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Galambos C, Bush D, Abman SH, Caplan M. Prominent Intrapulmonary Shunt Vessels and Altered Lung Development in Infants With Sudden Unexplained Infant Death. J Pediatr 2023; 255:214-219.e1. [PMID: 36336004 DOI: 10.1016/j.jpeds.2022.10.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 09/29/2022] [Accepted: 10/14/2022] [Indexed: 11/06/2022]
Abstract
The purpose of this study was to evaluate intrapulmonary arteriovenous shunts in patients with and without sudden unexplained infant death. We identified open intrapulmonary bronchopulmonary anastomoses as potential pathways for right-to-left shunt in a subset of infants with sudden unexplained infant death.
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Affiliation(s)
- Csaba Galambos
- Department of Pathology and Laboratory Medicine, University of Colorado School of Medicine, Aurora, CO; Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO.
| | - Douglas Bush
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Steven H Abman
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO
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2
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Clark AR, Burrowes KS, Tawhai MH. Integrative Computational Models of Lung Structure-Function Interactions. Compr Physiol 2021; 11:1501-1530. [PMID: 33577123 DOI: 10.1002/cphy.c200011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Anatomically based integrative models of the lung and their interaction with other key components of the respiratory system provide unique capabilities for investigating both normal and abnormal lung function. There is substantial regional variability in both structure and function within the normal lung, yet it remains capable of relatively efficient gas exchange by providing close matching of air delivery (ventilation) and blood delivery (perfusion) to regions of gas exchange tissue from the scale of the whole organ to the smallest continuous gas exchange units. This is despite remarkably different mechanisms of air and blood delivery, different fluid properties, and unique scale-dependent anatomical structures through which the blood and air are transported. This inherent heterogeneity can be exacerbated in the presence of disease or when the body is under stress. Current computational power and data availability allow for the construction of sophisticated data-driven integrative models that can mimic respiratory system structure, function, and response to intervention. Computational models do not have the same technical and ethical issues that can limit experimental studies and biomedical imaging, and if they are solidly grounded in physiology and physics they facilitate investigation of the underlying interaction between mechanisms that determine respiratory function and dysfunction, and to estimate otherwise difficult-to-access measures. © 2021 American Physiological Society. Compr Physiol 11:1501-1530, 2021.
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Affiliation(s)
- Alys R Clark
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Kelly S Burrowes
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Merryn H Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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3
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Stickland MK, Tedjasaputra V, Seaman C, Fuhr DP, Collins SÉ, Wagner H, van Diepen S, Byers BW, Wagner PD, Hopkins SR. Intra-pulmonary arteriovenous anastomoses and pulmonary gas exchange: evaluation by microspheres, contrast echocardiography and inert gas elimination. J Physiol 2019; 597:5365-5384. [PMID: 31429918 PMCID: PMC6858494 DOI: 10.1113/jp277695] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 08/12/2019] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS Imaging techniques such as contrast echocardiography suggest that anatomical intra-pulmonary arteriovenous anastomoses (IPAVAs) are present at rest and are recruited to a greater extent in conditions such as exercise. IPAVAs have the potential to act as a shunt, although gas exchange methods have not demonstrated significant shunt in the normal lung. To evaluate this discrepancy, we compared anatomical shunt with 25-µm microspheres to contrast echocardiography, and gas exchange shunt measured by the multiple inert gas elimination technique (MIGET). Intra-pulmonary shunt measured by 25-µm microspheres was not significantly different from gas exchange shunt determined by MIGET, suggesting that MIGET does not underestimate the gas exchange consequences of anatomical shunt. A positive agitated saline contrast echocardiography score was associated with anatomical shunt measured by microspheres. Agitated saline contrast echocardiography had high sensitivity but low specificity to detect a ≥1% anatomical shunt, frequently detecting small shunts inconsequential for gas exchange. ABSTRACT The echocardiographic visualization of transpulmonary agitated saline microbubbles suggests that anatomical intra-pulmonary arteriovenous anastomoses are recruited during exercise, in hypoxia, and when cardiac output is increased pharmacologically. However, the multiple inert gas elimination technique (MIGET) shows insignificant right-to-left gas exchange shunt in normal humans and canines. To evaluate this discrepancy, we measured anatomical shunt with 25-µm microspheres and compared the results to contrast echocardiography and MIGET-determined gas exchange shunt in nine anaesthetized, ventilated canines. Data were acquired under the following conditions: (1) at baseline, (2) 2 µg kg-1 min-1 i.v. dopamine, (3) 10 µg kg-1 min-1 i.v. dobutamine, and (4) following creation of an intra-atrial shunt (in four animals). Right to left anatomical shunt was quantified by the number of 25-µm microspheres recovered in systemic arterial blood. Ventilation-perfusion mismatch and gas exchange shunt were quantified by MIGET and cardiac output by direct Fick. Left ventricular contrast scores were assessed by agitated saline bubble counts, and separately by appearance of 25-µm microspheres. Across all conditions, anatomical shunt measured by 25-µm microspheres was not different from gas exchange shunt measured by MIGET (microspheres: 2.3 ± 7.4%; MIGET: 2.6 ± 6.1%, P = 0.64). Saline contrast bubble score was associated with microsphere shunt (ρ = 0.60, P < 0.001). Agitated saline contrast score had high sensitivity (100%) to detect a ≥1% shunt, but low specificity (22-48%). Gas exchange shunt by MIGET does not underestimate anatomical shunt measured using 25-µm microspheres. Contrast echocardiography is extremely sensitive, but not specific, often detecting small anatomical shunts which are inconsequential for gas exchange.
