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The systemic circulation to the lung supplies the trachea and airway walls and may be important in the pathophysiology of asthma and pulmonary oedema. An understanding of the venous drainage pathways of this bronchial blood flow may be therapeutically important. The purpose of this study was to understand the normal drainage pathways in sheep. In seven anaesthetized, ventilated sheep we injected echo contrast agents into a systemic vein or into the bronchial artery while performing echocardiography to determine whether the drainage could be observed to the right heart and/or to the left heart. During transoesophageal echo (n=5) or heart surface echo (n=2), cephalic vein injection of <8 microm diameter gelatin microballoons promptly opacified the right but never the left-sided circulation. Air in agitated saline in the seven animals showed the same result. By contrast, injection into the bronchial artery promptly opacified the left atrium, left ventricle, and aorta but not the right-sided circulation in all seven microballoon injections and all but one of the air in agitated saline injections. The failure of the echo agents to pass through the pulmonary circulation may be related to sheep pulmonary intravascular macrophages or the surface forces on air bubbles of small size promoting collapse. The main conclusion is that there are bronchopulmonary anastomoses that connect the bronchial circulation to the pulmonary venous circulation connecting distal to the pulmonary capillaries. Any bronchial venous drainage to the right-sided circulation must have been below the detection level of the instruments and would in any case appear to be much less that the post-pulmonary capillary anastomoses noted. Pulmonary venous hypertension would be expected to have a direct effect on the bronchial circulation.

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This study was designed to test the hypothesis that severe atherosclerosis changes aortic compliance. Compliance of a vessel is defined as change in volume per unit change in pressure and is a measure of the stiffness or distensibility of the vascular wall. Part of the energy delivered by the left ventricle in systole is used to propel the blood forward into the aorta and part of it to distend the aorta and major vessels. During diastole, the arterial walls recoil and provide energy for propulsion of blood, thereby making blood flow continuous. It is known that Watanabe hereditary hyperlipidemic rabbits develop severe atherosclerosis beginning at 6 months of age. Compliance of the ascending thoracic aorta was studied angiographically in eight Watanabe hereditary hyperlipidemic rabbits of ages greater than 6 months and six normal lipidemic New Zealand white rabbits of ages greater than 6 months, used as controls. The normal New Zealand white rabbits had an average blood cholesterol of 27.4 mg/dL, SD = 13.8, and a regional compliance in the ascending aorta of 0.004 mL/mm Hg, SD = 0.002, compared to the Watanabe hereditary hyperlipidemic rabbits with a cholesterol of 583.1 mg/dL, SD = 162.7, and a compliance of 0.0022 mL/mm Hg, SD = 0.0015. These are significant differences (p less than .05). In addition, the histopathology of the aorta of the Watanabe hyperlipidemic rabbit compared to that of the controls showed a significant decrease in the number of medial lamellar elastin units, an indicator of the decreased elasticity of the blood vessel wall.

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The author used blood flow measurements to guide partial splenic embolization procedures in five patients. The measurements were obtained by time density analysis of contrast medium injections in the splenic artery using digital subtraction angiographic techniques and modified software. The blood flow measurements demonstrated blood flow changes occurring as a result of the embolization. The embolization procedures continued until the blood flow in the splenic artery had been reduced to 50% of its original value. The blood flow measurements appear to predict the amount of parenchymal reduction achieved by embolization and show promise as a method of monitoring these procedures.

