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

2021 ◽  
Vol 12 ◽  
Author(s):  
Jacob Herrmann ◽  
Sarah E. Gerard ◽  
Wei Shao ◽  
Yi Xin ◽  
Maurizio Cereda ◽  
...  

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.

2011 ◽  
Vol 183 (9) ◽  
pp. 1193-1199 ◽  
Author(s):  
Giacomo Bellani ◽  
Luca Guerra ◽  
Guido Musch ◽  
Alberto Zanella ◽  
Nicolò Patroniti ◽  
...  

2008 ◽  
Vol 295 (4) ◽  
pp. L718-L724 ◽  
Author(s):  
Tobias Eckle ◽  
Lars Füllbier ◽  
Almut Grenz ◽  
Holger K. Eltzschig

Acute lung injury (ALI), as occurs with prolonged mechanical ventilation, contributes to morbidity and mortality of critical illness, and studies on novel genetic or pharmacological targets are areas of intense investigation. Here, we systematically tested a murine model of ALI by using pressure-controlled ventilation to induce ventilator-induced lung injury. For this purpose, C57BL/6 or Sv129 mice were anesthetized and underwent tracheotomy followed by induction of ALI via mechanical ventilation. Mice were ventilated in a pressure-controlled setting at different inspiratory pressure levels (15–45 mbar) and over different times (0–90 min, 100% oxygen). As outcome parameters, we assessed pulmonary edema (wet-to-dry ratios), bronchoalveolar fluid albumin content, pulmonary myeloperoxidase activity, macrophage inflammatory protein-2, and pulmonary gas exchange. These studies revealed maximal differences in severity of lung injury between different mouse strains after 90 min of ventilation time at 45 mbar. Use of lower concentrations of inspired oxygen did not alter disease severity. Increases of CD73 transcript (5′-ectonucleotidase, pacemaker of extracellular adenosine production) or total pulmonary adenosine levels with mechanical ventilation were less pronounced in C57BL/6 mice, suggesting attenuated adenosine protection in C57BL/6 mice. Together, these studies demonstrate feasibility of this model to induce murine ALI.


2018 ◽  
Vol 42 (6) ◽  
pp. 866-872 ◽  
Author(s):  
Fernando Uliana Kay ◽  
Marcelo A. Beraldo ◽  
Maria A. M. Nakamura ◽  
Roberta De Santis Santiago ◽  
Vinicius Torsani ◽  
...  

2003 ◽  
Vol 94 (3) ◽  
pp. 975-982 ◽  
Author(s):  
Timothy C. Bailey ◽  
Erica L. Martin ◽  
Lin Zhao ◽  
Ruud A. W. Veldhuizen

Mechanical ventilation is a necessary intervention for patients with acute lung injury. However, mechanical ventilation can propagate acute lung injury and increase systemic inflammation. The exposure to >21% oxygen is often associated with mechanical ventilation yet has not been examined within the context of lung stretch. We hypothesized that mice exposed to >90% oxygen will be more susceptible to the deleterious effects of high stretch mechanical ventilation. C57B1/6 mice were randomized into 48-h exposure of 21 or >90% oxygen; mice were then killed, and isolated lungs were randomized into a nonstretch or an ex vivo, high-stretch mechanical ventilation group. Lungs were assessed for compliance and lavaged for surfactant analysis, and cytokine measurements or lungs were homogenized for surfactant-associated protein analysis. Mice exposed to >90% oxygen + stretch had significantly lower compliance, altered pulmonary surfactant, and increased inflammatory cytokines compared with all other groups. Our conclusion is that 48 h of >90% oxygen and high-stretch mechanical ventilation deleteriously affect lung function to a greater degree than stretch alone.


Author(s):  
Iris Duroi ◽  
Frederik Van Durme ◽  
Tony Bruyns ◽  
Sofie Louage ◽  
Alex Heyse

Severe COVID-19 may predispose to both venous and arterial thrombosis. We describe a patient with acute ischaemic stroke while suffering from COVID-19 and respiratory failure, necessitating mechanical ventilation. Deep sedation may delay diagnosis.


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