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Cameron Norris H, Mangum TS, Duke JW, Straley TB, Hawn JA, Goodman RD, Lovering AT. Exercise- and hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses is reduced in older adults. J Appl Physiol (1985) 2014; 116:1324-33. [DOI: 10.1152/japplphysiol.01125.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mean pulmonary arterial pressure (Ppa) during exercise is significantly higher in individuals aged ≥50 yr compared with their younger counterparts, but the reasons for this are unknown. Blood flow through intrapulmonary arteriovenous anastomoses (IPAVA) can be detected during exercise or while breathing hypoxic gas mixtures using saline contrast echocardiography in almost all healthy young individuals. It has been previously hypothesized that a lower degree of exercise-induced blood flow through IPAVA is associated with high Ppa during exercise. This association may suggest that individuals who are known to have high Ppa during exercise, such as those ≥50 yr of age, may have lower blood flow through IPAVA, but the presence and degree of exercise-induced blood flow through IPAVA has not been specifically studied in older populations. Using transthoracic saline contrast echocardiography, we investigated the potential effects of age on exercise-induced blood flow through IPAVA in a cross-section of subjects aged 19–72 yr. To verify our findings, we assessed the effects of age on hypoxia-induced blood flow through IPAVA. Age groups were ≤41 yr (younger, n = 16) and ≥50 yr (older, n = 14). Qualitatively measured exercise- and hypoxia-induced blood flow through IPAVA was significantly lower in older individuals compared with younger controls. Older individuals also had significantly higher pulmonary arterial systolic pressure and total pulmonary resistance (TPR) during exercise. Low blood flow through IPAVA was independently associated with high TPR. The reasons for the age-related decrease in blood flow through IPAVA are unknown.
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Affiliation(s)
- H. Cameron Norris
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| | - Tyler S. Mangum
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| | - Joseph W. Duke
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| | - Taylor B. Straley
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
| | - Jerold A. Hawn
- Oregon Heart and Vascular Institute, RiverBend, Springfield, Oregon
| | - Randy D. Goodman
- Oregon Heart and Vascular Institute, RiverBend, Springfield, Oregon
| | - Andrew T. Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon; and
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52
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Vaidya VR, DeSimone CV, Asirvatham SJ, Chandra VM, Noheria A, Hodge DO, Slusser JP, Rabinstein AA, Friedman PA. Implanted endocardial lead characteristics and risk of stroke or transient ischemic attack. J Interv Card Electrophysiol 2014; 41:31-8. [PMID: 24771226 DOI: 10.1007/s10840-014-9900-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 03/24/2014] [Indexed: 10/25/2022]
Abstract
INTRODUCTION Patent foramen ovale (PFO) has been recently implicated as a strong predictor of stroke or transient ischemic attack (TIA) in patients with implanted pacemaker or defibrillation leads. Leads in the right heart can form thrombi that embolize to the pulmonary circulation and raise pulmonary pressure. This increases right-to-left shunting through PFO or intrapulmonary shunts and can result in paradoxical embolism. We sought to determine whether certain lead characteristics confer a higher thrombogenic risk resulting in stroke/TIAs in patients either with or without a PFO. METHODS We retrospectively analyzed 5,646 patients (mean age 67.3 ± 16.3 years, 64 % male) who had endocardial device leads implanted in 2000-2010. We performed univariate and multivariate-adjusted proportional hazards models to determine association of lead characteristics with stroke/TIA during follow-up. RESULTS On univariate analysis, passively fixated tined leads were associated with more stroke/TIAs (HR 1.77, 95 % CI 1.27, 2.47; p<0.001), whereas presence of defibrillation coil was associated with fewer stroke/TIAs (HR 0.59, 95 % CI 0.42-0.84; p=0.003). Number of leads per patient, presence of atrial lead, maximum lead size, tip shape, and type of insulating material were not associated with stoke/TIA. On multivariate analyses adjusting for age, sex, diagnosis of PFO, and prior history of stroke/TIA, the presence of tined leads was associated with stroke/TIA (HR 1.41, 95 % CI 1.00-1.97; p=0.049). Defibrillation coils were no longer associated with lower stroke/TIA on multivariate analysis. CONCLUSIONS Most physical characteristics of contemporary leads do not impact rate of stroke/TIA among patients receiving implantable devices. The presence of a PFO is a major risk factor for stroke/TIA in patients with endovascular leads.
