Exercise- and hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses is reduced in older adults

Norris, H. Cameron; Mangum, Tyler S.; Duke, Joseph W.; Straley, Taylor B.; Hawn, Jerold A.; Goodman, Randy D.; Lovering, Andrew T.

doi:10.1152/japplphysiol.01125.2013

Cited by 33 publications

(14 citation statements)

References 45 publications

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“…Every injection was scored by a registered diagnostic cardiac sonographer with Ͼ25 (R. D. Goodman; field study) or Ͼ10 (J. E. Futral; chamber study) yr of experience. The reproducibility of this scoring system has been validated previously in our laboratory in three separate studies (16,40,54), showing 92-100% agreement between independent and blinded observers, including a cardiologist. Both the field and chamber study include female subjects; however, previous work has shown that Q IPAVA during exercise does not differ between women and men (34).…”

Section: Bubble Scoringmentioning

confidence: 84%

“…It is believed that the maximal Q IPAVA ranges from 2 to 5% of the cardiac output (44). Although it is unlikely that redistribution of 2-5% of the cardiac output would have a significant impact on pulmonary arterial pressure, there is an association of Q IPAVA with pulmonary pressure during exercise in young and older adults (54). Specifically, high Q IPAVA is associated with low pulmonary pressure, whereas low Q IPAVA is associated with higher pulmonary artery pressures.…”

Section: Factors Affecting Contrast Bubbles In Hypobaria In Vivomentioning

confidence: 99%

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AltitudeOmics: effect of reduced barometric pressure on detection of intrapulmonary shunt, pulmonary gas exchange efficiency, and total pulmonary resistance

Petrassi

Davis

Beasley

et al. 2018

Journal of Applied Physiology

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Blood flow through intrapulmonary arteriovenous anastomoses (Q) occurs in healthy humans at rest and during exercise when breathing hypoxic gas mixtures at sea level and may be a source of right-to-left shunt. However, at high altitudes, Q is reduced compared with sea level, as detected using transthoracic saline contrast echocardiography (TTSCE). It remains unknown whether the reduction in Q (i.e., lower bubble scores) at high altitude is due to a reduction in bubble stability resulting from the lower barometric pressure (P) or represents an actual reduction in Q. To this end, Q, pulmonary artery systolic pressure (PASP), cardiac output (Q), and the alveolar-to-arterial oxygen difference (AaDO) were assessed at rest and during exercise (70-190 W) in the field (5,260 m) and in the laboratory (1,668 m) during four conditions: normobaric normoxia (NN; [Formula: see text] = 121 mmHg, P = 625 mmHg; n = 8), normobaric hypoxia (NH; [Formula: see text] = 76 mmHg, P = 625 mmHg; n = 7), hypobaric normoxia (HN; [Formula: see text] = 121 mmHg, P = 410 mmHg; n = 8), and hypobaric hypoxia (HH; [Formula: see text] = 75 mmHg, P = 410 mmHg; n = 7). We hypothesized Q would be reduced during exercise in isooxic hypobaria compared with normobaria and that the AaDO would be reduced in isooxic hypobaria compared with normobaria. Bubble scores were greater in normobaric conditions, but the AaDO was similar in both isooxic hypobaria and normobaria. Total pulmonary resistance (PASP/Q) was elevated in HN and HH. Using mathematical modeling, we found no effect of hypobaria on bubble dissolution time within the pulmonary transit times under consideration (<5 s). Consequently, our data suggest an effect of hypobaria alone on pulmonary blood flow. NEW & NOTEWORTHY Blood flow through intrapulmonary arteriovenous anastomoses, detected by transthoracic saline contrast echocardiography, was reduced during exercise in acute hypobaria compared with normobaria, independent of oxygen tension, whereas pulmonary gas exchange efficiency was unaffected. Modeling the effect(s) of reduced air density on contrast bubble lifetime did not result in a significantly reduced contrast stability. Interestingly, total pulmonary resistance was increased by hypobaria, independent of oxygen tension, suggesting that pulmonary blood flow may be changed by hypobaria.

