Expiratory Resistances Prevent Expiratory Diaphragm Contraction, Flow Limitation, and Lung Collapse

Pellegrini, Mariangela; Gudmundsson, Magni; Bencze, Reka; Segelsjö, Monica; Fredén, Filip; Rylander, Christian; Hedenstierna, Göran; Larsson, Anders; Perchiazzi, Gaetano

doi:10.1164/rccm.201909-1690oc

Cited by 10 publications

(16 citation statements)

References 42 publications

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“… 10 46 During excessive expiratory muscle activity, the pleural pressure increases, leading to markedly reduced P L, and collapse of most dependent lung regions, as well as of peripheral airways. 49 Thus, both high inspiratory and expiratory efforts may promote P-SILI, especially in lung diseases which feature inhomogeneous distribution, such as COVID-19. Inhomogeneous distribution of gas …”

Section: Mechanisms Of P-silimentioning

confidence: 99%

Noninvasive respiratory support and patient self-inflicted lung injury in COVID-19: a narrative review

Battaglini

Robba

Ball

et al. 2021

British Journal of Anaesthesia

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Coronavirus disease 2019 (COVID-19) pneumonia is associated with hypoxemic respiratory failure, ranging from mild to severe. Due to the worldwide shortage of intensive care unit beds, a relatively high number of patients with respiratory failure are receiving prolonged non-invasive respiratory support, even when their clinical status would have required invasive mechanical ventilation. There are few experimental and clinical data reporting that vigorous breathing effort during spontaneous ventilation can worsen lung injury and cause a phenomenon that has been termed patient self-inflicted lung injury (P-SILI). The aim of this narrative review is to provide an overview of P-SILI pathophysiology and the role of non-invasive respiratory support in COVID-19 pneumonia. Respiratory mechanics, vascular compromise, viscoelastic properties, lung inhomogeneity, work of breathing, and oesophageal pressure swings are discussed. The concept of P-SILI has been widely investigated in recent years, but controversies persist regarding its mechanisms. To minimize the risk of P-SILI, intensivists should better understand its underlying pathophysiology to optimize the type of non-invasive respiratory support provided to patients with COVID-19 pneumonia, as well as decide on the optimal timing of intubation for these patients.

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Section: Mechanisms Of P-silimentioning

confidence: 99%

Noninvasive respiratory support and patient self-inflicted lung injury in COVID-19: a narrative review

Battaglini

Robba

Ball

et al. 2021

British Journal of Anaesthesia

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“…In this issue of the Journal (pp. 1218-1229), Pellegrini and colleagues (5) propose a novel research technique that applies concepts from respiratory physiology to mechanical ventilation. The primary purpose of this study was to determine if the application of continuous external expiratory resistance is able to maintain the beneficial effects of diaphragm expiratory braking in terms of optimization of lung mechanics, prevention of expiratory flow limitation (EFL), and avoidance of lung collapse.…”

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confidence: 99%

“…To evaluate this, the authors inserted different resistors with the capability of slowing expiratory flow in the expiratory limb of a ventilator connected to pigs with induced mild acute respiratory distress syndrome (ARDS). The experiment was performed at various PEEP levels during both spontaneous breathing and mechanical ventilation (5). One of the main virtues of this study is the complexity and the wide range of the data obtained, including, among other measurements, esophageal pressure, expiratory electrical activity of the diaphragm, and analysis of the computed tomographic scan of the lung during expiration (5).…”

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confidence: 99%

“…Interestingly, the authors considered another fundamental aspect of respiratory pathophysiology: the presence of EFL. They showed that the expiratory flow was significantly reduced by the application of additional levels of external expiratory resistance (5). The presence of EFL can indicate increased inhomogeneity of ventilation (6), which is generally attributed to cyclic opening-closure of the relatively small airways, leading to the generation of abnormal shear stress.…”