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Affiliation(s)
- Vaibhav R Vaidya
- Department of Internal Medicine, Mayo Clinic, Rochester, MN, USA
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53
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Bates ML, Jacobson JE, Eldridge MW. Transient intrapulmonary shunting in a patient treated with β₂-adrenergic agonists for status asthmaticus. Pediatrics 2014; 133:e1087-91. [PMID: 24639274 PMCID: PMC3966497 DOI: 10.1542/peds.2013-1171] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Intrapulmonary arteriovenous anastomoses (IPAVs) are large-diameter 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 B2-adrenergic pathway. Our observation of IPAVs in a pediatric patient, mechanically ventilated with 100% O₂, suggests that these pathways are recruited in clinically important circumstances and challenges the notion that IPAVs are always closed by alveolar hyperoxia.
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Affiliation(s)
- Melissa L. Bates
- Critical Care Division, Department of Pediatrics and the John Rankin Laboratory of Pulmonary Medicine, and
| | - Joseph E. Jacobson
- Michigan State University College of Human Medicine, East Lansing, Michigan
| | - Marlowe W. Eldridge
- Critical Care Division, Department of Pediatrics and the John Rankin Laboratory of Pulmonary Medicine, and,Departments of Biomedical Engineering and Kinesiology, University of Wisconsin, Madison, Wisconsin; and
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54
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Foster GE, Ainslie PN, Stembridge M, Day TA, Bakker A, Lucas SJE, Lewis NCS, MacLeod DB, Lovering AT. Resting pulmonary haemodynamics and shunting: a comparison of sea-level inhabitants to high altitude Sherpas. J Physiol 2014; 592:1397-409. [PMID: 24396057 PMCID: PMC3961095 DOI: 10.1113/jphysiol.2013.266593] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 12/24/2013] [Indexed: 12/22/2022] Open
Abstract
The incidence of blood flow through intracardiac shunt and intrapulmonary arteriovenous anastomoses (IPAVA) may differ between Sherpas permanently residing at high altitude (HA) and sea-level (SL) inhabitants as a result of evolutionary pressure to improve gas exchange and/or resting pulmonary haemodynamics. To test this hypothesis we compared sea-level inhabitants at SL (SL-SL; n = 17), during acute isocapnic hypoxia (SL-HX; n = 7) and following 3 weeks at 5050 m (SL-HA; n = 8 non-PFO subjects) to Sherpas at 5050 m (n = 14). SpO2, heart rate, pulmonary artery systolic pressure (PASP) and cardiac index (Qi) were measured during 5 min of room air breathing at SL and HA, during 20 min of isocapnic hypoxia (SL-HX; PETO2 = 47 mmHg) and during 5 min of hyperoxia (FIO2 = 1.0; Sherpas only). Intracardiac shunt and IPAVA blood flow was evaluated by agitated saline contrast echocardiography. Although PASP was similar between groups at HA (Sherpas: 30.0 ± 6.0 mmHg; SL-HA: 32.7 ± 4.2 mmHg; P = 0.27), it was greater than SL-SL (19.4 ± 2.1 mmHg; P < 0.001). The proportion of subjects with intracardiac shunt was similar between groups (SL-SL: 41%; Sherpas: 50%). In the remaining subjects, IPAVA blood flow was found in 100% of subjects during acute isocapnic hypoxia at SL, but in only 4 of 7 Sherpas and 1 of 8 SL-HA subjects at rest. In conclusion, differences in resting pulmonary vascular regulation, intracardiac shunt and IPAVA blood flow do not appear to account for any adaptation to HA in Sherpas. Despite elevated pulmonary pressures and profound hypoxaemia, IPAVA blood flow in all subjects at HA was lower than expected compared to acute normobaric hypoxia.