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Affiliation(s)
- Michael K Stickland
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- G.F. MacDonald Centre for Lung Health, Covenant Health, Edmonton, Alberta, Canada
| | - Vincent Tedjasaputra
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Cameron Seaman
- Division of Pediatric Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
| | - Desi P Fuhr
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
| | - Sophie É Collins
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Alberta, Canada
| | - Harrieth Wagner
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of California San Diego, San Diego, USA
| | - Sean van Diepen
- Department of Critical Care and Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
| | - Bradley W Byers
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Canada
- Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Peter D Wagner
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of California San Diego, San Diego, USA
| | - Susan R Hopkins
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of California San Diego, San Diego, USA
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Abstract
The pulmonary circulation carries deoxygenated blood from the systemic veins through the pulmonary arteries to be oxygenated in the capillaries that line the walls of the pulmonary alveoli. The pulmonary circulation carries the cardiac output with a relatively low driving pressure, and so differs considerably in structure and function from the systemic circulation to maintain a low-resistance vascular system. The pulmonary circulation is often considered to be a quasi-static system in both experimental and computational studies of pulmonary perfusion and its matching to ventilation (air flow) for exchange. However, the system is highly dynamic, with cardiac output and regional perfusion changing with posture, exercise, and over time. Here we review this dynamic system, with a focus on understanding the physiology of pulmonary vascular dynamics across spatial and temporal scales, and the changes to these dynamics that are reflective of disease. © 2019 American Physiological Society. Compr Physiol 9:1081-1100, 2019.
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Affiliation(s)
- Alys Clark
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Merryn Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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5
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Galambos C, Bates ML, Bush D, Abman SH. Prominent Bronchopulmonary Vascular Anastomoses in Fatal Childhood Asthma. Ann Am Thorac Soc 2018; 15:1359-1362. [PMID: 30079749 PMCID: PMC6322010 DOI: 10.1513/annalsats.201804-262rl] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Csaba Galambos
- University of Colorado Anschutz Medical CenterAurora, Colorado
| | | | - Douglas Bush
- Icahn School of Medicine at Mount SinaiNew York, New York
| | - Steven H. Abman
- University of Colorado Anschutz Medical CenterAurora, Colorado
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Duke JW, Elliott JE, Lovering AT. Clinical consideration for techniques to detect and quantify blood flow through intrapulmonary arteriovenous anastomoses: lessons from physiological studies. Echocardiography 2015; 32 Suppl 3:S195-204. [PMID: 25693624 DOI: 10.1111/echo.12839] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Intrapulmonary arteriovenous anastomoses (IPAVA) are large diameter (>50 μm) vascular conduits, present in >95% of healthy humans. Because IPAVA are large diameter pathways that allow blood flow to bypass the pulmonary capillary network, blood flow through IPAVA (QIPAVA) can permit the transpulmonary passage of particles larger than pulmonary capillaries. IPAVA have been known to exist for over 50 years, but their physiological and clinical significance are still being established; although, currently suggested roles for QIPAVA include allowing emboli to reach the systemic circulation and providing a source of shunt. Studying QIPAVA is an important area of research and as the suggested roles become better established, detecting and quantifying QIPAVA may become significantly more important in the clinic. Several techniques that can be used to quantify and/or detect QIPAVA in animals, ex vivo human/animal lungs, and intact healthy humans; microspheres, radiolabeled macroaggregated albumin particles, and saline contrast echocardiography, are reviewed with limitations and advantages to each. The current body of literature using these techniques to study QIPAVA in animals, ex vivo lungs, and healthy humans has established conditions when QIPAVA is present, such as during exercise or with arterial hypoxemia and conditions when QIPAVA is absent, such as at rest or during exercise breathing 100% O2 . Many of these physiological studies have direct application to patient populations and we discuss each of these findings in the context of their potential to influence the clinical utility, and interpretation, of the results from these techniques highlighted in this review.
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Affiliation(s)
- Joseph W Duke
- Division of Exercise Physiology, Ohio University, Athens, Ohio
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McMullan DM, Riemer RK. Embryology and Anatomy of Intrapulmonary Shunts. Echocardiography 2015; 32 Suppl 3:S190-4. [DOI: 10.1111/echo.12888] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Affiliation(s)
| | - R. Kirk Riemer
- Department of Cardiothoracic Surgery; Pediatric Cardiac Surgery Division; Stanford University School of Medicine; Stanford California
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Lovering AT, Duke JW, Elliott JE. Intrapulmonary arteriovenous anastomoses in humans--response to exercise and the environment. J Physiol 2015; 593:507-20. [PMID: 25565568 DOI: 10.1113/jphysiol.2014.275495] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 12/05/2014] [Indexed: 12/17/2022] Open
Abstract
Intrapulmonary arteriovenous anastomoses (IPAVA) have been known to exist in human lungs for over 60 years. The majority of the work in this area has largely focused on characterizing the conditions in which IPAVA blood flow (Q̇IPAVA ) is either increased, e.g. during exercise, acute normobaric hypoxia, and the intravenous infusion of catecholamines, or absent/decreased, e.g. at rest and in all conditions with alveolar hyperoxia (FIO2 = 1.0). Additionally, Q̇IPAVA is present in utero and shortly after birth, but is reduced in older (>50 years) adults during exercise and with alveolar hypoxia, suggesting potential developmental origins and an effect of age. The physiological and pathophysiological roles of Q̇IPAVA are only beginning to be understood and therefore these data remain controversial. Although evidence is accumulating in support of important roles in both health and disease, including associations with pulmonary arterial pressure, and adverse neurological sequelae, there is much work that remains to be done to fully understand the physiological and pathophysiological roles of IPAVA. The development of novel approaches to studying these pathways that can overcome the limitations of the currently employed techniques will greatly help to better quantify Q̇IPAVA and identify the consequences of Q̇IPAVA on physiological and pathophysiological processes. Nevertheless, based on currently published data, our proposed working model is that Q̇IPAVA occurs due to passive recruitment under conditions of exercise and supine body posture, but can be further modified by active redistribution of pulmonary blood flow under hypoxic and hyperoxic conditions.
