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Koirala B, Concas A, Sun Y, Gladden LB, Lai N. Relationship between muscle venous blood oxygenation and near-infrared spectroscopy: quantitative analysis of the Hb and Mb contributions. J Appl Physiol (1985) 2023; 134:1063-1074. [PMID: 36927143 PMCID: PMC10125031 DOI: 10.1152/japplphysiol.00406.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 02/22/2023] [Accepted: 03/13/2023] [Indexed: 03/18/2023] Open
Abstract
A linear relationship between skeletal muscle venous ([Formula: see text]) and oxygenated (ΔHbMbO2,N) or deoxygenated (ΔHHbMbN) near-infrared spectroscopy (NIRS) signals suggest a main hemoglobin (Hb) contribution to the NIRS signal. However, experimental, and computational evidence supports a significant contribution of myoglobin (Mb) to the NIRS. Venous and NIRS measurements from a canine model of muscle oxidative metabolism (Sun Y, Ferguson BS, Rogatzki MJ, McDonald JR, Gladden LB. Med Sci Sports Exerc 48(10):2013-2020, 2016) were integrated into a computational model of muscle O2 transport and utilization to evaluate whether the relationship between venous and NIRS oxygenation can be affected by a significant Mb contribution to the NIRS signals. The mathematical model predicted well the measure of the changes of [Formula: see text] and NIRS signals for different O2 delivery conditions (blood flow, arterial O2 content) in muscle at rest (T1, T2) and during contraction (T3). Furthermore, computational analysis indicates that for adequate O2 delivery, Mb contribution to NIRS signals was significant (20%-30%) even in the presence of a linear [Formula: see text]-NIRS relationship; for a reduced O2 delivery the nonlinearity of the [Formula: see text]-NIRS relationship was related to the Mb contribution (50%). In this case (T3), the deviation from linearity is observed when O2 delivery is reduced from 1.3 to 0.7 L kg-1·min-1 ([Formula: see text] < 10 mLO2 100 mL-1) and Mb saturation decreased from 85% to 40% corresponding to an increase of the Mb contribution to ΔHHbMbN from 15% to 50% and the contribution to ΔHbMbO2,N from 0% to 30%. In contrast to a common assumption, our model indicates that both NIRS signals (ΔHHbMbN and ΔHbMbO2,N are significantly affected by Hb and Mb oxygenation changes.NEW & NOTEWORTHY Within the near-infrared spectroscopy (NIRS) signal, the contribution from hemoglobin is indistinguishable from that of myoglobin. A computation analysis indicates that a linear relationship between muscle venous oxygen content and NIRS signals does not necessarily indicate a negligible myoglobin contribution to the NIRS signal. A reduced oxygen delivery increases the myoglobin contribution to the NIRS signal. The integrative approach proposed is a powerful way to assist in interpreting the elements from which the NIRS signals are derived.
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Affiliation(s)
- Bhabuk Koirala
- Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia United States
- Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia, United States
| | - Alessandro Concas
- Department of Mechanical, Chemical and Materials Engineering, University of Cagliari, Italy
| | - Yi Sun
- Key Laboratory of Adolescent Health Assessment and Exercise Intervention of Ministry of Education, East China Normal University, Shanghai, China
- School of Physical Education & Health Care, East China Normal University, Shanghai, People's Republic of China
| | - L Bruce Gladden
- School of Kinesiology, Auburn University, Auburn, Alabama United States
| | - Nicola Lai
- Department of Mechanical, Chemical and Materials Engineering, University of Cagliari, Italy
- Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia United States
- Biomedical Engineering Institute, Old Dominion University, Norfolk, Virginia, United States
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Berger DC, Zwicker L, Nettelbeck K, Casoni D, Heinisch PP, Jenni H, Haenggi M, Gattinoni L, Bachmann KF. Integral assessment of gas exchange during veno-arterial ECMO: accuracy and precision of a modified Fick principle in a porcine model. Am J Physiol Lung Cell Mol Physiol 2023; 324:L102-L113. [PMID: 36511508 PMCID: PMC9870575 DOI: 10.1152/ajplung.00045.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Assessment of native cardiac output during extracorporeal circulation is challenging. We assessed a modified Fick principle under conditions such as dead space and shunt in 13 anesthetized swine undergoing centrally cannulated veno-arterial extracorporeal membrane oxygenation (V-A ECMO, 308 measurement periods) therapy. We assumed that the ratio of carbon dioxide elimination (V̇co2) or oxygen uptake (V̇o2) between the membrane and native lung corresponds to the ratio of respective blood flows. Unequal ventilation/perfusion (V̇/Q̇) ratios were corrected towards unity. Pulmonary blood flow was calculated and compared to an ultrasonic flow probe on the pulmonary artery with a bias of 99 mL/min (limits of agreement -542 to 741 mL/min) with blood content V̇o2 and no-shunt, no-dead space conditions, which showed good trending ability (least significant change from 82 to 129 mL). Shunt conditions led to underestimation of native pulmonary blood flow (bias -395, limits of agreement -1,290 to 500 mL/min). Bias and trending further depended on the gas (O2, CO2) and measurement approach (blood content vs. gas phase). Measurements in the gas phase increased the bias (253 [LoA -1,357 to 1,863 mL/min] for expired V̇o2 bias 482 [LoA -760 to 1,724 mL/min] for expired V̇co2) and could be improved by correction of V̇/Q̇ inequalities. Our results show that common assumptions of the Fick principle in two competing circulations give results with adequate accuracy and may offer a clinically applicable tool. Precision depends on specific conditions. This highlights the complexity of gas exchange in membrane lungs and may further deepen the understanding of V-A ECMO.
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Affiliation(s)
- David C. Berger
- 1Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Lena Zwicker
- 1Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Kay Nettelbeck
- 1Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland,2Experimental Surgery Facility (ESF), Department for BioMedical
Research, Faculty of Medicine, University of Bern, Bern, Switzerland
| | - Daniela Casoni
- 2Experimental Surgery Facility (ESF), Department for BioMedical
Research, Faculty of Medicine, University of Bern, Bern, Switzerland
| | - Paul Phillipp Heinisch
- 3Department of Congenital and Pediatric Heart Surgery, German Heart Center Munich, Technische Universität München, Munich, Germany
| | - Hansjörg Jenni
- 3Department of Congenital and Pediatric Heart Surgery, German Heart Center Munich, Technische Universität München, Munich, Germany
| | - Matthias Haenggi
- 1Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Luciano Gattinoni
- 5Department of Anesthesiology, Medical University of Göttingen, University Medical Center Göttingen, Göttingen, Germany
| | - Kaspar F. Bachmann
- 1Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland,4Department of Anesthesiology & Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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3
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Sten S, Podéus H, Sundqvist N, Elinder F, Engström M, Cedersund G. A quantitative model for human neurovascular coupling with translated mechanisms from animals. PLoS Comput Biol 2023; 19:e1010818. [PMID: 36607908 PMCID: PMC9821752 DOI: 10.1371/journal.pcbi.1010818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 12/13/2022] [Indexed: 01/07/2023] Open
Abstract
Neurons regulate the activity of blood vessels through the neurovascular coupling (NVC). A detailed understanding of the NVC is critical for understanding data from functional imaging techniques of the brain. Many aspects of the NVC have been studied both experimentally and using mathematical models; various combinations of blood volume and flow, local field potential (LFP), hemoglobin level, blood oxygenation level-dependent response (BOLD), and optogenetics have been measured and modeled in rodents, primates, or humans. However, these data have not been brought together into a unified quantitative model. We now present a mathematical model that describes all such data types and that preserves mechanistic behaviors between experiments. For instance, from modeling of optogenetics and microscopy data in mice, we learn cell-specific contributions; the first rapid dilation in the vascular response is caused by NO-interneurons, the main part of the dilation during longer stimuli is caused by pyramidal neurons, and the post-peak undershoot is caused by NPY-interneurons. These insights are translated and preserved in all subsequent analyses, together with other insights regarding hemoglobin dynamics and the LFP/BOLD-interplay, obtained from other experiments on rodents and primates. The model can predict independent validation-data not used for training. By bringing together data with complementary information from different species, we both understand each dataset better, and have a basis for a new type of integrative analysis of human data.
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Affiliation(s)
- Sebastian Sten
- Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
| | - Henrik Podéus
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
| | - Nicolas Sundqvist
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
| | - Fredrik Elinder
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Maria Engström
- Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Gunnar Cedersund
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
- * E-mail:
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Ltaief Z, Schneider AG, Liaudet L. Pathophysiology and clinical implications of the veno-arterial PCO 2 gap. Crit Care 2021; 25:318. [PMID: 34461974 PMCID: PMC8407023 DOI: 10.1186/s13054-021-03671-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2021. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2021 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from https://link.springer.com/bookseries/8901 .
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Affiliation(s)
- Zied Ltaief
- Service of Adult Intensive Care Medicine, Lausanne University Hospital, 1011, Lausanne, Switzerland
| | | | - Lucas Liaudet
- Service of Adult Intensive Care Medicine, Lausanne University Hospital, 1011, Lausanne, Switzerland
- Unit of Pathophysiology, Faculty of Biology and Medicine, University of Lausanne, 1011, Lausanne, Switzerland
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5
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Howden EJ, Ruiz-Carmona S, Claeys M, De Bosscher R, Willems R, Meyns B, Verbelen T, Maleux G, Godinas L, Belge C, Bogaert J, Claus P, La Gerche A, Delcroix M, Claessen G. Oxygen Pathway Limitations in Patients With Chronic Thromboembolic Pulmonary Hypertension. Circulation 2021; 143:2061-2073. [PMID: 33853383 DOI: 10.1161/circulationaha.120.052899] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Exertional intolerance is a limiting and often crippling symptom in patients with chronic thromboembolic pulmonary hypertension (CTEPH). Traditionally the pathogenesis has been attributed to central factors, including ventilation/perfusion mismatch, increased pulmonary vascular resistance, and right heart dysfunction and uncoupling. Pulmonary endarterectomy and balloon pulmonary angioplasty provide substantial improvement of functional status and hemodynamics. However, despite normalization of pulmonary hemodynamics, exercise capacity often does not return to age-predicted levels. By systematically evaluating the oxygen pathway, we aimed to elucidate the causes of functional limitations in patients with CTEPH before and after pulmonary vascular intervention. METHODS Using exercise cardiac magnetic resonance imaging with simultaneous invasive hemodynamic monitoring, we sought to quantify the steps of the O2 transport cascade from the mouth to the mitochondria in patients with CTEPH (n=20) as compared with healthy participants (n=10). Furthermore, we evaluated the effect of pulmonary vascular intervention (pulmonary endarterectomy or balloon angioplasty) on the individual components of the cascade (n=10). RESULTS Peak Vo2 (oxygen uptake) was significantly reduced in patients with CTEPH relative to controls (56±17 versus 112±20% of predicted; P<0.0001). The difference was attributable to impairments in multiple steps of the O2 cascade, including O2 delivery (product of cardiac output and arterial O2 content), skeletal muscle diffusion capacity, and pulmonary diffusion. The total O2 extracted in the periphery (ie, ΔAVo2 [arteriovenous O2 content difference]) was not different. After pulmonary vascular intervention, peak Vo2 increased significantly (from 12.5±4.0 to 17.8±7.5 mL/[kg·min]; P=0.036) but remained below age-predicted levels (70±11%). The O2 delivery was improved owing to an increase in peak cardiac output and lung diffusion capacity. However, peak exercise ΔAVo2 was unchanged, as was skeletal muscle diffusion capacity. CONCLUSIONS We demonstrated that patients with CTEPH have significant impairment of all steps in the O2 use cascade, resulting in markedly impaired exercise capacity. Pulmonary vascular intervention increased peak Vo2 by partly correcting O2 delivery but had no effect on abnormalities in peripheral O2 extraction. This suggests that current interventions only partially address patients' limitations and that additional therapies may improve functional capacity.