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Recent in vitro studies on isolated coronary and mesenteric arteries have shown that hyperlipidemia appears to hypersensitize the vascular arterial smooth muscle to drugs such as ergonovine and that this increased contractility seems to be mediated by a serotinergic mechanism. This results in vasospasm with exposure to certain vasoactive drugs such as serotonin or norepinephrine. However, in vivo quantification of this observed phenomenon has not been done. In the present study we used Watanabe hereditary hyperlipidemic (WHHL) rabbits (cholesterol level 459 +/- 216 mg/dL) and the normal lipidemic New Zealand white (NZW) rabbit (cholesterol level 35 +/- 19) as a control in the study of hyperlipidemia and blood flow changes in response to various vasoactive drugs. Blood flow measurements were made by the video dilution technique (VDT) following catheterization of the superior mesenteric artery. The serotinergic vasoactive drug ergonovine maleate was injected into the superior mesenteric artery at low dose (0.002) mg/kg) and high dose (0.004 mg/kg). A significant decrease (p less than .05) in blood flow was observed in response to high-dose ergonovine maleate in WHHL rabbits compared to the NZW rabbits. This in vivo experiment confirms the in vitro studies showing that hyperlipidemia sensitizes mesenteric arteries in the presence of serotinergic stimuli. The vasodilators verapamil hydrochloride and calcitonin gene-related peptide (CGRP) injected into the superior mesenteric artery caused a marked increase in flow in both the WHHL and the normal lipidemic NZW rabbits. This model can be used in the assessment of superior mesenteric artery ischemia and its reversal.

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Partial embolization of the spleen has been well established for the treatment of hypersplenism. A weakness of the technique is the lack of an objective method to quantitate the flow reduction during the procedure. The video dilution technique (VDT) has earlier been used to measure blood flow in regional arteries using video cassette replay. By adapting the VDT concept of relative flow to digital subtraction angiography, it is possible to calculate the flow reduction instantly following each injection of embolic material. We present a case of partial splenic embolization where the flow in the splenic artery was reduced to a predetermined level of 50 per cent of baseline flow. The clinical results were excellent. By observing the clinical results of partial embolization, terminated at different levels of flow reduction, it will be possible to optimize the results and prevent overembolization.

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Experimental embolization of the renal artery with cross-linked dextran (CLD) microspheres was performed in 6 dogs. The blood flow was monitored by electromagnetic flow meter (EM) in 3 dogs and by video dilution technique (VDT), adapted to an angiographic digital subtraction system, in a second group of 3 dogs. Retrograde flow in the embolized renal artery was detected by 99Tcm microspheres. Sequential emboli produce a predictable and equal flow response with both measuring techniques. Thus, the less invasive VDT can be used in the clinical setting to optimize and control embolization procedures. This type of flow monitoring has great potential in alerting the angiographer when approaching the risk level for retrograde flow.

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The intent of this experiment was to study the postsynaptic vasoactive response to tolazoline hydrochloride and sodium-meglumine diatrizoate (Renografin-76) after a unilateral lumbar sympathectomy in a dog model. Both lower extremities were examined using the video dilution technique before and 1-2 weeks after unilateral lumbar sympathectomy (SE). Results showed (1) resting blood flow in the femoral artery as a percentage of cardiac output did not change after sympathectomy (mean and SD before and after SE: 7.0% +/- 2.3 and 6.0% +/- 2.9 respectively n = 13); (2) the reactive hyperemia in the femoral artery caused by sodium-meglumine diatrizoate (Renografin-76) was unchanged after sympathectomy; (3) the vasodilator effect of tolazoline hydrochloride decreased significantly after sympathectomy (p less than 0.05).

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Since enhanced sensitivity to verapamil in essential hypertension has been noted, a relationship between verapamil and the sympathetic nervous system has been suggested. It has also been noted that both verapamil and lumbar sympathectomy appear to decrease the vasospasm seen in Raynaud's phenomenon. To further investigate the possible interrelationship between verapamil and the sympathetic nervous system, a unilateral lumbar sympathectomy was performed on eight dogs. Two weeks later the femoral artery blood flow response to intra-arterial verapamil was compared on the sympathectomy limb side and the non-sympathectomy limb side. Blood flow measurements were done without surgical trauma by video dilution technique. Although baseline femoral artery blood flow was unchanged and equal on both sides following sympathectomy (4.6% of cardiac output), there was a significant rise, p less than 0.05, in the blood flow response to verapamil on the side of sympathectomy. Therefore, sympathectomy appears to enhance the calcium channel blocking properties of verapamil.