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Affiliation(s)
- Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
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Acker SN, Mandell EW, Sims-Lucas S, Gien J, Abman SH, Galambos C. Histologic identification of prominent intrapulmonary anastomotic vessels in severe congenital diaphragmatic hernia. J Pediatr 2015; 166:178-83. [PMID: 25306189 PMCID: PMC4274215 DOI: 10.1016/j.jpeds.2014.09.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 07/30/2014] [Accepted: 09/05/2014] [Indexed: 10/24/2022]
Abstract
OBJECTIVE To determine whether prominent intrapulmonary anastomotic vessels (IPAVs) or bronchopulmonary "shunt" vessels can be identified in lungs from infants with fatal congenital diaphragmatic hernia (CDH). STUDY DESIGN We performed histology with immunostaining for CD31 (endothelium) and D2-40 (lymphatics), along with high-precision 3-dimensional (3D) reconstruction on lung tissue from 9 patients who died with CDH. RESULTS Each patient with CDH required mechanical ventilation, cardiotonic support, and pulmonary hypertension (PH)-targeted drug therapy. All patients were diagnosed with severe PH by echocardiography, and 5 received extracorporeal membrane oxygenation therapy. Death occurred at a median age of 24 days (range, 10-150 days) from refractory hypoxemia with severe PH, pneumonia, or tension pneumothorax. Histology showed decreased alveolarization with pulmonary vascular disease. In each patient, prominent IPAVs were identified as engorged, thin-walled vessels that connected pulmonary veins with microvessels surrounding pulmonary arteries and airways in lungs ipsilateral and contralateral to the CDH. Prominent anastomoses between pulmonary arteries and bronchial arteries were noted as well. The 3D reconstruction studies demonstrated that IPAVs connect pulmonary vasculature to systemic (bronchial) vessels both at the arterial and venous side. CONCLUSION Histology and 3D reconstruction identified prominent bronchopulmonary vascular anastamoses in the lungs of infants who died with severe CDH. We speculate that IPAVs connecting pulmonary and bronchial arteries contribute to refractory hypoxemia in severe CDH.
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MESH Headings
- Antibodies, Monoclonal, Murine-Derived/metabolism
- Arteriovenous Fistula/diagnosis
- Arteriovenous Fistula/metabolism
- Female
- Hernias, Diaphragmatic, Congenital/diagnosis
- Hernias, Diaphragmatic, Congenital/metabolism
- Hernias, Diaphragmatic, Congenital/mortality
- Humans
- Hypertension, Pulmonary/diagnosis
- Infant
- Infant, Newborn
- Lung/blood supply
- Male
- Platelet Endothelial Cell Adhesion Molecule-1/metabolism
- Pulmonary Artery/abnormalities
- Pulmonary Artery/pathology
- Pulmonary Veins/abnormalities
- Pulmonary Veins/pathology
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Affiliation(s)
- Shannon N Acker
- Division of Pediatric Surgery, Department of Surgery, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO; Pediatric Heart-Lung Center, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO.
| | - Erica W Mandell
- Pediatric Heart-Lung Center, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO; Section of Neonatology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO
| | - Sunder Sims-Lucas
- Division of Nephrology, Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA
| | - Jason Gien
- Pediatric Heart-Lung Center, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO; Section of Neonatology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO
| | - Steven H Abman
- Pediatric Heart-Lung Center, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO; Section of Pulmonary Medicine, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO
| | - Csaba Galambos
- Pediatric Heart-Lung Center, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO; Section of Pathology, Department of Pediatrics, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO
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10
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Abman SH, Baker C, Gien J, Mourani P, Galambos C. The Robyn Barst Memorial Lecture: Differences between the fetal, newborn, and adult pulmonary circulations: relevance for age-specific therapies (2013 Grover Conference series). Pulm Circ 2014; 4:424-40. [PMID: 25621156 PMCID: PMC4278602 DOI: 10.1086/677371] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 04/30/2014] [Indexed: 12/21/2022] Open
Abstract
Pulmonary arterial hypertension (PAH) contributes to poor outcomes in diverse diseases in newborns, infants, and children. Many aspects of pediatric PAH parallel the pathophysiology and disease courses observed in adult patients; however, critical maturational differences exist that contribute to distinct outcomes and therapeutic responses in children. In comparison with adult PAH, disruption of lung vascular growth and development, or angiogenesis, plays an especially prominent role in the pathobiology of pediatric PAH. In children, abnormalities of lung vascular development have consequences well beyond the adverse hemodynamic effects of PAH alone. The developing endothelium also plays critical roles in development of the distal airspace, establishing lung surface area for gas exchange and maintenance of lung structure throughout postnatal life through angiocrine signaling. Impaired functional and structural adaptations of the pulmonary circulation during the transition from fetal to postnatal life contribute significantly to poor outcomes in such disorders as persistent pulmonary hypertension of the newborn, congenital diaphragmatic hernia, bronchopulmonary dysplasia, Down syndrome, and forms of congenital heart disease. In addition, several studies support the hypothesis that early perinatal events that alter lung vascular growth or function may set the stage for increased susceptibility to PAH in adult patients ("fetal programming"). Thus, insights into basic mechanisms underlying unique features of the developing pulmonary circulation, especially as related to preservation of endothelial survival and function, may provide unique therapeutic windows and distinct strategies to improve short- and long-term outcomes of children with PAH.
