Quantifying Regional Lung Deformation Using Four-Dimensional Computed Tomography: A Comparison of Conventional and Oscillatory Ventilation

Herrmann, Jacob; Gerard, Sarah E.; Shao, Wei; Hawley, Monica L.; Reinhardt, Joseph M.; Christensen, Gary E.; Hoffman, Eric A.; Kaczka, David W.

doi:10.3389/fphys.2020.00014

Cited by 16 publications

(7 citation statements)

References 52 publications

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“…Considering the observed alterations in mechanical properties of fetal lung tissue under compression together with the impact of hydrostatic pressure on ENaC activity in fetal distal lung epithelia, we expect that ventilation techniques must carefully address correlations between tidal volumes, pressures and frequencies. As demonstrated by Kaczka et al (2015) and Herrmann et al (2020), in contrast to HFOV and conventional MV, multi-frequency oscillatory ventilation modalities (MFOV) might provide improved lung-protective ventilation by reducing strain magnitudes and spatial gradients of strain.…”

Section: Discussionmentioning

confidence: 99%

Mechanical properties of the premature lung: From tissue deformation under load to mechanosensitivity of alveolar cells

Naumann

Koppe

Thomé

et al. 2022

Front. Bioeng. Biotechnol.

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Many preterm infants require mechanical ventilation as life-saving therapy. However, ventilation-induced overpressure can result in lung diseases. Considering the lung as a viscoelastic material, positive pressure inside the lung results in increased hydrostatic pressure and tissue compression. To elucidate the effect of positive pressure on lung tissue mechanics and cell behavior, we mimic the effect of overpressure by employing an uniaxial load onto fetal and adult rat lungs with different deformation rates. Additionally, tissue expansion during tidal breathing due to a negative intrathoracic pressure was addressed by uniaxial tension. We found a hyperelastic deformation behavior of fetal tissues under compression and tension with a remarkable strain stiffening. In contrast, adult lungs exhibited a similar response only during compression. Young’s moduli were always larger during tension compared to compression, while only during compression a strong deformation-rate dependency was found. In fact, fetal lung tissue under compression showed clear viscoelastic features even for small strains. Thus, we propose that the fetal lung is much more vulnerable during inflation by mechanical ventilation compared to normal inspiration. Electrophysiological experiments with different hydrostatic pressure gradients acting on primary fetal distal lung epithelial cells revealed that the activity of the epithelial sodium channel (ENaC) and the sodium-potassium pump (Na,K-ATPase) dropped during pressures of 30 cmH2O. Thus, pressures used during mechanical ventilation might impair alveolar fluid clearance important for normal lung function.

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Section: Discussionmentioning

confidence: 99%

Mechanical properties of the premature lung: From tissue deformation under load to mechanosensitivity of alveolar cells

Naumann

Koppe

Thomé

et al. 2022

Front. Bioeng. Biotechnol.

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“…All experimental procedures were approved by the University of Iowa Institute for Animal Care and Use Committee (Protocol Number 5061428). Two other studies of respiratory mechanics, involving regional dynamic deformation (Herrmann et al, 2020a) and gas transport (Herrmann et al, 2021), were previously published using data collected from the subjects used in this study. Eleven pigs were used in this study, weighing between 9 and 13 kg.…”

Section: Methodsmentioning

confidence: 99%

“…The goal of this study was to quantify regional rates of lung deaeration during passive exhalation, using four-dimensional computed tomography (4DCT) dynamic imaging ( Herrmann et al, 2017 ) and 4D image registration ( Zhao et al, 2016 ; Herrmann et al, 2020a ) to track localized aeration changes with high spatial resolution. In addition to assessment of aeration based on CT density, it is also possible to account for specific gas volume changes using an intensity-corrected Jacobian determinant, which is more strongly correlated to specific ventilation ( Ding et al, 2012 ).…”