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Affiliation(s)
- Erin J Howden
- Baker Heart and Diabetes Institute (E.J.H., S.R.-C., A.L.G., G.C.), Melbourne, Australia
| | - Sergio Ruiz-Carmona
- Cambridge Baker Systems Genomics Initiative (S.R.-C.), Melbourne, Australia.,Baker Heart and Diabetes Institute (E.J.H., S.R.-C., A.L.G., G.C.), Melbourne, Australia
| | - Mathias Claeys
- Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Ruben De Bosscher
- Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Rik Willems
- Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Bart Meyns
- Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Tom Verbelen
- Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Geert Maleux
- Imaging & Pathology (G.M., J.B.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Laurent Godinas
- Chronic Diseases and Metabolism (L.G., C.B., M.D.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Catharina Belge
- Chronic Diseases and Metabolism (L.G., C.B., M.D.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Jan Bogaert
- Imaging & Pathology (G.M., J.B.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Piet Claus
- Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Andre La Gerche
- Baker Heart and Diabetes Institute (E.J.H., S.R.-C., A.L.G., G.C.), Melbourne, Australia.,Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium
| | - Marion Delcroix
- Chronic Diseases and Metabolism (L.G., C.B., M.D.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
| | - Guido Claessen
- Baker Heart and Diabetes Institute (E.J.H., S.R.-C., A.L.G., G.C.), Melbourne, Australia.,Departments of Cardiovascular Sciences (M.C., R.D.B., R.W., B.M., T.V., P.C., A.L.G., G.C.), KU Leuven, Belgium.,University Hospitals Leuven, Belgium (M.C., R.D.B., R.W., B.M., T.V., G.M., L.G., C.B., J.B., P.C., M.D., G.C.)
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6
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Angleys H, Østergaard L. Krogh’s capillary recruitment hypothesis, 100 years on: Is the opening of previously closed capillaries necessary to ensure muscle oxygenation during exercise? Am J Physiol Heart Circ Physiol 2020; 318:H425-H447. [DOI: 10.1152/ajpheart.00384.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In 1919, August Krogh published his seminal work on skeletal muscle oxygenation. Krogh’s observations indicated that muscle capillary diameter is actively regulated, rather than a passive result of arterial blood flow regulation. Indeed, combining a mathematical model with the number of ink-filled capillaries he observed in muscle cross sections taken at different workloads, Krogh was able to account for muscle tissue’s remarkably efficient oxygen extraction during exercise in terms of passive diffusion from nearby capillaries. Krogh was awarded the 1920 Nobel Prize for his account of muscle oxygenation. Today, his observations are engrained in the notion of capillary recruitment: the opening of previously closed capillaries. While the binary distinction between “closed” and “open” was key to Krogh’s model argument, he did in fact report a continuum of capillary diameters, degrees of erythrocyte deformation, and perfusion states. Indeed, modern observations question the presence of closed muscle capillaries. We therefore examined whether changes in capillary flow patterns and hematocrit among open capillaries can account for oxygen extraction in muscle across orders-of-magnitude changes in blood flow. Our four-compartment model of oxygen extraction in muscle confirms this notion and provides a framework for quantifying the impact of changes in microvascular function on muscle oxygenation in health and disease. Our results underscore the importance of capillary function for oxygen extraction in muscle tissue as first proposed by Krogh. While Krogh’s model calculations still hold, our model predictions support that capillary recruitment can be viewed in the context of continuous, rather than binary, erythrocyte distributions among capillaries. NEW & NOTEWORTHY Oxygen extraction in working muscle is extremely efficient in view of single capillaries properties. The underlying mechanisms have been widely debated. Here, we develop a four-compartment model to quantify the influence of each of the hypothesized mechanisms on muscle oxygenation. Our results show that changes in capillary flow pattern and hematocrit can account for the high oxygen extraction observed in working muscle, while capillary recruitment is not required to account for these extraction properties.
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Affiliation(s)
- Hugo Angleys
- Center of Functionally Integrative Neuroscience and MindLab, Aarhus University, Aarhus, Denmark
| | - Leif Østergaard
- Center of Functionally Integrative Neuroscience and MindLab, Aarhus University, Aarhus, Denmark
- Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark
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7
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Wisotzky EL, Uecker FC, Dommerich S, Hilsmann A, Eisert P, Arens P. Determination of optical properties of human tissues obtained from parotidectomy in the spectral range of 250 to 800 nm. JOURNAL OF BIOMEDICAL OPTICS 2019; 24:1-7. [PMID: 31797647 PMCID: PMC6890295 DOI: 10.1117/1.jbo.24.12.125001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 11/07/2019] [Indexed: 05/18/2023]
Abstract
The optical properties of human tissues are an important parameter in medical diagnostics and therapy. The knowledge of these parameters can encourage the development of automated, computer-driven optical tissue analysis methods. We determine the absorption coefficient μa and scattering coefficient μ s ' of different tissue types obtained during parotidectomy in the wavelength range of 250 to 800 nm. These values are determined by high precision integrating sphere measurements in combination with an optimized inverse Monte Carlo simulation. To conserve the optical behavior of living tissues, the optical spectroscopy measurements are performed immediately after tissue removal. Our study includes fresh samples of the ear, nose, and throat (ENT) region, as muscle tissue, nervous tissue, white adipose tissue, stromal tissue, parotid gland, and tumorous tissue of five patients. The measured behavior of adipose corresponds well with the literature, which sustains the applied method. It is shown that muscle is well supplied with blood as it features the same characteristic peaks at 430 and 555 nm in the absorption curve. The parameter μ s ' decreases for all tissue types above 570 nm. The accuracy is adequate for the purposes of providing μa and μ s ' of different human tissue types as muscle, fat, nerve, or gland tissue, which are embedded in large complex structures such as in the ENT area. It becomes possible for the first time to present reasonable results for the optical behavior of human soft tissue located in the ENT area and in the near-UV, visual, and near-infrared areas.
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Affiliation(s)
- Eric L. Wisotzky
- Fraunhofer Heinrich-Hertz-Institute, Computer Vision and Graphics, Berlin, Germany
- Humboldt-Universität zu Berlin, Visual Computing, Berlin, Germany
| | - Florian C. Uecker
- Charité—Universitätsmedizin Berlin, Department of Otorhinolaryngology, Berlin, Germany
| | - Steffen Dommerich
- Charité—Universitätsmedizin Berlin, Department of Otorhinolaryngology, Berlin, Germany
| | - Anna Hilsmann
- Fraunhofer Heinrich-Hertz-Institute, Computer Vision and Graphics, Berlin, Germany
| | - Peter Eisert
- Fraunhofer Heinrich-Hertz-Institute, Computer Vision and Graphics, Berlin, Germany
- Humboldt-Universität zu Berlin, Visual Computing, Berlin, Germany
| | - Philipp Arens
- Charité—Universitätsmedizin Berlin, Department of Otorhinolaryngology, Berlin, Germany
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8
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Experimental evolution of aerobic exercise performance and hematological traits in bank voles. Comp Biochem Physiol A Mol Integr Physiol 2019; 234:1-9. [DOI: 10.1016/j.cbpa.2019.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/07/2019] [Accepted: 04/11/2019] [Indexed: 01/19/2023]
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9
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Lücker A, Secomb TW, Weber B, Jenny P. The relative influence of hematocrit and red blood cell velocity on oxygen transport from capillaries to tissue. Microcirculation 2018; 24. [PMID: 27893186 DOI: 10.1111/micc.12337] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 11/24/2016] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Oxygen transport to parenchymal cells occurs mainly at the microvascular level and depends on convective RBC flux, which is proportional in an individual capillary to the product of capillary hematocrit and RBC velocity. This study investigates the relative influence of these two factors on tissue PO2 . METHODS A simple analytical model is used to quantify the respective influences of hematocrit, RBC velocity, and RBC flow on tissue oxygenation around capillaries. Predicted tissue PO2 levels are compared with a detailed computational model. RESULTS Hematocrit is shown to have a larger influence on tissue PO2 than RBC velocity. The effect of RBC velocity increases with distance from the arterioles. Good agreement between analytical and numerical results is obtained, and the discrepancies are explained. Significant dependence of MTCs on RBC velocity at low hematocrit is demonstrated. CONCLUSIONS For a given RBC flux in a capillary, the PO2 in the surrounding tissue increases with increasing hematocrit, as a consequence of decreasing IVR to diffusive oxygen transport from RBCs to tissue. These results contribute to understanding the effects of blood flow changes on oxygen transport, such as those that occur in functional hyperemia in the brain.
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Affiliation(s)
- Adrien Lücker
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland
| | - Timothy W Secomb
- Department of Physiology, University of Arizona, Tucson, AZ, USA
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Patrick Jenny
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland
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10
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Angleys H, Jespersen SN, Østergaard L. The effects of capillary transit time heterogeneity on the BOLD signal. Hum Brain Mapp 2018; 39:2329-2352. [PMID: 29498762 DOI: 10.1002/hbm.23991] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 12/06/2017] [Accepted: 01/23/2018] [Indexed: 12/18/2022] Open
Abstract
Neurovascular coupling mechanisms give rise to vasodilation and functional hyperemia upon neural activation, thereby altering blood oxygenation. This blood oxygenation level dependent (BOLD) contrast allows studies of activation patterns in the working human brain by functional MRI (fMRI). The BOLD-weighted fMRI signal shows characteristic transients in relation to functional activation, such as the so-called initial dip, overshoot, and post-stimulus undershoot. These transients are modulated by other physiological stimuli and in disease, but the underlying physiological mechanisms remain incompletely understood. Capillary transit time heterogeneity (CTH) has been shown to affect oxygen extraction, and hence blood oxygenation. Here, we examine how recently reported redistributions of capillary blood flow during functional activation would be expected to affect BOLD signal transients. We developed a three-compartment (hemoglobin, plasma, and tissue) model to predict the BOLD signal, incorporating the effects of dynamic changes in CTH. Our model predicts that the BOLD signal represents the superposition of a positive component resulting from increases in cerebral blood flow (CBF), and a negative component, resulting from elevated tissue metabolism and homogenization of capillary flows (reduced CTH). The model reproduces salient features of BOLD signal dynamics under conditions such as hypercapnia, hyperoxia, and caffeine intake, where both brain physiology and BOLD characteristics are altered. Neuroglial signaling and metabolism could affect CBF and capillary flow patterns differently. Further studies of neurovascular and neuro-capillary coupling mechanisms may help us relate BOLD signals to the firing of certain neuronal populations based on their respective BOLD "fingerprints."