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Affiliation(s)
- Steven H. Abman
- Department of Pediatrics, Pediatric Heart Lung Center, University of Colorado School of Medicine and Childrens Hospital Colorado, Aurora, Colorado, USA
| | - Christopher Baker
- Department of Pediatrics, Pediatric Heart Lung Center, University of Colorado School of Medicine and Childrens Hospital Colorado, Aurora, Colorado, USA
| | - Jason Gien
- Department of Pediatrics, Pediatric Heart Lung Center, University of Colorado School of Medicine and Childrens Hospital Colorado, Aurora, Colorado, USA
| | - Peter Mourani
- Department of Pediatrics, Pediatric Heart Lung Center, University of Colorado School of Medicine and Childrens Hospital Colorado, Aurora, Colorado, USA
| | - Csaba Galambos
- Department of Pathology, Pediatric Heart Lung Center, University of Colorado School of Medicine and Childrens Hospital Colorado, Aurora, Colorado, USA
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Histologic evidence of intrapulmonary anastomoses by three-dimensional reconstruction in severe bronchopulmonary dysplasia. Ann Am Thorac Soc 2014; 10:474-81. [PMID: 23987309 DOI: 10.1513/annalsats.201305-124oc] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
RATIONALE Bronchopulmonary dysplasia (BPD) is the chronic lung disease of infancy that occurs in premature infants after oxygen and ventilator therapy for acute respiratory disease at birth. Despite improvement in current therapies, the clinical course of infants with BPD is often characterized by marked hypoxemia that can become refractory to therapy. Preacinar anatomic and functional communications between systemic and pulmonary vascular systems has been established in fetal lungs, but whether increased intrapulmonary anastomotic vessels or their failure to regress after birth contributes to hypoxemia in preterm infants with BPD is unknown. OBJECTIVES We sought to find histologic evidence of intrapulmonary anastomotic vessels in lungs of patients who died of severe BPD. METHODS We collected lung tissues from fatal BPD cases and performed histology, immunohistochemistry, and high-precision three-dimensional reconstruction techniques. MEASUREMENTS AND MAIN RESULTS We report histologic evidence of intrapulmonary vessels that bridge pulmonary arteries and veins in the distal lungs of infants dying with severe BPD. These prominent vessels appear similar to "misaligned pulmonary veins" described in the lethal form of congenital lung disorder, alveolar capillary dysplasia. CONCLUSIONS We found striking histological evidence of precapillary arteriovenous anastomotic vessels in the lungs of infants with severe bronchopulmonary dysplasia. We propose that persistence or expansion of these vessels after premature birth provides the anatomic basis for intrapulmonary shunt and hypoxemia in neonates with severe bronchopulmonary dysplasia and may play a significant role in the morbidity and mortality of BPD.
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12
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Slattery E, Rumore MM, Douglas JS, Seres DS. 3-in-1 vs 2-in-1 Parenteral Nutrition in Adults. Nutr Clin Pract 2014; 29:631-5. [DOI: 10.1177/0884533614533611] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Eoin Slattery
- Department of Medicine, Division of Preventive Medicine and Nutrition, Columbia University Medical Center–New York Presbyterian Hospital, New York, New York
| | - Martha M. Rumore
- Department of Pharmacy, Cohen Children’s Medical Center, New Hyde Park, New York
| | - Janine S. Douglas
- Department of Pharmacy, Practice and Administration, University of St. Joseph, Hartford, Connecticut
| | - David S. Seres
- Department of Medicine, Division of Preventive Medicine and Nutrition, Columbia University Medical Center–New York Presbyterian Hospital, New York, New York
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Abstract
Severe cyanosis due to pulmonary arteriovenous fistulas occurs often after a bidirectional superior cavopulmonary anastomosis (Glenn operation) and also in some congenital anomalies in which hepatic venous blood bypasses the lungs in the first passage. Relocation of hepatic flow into the lungs usually causes these fistulas to disappear. Similar pulmonary arteriovenous fistulas are observed in hereditary haemorrhagic telangiectasia, and in liver disease (hepatopulmonary syndrome). There is no convincing identification yet of a responsible hepatic factor that produces these lesions. Candidates for such a factor are reviewed, and the possibility of angiotensin or bradykinin contributing to the fistulas is discussed.
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14
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Stickland MK, Lindinger MI, Olfert IM, Heigenhauser GJF, Hopkins SR. Pulmonary gas exchange and acid-base balance during exercise. Compr Physiol 2013; 3:693-739. [PMID: 23720327 PMCID: PMC8315793 DOI: 10.1002/cphy.c110048] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
As the first step in the oxygen-transport chain, the lung has a critical task: optimizing the exchange of respiratory gases to maintain delivery of oxygen and the elimination of carbon dioxide. In healthy subjects, gas exchange, as evaluated by the alveolar-to-arterial PO2 difference (A-aDO2), worsens with incremental exercise, and typically reaches an A-aDO2 of approximately 25 mmHg at peak exercise. While there is great individual variability, A-aDO2 is generally largest at peak exercise in subjects with the highest peak oxygen consumption. Inert gas data has shown that the increase in A-aDO2 is explained by decreased ventilation-perfusion matching, and the development of a diffusion limitation for oxygen. Gas exchange data does not indicate the presence of right-to-left intrapulmonary shunt developing with exercise, despite recent data suggesting that large-diameter arteriovenous shunt vessels may be recruited with exercise. At the same time, multisystem mechanisms regulate systemic acid-base balance in integrative processes that involve gas exchange between tissues and the environment and simultaneous net changes in the concentrations of strong and weak ions within, and transfer between, extracellular and intracellular fluids. The physicochemical approach to acid-base balance is used to understand the contributions from independent acid-base variables to measured acid-base disturbances within contracting skeletal muscle, erythrocytes and noncontracting tissues. In muscle, the magnitude of the disturbance is proportional to the concentrations of dissociated weak acids, the rate at which acid equivalents (strong acid) accumulate and the rate at which strong base cations are added to or removed from muscle.
