Assessing Changes in Airflow and Energy Loss in a Progressive Tracheal Compression Before and After Surgical Correction

Xiao, Qiwei; Cetto, R.; Doorly, D. J.; Bates, Alister J.; Rose, Jan N; McIntyre, Charlotte; Comerford, Andrew; Madani, Gitta; Tolley, Neil; Schroter, R. C.

doi:10.1007/s10439-019-02410-1

Cited by 20 publications

(7 citation statements)

References 40 publications

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“…Previous studies have shown that tracheal airflow is dominated by the jet emanating from the glottis and more extensive upstream anatomy does not affect the tracheal WOB or resistance. 11,25 The inlets were held at a constant pressure for each simulation. In vivo, the pressure in the nasopharynx will change during inhalation, but the pressure loss in the trachea is relative to this so the tracheal component of the WOB will not be affected by neglecting the nasal geometry.…”

Section: Cfd Simulation-boundary Conditionsmentioning

confidence: 99%

Subglottic Stenosis Position Affects Work of Breathing

et al. 2020

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Objectives: Subglottic stenosis (SGS) is the most common type of laryngeal stenosis in neonates. SGS severity is currently graded based on percent area of obstruction (%AO) via the Myer-Cotton grading scale. However, patients with similar %AO can have widely different clinical courses. Computational fluid dynamics (CFD) based on patient-specific imaging can quantify the relationship between airway geometry and flow dynamics. We investigated the effect of %AO and axial position of SGS on work of breathing (WOB) in neonates using magnetic resonance imaging. Methods: High-resolution ultrashort echo-time MRI of the chest and airway was obtained in three neonatal patients with no suspected airway abnormalities; images were segmented to construct three-dimensional (3D) models of the neonatal airways. These models were then modified with virtual SGSs of varying %AO and axial positioning. CFD simulations of peak inspiratory flow were used to calculate patient-specific WOB in nonstenotic and artificially stenosed airway models. Results: CFD simulations demonstrated a relationship between stenosis geometry and WOB increase. WOB rapidly increased with %AO greater than about 70%. Changes in axial position could also increase WOB by approximately the same amount as a 10% increase in %AO. Increased WOB was particularly pronounced when the SGS lumen was misaligned with the glottic jet. Conclusion: The results indicate a strong, predictable relationship between WOB and axial position of the stenotic lumen relative to the glottis, which has not been previously reported. These findings may lead to precision diagnosis and treatment prediction tools in individual patients.

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Section: Cfd Simulation-boundary Conditionsmentioning

confidence: 99%

Subglottic Stenosis Position Affects Work of Breathing

et al. 2020

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“…Lung mechanics research has delivered multiscale modelling methods to study both health and pathophysiology [ 1 ]. Studies have characterized the architecture and function of the upper airways [ 2 , 3 , 4 ], the tree-like airway structure and its mechanics [ 5 , 6 , 7 , 8 , 9 , 10 ] with its tight coupling to the circulatory system [ 11 ], and the smallest air-containing units of the lung: the alveoli [ 12 , 13 , 14 , 15 , 16 ].…”

Section: Introductionmentioning

confidence: 99%

Correlating Local Volumetric Tissue Strains with Global Lung Mechanics Measurements

et al. 2021

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The mechanics of breathing is a fascinating and vital process. The lung has complexities and subtle heterogeneities in structure across length scales that influence mechanics and function. This study establishes an experimental pipeline for capturing alveolar deformations during a respiratory cycle using synchrotron radiation micro-computed tomography (SR-micro-CT). Rodent lungs were mechanically ventilated and imaged at various time points during the respiratory cycle. Pressure-Volume (P-V) characteristics were recorded to capture any changes in overall lung mechanical behaviour during the experiment. A sequence of tomograms was collected from the lungs within the intact thoracic cavity. Digital volume correlation (DVC) was used to compute the three-dimensional strain field at the alveolar level from the time sequence of reconstructed tomograms. Regional differences in ventilation were highlighted during the respiratory cycle, relating the local strains within the lung tissue to the global ventilation measurements. Strains locally reached approximately 150% compared to the averaged regional deformations of approximately 80–100%. Redistribution of air within the lungs was observed during cycling. Regions which were relatively poorly ventilated (low deformations compared to its neighbouring region) were deforming more uniformly at later stages of the experiment (consistent with its neighbouring region). Such heterogenous phenomena are common in everyday breathing. In pathological lungs, some of these non-uniformities in deformation behaviour can become exaggerated, leading to poor function or further damage. The technique presented can help characterize the multiscale biomechanical nature of a given pathology to improve patient management strategies, considering both the local and global lung mechanics.

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“…The reason is that during an epidemic crude CFR estimation becomes an underestimate of the actual CFR [5]. However, because of both limited numbers of test and presence of asymptotic or mild cases, there exists unreported cases [25][26][27][28]. Therefore, after further adjustment for reporting rates lower than 50%, estimated CFRs became less than one-third compared to crude CFR, and survival interval adjusted CFR.…”

Section: Discussionmentioning

confidence: 99%

Finding the real COVID-19 case-fatality rates for SAARC countries

Shah¹,

Ahammed

Anjum³

et al. 2020

Preprint

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Crude case fatality rate (CFR) is the most accurate when the pandemic is over. Adjustments to the crude CFR measure can better explain the pandemic situation by improving the CFR estimation. However, no study has thoroughly investigated COVID-19 adjusted CFR of the South Asian Association for Regional Cooperation (SAARC) countries. In this study, we estimated both survival interval and underreporting adjusted CFR of COVID-19 for the SAARC countries and observed the CFR changes due to the imposition of fees on COVID-19 tests in Bangladesh. Using the daily records up to 9th October, we implemented a statistical method to remove both the bias in crude CFR, i.e., the delay between disease onset and outcome bias and due to asymptomatic or mild symptomatic cases, reporting rates lower than 50% (95% CI: 10%-50%) bias. According to our findings, Afghanistan had the highest CFR, followed by Pakistan, India, Bangladesh, Nepal, Maldives, and Sri Lanka. Our estimated crude CFR varied from 3.71% to 0.29%, survival interval adjusted CFR varied from 3.77% to 0.3% and further underreporting adjusted CFR varied from 1.1% to 0.08%. We have also found that crude CFR increased from 1.261% to 1.572% after imposing the COVID-19 test fees in Bangladesh. Therefore, the authorities of countries with higher CFR should be looking for strategic counsel from the countries with lower CFR to equip themselves with the necessary knowledge to combat the pandemic. Moreover, caution is needed to report the CFR.

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Assessing Changes in Airflow and Energy Loss in a Progressive Tracheal Compression Before and After Surgical Correction

Cited by 20 publications

References 40 publications

Subglottic Stenosis Position Affects Work of Breathing

Subglottic Stenosis Position Affects Work of Breathing

Correlating Local Volumetric Tissue Strains with Global Lung Mechanics Measurements

Finding the real COVID-19 case-fatality rates for SAARC countries

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