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Affiliation(s)
- Hugo Angleys
- Center of Functionally Integrative Neuroscience and MindLab, Aarhus University, Aarhus, Denmark
| | - Sune N Jespersen
- Center of Functionally Integrative Neuroscience and MindLab, Aarhus University, Aarhus, Denmark.,Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | - Leif Østergaard
- Center of Functionally Integrative Neuroscience and MindLab, Aarhus University, Aarhus, Denmark.,Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark
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11
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Viale JP. The venous-arterial partial pressure of carbon dioxide as a new monitoring of circulatory disorder: no so simple. J Clin Monit Comput 2017; 30:757-760. [PMID: 27038162 DOI: 10.1007/s10877-016-9872-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- J P Viale
- Université de Lyon, 69008, Lyon, France.
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12
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C. Arciero J, Causin P, Malgaroli F. Mathematical methods for modeling the microcirculation. AIMS BIOPHYSICS 2017. [DOI: 10.3934/biophy.2017.3.362] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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13
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A mathematical model of oxygenation during venovenous extracorporeal membrane oxygenation support. J Crit Care 2016; 36:178-186. [DOI: 10.1016/j.jcrc.2016.07.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 06/15/2016] [Accepted: 07/06/2016] [Indexed: 11/16/2022]
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14
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Dash RK, Korman B, Bassingthwaighte JB. Simple accurate mathematical models of blood HbO2 and HbCO2 dissociation curves at varied physiological conditions: evaluation and comparison with other models. Eur J Appl Physiol 2015. [PMID: 26298270 DOI: 10.1007/s00421‐015‐3228‐3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE Equations for blood oxyhemoglobin (HbO2) and carbaminohemoglobin (HbCO2) dissociation curves that incorporate nonlinear biochemical interactions of oxygen and carbon dioxide with hemoglobin (Hb), covering a wide range of physiological conditions, are crucial for a number of practical applications. These include the development of physiologically-based computational models of alveolar-blood and blood-tissue O2–CO2 transport, exchange, and metabolism, and the analysis of clinical and in vitro data. METHODS AND RESULTS To this end, we have revisited, simplified, and extended our previous models of blood HbO2 and HbCO2 dissociation curves (Dash and Bassingthwaighte, Ann Biomed Eng 38:1683–1701, 2010), validated wherever possible by available experimental data, so that the models now accurately fit the low HbO2 saturation (SHbO2) range over a wide range of values of PCO2, pH, 2,3-DPG, and temperature. Our new equations incorporate a novel PO2-dependent variable cooperativity hypothesis for the binding of O2 to Hb, and a new equation for P50 of O2 that provides accurate shifts in the HbO2 and HbCO2 dissociation curves over a wide range of physiological conditions. The accuracy and efficiency of these equations in computing PO2 and PCO2 from the SHbO2 and SHbCO2 levels using simple iterative numerical schemes that give rapid convergence is a significant advantage over alternative SHbO2 and SHbCO2 models. CONCLUSION The new SHbO2 and SHbCO2 models have significant computational modeling implications as they provide high accuracy under non-physiological conditions, such as ischemia and reperfusion, extremes in gas concentrations, high altitudes, and extreme temperatures.
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Affiliation(s)
- Ranjan K Dash
- Department of Physiology, Biotechnology and Bioengineering Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.
| | - Ben Korman
- Department of Anaesthesia and Pain Medicine, Royal Perth Hospital, Perth, WA, Australia.
| | - James B Bassingthwaighte
- Department of Bioengineering, University of Washington, Box 355061, N210G North Foege Bldg, Seattle, WA, 9895-5061, USA.
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15
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Dash RK, Korman B, Bassingthwaighte JB. Simple accurate mathematical models of blood HbO2 and HbCO2 dissociation curves at varied physiological conditions: evaluation and comparison with other models. Eur J Appl Physiol 2015; 116:97-113. [PMID: 26298270 DOI: 10.1007/s00421-015-3228-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 07/22/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE Equations for blood oxyhemoglobin (HbO2) and carbaminohemoglobin (HbCO2) dissociation curves that incorporate nonlinear biochemical interactions of oxygen and carbon dioxide with hemoglobin (Hb), covering a wide range of physiological conditions, are crucial for a number of practical applications. These include the development of physiologically-based computational models of alveolar-blood and blood-tissue O2–CO2 transport, exchange, and metabolism, and the analysis of clinical and in vitro data. METHODS AND RESULTS To this end, we have revisited, simplified, and extended our previous models of blood HbO2 and HbCO2 dissociation curves (Dash and Bassingthwaighte, Ann Biomed Eng 38:1683–1701, 2010), validated wherever possible by available experimental data, so that the models now accurately fit the low HbO2 saturation (SHbO2) range over a wide range of values of PCO2, pH, 2,3-DPG, and temperature. Our new equations incorporate a novel PO2-dependent variable cooperativity hypothesis for the binding of O2 to Hb, and a new equation for P50 of O2 that provides accurate shifts in the HbO2 and HbCO2 dissociation curves over a wide range of physiological conditions. The accuracy and efficiency of these equations in computing PO2 and PCO2 from the SHbO2 and SHbCO2 levels using simple iterative numerical schemes that give rapid convergence is a significant advantage over alternative SHbO2 and SHbCO2 models. CONCLUSION The new SHbO2 and SHbCO2 models have significant computational modeling implications as they provide high accuracy under non-physiological conditions, such as ischemia and reperfusion, extremes in gas concentrations, high altitudes, and extreme temperatures.
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Affiliation(s)
- Ranjan K Dash
- Department of Physiology, Biotechnology and Bioengineering Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.
| | - Ben Korman
- Department of Anaesthesia and Pain Medicine, Royal Perth Hospital, Perth, WA, Australia.
| | - James B Bassingthwaighte
- Department of Bioengineering, University of Washington, Box 355061, N210G North Foege Bldg, Seattle, WA, 9895-5061, USA.
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16
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Takakura H, Furuichi Y, Yamada T, Jue T, Ojino M, Hashimoto T, Iwase S, Hojo T, Izawa T, Masuda K. Endurance training facilitates myoglobin desaturation during muscle contraction in rat skeletal muscle. Sci Rep 2015; 5:9403. [PMID: 25801957 PMCID: PMC4371155 DOI: 10.1038/srep09403] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 03/03/2015] [Indexed: 11/30/2022] Open
Abstract
At onset of muscle contraction, myoglobin (Mb) immediately releases its bound O2 to the mitochondria. Accordingly, intracellular O2 tension (PmbO2) markedly declines in order to increase muscle O2 uptake (mO2). However, whether the change in PmbO2 during muscle contraction modulates mO2 and whether the O2 release rate from Mb increases in endurance-trained muscles remain unclear. The purpose of this study was, therefore, to determine the effect of endurance training on O2 saturation of Mb (SmbO2) and PmbO2 kinetics during muscle contraction. Male Wistar rats were subjected to a 4-week swimming training (Tr group; 6 days per week, 30 min × 4 sets per day) with a weight load of 2% body mass. After the training period, deoxygenated Mb kinetics during muscle contraction were measured using near-infrared spectroscopy under hemoglobin-free medium perfusion. In the Tr group, the mO2peak significantly increased by 32%. Although the PmbO2 during muscle contraction did not affect the increased mO2 in endurance-trained muscle, the O2 release rate from Mb increased because of the increased Mb concentration and faster decremental rate in SmbO2 at the maximal twitch tension. These results suggest that the Mb dynamics during muscle contraction are contributing factors to faster O2 kinetics in endurance-trained muscle.
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Affiliation(s)
- Hisashi Takakura
- 1] Faculty of Health and Sports Science, Doshisha University, Kyotanabe 610-0394, Japan [2] Faculty of Human Sciences, Kanazawa University, Kanazawa 920-1192, Japan
| | - Yasuro Furuichi
- 1] Faculty of Human Sciences, Kanazawa University, Kanazawa 920-1192, Japan [2] Department of Health Promotion Science, Tokyo Metropolitan University, Hachioji 192-0397, Japan
| | - Tatsuya Yamada
- Faculty of Human Sciences, Kanazawa University, Kanazawa 920-1192, Japan
| | - Thomas Jue
- Department of Biochemistry and Molecular Medicine, University of California Davis, Davis 95616-8635, USA
| | - Minoru Ojino
- Faculty of Human Sciences, Kanazawa University, Kanazawa 920-1192, Japan
| | - Takeshi Hashimoto
- Faculty of Sports and Health Science, Ritsumeikan University, Kusatsu 525-8577, Japan
| | - Satoshi Iwase
- Department of Physiology, Aichi Medical University, Nagakute 480-1195, Japan
| | - Tatsuya Hojo
- Faculty of Health and Sports Science, Doshisha University, Kyotanabe 610-0394, Japan
| | - Tetsuya Izawa
- Faculty of Health and Sports Science, Doshisha University, Kyotanabe 610-0394, Japan
| | - Kazumi Masuda
- Faculty of Human Sciences, Kanazawa University, Kanazawa 920-1192, Japan
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17
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Frisbee JC, Goodwill AG, Frisbee SJ, Butcher JT, Wu F, Chantler PD. Microvascular perfusion heterogeneity contributes to peripheral vascular disease in metabolic syndrome. J Physiol 2014; 594:2233-43. [PMID: 25384789 DOI: 10.1113/jphysiol.2014.285247] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 11/02/2014] [Indexed: 12/20/2022] Open
Abstract
A major challenge facing public health is the increased incidence and prevalence of the metabolic syndrome, a clinical condition characterized by excess adiposity, impaired glycaemic control, dyslipidaemia and moderate hypertension. The greatest concern for this syndrome is the profound increase in risk for development of peripheral vascular disease (PVD) in afflicted persons. However, ongoing studies suggest that reductions in bulk blood flow to skeletal muscle may not be the primary contributor to the premature muscle fatigue that is a hallmark of PVD. Compelling evidence has been provided suggesting that an increasingly spatially heterogeneous and temporally stable distribution of blood flow at successive arteriolar bifurcations in metabolic syndrome creates an environment where a large number of the pre-capillary arterioles have low perfusion, low haematocrit, and are increasingly confined to this state, with limited ability to adapt perfusion in response to a challenged environment. Single pharmacological interventions are unable to significantly restore function owing to a divergence in their spatial effectiveness, although combined therapeutic approaches to correct adrenergic dysfunction, elevated oxidant stress and increased thromboxane A2 improve perfusion-based outcomes. Integrated, multi-target therapeutic interventions designed to restore healthy network function and flexibility may provide for superior outcomes in subjects with metabolic syndrome-associated PVD.