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Affiliation(s)
- Glen E Foster
- School of Health and Exercise Science, Faculty of Health and Social Development, University of British Columbia Okanagan, 3333 University Way, Kelowna, BC, V1V 1V7 Canada.
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55
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Kim TJ, Kim SA, Hong SE, Jung DM, Choi NY, Kim YK, Park SA, Kim SY, Park WJ. Exercise-Induced Intrapulmonary Arteriovenous Shunt in a Patient Complaining of Dyspnea during Strenuous Exercise. J Cardiovasc Ultrasound 2014; 22:88-90. [PMID: 25031800 PMCID: PMC4096671 DOI: 10.4250/jcu.2014.22.2.88] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Revised: 11/23/2013] [Accepted: 05/15/2014] [Indexed: 11/22/2022] Open
Affiliation(s)
- Tae-Jun Kim
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Sung-Ai Kim
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Seong-Eun Hong
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Dong-Min Jung
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Nan-Young Choi
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Yong-Kyun Kim
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Seung-Ah Park
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Soon-Young Kim
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
| | - Woo-Jung Park
- Division of Cardiology, Hallym Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea
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56
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Lovering AT, Laurie SS, Elliott JE, Beasley KM, Yang X, Gust CE, Mangum TS, Goodman RD, Hawn JA, Gladstone IM. Normal pulmonary gas exchange efficiency and absence of exercise-induced arterial hypoxemia in adults with bronchopulmonary dysplasia. J Appl Physiol (1985) 2013; 115:1050-6. [DOI: 10.1152/japplphysiol.00592.2013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cardiopulmonary function is reduced in adults born very preterm, but it is unknown if this results in reduced pulmonary gas exchange efficiency during exercise and, consequently, leads to reduced aerobic capacity in subjects with and without bronchopulmonary dysplasia (BPD). We hypothesized that an excessively large alveolar to arterial oxygen difference (AaDO2) and resulting exercise-induced arterial hypoxemia (EIAH) would contribute to reduced aerobic fitness in adults born very preterm with and without BPD. Measurements of pulmonary function, lung volumes and diffusion capacity for carbon monoxide (DLco) were made at rest. Measurements of maximal oxygen consumption, peak workload, temperature- and tonometry-corrected arterial blood gases, and direct measure of hemoglobin saturation with oxygen (SaO2) were made preexercise and during cycle ergometer exercise in ex-preterm subjects ≤32-wk gestational age, with BPD ( n = 12), without BPD (PRE; n = 12), and full term controls (CONT; n = 12) breathing room air. Both BPD and PRE had reduced pulmonary function and reduced DLco compared with CONT. The AaDO2 was not significantly different between groups, and there was no evidence of EIAH (SaO2 < 95% and/or AaDO2 ≥ 40 Torr) in any subject group preexercise or at any workload. Arterial O2 content was not significantly different between the groups preexercise or during exercise. However, peak power output was decreased in BPD and PRE subjects compared with CONT. We conclude that EIAH in adult subjects born very preterm with and without BPD does not likely contribute to the reduction in aerobic exercise capacity observed in these subjects.