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Bronchial blood flow was studied with the video dilution technique (VDT) in seven sheep. All animals were anesthetized (thiamylal and halothane) and ventilated. A videodensitometer and a videotape replay of the fluoroscopic image of dye moving through the common bronchial artery were used to construct dye mass vs. time curves. The areas under the curves were inversely proportional to flow in the bronchoesophageal artery, the site of dye injection. At thoracotomy, an electromagnetic flow probe (EMFP) was placed on the common bronchial artery (the major branch of the bronchoesophageal artery) to measure blood flow changes simultaneously by EMFP and by VDT. These two methods of measurement of blood flow to the airways were compared to validate the use of VDT in this circulation. Common bronchial artery blood flow was increased by injection of radiocontrast dye into the fluoroscopically positioned bronchoesophageal artery catheter causing hyperosmotically induced hyperemia. In 160 simultaneous measurements in five sheep, the percent change in flow as measured by EMFP and VDT correlated closely (r = 0.96). When flow changed because of spontaneous aortic pressure changes or pharmacologic intervention (28 simultaneous measurements in five sheep), the percent change in flow by EMFP and VDT also correlated well (r = 0.98). Bronchial blood flow changes in sheep can be measured accurately using the video dilution technique.

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Quantitative flow measurements were assessed in both laboratory and canine models using pulsed Doppler ultrasonography (US). A hydrodynamic model consisting of a Harvard pulsatile pump, a water bath, tubing, and a variable resistance reservoir was used to obtain absolute volumetric flow measurements. Parameters including angle of incidence, size of tubing, stroke volume, stroke rate, sample volume, and transducer frequency were changed independently. The effect of varying these parameters on the determination of absolute flow was analyzed. Absolute flow measurements using duplex US were performed in the canine aorta and femoral artery with reference to the electromagnetic flow probe. These data are presented, along with methods to reduce error in flow measurements that can be directly applied to quantitative estimates of blood flow in humans.

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Bronchial blood flow was determined in five adult anaesthetised sheep by the video dilution technique. This is a new fluoroscopic technique for measuring blood flow that requires only arterial catheterisation. Catheters were placed into the broncho-oesophageal artery and ascending aorta from the femoral arteries for contrast injections and subsequent videotape recording. The technique yields bronchial blood flow as a percentage of cardiac output. The average bronchial artery blood flow was 0.6% (SD 0.20%) of cardiac output. In one sheep histamine (90 micrograms) injected directly into the bronchial artery increased bronchial blood flow by a factor of 6 and histamine (90 micrograms) plus methacholine (4.5 micrograms) augmented flow by a factor of 7.5 while leaving cardiac output unchanged. This study confirms the high degree of reactivity of the bronchial circulation and demonstrates the feasibility of using the video dilution technique to investigate the determinants of total bronchial artery blood flow in a stable animal model avoiding thoracotomy.

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The pneumatic antishock garment is widely used in trauma patients because it compresses small veins and should augment venous return. If the garment does augment venous return, it should probably be used in all injured patients in shock, regardless of injuries and regardless of anticipated transport time. On the other hand, the garment could distort and narrow large retroperitoneal and abdominal veins and impede venous return. We quantitated venous return in normovolemic and hypovolemic baboons. The garment both augmented and impeded venous return, the two effects counteracting each other. We believe that the pneumatic antishock garment should be used selectively.

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A rare occurrence of carotid subclavian steal syndrome following carotid subclavian bypass for arm ischemia was described. Blood flows in the carotid artery and carotid subclavian bypass, at rest and following arm exercise, were determined by video dilution technique during the angiographic procedure. There was no obstruction of the inflow or outflow of the proximal or distal anastomoses to account for the steal (55%). Rather, increased arterial flow to the subclavian artery due to the patient's status as a bilateral amputee was thought to be the cause. The diagnosis and subsequent correction by takedown of this bypass and conversion to an axillary-to-axillary bypass were performed. Video dilution technique offers a unique and accurate way to study steal phenomena in conjunction with routine angiography and does not add to the patient's cost or risk.