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confidence: 99%

“…In the last decade, a number of studies assessing radiological changes in longitudinal cohorts of people without obvious IPF-identified parenchymal changes, referred to as interstitial lung abnormalities (ILAs), have demonstrated an increase in both all-cause mortality and mortality from pulmonary fibrosis (3,4), raising the prospect that ILAs may be the precursor lesions for IPF. Furthermore, there is overlap in the genetic architecture of IPF and ILA (5), and, indeed, serum biomarkers associated with pulmonary fibrosis are associated with ILA (6). This raises two fundamental questions: 1) are ILAs a precursor lesion for IPF and, if so, 2) should at-risk populations be screened for them?…”

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confidence: 99%

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A Physiological Point of View on Expiratory (Re)action during Mechanical Ventilation

Spadaro

Volta

2020

Am J Respir Crit Care Med

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One of the most provocative observations is that, by stereology measures, smokers do not appear to have an increase in AM numbers. This is in conflict with studies demonstrating an increase in BAL macrophages from smokers (12). Interestingly, prior data support the authors' present observation, suggesting that the extent of the response in BAL was overrepresented by an analysis in lung tissue sections (13). Though not directly explored in this study, a possible explanation for these divergent findings is that AMs from smokers may be easier to lavage during BAL, thereby increasing their measured numbers. Alternatively, the authors identified that IMs were increased in smoker lung tissue, which appeared to be mostly due to an increase in macrophages in the alveolar septum. The role of the IMs in this setting were not clearly defined but these data do suggest the potential importance of defining IM function in exposure conditions like cigarette smoke and, ultimately, in disease states like chronic obstructive pulmonary disease. In total, this study continues to expand on our understanding of macrophages based on lung tissue location. It offers tantalizing insights into further tissue specification of macrophages and suggests that more work needs to be done, both to identify tools for isolation but also to focus on macrophage functions in these distinct regions. Ultimately, further work in these areas will allow the research community to truly grasp the diverse functional roles of macrophages with a goal of being able to tune these functions to limit tissue damage and/or injury and mitigate chronic lung disease. n Author disclosures are available with the text of this article at www.atsjournals.org.

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Collagen Tubular Airway‐on‐Chip for Extended Epithelial Culture and Investigation of Ventilation Dynamics

Gao,

Kanagarajah,

Graham

et al. 2024

Small

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The lower respiratory tract is a hierarchical network of compliant tubular structures that are made from extracellular matrix proteins with a wall lined by an epithelium. While microfluidic airway‐on‐a‐chip models incorporate the effects of shear and stretch on the epithelium, week‐long air‐liquid‐interface culture at physiological shear stresses, the circular cross‐section, and compliance of native airway walls have yet to be recapitulated. To overcome these limitations, a collagen tube‐based airway model is presented. The lumen is lined with a confluent epithelium during two‐week continuous perfusion with warm, humid air while presenting culture medium from the outside and compensating for evaporation. The model recapitulates human small airways in extracellular matrix composition and mechanical microenvironment, allowing for the first time dynamic studies of elastocapillary phenomena associated with regular breathing and mechanical ventilation, as well as their impacts on the epithelium. A case study reveales increasing damage to the epithelium during repetitive collapse and reopening cycles as opposed to overdistension, suggesting expiratory flow resistance to reduce atelectasis. The model is expected to promote systematic comparisons between different clinically used ventilation strategies and, more broadly, to enhance human organ‐on‐a‐chip platforms for a variety of tubular tissues.

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Expiratory Resistances Prevent Expiratory Diaphragm Contraction, Flow Limitation, and Lung Collapse

Cited by 10 publications

References 42 publications

Noninvasive respiratory support and patient self-inflicted lung injury in COVID-19: a narrative review

Noninvasive respiratory support and patient self-inflicted lung injury in COVID-19: a narrative review

A Physiological Point of View on Expiratory (Re)action during Mechanical Ventilation

Collagen Tubular Airway‐on‐Chip for Extended Epithelial Culture and Investigation of Ventilation Dynamics

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