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Affiliation(s)
| | - Steven S. Laurie
- University of Oregon, Department of Human Physiology, Eugene, Oregon
| | | | - Kara M. Beasley
- University of Oregon, Department of Human Physiology, Eugene, Oregon
| | - Ximeng Yang
- University of Oregon, Department of Human Physiology, Eugene, Oregon
| | - Caitlyn E. Gust
- University of Oregon, Department of Human Physiology, Eugene, Oregon
| | - Tyler S. Mangum
- University of Oregon, Department of Human Physiology, Eugene, Oregon
| | - Randall D. Goodman
- University of Oregon, Department of Human Physiology, Eugene, Oregon
- Oregon Heart and Vascular Institute, Springfield, Oregon; and
| | - Jerold A. Hawn
- University of Oregon, Department of Human Physiology, Eugene, Oregon
- Oregon Heart and Vascular Institute, Springfield, Oregon; and
| | - Igor M. Gladstone
- University of Oregon, Department of Human Physiology, Eugene, Oregon
- Department of Pediatrics, Oregon Health and Science University, Portland, Oregon
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57
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Elliott JE, Nigam SM, Laurie SS, Beasley KM, Goodman RD, Hawn JA, Gladstone IM, Chesnutt MS, Lovering AT. Prevalence of left heart contrast in healthy, young, asymptomatic humans at rest breathing room air. Respir Physiol Neurobiol 2013; 188:71-8. [PMID: 23648476 DOI: 10.1016/j.resp.2013.04.019] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 04/01/2013] [Accepted: 04/23/2013] [Indexed: 10/26/2022]
Abstract
Our purpose was to report the prevalence of healthy, young, asymptomatic humans who demonstrate left heart contrast at rest, breathing room air. We evaluated 176 subjects (18-41 years old) using transthoracic saline contrast echocardiography. Left heart contrast appearing ≤3 cardiac cycles, consistent with a patent foramen ovale (PFO), was detected in 67 (38%) subjects. Left heart contrast appearing >3 cardiac cycles, consistent with the transpulmonary passage of contrast, was detected in 49 (28%) subjects. Of these 49 subjects, 31 were re-evaluated after breathing 100% O2 for 10-15min and 6 (19%) continued to demonstrate the transpulmonary passage of contrast. Additionally, 18 of these 49 subjects were re-evaluated in the upright position and 1 (5%) continued to demonstrate the transpulmonary passage of contrast. These data suggest that ~30% of healthy, young, asymptomatic subjects demonstrate the transpulmonary passage of contrast at rest which is reduced by breathing 100% O2 and assuming an upright body position.
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Affiliation(s)
- Jonathan E Elliott
- University of Oregon, Department of Human Physiology, Eugene, OR 97403-1240, USA
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58
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Laurie SS, Elliott JE, Goodman RD, Lovering AT. Catecholamine-induced opening of intrapulmonary arteriovenous anastomoses in healthy humans at rest. J Appl Physiol (1985) 2012; 113:1213-22. [PMID: 22858627 DOI: 10.1152/japplphysiol.00565.2012] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanism or mechanisms that cause intrapulmonary arteriovenous anastomoses (IPAVA) to either open during exercise in subjects breathing room air and at rest when breathing hypoxic gas mixtures, or to close during exercise while breathing 100% oxygen, remain unknown. During conditions when IPAVA are open, plasma epinephrine (EPI) and dopamine (DA) concentrations both increase, potentially representing a common mechanism. The purpose of this study was to determine whether EPI or DA infusions open IPAVA in resting subjects breathing room air and, subsequently, 100% oxygen. We hypothesized that these catecholamine infusions would open IPAVA. We performed saline-contrast echocardiography in nine subjects without a patent foramen ovale before and during serial EPI and DA infusions while breathing room air and then while breathing 100% oxygen. Bubble scores (0-5) were assigned based on the number and spatial distribution of bubbles in the left ventricle. Pulmonary artery systolic pressure (PASP) was estimated using Doppler ultrasound, while cardiac output (Q(C)) was measured using echocardiography. Bubble scores were significantly greater during EPI infusions of 80-320 ng·kg(-1)·min(-1) compared with baseline when subjects breathed room air; however, bubble scores did not increase when they breathed 100% oxygen. At comparable Q(C) and PASP, intravenous DA (16 μg·kg(-1)·min(-1)) and EPI (40 ng·kg(-1)·min(-1)) resulted in identical bubble scores. Subsequent studies revealed that β-blockade did not prevent hypoxia-induced opening of IPAVA. We suggest that increases in Q(C) or PASP (or both) secondary to EPI or DA infusions open IPAVA in normoxia. The closing mechanism associated with breathing 100% oxygen is independent from the opening mechanisms.