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The vasoactive effect of the angiographic contrast medium Conray-60 (iothalamate meglumine 60%) on carotid blood flow was studied by the video dilution technique in 26 subjects during routine neuroangiography. After a test series of 1 ml injections of contrast material into the carotid arteries at designated time intervals, an increase in carotid blood flow was found in normal controls at 30 sec, while a significant decrease in flow was observed in patients with atheromatous disease and avascular intracranial masses (p less than 0.01). Test responses in patients with intracranial aneurysm, neoplasm, and granulomatous vasculitis are also reported. The differential effect of contrast material on the cerebral circulation correlates well with several pathologic states of the central nervous system and may be used as a simple test to diagnose and evaluate a variety of vascular disorders.

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Carotid blood flows were evaluated in 31 individuals with vascular abnormalities using the video dilution technique. In patients with stenoses, angiographically estimated at 70%, blood flow was usually, but not always, measured less than normal. The technique proved to be useful in the evaluation of the efficiency of collateral arterial pathways and in the evaluation of superficial temporal-middle cerebral arterial bypass grafts. It was also helpful in estimating contralateral increase in arterial flows with cross compression techniques for the preoperative evaluation of patients subjected to carotid sacrifice. In a limited number of patients video dilution flows correlated with the degree or proximal arterial spasm and were useful in the preoperative study of these patients. The demonstration of flow abnormalities in patient with seizure disorders may be useful in the medical and surgical management of these individuals.

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A new functional test is presented whereby the severity of peripheral obstructive disease can be evaluated during routine angiography utilizing the vasodilator effect of standard contrast medium. The hyperemic response following a sequence of 1 or 2 ml contrast injections into the iliac or femoral arteries is recorded by video dilution technique. The method allows quantitative measure of the functional state of the lower extremity. The vasodilator response in 10 normal human subjects and 23 patients with arterial obstructive disease in compared. Increasing depression of peak flow correlates with increasing symptomatology and a delay in the time to peak flow is seen with small vessel (outflow) disease. The functional severity of outflow disease (trifurcation and superficial femoral artery) as compared with inflow obstruction (iliac arteries) seen at angiography is documented by the test. A new staging of peripheral obstructive disease is proposed based on the results.

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The vasodilator response induced by injections of contrast medium was observed in 11 dogs by electromagnetic flow technique. The experiments were performed to further understand video dilution technique (VDT) measurements in patients with arterial obstructive disease. Responses were observed with regard to the contrast dose relationship, time to peak flow, and abnormal flow produced up to 4 ml caused increasing magnitude of peak flow. The time to peak flow was relatively constant for all doses. Mechanical constrictions depressed th peak flow magnitude but did not affect the time to peak. Emboli produced both depression of the flow magnitude and a delay in time to peak flow. The data suggest that the VDT vasodilatory response curves obtained in patients should correlate with the degree of obstructive disease and delay in the peak flow implies outflow disease.

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A standardized test series of contrast medium injections was performed in the iliac and femoral arteries to evaluate the immediate effect of percutaneous transluminal angioplasty. The vasodilator response recorded by video dilution technique was correlated to radiographic anatomy and symptomatology. Discrepancy between anatomic success and clinical relief of symptoms was found in 26 per cent of the dilatations. The severity of disease at the trifurcation was more marked in combination with femoral lesions than with corresponding iliac lesions. Rest pain was a common symptom with femoral lesions and rare with iliac lesions. Resting blood flow increased significantly after femoral dilatation but was unaffected by iliac dilatations. The video dilution technique provided an accurate staging of the severity of obstructive disease, and was an excellent predictor of subsequent symptomatic success or failure of percutaneous transluminal angioplasty.

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