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Affiliation(s)
- Jefferson C Frisbee
- Department of Physiology and Pharmacology, West Virginia University Health Sciences Center, Morgantown, WV, USA.,Center for Cardiovascular and Respiratory Sciences, West Virginia University Health Sciences Center, Morgantown, WV, USA
| | - Adam G Goodwill
- Department of Physiology and Pharmacology, West Virginia University Health Sciences Center, Morgantown, WV, USA.,Center for Cardiovascular and Respiratory Sciences, West Virginia University Health Sciences Center, Morgantown, WV, USA
| | - Stephanie J Frisbee
- Center for Cardiovascular and Respiratory Sciences, West Virginia University Health Sciences Center, Morgantown, WV, USA.,Department of Health Policy, Management and Leadership, West Virginia University Health Sciences Center, Morgantown, WV, USA
| | - Joshua T Butcher
- Department of Physiology and Pharmacology, West Virginia University Health Sciences Center, Morgantown, WV, USA.,Center for Cardiovascular and Respiratory Sciences, West Virginia University Health Sciences Center, Morgantown, WV, USA
| | - Fan Wu
- Novartis Institutes for BioMedical Research, Drug Metabolism and Pharmacokinetics, East Hanover, NJ, USA
| | - Paul D Chantler
- Center for Cardiovascular and Respiratory Sciences, West Virginia University Health Sciences Center, Morgantown, WV, USA.,Division of Exercise Physiology, West Virginia University Health Sciences Center, Morgantown, WV, USA
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18
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Lücker A, Weber B, Jenny P. A dynamic model of oxygen transport from capillaries to tissue with moving red blood cells. Am J Physiol Heart Circ Physiol 2014; 308:H206-16. [PMID: 25398979 DOI: 10.1152/ajpheart.00447.2014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Most oxygen required to support the energy needs of vertebrate tissues is delivered by diffusion from microvessels. The presence of red blood cells (RBCs) makes blood flow in the microcirculation highly heterogeneous. Additionally, flow regulation mechanisms dynamically respond to changes in tissue energy demand. These spatiotemporal variations directly affect the supply of oxygen to parenchymal cells. Due to various limiting assumptions, current models of oxygen transport cannot fully capture the consequences of complex hemodynamic effects on tissue oxygenation and are often not suitable for studying unsteady phenomena. With our new approach based on moving RBCs, the impact of blood flow heterogeneity on oxygen partial pressure (Po2) in the tissue can be quantified. Oxygen transport was simulated using parachute-shaped solid RBCs flowing through a capillary. With the use of a conical tissue domain with radii 19 and 13 μm, respectively, our computations indicate that Po2 at the RBC membrane exceeds Po2 between RBCs by 30 mmHg on average and that the mean plasma Po2 decreases by 9 mmHg over 50 μm. These results reproduce well recent intravascular Po2 measurements in the rodent brain. We also demonstrate that instantaneous variations of capillary hematocrit cause associated fluctuations of tissue Po2. Furthermore, our results suggest that homogeneous tissue oxygenation requires capillary networks to be denser on venular side than on arteriolar side. Our new model for oxygen transport will make it possible to quantify in detail the effects of blood flow heterogeneity on tissue oxygenation in realistic capillary networks.
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Affiliation(s)
- Adrien Lücker
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland; and
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Patrick Jenny
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland; and
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19
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Barrett MJP, Suresh V. Extra permeability is required to model dynamic oxygen measurements: evidence for functional recruitment? J Cereb Blood Flow Metab 2013; 33:1402-11. [PMID: 23673433 PMCID: PMC3764383 DOI: 10.1038/jcbfm.2013.74] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 02/14/2013] [Accepted: 04/02/2013] [Indexed: 01/29/2023]
Abstract
Neural activation triggers a rapid, focal increase in blood flow and thus oxygen delivery. Local oxygen consumption also increases, although not to the same extent as oxygen delivery. This 'uncoupling' enables a number of widely-used functional neuroimaging techniques; however, the physiologic mechanisms that govern oxygen transport under these conditions remain unclear. Here, we explore this dynamic process using a new mathematical model. Motivated by experimental observations and previous modeling, we hypothesized that functional recruitment of capillaries has an important role during neural activation. Using conventional mechanisms alone, the model predictions were inconsistent with in vivo measurements of oxygen partial pressure. However, dynamically increasing net capillary permeability, a simple description of functional recruitment, led to predictions consistent with the data. Increasing permeability in all vessel types had the same effect, but two alternative mechanisms were unable to produce predictions consistent with the data. These results are further evidence that conventional models of oxygen transport are not sufficient to predict dynamic experimental data. The data and modeling suggest that it is necessary to include a mechanism that dynamically increases net vascular permeability. While the model cannot distinguish between the different possibilities, we speculate that functional recruitment could have this effect in vivo.
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Affiliation(s)
- Matthew J P Barrett
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
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20
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Modeling to link regional myocardial work, metabolism and blood flows. Ann Biomed Eng 2012; 40:2379-98. [PMID: 22915334 DOI: 10.1007/s10439-012-0613-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 06/21/2012] [Indexed: 12/13/2022]
Abstract
Given the mono-functional, highly coordinated processes of cardiac excitation and contraction, the observations that regional myocardial blood flows, rMBF, are broadly heterogeneous has provoked much attention, but a clear explanation has not emerged. In isolated and in vivo heart studies the total coronary flow is found to be proportional to the rate-pressure product (systolic mean blood pressure times heart rate), a measure of external cardiac work. The same relationship might be expected on a local basis: more work requires more flow. The validity of this expectation has never been demonstrated experimentally. In this article we review the concepts linking cellular excitation and contractile work to cellular energetics and ATP demand, substrate utilization, oxygen demand, vasoregulation, and local blood flow. Mathematical models of these processes are now rather well developed. We propose that the construction of an integrated model encompassing the biophysics, biochemistry and physiology of cardiomyocyte contraction, then combined with a detailed three-dimensional structuring of the fiber bundle and sheet arrangements of the heart as a whole will frame an hypothesis that can be quantitatively evaluated to settle the prime issue: Does local work drive local flow in a predictable fashion that explains the heterogeneity? While in one sense one can feel content that work drives flow is irrefutable, the are no cardiac contractile models that demonstrate the required heterogeneity in local strain-stress-work; quite the contrary, cardiac contraction models have tended toward trying to show that work should be uniform. The object of this review is to argue that uniformity of work does not occur, and is impossible in any case, and that further experimentation and analysis are necessary to test the hypothesis.
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21
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Gauthier CJ, Hoge RD. Magnetic resonance imaging of resting OEF and CMRO₂ using a generalized calibration model for hypercapnia and hyperoxia. Neuroimage 2011; 60:1212-25. [PMID: 22227047 DOI: 10.1016/j.neuroimage.2011.12.056] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 11/18/2011] [Accepted: 12/15/2011] [Indexed: 12/19/2022] Open
Abstract
We present a method allowing determination of resting cerebral oxygen metabolism (CMRO₂) from MRI and end-tidal O₂ measurements acquired during a pair of respiratory manipulations producing different combinations of hypercapnia and hyperoxia. The approach is based on a recently introduced generalization of calibrated MRI signal models that is valid for arbitrary combinations of blood flow and oxygenation change. Application of this model to MRI and respiratory data during a predominantly hyperoxic gas manipulation yields a specific functional relationship between the resting BOLD signal M and the resting oxygen extraction fraction OEF₀. Repeating the procedure using a second, primarily hypercapnic, manipulation provides a different functional form of M vs. OEF₀. These two equations can be readily solved for the two unknowns M and OEF₀. The procedure also yields the resting arterial O₂ content, which when multiplied by resting cerebral blood flow provides the total oxygen delivery in absolute physical units. The resultant map of oxygen delivery can be multiplied by the map of OEF₀ to obtain a map of the resting cerebral metabolic rate of oxygen consumption (CMRO₂) in absolute physical units. Application of this procedure in a group of seven human subjects provided average values of 0.35 ± 0.04 and 6.0 ± 0.7% for OEF₀ and M, respectively in gray-matter (M valid for 30 ms echo-time at 3T). Multiplying OEF₀ estimates by the individual values of resting gray-matter CBF (mean 52 ± 5 ml/100 g/min) and the measured arterial O₂ content gave a group average resting CMRO₂ value of 145 ± 30 μmol/100 g/min. The method also allowed the generation of maps depicting resting OEF, BOLD signal, and CMRO₂.
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Affiliation(s)
- C J Gauthier
- Physiology/Biomedical Engineering, Université de Montréal, Montreal, Quebec, Canada.
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22
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BIGDELI MOHAMMADREZA, HAJIZADEH SOHRAB, BANIEGHBAL BEHZAD, MASJDI MOHAMMADREZA. A COMPREHENSIVE SIMULATOR OF THE HUMAN PULMONARY SYSTEM: VALIDATION WITH DETERMINATION OF TOTALCO2AND DIAGNOSIS OF ACID-BASE ABNORMALITIES. J BIOL SYST 2011. [DOI: 10.1142/s0218339009002818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In previous models, heart-lung-blood interactions and their physicochemical properties have not been considered in comprehensive simulators and an integrated mathematical model has not been presented. The aim of the present study is to combine different phenomena involved in the cardiopulmonary function, which are often considered separately. In this study, the variables that constitute a comprehensive model; which includes physicochemical reactions of O2and CO2in the blood and fluid compartments, V/Q, pH , body temperature and diffusion limitation in the adult human and its ability to provide realistic response under different physiological and pathophysiological conditions; have been evaluated. The new biological system model consists of two subsystems: physicochemical properties of blood and physiological subsystem models. Based on the mentioned parameters, comprehensive simulator model has been suggested as following: [Formula: see text] According to the literature, all patients [COPD (20) and asthma (20)] showed acid-base imbalances. The mathematical model has been validated by diagnosis of acid-base abnormalities via calculating the total CO2and T40HCO3in physiological and pathophysiological conditions, and then the results compared to literature experimental data. Our comprehensive model provides results consistent with dynamic and steady state responses measured in subjects undergoing physiological and pathophysiological conditions. This might enable us to deepen our understanding of the cardiopulmonary system as a whole.