Section: Introductionmentioning

confidence: 99%

Effects of Lung Injury on Regional Aeration and Expiratory Time Constants: Insights From Four-Dimensional Computed Tomography Image Registration

et al. 2021

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Rationale: Intratidal changes in regional lung aeration, as assessed with dynamic four-dimensional computed tomography (CT; 4DCT), may indicate the processes of recruitment and derecruitment, thus portending atelectrauma during mechanical ventilation. In this study, we characterized the time constants associated with deaeration during the expiratory phase of pressure-controlled ventilation in pigs before and after acute lung injury using respiratory-gated 4DCT and image registration.Methods: Eleven pigs were mechanically ventilated in pressure-controlled mode under baseline conditions and following an oleic acid model of acute lung injury. Dynamic 4DCT scans were acquired without interrupting ventilation. Automated segmentation of lung parenchyma was obtained by a convolutional neural network. Respiratory structures were aligned using 4D image registration. Exponential regression was performed on the time-varying CT density in each aligned voxel during exhalation, resulting in regional estimates of intratidal aeration change and deaeration time constants. Regressions were also performed for regional and total exhaled gas volume changes.Results: Normally and poorly aerated lung regions demonstrated the largest median intratidal aeration changes during exhalation, compared to minimal changes within hyper- and non-aerated regions. Following lung injury, median time constants throughout normally aerated regions within each subject were greater than respective values for poorly aerated regions. However, parametric response mapping revealed an association between larger intratidal aeration changes and slower time constants. Lower aeration and faster time constants were observed for the dependent lung regions in the supine position. Regional gas volume changes exhibited faster time constants compared to regional density time constants, as well as better correspondence to total exhaled volume time constants.Conclusion: Mechanical time constants based on exhaled gas volume underestimate regional aeration time constants. After lung injury, poorly aerated regions experience larger intratidal changes in aeration over shorter time scales compared to normally aerated regions. However, the largest intratidal aeration changes occur over the longest time scales within poorly aerated regions. These dynamic 4DCT imaging data provide supporting evidence for the susceptibility of poorly aerated regions to ventilator-induced lung injury, and for the functional benefits of short exhalation times during mechanical ventilation of injured lungs.

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“…A saline lavage model of sheep found that transpulmonary pressure was lowest at 9 Hz, which coincided with the lowest degree of lung inflammation ( Liu et al, 2013 ). A porcine model of oleic acid lung injury found greater lung strain at lower frequency, with the lowest strain noted at a frequency of 20 Hz ( Herrmann et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

The Physiological Basis of High-Frequency Oscillatory Ventilation and Current Evidence in Adults and Children: A Narrative Review

Miller

Tan²,

Smith³

et al. 2022

Front. Physiol.

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High-frequency oscillatory ventilation (HFOV) is a type of invasive mechanical ventilation that employs supra-physiologic respiratory rates and low tidal volumes (VT) that approximate the anatomic deadspace. During HFOV, mean airway pressure is set and gas is then displaced towards and away from the patient through a piston. Carbon dioxide (CO2) is cleared based on the power (amplitude) setting and frequency, with lower frequencies resulting in higher VT and CO2 clearance. Airway pressure amplitude is significantly attenuated throughout the respiratory system and mechanical strain and stress on the alveoli are theoretically minimized. HFOV has been purported as a form of lung protective ventilation that minimizes volutrauma, atelectrauma, and biotrauma. Following two large randomized controlled trials showing no benefit and harm, respectively, HFOV has largely been abandoned in adults with ARDS. A multi-center clinical trial in children is ongoing. This article aims to review the physiologic rationale for the use of HFOV in patients with acute respiratory failure, summarize relevant bench and animal models, and discuss the potential use of HFOV as a primary and rescue mode in adults and children with severe respiratory failure.

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Quantifying Regional Lung Deformation Using Four-Dimensional Computed Tomography: A Comparison of Conventional and Oscillatory Ventilation

Cited by 16 publications

References 52 publications

Mechanical properties of the premature lung: From tissue deformation under load to mechanosensitivity of alveolar cells

Mechanical properties of the premature lung: From tissue deformation under load to mechanosensitivity of alveolar cells

Effects of Lung Injury on Regional Aeration and Expiratory Time Constants: Insights From Four-Dimensional Computed Tomography Image Registration

The Physiological Basis of High-Frequency Oscillatory Ventilation and Current Evidence in Adults and Children: A Narrative Review

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