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Affiliation(s)
- Steven S Laurie
- Department of Human Physiology, University of Oregon, Eugene, OR 97403, USA
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59
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Kennedy JM, Foster GE, Koehle MS, Potts JE, Sandor GG, Potts MT, Houghton KM, Henderson WR, Sheel AW. Exercise-induced intrapulmonary arteriovenous shunt in healthy women. Respir Physiol Neurobiol 2012; 181:8-13. [DOI: 10.1016/j.resp.2012.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 12/15/2011] [Accepted: 01/10/2012] [Indexed: 12/18/2022]
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60
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Bates ML, Fulmer BR, Farrell ET, Drezdon A, Pegelow DF, Conhaim RL, Eldridge MW. Hypoxia recruits intrapulmonary arteriovenous pathways in intact rats but not isolated rat lungs. J Appl Physiol (1985) 2012; 112:1915-20. [PMID: 22422800 DOI: 10.1152/japplphysiol.00985.2011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intrapulmonary arteriovenous anastomoses (IPAVS) directly connect the arterial and venous circulations in the lung, bypassing the capillary network. Here, we used solid, latex microspheres and isolated rat lung and intact, spontaneously breathing rat models to test the hypothesis that IPAVS are recruited by alveolar hypoxia. We found that hypoxia recruits IPAVS in the intact rat, but not the isolated lung. IPAVS are at least 70 μm in the rat and, interestingly, appear to be recruited when the mixed venous Po(2) falls below 22 mmHg. These data provide evidence that large-diameter, direct arteriovenous connections exist in the lung and are recruitable by hypoxia in the intact animal.
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Affiliation(s)
- Melissa L Bates
- Department of Pediatrics and the John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
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61
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Elliott JE, Choi Y, Laurie SS, Yang X, Gladstone IM, Lovering AT. Reply to Van Liew and Vann. J Appl Physiol (1985) 2011. [DOI: 10.1152/japplphysiol.01229.2010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
| | - Yujung Choi
- University of Puget Sound, Tacoma, Washington; and
| | - Steven S. Laurie
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Ximeng Yang
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Igor M. Gladstone
- Department of Human Physiology, University of Oregon, Eugene, Oregon
- Department of Pediatrics, Oregon Health and Science University, Portland, Oregon
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62
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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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63
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Elliott JE, Choi Y, Laurie SS, Yang X, Gladstone IM, Lovering AT. Effect of initial gas bubble composition on detection of inducible intrapulmonary arteriovenous shunt during exercise in normoxia, hypoxia, or hyperoxia. J Appl Physiol (1985) 2010; 110:35-45. [PMID: 20847134 DOI: 10.1152/japplphysiol.00145.2010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Concern has been raised that altering the fraction of inspired O₂ (Fi(O₂)) could accelerate or decelerate microbubble dissolution time within the pulmonary vasculature and thereby invalidate the ability of saline contrast echocardiography to detect intrapulmonary arteriovenous shunt in subjects breathing either a low or a high Fi(O₂). The present study determined whether the gaseous component used for saline contrast echocardiography affects the detection of exercise-induced intrapulmonary arteriovenous shunt under varying Fi(O₂). Twelve healthy human subjects (6 men, 6 women) performed three 11-min bouts of cycle ergometer exercise at 60% peak O₂ consumption (Vo(2peak)) in normoxia, hypoxia (Fi(O₂) = 0.14), and hyperoxia (Fi(O₂) = 1.0). Five different gases were used to create saline contrast microbubbles by two separate methods and were injected intravenously in the following order at 2-min intervals: room air, 100% N₂, 100% O₂, 100% CO₂, and 100% He. Breathing hyperoxia prevented exercise-induced intrapulmonary arteriovenous shunt, whereas breathing hypoxia and normoxia resulted in a significant level of exercise-induced intrapulmonary arteriovenous shunt. During exercise, for any Fi(O₂) there was no significant difference in bubble score when the different microbubble gas compositions made with either method were used. The present results support our previous work using saline contrast echocardiography and validate the use of room air as an acceptable gaseous component for use with saline contrast echocardiography to detect intrapulmonary arteriovenous shunt during exercise or at rest with subjects breathing any Fi(O₂). These results suggest that in vivo gas bubbles are less susceptible to changes in the ambient external environment than previously suspected.
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Affiliation(s)
- Jonathan E Elliott
- Department of Human Physiology, University of Oregon, Eugene, Oregon, USA
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