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Affiliation(s)
- Michael K. Stickland
- Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Michael I. Lindinger
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - I. Mark Olfert
- Robert C. Byrd Health Sciences Center, Center for Cardiovascular and Respiratory Sciences, Division of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia
| | | | - Susan R. Hopkins
- Departments of Medicine and Radiology, University of California, San Diego, San Diego, California
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15
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Foo E, Williams D, Singh H, Bridgman PG, McCall J, Connor S. Successful management of a large air embolus during an extended right hepatectomy with an emergency cardiopulmonary bypass. HPB (Oxford) 2012; 14:871-3. [PMID: 23134190 PMCID: PMC3521917 DOI: 10.1111/j.1477-2574.2012.00550.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 07/18/2012] [Indexed: 12/12/2022]
Abstract
BACKGROUND An air embolus is a recognized but rare complication of a partial hepatectomy. The aim of this report was to describe the diagnosis and management of a large paradoxical air embolus during hepatic resection. METHODS Case report. RESULTS A single patient report of a massive paradoxical air embolus during an extended right hepatectomy is described. The diagnosis was confirmed by trans-oesophageal echo (video provided). After failed conservative management an emergency cardiopulmonary bypass was instituted with a successful outcome. CONCLUSION Surgeons and anaesthetists involved in hepatic surgery should be aware of signs, investigations and management of this life-threatening intra-operative complication.
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Affiliation(s)
- Elizabeth Foo
- Department of General Surgery, Christchurch HospitalChristchurch, New Zealand
| | - Duncan Williams
- Department of General Anaesthesia, Christchurch HospitalChristchurch, New Zealand
| | - Harsh Singh
- Department of General Cardiothoracic Surgery, Christchurch HospitalChristchurch, New Zealand
| | - Paul G Bridgman
- Department of General Cardiology, Christchurch HospitalChristchurch, New Zealand
| | - John McCall
- Department of Surgery, Dunedin HospitalDunedin, New Zealand
| | - Saxon Connor
- Department of General Surgery, Christchurch HospitalChristchurch, New Zealand
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Schlundt J, Tzanova I, Werner C. A case of intrapulmonary transmission of air while transitioning a patient from a sitting to a supine position after venous air embolism during a craniotomy. Can J Anaesth 2012; 59:478-82. [DOI: 10.1007/s12630-012-9680-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2011] [Accepted: 02/14/2012] [Indexed: 10/28/2022] Open
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17
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Lovering AT, Elliott JE, Beasley KM, Laurie SS. Pulmonary pathways and mechanisms regulating transpulmonary shunting into the general circulation: an update. Injury 2010; 41 Suppl 2:S16-23. [PMID: 21144922 PMCID: PMC4385739 DOI: 10.1016/s0020-1383(10)70004-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Embolic insults account for a significant number of neurologic sequelae following many routine surgical procedures. Clearly, these post-intervention embolic events are a serious public health issue as they are potentially life altering. However, the pathway these emboli utilize to bypass the pulmonary microcirculatory sieve in patients without an intracardiac shunt such as an atrial septal defect or patent foramen ovale, remains unclear. In the absence of intracardiac routes and large diameter pulmonary arteriovenous malformations, inducible large diameter intrapulmonary arteriovenous anastomoses in otherwise healthy adult humans may prove to be the best explanation. Our group and others have demonstrated that inducible large diameter intrapulmonary arteriovenous anastomoses are closed at rest but can open during hyperdynamic conditions such as exercise in more than 90% of healthy humans. Furthermore, the patency of these intrapulmonary anastomoses can be modulated through the fraction of inspired oxygen and by body positioning. Of particular clinical interest, there appears to be a strong association between arterial hypoxemia and neurologic insults, suggesting a breach in the filtering ability of the pulmonary microvasculature under these conditions. In this review, we present evidence demonstrating the existence of inducible intrapulmonary arteriovenous anastomoses in healthy humans that are modulated by exercise, oxygen tension and body positioning. Additionally, we identify several clinical conditions associated with both arterial hypoxemia and an increased risk for embolic insults. Finally, we suggest some precautionary measures that should be taken during interventions to keep intrapulmonary arteriovenous anastomoses closed in order to prevent or reduce the incidence of paradoxical embolism.
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Affiliation(s)
- Andrew T Lovering
- Department of Human Physiology, University of Oregon, Cardiopulmonary & Respiratory Physiology Laboratory, Eugene, OR 97401, USA.
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Lovering AT, Haverkamp HC, Romer LM, Hokanson JS, Eldridge MW. Transpulmonary passage of 99mTc macroaggregated albumin in healthy humans at rest and during maximal exercise. J Appl Physiol (1985) 2009; 106:1986-92. [PMID: 19372301 PMCID: PMC2692773 DOI: 10.1152/japplphysiol.01357.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 04/10/2009] [Indexed: 11/22/2022] Open
Abstract
We have demonstrated that 50-mum-diameter arteriovenous pathways exist in isolated, healthy human and baboon lungs, ventilated and perfused under physiological pressures. These findings have been confirmed and extended by demonstrating the passage of 25-microm microspheres through the lungs of exercising dogs, but not at rest. Determination of blood flow through these large-diameter intrapulmonary arteriovenous pathways would be an important first step to establish a physiological role for these vessels. Currently, we sought to estimate blood flow through these arteriovenous pathways using technetium-99m ((99m)Tc)-labeled macroaggregated albumin (MAA) in healthy humans at rest and during maximal treadmill exercise. We hypothesized that the percentage of (99m)Tc MAA able to traverse the pulmonary circulation (%transpulmonary passage) would increase during exercise. Seven male subjects without patent foramen ovale were injected with (99m)Tc MAA at rest on 1 day and during maximal treadmill exercise on a separate day (>6 days). Within 5 min after injection, subjects began whole body imaging in the supine position. Six of the seven subjects showed an increase in transpulmonary passage of MAA with maximal exercise. Using two separate analysis methods, percent transpulmonary passage significantly increased with exercise from baseline to absolute values of 1.2 +/- 0.8% (P = 0.008) and 1.3 +/- 1.0% (P = 0.016), respectively (means +/- SD; paired t-test). We conclude that MAA may be traversing the pulmonary circulation via large-diameter intrapulmonary arteriovenous conduits in healthy humans during exercise. Recruitment of these pathways may divert blood flow away from pulmonary capillaries during exercise and compromise the lung's function as a biological filter.
