Intrapulmonary Shunt During Normoxic and Hypoxic Exercise in Healthy Humans

Lovering, Andrew T.; Stickland, Michael K.; Eldridge, Marlowe W.

doi:10.1007/978-0-387-34817-9_4

Cited by 25 publications

(18 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Despite our current findings and the findings of others (24 -26, 28), there are reports that suggest these vessels do not exist in humans (12,27). Based on our findings in exercising humans, these pathways appear to be recruitable since they are not open at rest but become functional during exercise (5,14,22). Furthermore, these pathways are likely small in number, as suggested by our findings of small shunt fractions.…”

Section: Discussionmentioning

confidence: 80%

“…intrapulmonary arteriovenous anastomoses; shunt; baboon; pulmonary circulation RECENT WORK has demonstrated the transpulmonary passage of saline contrast microbubbles during exercise, but not at rest, in healthy adult human subjects without cardiac anomalies, suggesting that intrapulmonary arteriovenous pathways are recruited during hyperdynamic conditions (5,14,22). Although the actual size of the saline contrast microbubbles is not known, theoretical and experimental data have estimated that the size distribution of microbubbles that survive to enter the pulmonary microcirculation to be 60 to 90 m in diameter (8,10,16,31,32).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Direct demonstration of 25- and 50-μm arteriovenous pathways in healthy human and baboon lungs

Lovering

Stickland²,

Kelso³

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

Self Cite

View full text Add to dashboard Cite

Lovering AT, Stickland MK, Kelso AJ, Eldridge MW. Direct demonstration of 25-and 50-m arteriovenous pathways in healthy human and baboon lungs. Am J Physiol Heart Circ Physiol 292: H1777-H1781, 2007. First published December 1, 2006; doi:10.1152/ajpheart.01024.2006.-Postmortem microsphere studies in adult human lungs have demonstrated the existence of intrapulmonary arteriovenous pathways using nonphysiological conditions. The aim of the current study was to determine whether large diameter (Ͼ25 and 50 m) intrapulmonary arteriovenous pathways are functional in human and baboon lungs under physiological perfusion and ventilation pressures. We used fresh healthy human donor lungs obtained for transplantion and fresh lungs from baboons (Papio c. anubis). Lungs were ventilated with room air by using a peak inflation pressure of 15 cmH 2O and a positive end-expiratory pressure of 5 cmH2O. Lungs were perfused between 10 and 20 cmH2O by using a phosphate-buffered saline solution with 5% albumin. We infused a mixture of 25-and 50-m microspheres (0.5 and 1 million total for baboons and human studies, respectively) into the pulmonary artery and collected the entire pulmonary venous outflow. Under these conditions, evidence of intrapulmonary arteriovenous anastomoses was found in baboon (n ϭ 3/4) and human (n ϭ 4/6) lungs. In those lungs showing evidence of arteriovenous pathways, 50-m microspheres were always able to traverse the pulmonary circulation, and the fraction of transpulmonary passage ranged from 0.0003 to 0.42%. These data show that intrapulmonary arteriovenous pathways Ͼ50 m in diameter are functional under physiological ventilation and perfusion pressures in the isolated lung. These pathways provide an alternative conduit for pulmonary blood flow that likely bypasses the areas of gas exchange at the capillary-alveolar interface that could compromise both gas exchange and the ability of the lung to filter out microemboli.intrapulmonary arteriovenous anastomoses; shunt; baboon; pulmonary circulation RECENT WORK has demonstrated the transpulmonary passage of saline contrast microbubbles during exercise, but not at rest, in healthy adult human subjects without cardiac anomalies, suggesting that intrapulmonary arteriovenous pathways are recruited during hyperdynamic conditions (5,14,22). Although the actual size of the saline contrast microbubbles is not known, theoretical and experimental data have estimated that the size distribution of microbubbles that survive to enter the pulmonary microcirculation to be 60 to 90 m in diameter (8,10,16,31,32). These estimates prompted Eldridge et al. (5) to suggest that these inducible intrapulmonary arteriovenous pathways must be at least 60 m in diameter. Postmortem studies in adult human lungs have documented the existence of intrapulmonary arteriovenous pathways for more than 100 years (20). More recent studies using microspheres have demonstrated that these vessels are functional under various conditions. For example, Tobin and Zariquiey (25) demonstrated that arteriove...

show abstract

Section: Discussionmentioning

confidence: 80%

mentioning

confidence: 99%

Direct demonstration of 25- and 50-μm arteriovenous pathways in healthy human and baboon lungs