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Section: Bubble Scoringmentioning

confidence: 84%

Section: Factors Affecting Contrast Bubbles In Hypobaria In Vivomentioning

confidence: 99%

AltitudeOmics: effect of reduced barometric pressure on detection of intrapulmonary shunt, pulmonary gas exchange efficiency, and total pulmonary resistance

Petrassi

Davis

Beasley

et al. 2018

Journal of Applied Physiology

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“…These pathways, which are ≥70 μm in diameter in the rat (Bates et al, 2012), and are recruited by exercise (Eldridge et al, 2004; Lovering et al, 2006, 2008a,b, 2009; Bates et al, 2014a; Cameron Norris et al, 2014), hypoxia (Lovering et al, 2006; Bates et al, 2012, 2014a), and exogenous catecholamines (Bryan et al, 2012; Laurie et al, 2012; Elliott et al, 2014) in humans. They provide a potential route for thrombi and other particles to bypass the lung filter and embolize the systemic vasculature (Lovering et al, 2010; Laurie et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Beta Adrenergic Regulation of Intrapulmonary Arteriovenous Anastomoses in Intact Rat and Isolated Rat Lungs

2017

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Intrapulmonary arteriovenous anastomoses (IPAVA) allow large diameter particles of venous origin to bypass the pulmonary capillary bed and embolize the systemic arterial circulation. IPAVA have been routinely observed in healthy humans with exercise, hypoxia, and catecholamine infusion, but the mechanism by which they are recruited is not well-defined. We hypothesized that beta-adrenergic receptor stimulation recruits IPAVA and that receptor blockade would limit hypoxia-induced IPAVA recruitment. To test our hypothesis, we evaluated the transpulmonary passage of microspheres in intact rats and isolated rats lung infused with the beta-adrenergic receptor agonist isoproterenol. We also evaluated IPAVA recruitment in intact rats with hypoxia and the beta-adrenergic receptor blocker propranolol. We found that IPAVA are recruited in the intact rat by isoproterenol and their recruitment by hypoxia can be minimized by propranolol, suggesting a role for the adrenergic system in the recruitment of IPAVA by hypoxia. IPAVA recruitment is completely abolished by ventilation with 100% oxygen. Isoproterenol also recruits IPAVA in isolated rat lungs. The fact that isoproterenol can recruit IPAVA in isolated lungs, without increased pulmonary flow, suggests that elevated cardiac output is not required for IPAVA recruitment.

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“…Whatever the cause, we hypothesized that the increase of PAP may have induced the closure of the IPAVAs with the appearance of PH. An alternative hypothesis is that IPAVAs may be localized in areas of the pulmonary circulation that are recruited under conditions of elevated pulmonary blood flow and pressure [38]. If true, then a reduction in blood flow through IPAVAs may indicate the loss of these areas of the lungs because of the pulmonary lesions secondary to A. vasorum infection.…”

Section: Discussionmentioning

confidence: 99%

Pulmonary arterial response to Angiostrongylus vasorum in naturally infected dogs: echocardiographic findings in two cases

et al. 2019

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Background Angiostrongylus vasorum is a nematode living in the pulmonary arteries of canids. Infected dogs develop severe pulmonary lesions which can potentially lead to pulmonary hypertension (PH). However, reports of PH in natural infected dogs are scant. One of the possible causes of the low prevalence of PH in A. vasorum -infected dogs could be the establishment of large diameter intrapulmonary arteriovenous anastomoses (IPAVAs), which attenuate pulmonary vascular resistance, thus reducing the pulmonary arterial pressure. The present report describes the pulmonary arterial pressure (PAP) response to A. vasorum natural infection in two dogs, assessed by echocardiography and by the saline contrast echocardiographic test (SCE). Results Both dogs showed clinical signs of respiratory disease. At presentation, case 1 did not show echocardiographic signs of PH and the SCE test was positive proving the presence of IPAVAs. However, at the follow-up visit, despite A. vasorum infection resolution, the same dog showed PH and the SCE test resulted negative, which ruled out the presence of IPAVAs. Case 2 suffered from severe pulmonary arterial hypertension and right-side congestive heart failure since the day of presentation. Saline contrast echocardiography was negative both at the time of presentation and at the follow-up visit. Conclusions In the two cases described above, the PH was not associated with IPAVAs. During A. vasorum infection, IPAVAs recruitment mechanism is able to contrast the rise of PAP until a certain level. It probably represents an initial escape mechanism of PH that, over time, exhausts its compensatory capacities allowing PAP to rise and to be detectable on echocardiography. Electronic supplementary material The online version of this article (10.1186/s13071-019-3544-2) contains supplementary material, which is available to authorized users.

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Exercise- and hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses is reduced in older adults

Cited by 33 publications

References 45 publications

AltitudeOmics: effect of reduced barometric pressure on detection of intrapulmonary shunt, pulmonary gas exchange efficiency, and total pulmonary resistance

AltitudeOmics: effect of reduced barometric pressure on detection of intrapulmonary shunt, pulmonary gas exchange efficiency, and total pulmonary resistance

Beta Adrenergic Regulation of Intrapulmonary Arteriovenous Anastomoses in Intact Rat and Isolated Rat Lungs

Pulmonary arterial response to Angiostrongylus vasorum in naturally infected dogs: echocardiographic findings in two cases

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