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Affiliation(s)
- Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR 97403-1240, USA.
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Vodoz JF, Cottin V, Glérant JC, Derumeaux G, Khouatra C, Blanchet AS, Mastroïanni B, Bayle JY, Mornex JF, Cordier JF. Right-to-left shunt with hypoxemia in pulmonary hypertension. BMC Cardiovasc Disord 2009; 9:15. [PMID: 19335916 PMCID: PMC2671488 DOI: 10.1186/1471-2261-9-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Accepted: 03/31/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Hypoxemia is common in pulmonary hypertension (PH) and may be partly related to ventilation/perfusion mismatch, low diffusion capacity, low cardiac output, and/or right-to-left (RL) shunting. METHODS To determine whether true RL shunting causing hypoxemia is caused by intracardiac shunting, as classically considered, a retrospective single center study was conducted in consecutive patients with precapillary PH, with hypoxemia at rest (PaO2 < 10 kPa), shunt fraction (Qs/Qt) greater than 5%, elevated alveolar-arterial difference of PO2 (AaPO2), and with transthoracic contrast echocardiography performed within 3 months. RESULTS Among 263 patients with precapillary PH, 34 patients were included: pulmonary arterial hypertension, 21%; PH associated with lung disease, 47% (chronic obstructive pulmonary disease, 23%; interstitial lung disease, 9%; other, 15%); chronic thromboembolic PH, 26%; miscellaneous causes, 6%. Mean pulmonary artery pressure, cardiac index, and pulmonary vascular resistance were 45.8 +/- 10.8 mmHg, 2.2 +/- 0.6 L/min/m2, and 469 +/- 275 dyn.s.cm-5, respectively. PaO2 in room air was 6.8 +/- 1.3 kPa. Qs/Qt was 10.2 +/- 4.2%. AaPO2 under 100% oxygen was 32.5 +/- 12.4 kPa. Positive contrast was present at transthoracic contrast echocardiography in 6/34 (18%) of patients, including only 4/34 (12%) with intracardiac RL shunting. Qs/Qt did not correlate with hemodynamic parameters. Patients' characteristics did not differ according to the result of contrast echocardiography. CONCLUSION When present in patients with precapillary PH, RL shunting is usually not related to reopening of patent foramen ovale, whatever the etiology of PH.
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Affiliation(s)
- Jean-Frédéric Vodoz
- Service de pneumologie et centre de référence des maladies orphelines pulmonaires, Hôpital Louis Pradel, Hospices Civils de Lyon, Lyon, France.
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Rademaker B, Groenman F, van der Wouw P, Bakkum E. Paradoxical gas embolism by transpulmonary passage of venous emboli during hysteroscopic surgery: a case report and discussion. Br J Anaesth 2008; 101:230-3. [DOI: 10.1093/bja/aen138] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Lovering AT, Romer LM, Haverkamp HC, Pegelow DF, Hokanson JS, Eldridge MW. Intrapulmonary shunting and pulmonary gas exchange during normoxic and hypoxic exercise in healthy humans. J Appl Physiol (1985) 2008; 104:1418-25. [DOI: 10.1152/japplphysiol.00208.2007] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Exercise-induced intrapulmonary arteriovenous shunting, as detected by saline contrast echocardiography, has been demonstrated in healthy humans. We have previously suggested that increases in both pulmonary pressures and blood flow associated with exercise are responsible for opening these intrapulmonary arteriovenous pathways. In the present study, we hypothesized that, although cardiac output and pulmonary pressures would be higher in hypoxia, the potent pulmonary vasoconstrictor effect of hypoxia would actually attenuate exercise-induced intrapulmonary shunting. Using saline contrast echocardiography, we examined nine healthy men during incremental (65 W + 30 W/2 min) cycle exercise to exhaustion in normoxia and hypoxia (fraction of inspired O2 = 0.12). Contrast injections were made into a peripheral vein at rest and during exercise and recovery (3–5 min postexercise) with pulmonary gas exchange measured simultaneously. At rest, no subject demonstrated intrapulmonary shunting in normoxia [arterial Po2 (PaO2) = 98 ± 10 Torr], whereas in hypoxia (PaO2 = 47 ± 5 Torr), intrapulmonary shunting developed in 3/9 subjects. During exercise, ∼90% (8/9) of the subjects shunted during normoxia, whereas all subjects shunted during hypoxia. Four of the nine subjects shunted at a lower workload in hypoxia. Furthermore, all subjects continued to shunt at 3 min, and five subjects shunted at 5 min postexercise in hypoxia. Hypoxia has acute effects by inducing intrapulmonary arteriovenous shunt pathways at rest and during exercise and has long-term effects by maintaining patency of these vessels during recovery. Whether oxygen tension specifically regulates these novel pathways or opens them indirectly via effects on the conventional pulmonary vasculature remains unclear.
