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Pulmonary gas exchange
Published in Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson, Ward, Milledge and West's High Altitude Medicine and Physiology, 2021
Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson
Another suggested source of right-to-left shunt is intrapulmonary arteriovenous anastomoses (Lovering et al. 2015). Following three weeks of acclimatization to 5050 m in volunteers without a PFO, it was reported that the bubble score, an index of blood flow through the intrapulmonary arteriovenous anastomoses assessed using transthoracic saline contrast echocardiography, was significantly reduced at maximal exercise when compared to sea level (Foster et al. 2014). These findings, in the absence of any changes in the (A-a)ΔO2, were confirmed upon measurement within a few hours of arrival to 5260 m; similar findings were also apparent in a chamber study in both normoxic and hypobaric hypoxia (Petrassi et al. 2018). The physiological significance of intrapulmonary arteriovenous anastomoses at altitude remain unclear but they do not seem important from the perspective of gas exchange efficiency.
Stomach Microcirculation
Published in John H. Barker, Gary L. Anderson, Michael D. Menger, Clinically Applied Microcirculation Research, 2019
The presence of arteriovenous communications in the gastric submucosa or mucosa is controversial. Arteriovenous anastomoses has been described by Barlow et al.2 in human subjects and by Hase and Moss8 and Nylander and Olerud9 in rats, employing arterial injection techniques. However, Guth and Rosenberg3 and Gannon et al.,7 using vital microscopy, did not find either type of shunt, observing the gastric microcirculation of rats.
Aspects of Circulatory Responses in Animals Pertinent to the Use of Hyperthermia in Cancer Treatment
Published in Leopold J. Anghileri, Jacques Robert, Hyperthermia in Cancer Treatment, 2019
Note in Figure 2 that up to a mean of 11% (30% in rare individual cases) of the cardiac output passed through arteriovenous anastomoses (AVAs). These vessels provide high volume, low resistance pathways for blood which does not participate in exchanges of nutrients. The other microsphere-measured tissue blood flow values reported represent capillary or nutrient blood flow, which will be less than total flow if AVAs are patent.
An ultrasound-guided no incision banding method for the treatment of arteriovenous fistula high-flow in hemodialysis
Published in Renal Failure, 2023
Yanan Wang, Jin Li, Wenjun Liu, Ying Zhang, Qing Li, Fan He
The whole procedure was guided with the duplex Doppler ultrasound (DUS). A surgical suture (Ethicon Vicryl, 2-0 size) was used with an indwelling needle (BRAUN Germany, 18 G) to traverse the arteriovenous anastomosis. DUS was performed to facilitate visualization of the needle and to determine brachial artery flow. Firstly, 2 indwelling needles were prepared, one with the original shape and the other bent for standby (Figure 2(a)). The curved indwelling needle passed through the bottom of the vessel proximity to the anastomosis under the guidance of ultrasound, and then the needle was pulled out to let the surgical suture reach the other side through the sheath (Figure 2(b)). The other indwelling needle was used to bypass the thread above the anastomosis (Figure 2(c)). Finally, the brachial artery flow was monitored by DUS, and the thread was knotted subcutaneously until the appropriate artery flow was reached (600-800 mL/min) (Figure 2(d)). The ultrasonic performance of the operation process is shown in Video S1.
Advances in thermal physiology of diving marine mammals: The dual role of peripheral perfusion
Published in Temperature, 2022
Arina B. Favilla, Markus Horning, Daniel P. Costa
What makes blubber the ideal insulator also makes it challenging for in vivo studies. Blubber is internal, which allows for blood to bypass this insulation when needed (Figure 3a). A complex microvasculature network exists within the skin and blubber of marine mammals [23,24,30–32]. Superficial vessels are associated with arteriovenous anastomoses. These structures allow fine-scale adjustment to blubber’s insulative and transmissive properties by either constricting or dilating to regulate peripheral perfusion. By effectively modifying their conductance, marine mammals control the characteristics of the thermal gradient (Figure 3b) and can maintain a high core body temperature while immersed in water [33,34]. Therefore, understanding the thermoregulatory strategies of diving marine mammals requires examining the physiological mechanisms that influence heat transfer at their periphery.
Ocular Manifestations in an Italian Cohort of Patients with Takayasu Arteritis
Published in Ocular Immunology and Inflammation, 2023
Rosanna Dammacco, Luca Cimino, Luca De Simone, Giovanni Alessio, Franco Dammacco
Takayasu retinopathy (TR), characterized by chronic ischemia, was staged according to the classification system of Uyama and Asayama30: stage 1) dilation of retinal veins; stage 2) microaneurysm formation, mostly in the posterior pole; stage 3) arteriovenous anastomosis, usually in the peripapillary area; stage 4) ischemic complications such as retinal neovascularization, iris rubeosis, proliferative retinopathy, vitreous hemorrhage, and neovascular glaucoma (Figure 1).