Ventilation/Perfusion Relationships and Gas Exchange: Measurement Approaches

Hopkins, Susan R.

doi:10.1002/cphy.c180042

Cited by 16 publications

(13 citation statements)

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“…The

for compartment 1 is shown in light blue and for compartment 2 is shown in gray. Reproduced with permission from Reference 371 .…”

Section: Assessing Regional Ventilation–perfusion Mismatchmentioning

confidence: 99%

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

Hsia¹,

Bates²,

Driehuys³

et al. 2023

Annals ATS

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Multiple thoracic imaging modalities have been developed to link structure to function in the diagnosis and monitoring of lung disease. Volumetric computed tomography (CT) renders three-dimensional maps of lung structures and may be combined with positron emission tomography (PET) to obtain dynamic physiological data. Magnetic resonance imaging (MRI) using ultrashort–echo time (UTE) sequences has improved signal detection from lung parenchyma; contrast agents are used to deduce airway function, ventilation–perfusion–diffusion, and mechanics. Proton MRI can measure regional ventilation-perfusion ratio. Quantitative imaging (QI)–derived endpoints have been developed to identify structure–function phenotypes, including air–blood–tissue volume partition, bronchovascular remodeling, emphysema, fibrosis, and textural patterns indicating architectural alteration. Coregistered landmarks on paired images obtained at different lung volumes are used to infer airway caliber, air trapping, gas and blood transport, compliance, and deformation. This document summarizes fundamental “good practice” stereological principles in QI study design and analysis; evaluates technical capabilities and limitations of common imaging modalities; and assesses major QI endpoints regarding underlying assumptions and limitations, ability to detect and stratify heterogeneous, overlapping pathophysiology, and monitor disease progression and therapeutic response, correlated with and complementary to, functional indices. The goal is to promote unbiased quantification and interpretation of in vivo imaging data, compare metrics obtained using different QI modalities to ensure accurate and reproducible metric derivation, and avoid misrepresentation of inferred physiological processes. The role of imaging-based computational modeling in advancing these goals is emphasized. Fundamental principles outlined herein are critical for all forms of QI irrespective of acquisition modality or disease entity.

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“…The

for compartment 1 is shown in light blue and for compartment 2 is shown in gray. Reproduced with permission from Reference 371 .…”

Section: Assessing Regional Ventilation–perfusion Mismatchmentioning

confidence: 99%

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

Hsia¹,

Bates²,

Driehuys³

et al. 2023

Annals ATS

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“…Reference to interstitial lung edema as a potential cause of mismatch was made by Schaffartzik et al ( 1992 ) during maximal exercise. Log standard deviation of perfusion and ventilation distributions (Log SDQ, and log SDv, respectively) were correlated with the increase in ΔA-aO 2 and diffusion limitation (Hopkins et al 1998a ; Hopkins 2005 , 2020 ). More recent data confirm that 45 min at about 80% increased mismatch in the basal lung after exercise, likely reflecting gravitationally dependent interstitial pulmonary edema (Tedjasaputra et al 2019 ).…”

Section: Data That Are Consistent With But Not Proof Of Interstitial ...mentioning

confidence: 99%

“…Most of the controversies concerning the development of exercise induced edema reflect the sensitivity of the imaging methods available to detect an increase in extravascular water (Hopkins 2020 ).…”

Section: Data After Exercisementioning

confidence: 99%

A century of exercise physiology: lung fluid balance during and following exercise