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Stickland MK, Lovering AT, Eldridge MW. Exercise-induced arteriovenous intrapulmonary shunting in dogs. Am J Respir Crit Care Med 2007; 176:300-5. [PMID: 17478619 PMCID: PMC1994218 DOI: 10.1164/rccm.200702-206oc] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE We have previously shown, using contrast echocardiography, that intrapulmonary arteriovenous pathways are inducible in healthy humans during exercise; however, this technique does not allow for determination of arteriovenous vessel size or shunt magnitude. OBJECTIVES The purpose of this study was to determine whether large-diameter (more than 25 microm) intrapulmonary arteriovenous pathways are present in the dog, and whether exercise recruits these conduits. METHODS Through the right forelimb, 10.8 million 25-microm stable isotope-labeled microspheres (BioPAL, Inc., Worcester, MA) were injected either at rest (n = 8) or during high-intensity exercise (6- 8 mph, 10-15% grade, n = 6). Systemic arterial blood was continuously sampled during and for 3 minutes after injection. After euthanasia, tissue samples were obtained from the heart, liver, kidney, and skeletal muscle. In addition, 25- and 50-microm microspheres were infused into four isolated dog lungs that were ventilated and perfused at constant pressures similar to exercise. MEASUREMENTS AND MAIN RESULTS Blood and tissue samples were commercially analyzed for the presence of microspheres. No microspheres were detected in the arterial blood or tissue samples from resting dogs. In contrast, five of six exercising dogs showed evidence of exercise-induced intrapulmonary arteriovenous shunting, as microspheres were detected in arterial blood and/or tissue. Furthermore, shunt magnitude was calculated to be 1.4 +/- 0.8% of cardiac output (n = 3). Evidence of intrapulmonary arteriovenous anastomoses was also found in three of four isolated lungs. CONCLUSIONS Consistent with previous human findings, these data demonstrate that intrapulmonary arteriovenous pathways are functional in the dog and are recruited with exercise.
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Affiliation(s)
- Michael K Stickland
- John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
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Lovering AT, Stickland MK, Eldridge MW. Intrapulmonary shunt during normoxic and hypoxic exercise in healthy humans. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 588:31-45. [PMID: 17089877 DOI: 10.1007/978-0-387-34817-9_4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This review presents evidence for the recruitment of intrapulmonary arteriovenous shunts (IPAVS) during exercise in normal healthy humans. Support for pre-capillary connections between the arterial and venous circulation in lungs of humans and animals have existed for over one-hundred years. Right-to-left physiological shunt has not been detected during exercise with gas exchange-dependent techniques. However, fundamental assumptions of these techniques may not allow for measurement of a small (1-3%) anatomical shunt, the magnitude of which would explain the entire A-aDO2 typically observed during normoxic exercise. Data from contrast echocardiograph studies are presented demonstrating the development of IPAVS with exercise in 90% of subjects tested. Technetium-99m labeled macroaggregated albumin studies also found exercise IPAVS and calculated shunt to be approximately 2% at max exercise. These exercise IPAVS appear strongly related to the alveolar to arterial PO2 difference, pulmonary blood flow and mean pulmonary artery pressure. Hypoxic exercise was found to induce IPAVS at lower workloads than during normoxic exercise in 50% of subjects, while all subjects continued to shunt during recovery from hypoxic exercise, but only three subjects demonstrated intrapulmonary shunt during recovery from normoxic exercise. We suggest that these previously under-appreciated intrapulmonary arteriovenous shunts develop during exercise, contributing to the impairment in gas exchange typically observed with exercise. Future work will better define the conditions for shunt recruitment as well as their physiologic consequence.
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Affiliation(s)
- Andrew T Lovering
- The John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, University of Wisconsin-Madison, Wisconsin, USA.
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Stickland MK, Lovering AT. Exercise-induced intrapulmonary arteriovenous shunting and pulmonary gas exchange. Exerc Sport Sci Rev 2006; 34:99-106. [PMID: 16829736 DOI: 10.1249/00003677-200607000-00003] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent research suggests the recruitment of intrapulmonary shunt vessels during exercise, which may contribute to the exercise-induced impairment in pulmonary gas exchange. These findings are consistent with substantial anatomical data demonstrating large-diameter (> 25 microm) anatomical shunts in the lung, but are contrary to the considerable functional gas exchange-dependent research that has not detected right-to-left physiological shunt during exercise.
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Affiliation(s)
- Michael K Stickland
- The John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706-1532, USA.
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Lovering AT, Haverkamp HC, Eldridge MW. Responses and limitations of the respiratory system to exercise. Clin Chest Med 2005; 26:439-57, vi. [PMID: 16140137 DOI: 10.1016/j.ccm.2005.05.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
During maximal exercise, the gas exchange function of the lung is challenged because of the major cardiopulmonary changes that must occur to meet the increased metabolic demands imposed by exercise. In healthy untrained young adults, the respiratory system is able to meet these demands imposed on it during maximal exercise by implementing several key mechanisms. Nonetheless, there are several exceptional cases in which the lung is unable to accommodate the demands of exercise because of vascular or airway limitations.
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Affiliation(s)
- Andrew T Lovering
- The John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, University of Wisconsin at Madison, Madison, WI 53706-1532, USA.
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Pulmonary arteriovenous shunting in the normal fetal lung. J Am Coll Cardiol 2004; 44:1497-500. [PMID: 15464334 DOI: 10.1016/j.jacc.2004.06.064] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2004] [Revised: 05/14/2004] [Accepted: 06/01/2004] [Indexed: 11/25/2022]
Abstract
OBJECTIVES We hypothesized that pulmonary arteriovenous shunting (PAVS) is normally present in fetal lungs and that cavopulmonary anastomosis-induced PAVS may represent a return to an earlier morphologic stage of development. BACKGROUND The surgical superior cavopulmonary anastomosis is performed as part of the staged Fontan pathway to treat univentricular forms of congenital heart disease; PAVS is a known sequela after superior cavopulmonary anastomosis and may have important clinical consequences. Although the etiology and true morphology of the structures responsible for PAVS are unknown, a leading theory is that PAVS is caused by absence of normal hepatic venous drainage to the pulmonary circulation. METHODS To determine whether normal fetal lungs demonstrate PAVS, we performed contrast echocardiograms on 13 fetal lambs, 8 neonatal lambs, 4 juvenile lambs, and 4 adult sheep using a blended mixture of saline and blood injected directly into the proximal pulmonary artery. RESULTS Pulmonary arteriovenous shunting was detected by direct epicardial echocardiography in all fetal lambs (n = 13) and neonatal animals studied at one and three days of life (n = 4) and in two of four animals studied at six to nine days of life. Pulmonary arteriovenous shunting was not present in animals studied at four weeks of life (n = 2) and in adult sheep (n = 5). CONCLUSIONS These studies demonstrate that PAVS is normally present in late gestation fetal and early neonatal lambs but then disappears during the later neonatal period. Furthermore, these findings suggest that PAVS associated with cavopulmonary anastomosis or other processes affecting the developing pulmonary circulation may represent a return to an earlier morphologic stage of development.