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Affiliation(s)
- MOHAMMAD REZA BIGDELI
- Faculty of Biological Sciences, Shahid Beheshti University, G.C., B.P. 1983963113, Tehran, Iran
| | - SOHRAB HAJIZADEH
- Department of Physiology, Tarbiat Modares University, Tehran, Iran
| | - BEHZAD BANIEGHBAL
- Pulmonary Division, Department of Internal Medicine, Ateyh Hospital, Tehran, Iran
| | - MOHAMMAD REZA MASJDI
- Chronic Respiratory Diseases Research Center (CRDRC), National Research Institute of Tuberculosis and Lung Disease (NRITLD), Shahid Beheshti University, MC, Tehran, Iran
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23
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Turri F, Yanagihara JI. Computer-assisted numerical analysis for oxygen and carbon dioxide mass transfer in blood oxygenators. Artif Organs 2011; 35:579-92. [PMID: 21671959 DOI: 10.1111/j.1525-1594.2010.01150.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A two-dimensional numeric simulator is developed to predict the nonlinear, convective-reactive, oxygen mass exchange in a cross-flow hollow fiber blood oxygenator. The numeric simulator also calculates the carbon dioxide mass exchange, as hemoglobin affinity to oxygen is affected by the local pH value, which depends mostly on the local carbon dioxide content in blood. Blood pH calculation inside the oxygenator is made by the simultaneous solution of an equation that takes into account the blood buffering capacity and the classical Henderson-Hasselbach equation. The modeling of the mass transfer conductance in the blood comprises a global factor, which is a function of the Reynolds number, and a local factor, which takes into account the amount of oxygen reacted to hemoglobin. The simulator is calibrated against experimental data for an in-line fiber bundle. The results are: (i) the calibration process allows the precise determination of the mass transfer conductance for both oxygen and carbon dioxide; (ii) very alkaline pH values occur in the blood path at the gas inlet side of the fiber bundle; (iii) the parametric analysis of the effect of the blood base excess (BE) shows that (.)V(CO₂) is similar in the case of blood metabolic alkalosis, metabolic acidosis, or normal BE, for a similar blood inlet P(CO₂), although the condition of metabolic alkalosis is the worst case, as the pH in the vicinity of the gas inlet is the most alkaline; (iv) the parametric analysis of the effect of the gas flow to blood flow ratio (QG/QB) shows that (.)V(CO₂) variation with the gas flow is almost linear up to QG/QB = 2.0. (.)V(O₂) is not affected by the gas flow as it was observed that by increasing the gas flow up to eight times, the (.)V(O₂) grows only 1%. The mass exchange of carbon dioxide uses the full length of the hollow-fiber only if Q(G) /Q(B)> 2.0, as it was observed that only in this condition does the local variation of pH and blood P(CO₂) comprise the whole fiber bundle.
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Affiliation(s)
- Fabio Turri
- Pulmonary Division, Medical School Laboratory of Environmental and Thermal Engineering, Department of Mechanical Engineering, Escola Politecnica, University of São Paulo, São Paulo, Brazil.
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24
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Cerqueira LS, Nogueira FS, Carvalho J, Pompeu FA. Resposta da cinética de consumo de oxigênio e da eficiência mecânica delta de homens e mulheres em diferentes intensidades de esforço. REV BRAS MED ESPORTE 2011. [DOI: 10.1590/s1517-86922011000400013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
INTRODUÇÃO:A eficiência mecânica delta (EMΔ ) e a cinética do consumo de oxigênio (K<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2) são influenciadas por parâmetros metabólicos musculares e pelo transporte de <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2. O objetivo do presente estudo foi determinar a diferença na K<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 e na EMΔ em três intensidades de esforço nos dois gêneros. MÉTODOS: 56 sujeitos (26 mulheres) foram submetidos ao protocolo de esforço escalonado, contínuo e máximo (GxT) no cicloergômetro mecânico para determinação da potência aeróbia máxima (<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2máx), carga máxima (Wmax), limiar anaeróbio (AT) e ponto de compensação respiratória (PCR). O AT foi determinado através dos métodos V-slope e E <img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" /><img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" />E / <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2; o PCR através da relação <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus <img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" />E ; ambos por dois avaliadores. A EMΔ e a K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 foram consideradas como a inclinação entre <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus Watts e <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus tempo (s), respectivamente, do começo do teste até o AT (S1), do AT ao PCR (S2) e do PCR ao <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2máx (S3), determinada por análise de regressão linear. RESULTADOS: Para a EMΔ, diferenças significativas foram observadas entre S1 versus S2 (p = 0,001), S1 versus S3 (p = 0,001) e S2 versus S3 (p = 0,006). Não foi observada diferença (p = 0,060) ou interação significativa (p = 0,062) entre homens versus mulheres. Para a K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 diferenças significativas foram observadas entre S1 versus S3 (p = 0,001) e S2 versus S3 (p = 0,001) em ambos gêneros. Diferenças (p = 0,001) e interação significativa (p = 0,006) foram observadas entre homens versus mulheres, no último parâmetro. CONCLUSÕES: A EMΔ decresce com o incremento da intensidade de trabalho, porém, não há diferenças quando se compara homens e mulheres. Por outro lado, as mulheres apresentam K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 mais rápida do que os homens.
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Aguado-Sierra J, Krishnamurthy A, Villongco C, Chuang J, Howard E, Gonzales MJ, Omens J, Krummen DE, Narayan S, Kerckhoffs RCP, McCulloch AD. Patient-specific modeling of dyssynchronous heart failure: a case study. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:147-55. [PMID: 21763714 DOI: 10.1016/j.pbiomolbio.2011.06.014] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 06/30/2011] [Indexed: 11/19/2022]
Abstract
The development and clinical use of patient-specific models of the heart is now a feasible goal. Models have the potential to aid in diagnosis and support decision-making in clinical cardiology. Several groups are now working on developing multi-scale models of the heart for understanding therapeutic mechanisms and better predicting clinical outcomes of interventions such as cardiac resynchronization therapy. Here we describe the methodology for generating a patient-specific model of the failing heart with a myocardial infarct and left ventricular bundle branch block. We discuss some of the remaining challenges in developing reliable patient-specific models of cardiac electromechanical activity, and identify some of the main areas for focusing future research efforts. Key challenges include: efficiently generating accurate patient-specific geometric meshes and mapping regional myofiber architecture to them; modeling electrical activation patterns based on cellular alterations in human heart failure, and estimating regional tissue conductivities based on clinically available electrocardiographic recordings; estimating unloaded ventricular reference geometry and material properties for biomechanical simulations; and parameterizing systemic models of circulatory dynamics from available hemodynamic measurements.
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Affiliation(s)
- Jazmin Aguado-Sierra
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA.
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Mohammed FS, Wuttigul S, Kitchens CL. Dynamic Surface Properties of Amino-Terminated Self-Assembled Monolayers Incorporating Reversible CO2 Chemistry. Ind Eng Chem Res 2011. [DOI: 10.1021/ie102526s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fiaz S. Mohammed
- Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, United States
| | - Sirikanya Wuttigul
- Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, United States
| | - Christopher L. Kitchens
- Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, United States
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Baete SH, Vandecasteele J, De Deene Y. 19F MRI oximetry: simulation of perfluorocarbon distribution impact. Phys Med Biol 2011; 56:2535-57. [PMID: 21444970 DOI: 10.1088/0031-9155/56/8/013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In (19)F MRI oximetry, a method used to image tumour hypoxia, perfluorocarbons serve as oxygenation markers. The goal of this study is to evaluate the impact of perfluorocarbon distribution and concentration in (19)F MRI oximetry through a computer simulation. The simulation studies the correspondence between (19)F measured (pO(FNMR)(2)) and actual tissue oxygen tension (pO(2)) for several tissue perfluorocarbon distributions. For this, a Krogh tissue model is implemented which incorporates the presence of perfluorocarbons in blood and tissue. That is, in tissue the perfluorocarbons are distributed homogeneously according to Gaussian diffusion profiles, or the perfluorocarbons are concentrated in the capillary wall. Using these distributions, the oxygen tension in the simulation volume is calculated. The simulated mean oxygen tension is then compared with pO(FNMR)(2), the (19)F MRI-based measure of pO(2) and with pO(0)(2), pO(2) in the absence of perfluorocarbons. The agreement between pO(FNMR)(2) and actual pO(2) is influenced by vascular density and perfluorocarbon distribution. The presence of perfluorocarbons generally gives rise to a pO(2) increase in tissue. This effect is enhanced when perfluorocarbons are also present in blood. Only the homogeneous perfluorocarbon distribution in tissue with no perfluorocarbons in blood guarantees small deviations of pO(FNMR)(2) from pO(2). Hence, perfluorocarbon distribution in tissue and blood has a serious impact on the reliability of (19)F MRI-based measures of oxygen tension. In addition, the presence of perfluorocarbons influences the actual oxygen tension. This finding may be of great importance for further development of (19)F MRI oximetry.
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Affiliation(s)
- S H Baete
- Department of Radiation Oncology and Experimental Cancer Research, Ghent University, De Pintelaan 185, 9000 Gent, Belgium.
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A metabolic model of human erythrocytes: practical application of the E-Cell Simulation Environment. J Biomed Biotechnol 2010; 2010:642420. [PMID: 20625505 PMCID: PMC2896712 DOI: 10.1155/2010/642420] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2010] [Accepted: 05/19/2010] [Indexed: 11/18/2022] Open
Abstract
The human red blood cell (RBC) has long been used for modeling of complex biological networks, for elucidation of a wide variety of dynamic phenomena, and for understanding the fundamental topology of metabolic pathways. Here, we introduce our recent work on an RBC metabolic model using the E-Cell Simulation Environment. The model is sufficiently detailed to predict the temporal hypoxic response of each metabolite and, at the same time, successfully integrates modulation of metabolism and of the oxygen transporting capacity of hemoglobin. The model includes the mechanisms of RBC maintenance as a single cell system and the functioning of RBCs as components of a higher order system. Modeling of RBC metabolism is now approaching a fully mature stage of realistic predictions at the molecular level and will be useful for predicting conditions in biotechnological applications such as long-term cold storage of RBCs.