Lovering

Stickland²,

Kelso³

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

Self Cite

View full text Add to dashboard Cite

show abstract

“…Recanalisation vessels within organised pulmonary arterial emboli, as well as peripheral pulmonary arteries displaying eccentric intimal fibrosis, showed intermixture of green and blue ink, suggesting not only a direct connection between systemic and pulmonary arteries, but also between the latter and pulmonary veins, in other words pulmonary arteriovenous shunting. Although we will not discuss this point extensively, since these findings were sparse in our analysis, the phenomenon has been shown for humans and animals under exercise conditions [26][27][28]. The pattern of hypertrophy and enlargement of systemic bronchial arteries is well known in CTEPH [25,29].…”

Section: Intrapulmonary Systemic Vesselsmentioning

confidence: 89%

Microvascular disease in chronic thromboembolic pulmonary hypertension: a role for pulmonary veins and systemic vasculature

et al. 2014

View full text Add to dashboard Cite

Limited numbers of operated patients with chronic thromboembolic pulmonary hypertension (CTEPH) are refractory to pulmonary endarterectomy (PEA) and experience persistent pulmonary hypertension (PH).We retrospectively assessed lung histology available from nine patients with persistent PH (ineffective PEA (inPEA) group) and from eight patients transplanted for distal CTEPH inaccessible by PEA (noPEA group). Microscopically observed peculiarities were compared with the histology of a recently developed CTEPH model in piglets. Pre-interventional clinical/haemodynamic data and medical history of patients from the inPEA and noPEA groups were collected and analysed.Conspicuous remodelling of small pulmonary arteries/arterioles, septal veins and pre-septal venules, including focal capillary haemangiomatosis, as well as pronounced hypertrophy and enlargement of bronchial systemic vessels, were the predominant pattern in histology from both groups. Most findings were reproduced in our porcine CTEPH model. Ink injection experiments unmasked abundant venular involvement in so-called small vessel or microvascular disease, as well as post-capillary bronchopulmonary shunting in human and experimental CTEPH.Microvascular disease is partly due to post-capillary remodelling in human and experimental CTEPH and appears to be related to bronchial-to-pulmonary venous shunting. Further studies are needed to clinically assess the functional importance of this finding. @ERSpublications Pulmonary veins and systemic vasculature contribute to microvascular disease in CTEPH

show abstract

“…We and others have documented the presence of transiently recruitable IPAVs in ∼90% of healthy humans. [2][3][4]8,9,[29][30] Although the size of IPAVs has never been directly determined in humans under physiologic conditions, data from isolated lung and intact animal studies suggest that these pathways are large (.200 mm) and are located early in the pulmonary vascular tree. 1,[31][32][33] Why Is This Case Relevant to the Clinician?…”

Section: Discussionmentioning

confidence: 99%

“…We and others have speculated that IPAVs might exist to modulate the distribution of perfusion in the face of high pulmonary pressures and flows. 1,[6][7][8][9][10][11] Experimentally, IPAV recruitment can be prevented or reversed by 100% O 2 breathing. 4 The fact that only brief periods of hyperoxia are needed suggests that O 2 acts locally on the vasculature.…”

mentioning

confidence: 99%

Transient Intrapulmonary Shunting in a Patient Treated With β2-Adrenergic Agonists for Status Asthmaticus

Bates¹,

Jacobson

Eldridge

2014

Pediatrics

Self Cite

View full text Add to dashboard Cite

Intrapulmonary arteriovenous anastomoses (IPAVs) are largediameter pathways that directly connect the arterial and venous networks, bypassing the pulmonary capillaries. Ubiquitously present in healthy humans, these pathways are recruited in experimental conditions by exercise, hypoxia, and catecholamines and have been previously shown to be closed by hyperoxia. Whether they play a role in pulmonary pathophysiology is unknown. Here, we describe IPAV recruitment associated with hypoxemia and right-to-left shunt in a patient with status asthmaticus, treated with agonists of the B 2 -adrenergic pathway. Our observation of IPAVs in a pediatric patient, mechanically ventilated with 100% O 2 , suggests that these pathways are recruited in clinically important circumstances and challenges the notion that IPAVs are always closed by alveolar hyperoxia.

show abstract

Intrapulmonary Shunt During Normoxic and Hypoxic Exercise in Healthy Humans

Cited by 25 publications

References 60 publications

Direct demonstration of 25- and 50-μm arteriovenous pathways in healthy human and baboon lungs

Direct demonstration of 25- and 50-μm arteriovenous pathways in healthy human and baboon lungs

Microvascular disease in chronic thromboembolic pulmonary hypertension: a role for pulmonary veins and systemic vasculature

Transient Intrapulmonary Shunting in a Patient Treated With β2-Adrenergic Agonists for Status Asthmaticus

Contact Info

Product

Resources

About