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Eldridge MW, Dempsey JA, Haverkamp HC, Lovering AT, Hokanson JS. Exercise-induced intrapulmonary arteriovenous shunting in healthy humans. J Appl Physiol (1985) 2004; 97:797-805. [PMID: 15107409 DOI: 10.1152/japplphysiol.00137.2004] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that increasing exercise intensity recruits dormant arteriovenous intrapulmonary shunts, which may contribute to the widened alveolar-arterial oxygen difference seen with exercise. Twenty-three healthy volunteers (13 men and 10 women, aged 23-48 yr) with normal lung function and a wide range of fitness (mean maximal oxygen uptake = 126% predicted; range = 78-200% predicted) were studied by agitated saline contrast echocardiography (4-chamber apical view). All 23 subjects had normal resting contrast echocardiograms without evidence of intracardiac or intrapulmonary shunting. However, with cycle ergometer exercise, 21 of 23 (91%) of the subjects showed a delayed (>3 cardiac cycles) appearance of contrast bubbles in the left heart. This pattern is consistent with passage of contrast bubbles through the pulmonary circulation. Because the contrast bubbles are known to be significantly larger than pulmonary capillaries, we propose that they are traveling through direct arteriovenous intrapulmonary shunts. In all cases, the intrapulmonary shunting developed at submaximal oxygen uptakes [%maximal oxygen uptake = 59 +/- 20 (SD)] and once evident persisted at all subsequent work rates. Within 3 min of exercise termination, the contrast echocardiograms with bubble injection showed no evidence of intrapulmonary shunting. These dynamic shunts will contribute significantly to the widened alveolar-arterial oxygen difference seen with exercise. They may also act as a protective parallel vascular network limiting the rise in regional pulmonary vascular pressure while preserving cardiac output during exercise.
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Affiliation(s)
- Marlowe W Eldridge
- John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin, Medical School, Madison, Wisconsin 53792-4108, USA.
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Bethune K, Allwood M, Grainger C, Wormleighton C. Use of filters during the preparation and administration of parenteral nutrition: position paper and guidelines prepared by a British pharmaceutical nutrition group working party. Nutrition 2001; 17:403-8. [PMID: 11377134 DOI: 10.1016/s0899-9007(01)00536-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- K Bethune
- British Pharmaceutical Nutrition Group, Derby, United Kingdom
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Abstract
Two particularly common, and frequently frightening, forms of syncope and anoxic seizure in early childhood are pallid and cyanotic breath-holding spells. Pallid breath-holding spells result from exuberant vagally-mediated cardiac inhibition. Cyanotic breath-holding spells are of more complex pathogenesis, involving an interplay among hyperventilation, Valsalva maneuver, expiratory apnea, and intrinsic pulmonary mechanisms. The history is the mainstay of diagnosis; videotape documentation may be possible. Performance of an electrocardiogram to evaluate for prolonged QT syndrome should be strongly considered. In patients with pallid breath-holding spells, a characteristic sequence of changes may be documented on an electroencephalogram with ocular compression, if this study is performed. Spontaneous resolution of breath-holding spell, without sequelae, is anticipated. Reassurance is the mainstay of therapy. Occasionally, pharmacologic intervention may be of benefit.
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Affiliation(s)
- G N Breningstall
- Department of Pediatrics (Neurology), Park Nicollet Medical Center; Minneapolis, MN 55404, USA
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Bolivar JM, Gerhardt T, Gonzalez A, Hummler H, Claure N, Everett R, Bancalari E. Mechanisms for episodes of hypoxemia in preterm infants undergoing mechanical ventilation. J Pediatr 1995; 127:767-73. [PMID: 7472834 DOI: 10.1016/s0022-3476(95)70171-0] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVE To ascertain possible mechanisms implicated in the development of transient episodes of hypoxemia (oxygen saturation < 85%) frequently observed in preterm infants undergoing mechanical ventilation, even after the acute phase of respiratory failure has passed. STUDY DESIGN Tidal flow, airway and esophageal pressure, and oxygen saturation were continuously recorded in 10 infants (mean +/- SD, birth weight 733 +/- 149 gm, gestational age 25.5 +/- 2.2 weeks, age 26.3 +/- 11.9 days) who had repeated episodes of hypoxemia without any evident cause. Measurements of minute ventilation (VE) inspiratory compliance (Ci), and inspiratory resistance (Ri) were compared before and during episodes of hypoxemia. RESULTS All episodes of hypoxemia were preceded by an active exhalation that produced a mean decrease in end-expiratory lung volume of 6.4 +/- 2.8 ml/kg. The reduction in lung volume was immediately followed by a sudden decrease in tidal flow and volume, despite continuation of mechanical ventilation at the same rate and peak pressure. The resulting hypoventilation was associated with a drop in Ci to approximately one half and an increase in Ri to more than double the baseline values. Approximately 30 seconds after the beginning of hypoventilation, the arterial oxygen saturation reached a hypoxemic level (oxygen saturation < 85%)> CONCLUSION Most hypoxemic episodes were triggered by an expiratory effort that produced a large decrease in lung volume. This reduction in lung volume probably leads to closure of small airways and the development of intrapulmonary shunts, which would explain the rapid development of hypoxemia.
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Affiliation(s)
- J M Bolivar
- Department of Pediatrics, University of Miami School of Medicine, Florida 33101, USA
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