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Yan X, Jiang N, Ma J. Theoretical study of interactions between human adult hemoglobin and acetate ion by polarizable force field and fragmentation quantum chemistry methods. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/s11426-009-0273-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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30
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Erupaka K, Bruce EN, Bruce MC. Prediction of Extravascular Burden of Carbon Monoxide (CO) in the Human Heart. Ann Biomed Eng 2009; 38:403-38. [DOI: 10.1007/s10439-009-9814-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Accepted: 09/26/2009] [Indexed: 11/30/2022]
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31
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Tisdall MM, Taylor C, Tachtsidis I, Leung TS, Pritchard C, Elwell CE, Smith M. The effect on cerebral tissue oxygenation index of changes in the concentrations of inspired oxygen and end-tidal carbon dioxide in healthy adult volunteers. Anesth Analg 2009; 109:906-13. [PMID: 19690266 PMCID: PMC2742623 DOI: 10.1213/ane.0b013e3181aedcdc] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND A variety of near-infrared spectroscopy devices can be used to make noninvasive measurements of cerebral tissue oxygen saturation (ScO2). The ScO2 measured by the NIRO 300 spectrometer (Hamamatsu Photonics, Japan) is called the cerebral tissue oxygenation index (TOI) and is an assessment of the balance between cerebral oxygen delivery and utilization. We designed this study to investigate the effect of systemic and intracranial physiological changes on TOI. METHODS Fifteen healthy volunteers were studied during isocapneic hyperoxia and hypoxemia, and normoxic hypercapnea and hypocapnea. Absolute cerebral TOI and changes in oxy- and deoxyhemoglobin concentrations were measured using a NIRO 300 spectrometer. Changes in arterial oxygen saturation (SaO2), ETCO2, heart rate, mean arterial blood pressure (MBP), and middle cerebral artery blood flow velocity (Vmca) were also measured during these physiological challenges. Changes in cerebral blood volume (CBV) were subsequently calculated from changes in total cerebral hemoglobin concentration. RESULTS Baseline TOI was 67.3% with an interquartile range (IQR) of 65.2%-71.9%. Hypoxemia was associated with a median decrease in TOI of 7.1% (IQR -9.1% to -5.4%) from baseline (P < 0.0001) and hyperoxia with a median increase of 2.3% (IQR 2.0%-2.5%) (P < 0.0001). Hypocapnea caused a reduction in TOI of 2.1% (IQR -3.3% to -1.3%) from baseline (P < 0.0001) and hypercapnea an increase of 2.6% (IQR 1.4%-3.7%) (P < 0.0001). Changes in SaO2 (P < 0.0001), ETCO2 (P < 0.0001), CBV (P = 0.0003), and MBP (P = 0.03) were significant variables affecting TOI. Changes in Vmca (P = 0.7) and heart rate (P = 0.2) were not significant factors. CONCLUSION TOI is an easy-to-monitor variable that provides real-time, multisite, and noninvasive assessment of the balance between cerebral oxygen delivery and utilization. However, TOI is a complex variable that is affected by SaO2 and ETCO2, and, to a lesser extent, by MBP and CBV. Clinicians need to be aware of the systemic and cerebral physiological changes that can affect TOI to interpret changes in this variable during clinical monitoring.
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Affiliation(s)
- Martin M Tisdall
- Department of Neuroanaesthesia & Neurocritical Care, The National Hospital for Neurology & Neurosurgery, University College London Hospitals
| | - Christopher Taylor
- Department of Neuroanaesthesia & Neurocritical Care, The National Hospital for Neurology & Neurosurgery, University College London Hospitals
| | - Ilias Tachtsidis
- Department of Medical Physics and Bioengineering, University College London
| | - Terence S Leung
- Department of Medical Physics and Bioengineering, University College London
| | - Caroline Pritchard
- Department of Neuroanaesthesia & Neurocritical Care, The National Hospital for Neurology & Neurosurgery, University College London Hospitals
| | - Clare E Elwell
- Department of Medical Physics and Bioengineering, University College London
| | - Martin Smith
- Department of Neuroanaesthesia & Neurocritical Care, The National Hospital for Neurology & Neurosurgery, University College London Hospitals
- Department of Medical Physics and Bioengineering, University College London
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Abstract
To improve understanding of microvascular O(2) transport, theoretical modeling has been pursued for many years. The large number of studies in this area attests to the complexities (i.e., biochemical, structural, and hemodynamic) involved. This article focuses on theoretical studies from the last two decades and, in particular, on models of O(2) transport to tissue by discrete microvessels. A brief discussion of intravascular O(2) transport is first given, highlighting the physiological importance of intravascular resistance to blood-tissue O(2) transfer. This is followed by a description of the Krogh tissue cylinder model of O(2) transport by a single capillary, which is shown to remain relevant in modified forms that relax many of the original biophysical assumptions. However, there are many geometric and hemodynamic complexities that require the consideration of microvascular arrays and networks. Multivessel models are discussed that have shown the physiological importance of heterogeneities in vessel spacing, O(2) supply, red blood cell flow path, as well as interactions between capillaries and arterioles. These realistic models require sophisticated methods for solving the governing partial differential equations, and a range of solution techniques are described. Finally, the issue of experimental validation of microvascular O(2) delivery models is discussed, and new directions in O(2) transport modeling are outlined.
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Affiliation(s)
- Daniel Goldman
- Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada.
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Hald B, Madsen MF, Danø S, Quistorff B, Sørensen PG. Quantitative evaluation of respiration induced metabolic oscillations in erythrocytes. Biophys Chem 2008; 141:41-8. [PMID: 19162390 DOI: 10.1016/j.bpc.2008.12.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 12/15/2008] [Accepted: 12/20/2008] [Indexed: 11/19/2022]
Abstract
The changes in the partial pressures of oxygen and carbon dioxide (P(O(2)) and P(CO(2))) during blood circulation alter erythrocyte metabolism, hereby causing flux changes between oxygenated and deoxygenated blood. In the study we have modeled this effect by extending the comprehensive kinetic model by Mulquiney and Kuchel [P.J. Mulquiney, and P.W. Kuchel. Model of 2,3-bisphosphoglycerate metabolism in the human erythrocyte based on detailed enzyme kinetic equations: equations and parameter refinement, Biochem. J. 1999, 342, 581-596.] with a kinetic model of hemoglobin oxy-/deoxygenation transition based on an oxygen dissociation model developed by Dash and Bassingthwaighte [R. Dash, and J. Bassingthwaighte. Blood HbO(2) and HbCO(2) dissociation curves at varied O(2), CO(2), pH, 2,3-DPG and temperature levels, Ann. Biomed. Eng., 2004, 32(12), 1676-1693.]. The system has been studied during transitions from the arterial to the venous phases by simply forcing P(O(2)) and P(CO(2)) to follow the physiological values of venous and arterial blood. The investigations show that the system passively follows a limit cycle driven by the forced oscillations of P(O(2)) and is thus inadequately described solely by steady state consideration. The metabolic system exhibits a broad distribution of time scales. Relaxations of modes with hemoglobin and Mg(2+) binding reactions are very fast, while modes involving glycolytic, membrane transport and 2,3-BPG shunt reactions are much slower. Incomplete slow mode relaxations during the 60 s period of the forced transitions cause significant overshoots of important fluxes and metabolite concentrations - notably ATP, 2,3-BPG, and Mg(2+). The overshoot phenomenon arises in consequence of a periodical forcing and is likely to be widespread in nature - warranting a special consideration for relevant systems.
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Affiliation(s)
- Bjørn Hald
- Department of Biomedical Sciences, University of Copenhagen, Denmark.
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Li Y, Dash RK, Kim J, Saidel GM, Cabrera ME. Role of NADH/NAD+ transport activity and glycogen store on skeletal muscle energy metabolism during exercise: in silico studies. Am J Physiol Cell Physiol 2008; 296:C25-46. [PMID: 18829894 DOI: 10.1152/ajpcell.00094.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle can maintain ATP concentration constant during the transition from rest to exercise, whereas metabolic reaction rates may increase substantially. Among the key regulatory factors of skeletal muscle energy metabolism during exercise, the dynamics of cytosolic and mitochondrial NADH and NAD+ have not been characterized. To quantify these regulatory factors, we have developed a physiologically based computational model of skeletal muscle energy metabolism. This model integrates transport and reaction fluxes in distinct capillary, cytosolic, and mitochondrial domains and investigates the roles of mitochondrial NADH/NAD+ transport (shuttling) activity and muscle glycogen concentration (stores) during moderate intensity exercise (60% maximal O2 consumption). The underlying hypothesis is that the cytosolic redox state (NADH/NAD+) is much more sensitive to a metabolic disturbance in contracting skeletal muscle than the mitochondrial redox state. This hypothesis was tested by simulating the dynamic metabolic responses of skeletal muscle to exercise while altering the transport rate of reducing equivalents (NADH and NAD+) between cytosol and mitochondria and muscle glycogen stores. Simulations with optimal parameter estimates showed good agreement with the available experimental data from muscle biopsies in human subjects. Compared with these simulations, a 20% increase (or approximately 20% decrease) in mitochondrial NADH/NAD+ shuttling activity led to an approximately 70% decrease (or approximately 3-fold increase) in cytosolic redox state and an approximately 35% decrease (or approximately 25% increase) in muscle lactate level. Doubling (or halving) muscle glycogen concentration resulted in an approximately 50% increase (or approximately 35% decrease) in cytosolic redox state and an approximately 30% increase (or approximately 25% decrease) in muscle lactate concentration. In both cases, changes in mitochondrial redox state were minimal. In conclusion, the model simulations of exercise response are consistent with the hypothesis that mitochondrial NADH/NAD+ shuttling activity and muscle glycogen stores affect primarily the cytosolic redox state. Furthermore, muscle lactate production is regulated primarily by the cytosolic redox state.