Miserocchi

Beretta

2022

Eur J Appl Physiol

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Purpose This review recalls the principles developed over a century to describe trans-capillary fluid exchanges concerning in particular the lung during exercise, a specific condition where dyspnea is a leading symptom, the question being whether this symptom simply relates to fatigue or also implies some degree of lung edema. Method Data from experimental models of lung edema are recalled aiming to: (1) describe how extravascular lung water is strictly controlled by “safety factors” in physiological conditions, (2) consider how waning of “safety factors” inevitably leads to development of lung edema, (3) correlate data from experimental models with data from exercising humans. Results Exercise is a strong edemagenic condition as the increase in cardiac output leads to lung capillary recruitment, increase in capillary surface for fluid exchange and potential increase in capillary pressure. The physiological low microvascular permeability may be impaired by conditions causing damage to the interstitial matrix macromolecular assembly leading to alveolar edema and haemorrhage. These conditions include hypoxia, cyclic alveolar unfolding/folding during hyperventilation putting a tensile stress on septa, intensity and duration of exercise as well as inter-individual proneness to develop lung edema. Conclusion Data from exercising humans showed inter-individual differences in the dispersion of the lung ventilation/perfusion ratio and increase in oxygen alveolar-capillary gradient. More recent data in humans support the hypothesis that greater vasoconstriction, pulmonary hypertension and slower kinetics of alveolar-capillary O2 equilibration relate with greater proneness to develop lung edema due higher inborn microvascular permeability possibly reflecting the morpho-functional features of the air–blood barrier.

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“…The ventilation (V) characterizes the volume of air/gas that reaches alveoli per time unit, and the perfusion (Q) is related to the volume of blood coming to alveoli per time unit (i.e., it is a measure of blood supply to the lungs). The V/Q value is a common diagnostic parameter of the lung functionality, and it can be determined from the alveoli gas composition 13,14 . In 2000, 15 the possibility of obtaining information about V/Q ratio in lungs with 19 F MRI was shown.…”

Section: Introductionmentioning

confidence: 99%

Т₁ mapping of rat lungs in ¹⁹F MRI using octafluorocyclobutane

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Gulyaev

Gervits

et al. 2023

Magnetic Resonance in Med

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Purpose To demonstrate the feasibility of using octafluorocyclobutane (OFCB, c‐C4F8) for T1 mapping of lungs in 19F MRI. Methods The study was performed at 7 T in three healthy rats and three rats with pulmonary hypertension. To increase the sensitivity of 19F MRI, a bent‐shaped RF coil with periodic metal strips structure was used. The double flip angle method was used to calculate normalized transmitting RF field (B1n+) maps and for correcting T1 maps built with the variable flip angle (VFA) method. The ultrashort TE pulse sequence was applied for acquiring MR images throughout the study. Results The dependencies of OFCB relaxation times on its partial pressure in mixtures with oxygen, air, helium, and argon were obtained. T1 of OFCB linearly depended on its partial pressure with the slope of about 0.35 ms/kPa in the case of free diffusion. RF field inhomogeneity leads to distortion of T1 maps built with the VFA method, and therefore to high standard deviation of T1 in these maps. To improve the accuracy of the T1 maps, the B1n+ maps were applied for VFA correction. This contributed to a 2–3‐fold decrease in the SD of T1 values in the corresponding maps compared with T1 maps calculated without the correction. Three‐dimensional T1 maps were obtained, and the mean T1 in healthy rat lungs was 35 ± 10 ms, and in rat lungs with pulmonary hypertension – 41 ± 9 ms. Conclusion OFCB has a spin‐rotational relaxation mechanism and can be used for 19F T1 mapping of lungs. The calculated OFCB maps captured ventilation defects induced by edema.

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Ventilation/Perfusion Relationships and Gas Exchange: Measurement Approaches

Cited by 16 publications

References 314 publications

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

A century of exercise physiology: lung fluid balance during and following exercise

Т₁ mapping of rat lungs in ¹⁹F MRI using octafluorocyclobutane

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Ventilation/Perfusion Relationships and Gas Exchange: Measurement Approaches

Cited by 16 publications

References 314 publications

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

Quantitative Imaging Metrics for the Assessment of Pulmonary Pathophysiology: An Official American Thoracic Society and Fleischner Society Joint Workshop Report

A century of exercise physiology: lung fluid balance during and following exercise

Т1 mapping of rat lungs in 19F MRI using octafluorocyclobutane

Contact Info

Product

Resources

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Т₁ mapping of rat lungs in ¹⁹F MRI using octafluorocyclobutane