in the hypoxic response.

Influence of vessel diameter on red cell distribution at microvascular bifurcations

The uneven distribution of red blood cells (RBCs) to daughter branches at microvascular bifurcations, often referred to as “plasma skimming,” has been characterized in previous studies by comparisons of flux-flow plots of red cell flow fraction ( F∗) versus volumetric flow fraction ( Q∗) at single junctions. Comparisons of flux-flow plots for single bifurcations with differing daughter/parent vessel diameter ratios ( D d D p = 1.0 vs 0.5 ) have been made to reveal the influence of vessel size on red cell distribution at vessel junctions of four different geometries (100 × 100, 50 × 50, 100 × 50, 50 × 25 μm). Experimental data determined by effluent collection were compared to those from video fluorescence microscopy experiments, as well as to numerical computations from theoretical models. Statistical comparisons using a likelihood ratio test indicate that vessel diameter ratio, D d D p has no detectable influence on RBC distribution in these microvascular bifurcations.

Surface geometry of a liquid explosive burning beyond the stability limit

After L. D. Landau's work [1] on the stability of normal burning of liquid explosives, many experimental studies of this phenomenon, e. g., [2, 3], were published. In this paper, on the basis of Landau's theory, we investigate the geometry of the perturbations which develop on the surface of the liquid explosive in a vessel of circular cross section and consider the influence of vessel diameter on burning stability. Results of an experimental observation of the geometry of the liquid surface are also presented for developed turbulent combustion in a circular cylindrical tube. The calculation was based on the usual assumptions that the chemical reaction of combustion proceeds in a thin layer of vapor over the plane (meniscus neglected) surface of the inviscid liquid explosive.