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Affiliation(s)
- Yanjun Li
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, 11100 Euclid Ave., Cleveland, OH 44106-6011, USA
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Smith JM, Serebrennikova YM, Huffman DE, Leparc GF, García-Rubio LH. A new method for the detection of microorganisms in blood cultures: Part I. Theoretical analysis and simulation of blood culture processes. CAN J CHEM ENG 2008. [DOI: 10.1002/cjce.20095] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Jennifer M. Smith
- Claro Scientific, LLC., 10100 Dr. Martin Luther King Jr. St. N., St. Petersburg, FL 33716, U.S.A
| | - Yulia M. Serebrennikova
- Claro Scientific, LLC., 10100 Dr. Martin Luther King Jr. St. N., St. Petersburg, FL 33716, U.S.A
- College of Marine Science University of South Florida, 140 Seventh Avenue S, St. Petersburg, FL 33701, U.S.A
| | - Debra E. Huffman
- Claro Scientific, LLC., 10100 Dr. Martin Luther King Jr. St. N., St. Petersburg, FL 33716, U.S.A
| | - German F. Leparc
- Florida Blood Services, 10100 Dr. Martin Luther King Jr. St. N., St. Petersburg, FL 33716, U.S.A
| | - Luis H. García-Rubio
- Claro Scientific, LLC., 10100 Dr. Martin Luther King Jr. St. N., St. Petersburg, FL 33716, U.S.A
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Dash RK, Li Y, Kim J, Beard DA, Saidel GM, Cabrera ME. Metabolic dynamics in skeletal muscle during acute reduction in blood flow and oxygen supply to mitochondria: in-silico studies using a multi-scale, top-down integrated model. PLoS One 2008; 3:e3168. [PMID: 18779864 PMCID: PMC2526172 DOI: 10.1371/journal.pone.0003168] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 07/19/2008] [Indexed: 11/18/2022] Open
Abstract
Control mechanisms of cellular metabolism and energetics in skeletal muscle that may become evident in response to physiological stresses such as reduction in blood flow and oxygen supply to mitochondria can be quantitatively understood using a multi-scale computational model. The analysis of dynamic responses from such a model can provide insights into mechanisms of metabolic regulation that may not be evident from experimental studies. For the purpose, a physiologically-based, multi-scale computational model of skeletal muscle cellular metabolism and energetics was developed to describe dynamic responses of key chemical species and reaction fluxes to muscle ischemia. The model, which incorporates key transport and metabolic processes and subcellular compartmentalization, is based on dynamic mass balances of 30 chemical species in both capillary blood and tissue cells (cytosol and mitochondria) domains. The reaction fluxes in cytosol and mitochondria are expressed in terms of a general phenomenological Michaelis-Menten equation involving the compartmentalized energy controller ratios ATP/ADP and NADH/NAD(+). The unknown transport and reaction parameters in the model are estimated simultaneously by minimizing the differences between available in vivo experimental data on muscle ischemia and corresponding model outputs in coupled with the resting linear flux balance constraints using a robust, nonlinear, constrained-based, reduced gradient optimization algorithm. With the optimal parameter values, the model is able to simulate dynamic responses to reduced blood flow and oxygen supply to mitochondria associated with muscle ischemia of several key metabolite concentrations and metabolic fluxes in the subcellular cytosolic and mitochondrial compartments, some that can be measured and others that can not be measured with the current experimental techniques. The model can be applied to test complex hypotheses involving dynamic regulation of cellular metabolism and energetics in skeletal muscle during physiological stresses such as ischemia, hypoxia, and exercise.
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Affiliation(s)
- Ranjan K. Dash
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Yanjun Li
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Jaeyeon Kim
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Daniel A. Beard
- Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Gerald M. Saidel
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Marco E. Cabrera
- Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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Moore S, David T. A model of autoregulated blood flow in the cerebral vasculature. Proc Inst Mech Eng H 2008; 222:513-30. [DOI: 10.1243/09544119jeim298] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The circle of Willis is a ring-like arterial structure located in the base of the brain, and is responsible for the distribution of oxygenated blood throughout the cerebral mass. Among the general population, approximately 50 per cent have a complete circle of Willis; for the others a multitude of possible anatomical variations are present, with absent or hypoplastic vessels being common. Certain conditions such as a build-up of atherosclerotic plaque on the arterial wall can result in ischaemic damage and stroke-like symptoms. A three-dimensional computer model has been developed based on the results of magnetic resonance imaging data, incorporating a numerical algorithm to simulate the body's autoregulation mechanism, such that oxygen delivery to the cerebral territories can be predicted in response events, leading to a reduction in cerebral blood flow. Sample results are presented for combinations of occlusion and stenosis.
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Affiliation(s)
- S Moore
- Centre for Bioengineering, Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
| | - T David
- Centre for Bioengineering, Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
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Dash RK, Li Y, Kim J, Saidel GM, Cabrera ME. Modeling cellular metabolism and energetics in skeletal muscle: large-scale parameter estimation and sensitivity analysis. IEEE Trans Biomed Eng 2008; 55:1298-318. [PMID: 18390321 DOI: 10.1109/tbme.2007.913422] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Skeletal muscle plays a major role in the regulation of whole-body energy metabolism during physiological stresses such as ischemia, hypoxia, and exercise. Current experimental techniques provide relatively little in vivo data on dynamic responses of metabolite concentrations and metabolic fluxes in skeletal muscle to such physiological stimuli. As a complementary approach to experimental measurements and as a framework for quantitatively analyzing available in vivo data, a physiologically based model of skeletal muscle cellular metabolism and energetics is developed. This model, which incorporates key transport and reaction processes, is based on dynamic mass balances of 30 chemical species in capillary (blood) and tissue (cell) domains. The reaction fluxes in the cellular domain are expressed in terms of a generalized Michaelis?Menten equation involving energy controller ratios ATP/ADP and ATP/ADP and NADH/NAD+ . This formalism introduces a large number of unknown parameters ( approximately 90). Estimating these parameters from in vivo sparse data and evaluating dynamic sensitivities of the model outputs with respect to these parameters is a challenging problem. Parameter estimation is accomplished using an efficient, nonlinear, constraint-based, optimization algorithm that minimizes differences between available experimental data and corresponding model outputs by explicitly utilizing equality constraints on resting fluxes and concentrations. With the estimated parameter values, the model is able to simulate dynamic responses to reduced blood flow (ischemia) of key metabolite concentrations and metabolic fluxes, both measured and nonmeasured. A general parameter sensitivity analysis is carried out to determine and characterize the parameters having the most and least effects on the measured outputs.
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Affiliation(s)
- Ranjan K Dash
- Center for Modeling Integrated Metabolic Systems and Pediatrics, Case Western Reserve University, Cleveland, OH 44106, USA
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Modeling oxygen and carbon dioxide transport and exchange using a closed loop circulatory system. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008. [PMID: 18290346 DOI: 10.1007/978-0-387-74911-2_39] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
The binding and buffering of O2 and CO2 in the blood influence their exchange in lung and tissues and their transport through the circulation. To investigate the binding and buffering effects, a model of blood-tissue gas exchange is used. The model accounts for hemoglobin saturation, the simultaneous binding of O2, CO2, H+, 2,3-DPG to hemoglobin, and temperature effects. Invertible Hill-type saturation equations facilitate rapid calculation of respiratory gas redistribution among the plasma, red blood cell and tissue that occur along the concentration gradients in the lung and in the capillary-tissue exchange regions. These equations are well-suited to analysis of transients in tissue metabolism and partial pressures of inhaled gas. The modeling illustrates that because red blood cell velocities in the flowing blood are higher than plasma velocities after a transient there can be prolonged differences between RBC and plasma oxygen partial pressures. The blood-tissue gas exchange model has been incorporated into a higher level model of the circulatory system plus pulmonary mechanics and gas exchange using the RBC and plasma equations to account for pH and CO2 buffering in the blood.
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Neal ML, Bassingthwaighte JB. Subject-specific model estimation of cardiac output and blood volume during hemorrhage. ACTA ACUST UNITED AC 2007; 7:97-120. [PMID: 17846886 PMCID: PMC3629970 DOI: 10.1007/s10558-007-9035-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have developed a novel method for estimating subject-specific hemodynamics during hemorrhage. First, a mathematical model representing a closed-loop circulation and baroreceptor feedback system was parameterized to match the baseline physiology of individual experimental subjects by fitting model results to 1 min of pre-injury data. This automated parameterization process matched pre-injury measurements within 1.4 +/- 1.3% SD. Tuned parameters were then used in similar open-loop models to simulate dynamics post-injury. Cardiac output (CO) estimates were obtained continuously using post-injury measurements of arterial blood pressure (ABP) and heart rate (HR) as inputs to the first open-loop model. Secondarily, total blood volume (TBV) estimates were obtained by summing the blood volumes in all the circulatory segments of a second open-loop model that used measured CO as an additional input. We validated the estimation method by comparing model CO results to flowprobe measurements in 14 pigs. Overall, CO estimates had a Bland-Altman bias of -0.30 l/min with upper and lower limits of agreement 0.80 and -1.40 l/min. The negative bias is likely due to overestimation of the peripheral resistance response to hemorrhage. There was no reference measurement of TBV; however, the estimates appeared reasonable and clearly predicted survival versus death during the post-hemorrhage period. Both open-loop models ran in real time on a computer with a 2.4 GHz processor, and their clinical applicability in emergency care scenarios is discussed.
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Affiliation(s)
- Maxwell Lewis Neal
- Department of Medical Education and Biomedical Informatics,
University of Washington, Seattle, WA 98195, USA
| | - James B. Bassingthwaighte
- Department of Bioengineering, University of Washington, 1705 NE
Pacific St., Box 355061, Seattle, WA 98195-5061, USA
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Zierenberg JR, Fujioka H, Hirschl RB, Bartlett RH, Grotberg JB. Pulsatile Blood Flow and Oxygen Transport Past a Circular Cylinder. J Biomech Eng 2007; 129:202-15. [PMID: 17408325 DOI: 10.1115/1.2485961] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The fundamental study of blood flow past a circular cylinder filled with an oxygen source is investigated as a building block for an artificial lung. The Casson constitutive equation is used to describe the shear-thinning and yield stress properties of blood. The presence of hemoglobin is also considered. Far from the cylinder, a pulsatile blood flow in the x direction is prescribed, represented by a time periodic (sinusoidal) component superimposed on a steady velocity. The dimensionless parameters of interest for the characterization of the flow and transport are the steady Reynolds number (Re), Womersley parameter (α), pulsation amplitude (A), and the Schmidt number (Sc). The Hill equation is used to describe the saturation curve of hemoglobin with oxygen. Two different feed-gas mixtures were considered: pure O2 and air. The flow and concentration fields were computed for Re=5, 10, and 40, 0≤A≤0.75, α=0.25, 0.4, and Schmidt number, Sc=1000. The Casson fluid properties result in reduced recirculations (when present) downstream of the cylinder as compared to a Newtonian fluid. These vortices oscillate in size and strength as A and α are varied. Hemoglobin enhances mass transport and is especially important for an air feed which is dominated by oxyhemoglobin dispersion near the cylinder. For a pure O2 feed, oxygen transport in the plasma dominates near the cylinder. Maximum oxygen transport is achieved by operating near steady flow (small A) for both feed-gas mixtures. The time averaged Sherwood number, Sh̿, is found to be largely influenced by the steady Reynolds number, increasing as Re increases and decreasing with A. Little change is observed with varying α for the ranges investigated. The effect of pulsatility on Sh̿ is greater at larger Re. Increasing Re aids transport, but yields a higher cylinder drag force and shear stresses on the cylinder surface which are potentially undesirable.
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Affiliation(s)
- Jennifer R Zierenberg
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109-2099, USA
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Chan KY, Fujioka H, Hirshl RB, Bartlett RH, Grotberg JB. Pulsatile Blood Flow and Gas Exchange Across a Cylindrical Fiber Array. J Biomech Eng 2007; 129:676-87. [PMID: 17887893 DOI: 10.1115/1.2768105] [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: 11/08/2022]
Abstract
The pulsatile blood flow and gas transport of oxygen and carbon dioxide through a cylindrical array of microfibers are numerically simulated. Blood is modeled as a homogeneous Casson fluid, and hemoglobin molecules in blood are assumed to be in local equilibrium with oxygen and carbon dioxide. It is shown that flow pulsatility enhances gas transport and the amount of gas exchange is sensitive to the blood flow field across the fibers. The steady Sherwood number dependence on Reynolds number was shown to have a linear relation consistent with experimental findings. For most cases, an enhancement in gas transport is accompanied with an increase in flow resistance. Maximum local shear stress is provided as a possible indicator of thrombosis, and the computed shear stress is shown to be below the threshold value for thrombosis formation for all cases evaluated.
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Affiliation(s)
- Kit Yan Chan
- Department of Biomedical Engineering, The University of Michigan, Ann Arbor, Michigan 48109, USA
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Kinoshita A, Tsukada K, Soga T, Hishiki T, Ueno Y, Nakayama Y, Tomita M, Suematsu M. Roles of hemoglobin Allostery in hypoxia-induced metabolic alterations in erythrocytes: simulation and its verification by metabolome analysis. J Biol Chem 2007; 282:10731-41. [PMID: 17289676 DOI: 10.1074/jbc.m610717200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
When erythrocytes are exposed to hypoxia, hemoglobin (Hb) stabilizes in the T-state by capturing 2,3-bisphosphoglycerate. This process could reduce the intracellular pool of glycolytic substrates, jeopardizing cellular energetics. Recent observations suggest that hypoxia-induced activation of glycolytic enzymes is correlated with their release from Band III (BIII) on the cell membrane. Based on these data, we developed a mathematical model of erythrocyte metabolism and compared hypoxia-induced differences in predicted activities of the enzymes, their products, and cellular energetics between models with and without the interaction of Hb with BIII. The models predicted that the allostery-dependent Hb interaction with BIII accelerates consumption of upstream glycolytic substrates such as glucose 6-phosphate and increases downstream products such as phosphoenolpyruvate. This prediction was consistent with metabolomic data from capillary electrophoresis mass spectrometry. The hypoxia-induced alterations in the metabolites resulted from acceleration of glycolysis, as judged by increased conversion of [(13)C]glucose to [(13)C]lactate. The allostery-dependent interaction of Hb with BIII appeared to contribute not only to maintenance of energy charge but also to further synthesis of 2,3-bisphosphoglycerate, which could help sustain stabilization of T-state Hb during hypoxia. Furthermore, such an activation of glycolysis was not observed when Hb was stabilized in R-state by treating the cells with CO. These results suggest that Hb allostery in erythrocytes serves as an O(2)-sensing trigger that drives glycolytic acceleration to stabilize intracellular energetics and promote the ability to release O(2) from the cells.
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Affiliation(s)
- Ayako Kinoshita
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
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Zhou H, Saidel GM, Cabrera ME. Multi-organ system model of O2 and CO2 transport during isocapnic and poikilocapnic hypoxia. Respir Physiol Neurobiol 2006; 156:320-30. [PMID: 17188027 DOI: 10.1016/j.resp.2006.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Revised: 10/31/2006] [Accepted: 11/01/2006] [Indexed: 11/15/2022]
Abstract
A multi-organ systems model of O(2) and CO(2) transport is developed to analyze the control of ventilation and blood flow during hypoxia. Among the aspects of the control processes that this model addressed are possible mechanisms responsible for the second phase of the ventilatory hypoxic response to mild hypoxia, i.e., hypoxic ventilatory decline (HVD). Species mass transport processes are described by compartmental mass balances in brain, heart, skeletal muscle, and "other tissues" connected in parallel via the circulation. In pulmonary and systemic capillaries and in the vasculature connecting the systemic tissues, species transport processes are represented by a one-dimensional, convection-dispersion model. The effects of bicarbonate acid-base buffering, hemoglobin, and myoglobin on the transport processes are included. The model incorporates feedback control mechanisms through a cardiorespiratory control system in which peripheral and central chemoreceptors sense O(2) and CO(2) partial pressures. Model simulations of the ventilatory responses to isocapnic and poikilocapnic hypoxia show two phases with distinct dynamics. A fast phase is discernable immediately after switching from normoxic to hypoxic conditions, while a delayed slow phase (HVD) typically becomes manifested after several minutes. Model simulations allow quantitative evaluation of several proposed mechanisms to account for HVD. Under isocapnic hypoxia, simulations indicate that an increase in brain blood flow has no effect on HVD, but that HVD can be entirely described by central ventilatory depression (CVD). Under poikilocapnic hypoxia, the hypocapnia caused by hypoxic hyperventilation has no effect on HVD.
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Affiliation(s)
- Haiying Zhou
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
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Lai N, Dash RK, Nasca MM, Saidel GM, Cabrera ME. Relating pulmonary oxygen uptake to muscle oxygen consumption at exercise onset: in vivo and in silico studies. Eur J Appl Physiol 2006; 97:380-94. [PMID: 16636861 PMCID: PMC4124916 DOI: 10.1007/s00421-006-0176-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2006] [Indexed: 11/25/2022]
Abstract
Assessment of the rate of muscle oxygen consumption, UO(2m), in vivo during exercise involving a large muscle mass is critical for investigating mechanisms regulating energy metabolism at exercise onset. While UO(2m) is technically difficult to obtain under these circumstances, pulmonary oxygen uptake, VO(2p), can be readily measured and used as a proxy to UO(2m). However, the quantitative relationship between VO(2p) and UO(2m) during the nonsteady phase of exercise in humans, needs to be established. A computational model of oxygen transport and utilization--based on dynamic mass balances in blood and tissue cells--was applied to quantify the dynamic relationship between model-simulated UO(2m) and measured VO(2p) during moderate (M), heavy (H), and very heavy (V) intensity exercise. In seven human subjects, VO(2p) and muscle oxygen saturation, StO(2m), were measured with indirect calorimetry and near infrared spectroscopy (NIRS), respectively. The dynamic responses of VO(2p) and StO(2m) at each intensity were in agreement with previously published data. The response time of muscle oxygen consumption, tauUO(2m) estimated by direct comparison between model results and measurements of StO(2m) was significantly faster (P < 0.001) than that of pulmonary oxygen uptake, tauVO(2p) (M: 13 +/- 4 vs. 65 +/- 7 s; H: 13 +/- 4 vs. 100 +/- 24 s; V: 15 +/- 5 vs. 82 +/- 31 s). Thus, by taking into account the dynamics of oxygen stores in blood and tissue and determining muscle oxygen consumption from muscle oxygenation measurements, this study demonstrates a significant temporal dissociation between UO(2m) and VO(2p) at exercise onset.
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Affiliation(s)
- N. Lai
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106-6011, USA. Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, OH 44106-6011, USA
| | - R. K. Dash
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106-6011, USA. Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, OH 44106-6011, USA
| | - M. M. Nasca
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106-6011, USA
| | - G. M. Saidel
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106-6011, USA. Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, OH 44106-6011, USA
| | - M. E. Cabrera
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106-6011, USA. Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106-6011, USA. Center for Modeling Integrated Metabolic Systems, Case Western Reserve University, Cleveland, OH 44106-6011, USA. Pediatric Cardiology, Rainbow Babies and Children’s Hospital, MS 6011, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106-6011, USA, Tel.: +1-216-8445085, Fax: +1-216-8445478
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Dash RK, Bassingthwaighte JB. Simultaneous blood-tissue exchange of oxygen, carbon dioxide, bicarbonate, and hydrogen ion. Ann Biomed Eng 2006; 34:1129-48. [PMID: 16775761 PMCID: PMC4232240 DOI: 10.1007/s10439-005-9066-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Accepted: 10/13/2005] [Indexed: 11/25/2022]
Abstract
A detailed nonlinear four-region (red blood cell, plasma, interstitial fluid, and parenchymal cell) axially distributed convection-diffusion-permeation-reaction-binding computational model is developed to study the simultaneous transport and exchange of oxygen (O2) and carbon dioxide (CO2) in the blood-tissue exchange system of the heart. Since the pH variation in blood and tissue influences the transport and exchange of O2 and CO2 (Bohr and Haldane effects), and since most CO2 is transported as HCO3(-) (bicarbonate) via the CO2 hydration (buffering) reaction, the transport and exchange of HCO3(-) and H+ are also simulated along with that of O2 and CO2. Furthermore, the model accounts for the competitive nonlinear binding of O2 and CO2 with the hemoglobin inside the red blood cells (nonlinear O2-CO2 interactions, Bohr and Haldane effects), and myoglobin-facilitated transport of O2 inside the parenchymal cells. The consumption of O2 through cytochrome-c oxidase reaction inside the parenchymal cells is based on Michaelis-Menten kinetics. The corresponding production of CO2 is determined by respiratory quotient (RQ), depending on the relative consumption of carbohydrate, protein, and fat. The model gives a physiologically realistic description of O2 transport and metabolism in the microcirculation of the heart. Furthermore, because model solutions for tracer transients and steady states can be computed highly efficiently, this model may be the preferred vehicle for routine data analysis where repetitive solutions and parameter optimization are required, as is the case in PET imaging for estimating myocardial O2 consumption.
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Affiliation(s)
- Ranjan K. Dash
- Department of Bioengineering, University of Washington, Seattle, WA
98195
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Bassingthwaighte JB, Chizeck HJ, Atlas LE, Qian H. Multiscale modeling of cardiac cellular energetics. Ann N Y Acad Sci 2005; 1047:395-424. [PMID: 16093514 PMCID: PMC2864600 DOI: 10.1196/annals.1341.035] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Multiscale modeling is essential to integrating knowledge of human physiology starting from genomics, molecular biology, and the environment through the levels of cells, tissues, and organs all the way to integrated systems behavior. The lowest levels concern biophysical and biochemical events. The higher levels of organization in tissues, organs, and organism are complex, representing the dynamically varying behavior of billions of cells interacting together. Models integrating cellular events into tissue and organ behavior are forced to resort to simplifications to minimize computational complexity, thus reducing the model's ability to respond correctly to dynamic changes in external conditions. Adjustments at protein and gene regulatory levels shortchange the simplified higher-level representations. Our cell primitive is composed of a set of subcellular modules, each defining an intracellular function (action potential, tricarboxylic acid cycle, oxidative phosphorylation, glycolysis, calcium cycling, contraction, etc.), composing what we call the "eternal cell," which assumes that there is neither proteolysis nor protein synthesis. Within the modules are elements describing each particular component (i.e., enzymatic reactions of assorted types, transporters, ionic channels, binding sites, etc.). Cell subregions are stirred tanks, linked by diffusional or transporter-mediated exchange. The modeling uses ordinary differential equations rather than stochastic or partial differential equations. This basic model is regarded as a primitive upon which to build models encompassing gene regulation, signaling, and long-term adaptations in structure and function. During simulation, simpler forms of the model are used, when possible, to reduce computation. However, when this results in error, the more complex and detailed modules and elements need to be employed to improve model realism. The processes of error recognition and of mapping between different levels of model form complexity are challenging but are essential for successful modeling of large-scale systems in reasonable time. Currently there is to this end no established methodology from computational sciences.
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