The effect of tissue elastic properties and surfactant on alveolar stability

Andreassen, Steen; Steimle, Kristoffer Lindegaard; Mogensen, Mads Lause; Serna, Jorge Bernardino de la; Rees, Stephen Edward; Karbing, Dan Stieper

doi:10.1152/japplphysiol.00844.2009

Cited by 30 publications

(24 citation statements)

References 43 publications

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“…Because recruitment is a function of PEEP and time [31,32], true minimal E rsIB , E static and K can only be determined after a stabilisation period at each PEEP level. Decrease of elastance over time to a specific minimum can be described by increasing recruitment and/or the lung’s viscoelastic properties, which causes hysteresis [33,34]. Setting PEEP at minimum elastance theoretically benefits ventilation by maximising recruitment, reducing work of breathing and avoiding overdistension [12,14,15,35].…”

Section: Resultsmentioning

confidence: 99%

Expiratory model-based method to monitor ARDS disease state

et al. 2013

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IntroductionModel-based methods can be used to characterise patient-specific condition and response to mechanical ventilation (MV) during treatment for acute respiratory distress syndrome (ARDS). Conventional metrics of respiratory mechanics are based on inspiration only, neglecting data from the expiration cycle. However, it is hypothesised that expiratory data can be used to determine an alternative metric, offering another means to track patient condition and guide positive end expiratory pressure (PEEP) selection.MethodsThree fully sedated, oleic acid induced ARDS piglets underwent three experimental phases. Phase 1 was a healthy state recruitment manoeuvre. Phase 2 was a progression from a healthy state to an oleic acid induced ARDS state. Phase 3 was an ARDS state recruitment manoeuvre. The expiratory time-constant model parameter was determined for every breathing cycle for each subject. Trends were compared to estimates of lung elastance determined by means of an end-inspiratory pause method and an integral-based method. All experimental procedures, protocols and the use of data in this study were reviewed and approved by the Ethics Committee of the University of Liege Medical Faculty.ResultsThe overall median absolute percentage fitting error for the expiratory time-constant model across all three phases was less than 10 %; for each subject, indicating the capability of the model to capture the mechanics of breathing during expiration. Provided the respiratory resistance was constant, the model was able to adequately identify trends and fundamental changes in respiratory mechanics.ConclusionOverall, this is a proof of concept study that shows the potential of continuous monitoring of respiratory mechanics in clinical practice. Respiratory system mechanics vary with disease state development and in response to MV settings. Therefore, titrating PEEP to minimal elastance theoretically results in optimal PEEP selection. Trends matched clinical expectation demonstrating robustness and potential for guiding MV therapy. However, further research is required to confirm the use of such real-time methods in actual ARDS patients, both sedated and spontaneously breathing.

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Section: Resultsmentioning

confidence: 99%

Expiratory model-based method to monitor ARDS disease state

et al. 2013

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“…This indicates that the surfactants released from cells exposed to S. chartarum extracts are unable to sufficiently lower the surface tension to enable bubble expansion. This is a critical function in the lung in which alveolar expansion and stabilization is dependent on the ability of surfactant to lower the surface tension [44]. The more important trend clinically, is the fact that minimum surface tensions are increased with an increase in minimum bubble volume as well.…”

Section: Discussionmentioning

confidence: 99%

<i>Stachybotrys chartarum</i> (<i>atra</i>) spore extract alters surfactant protein expression and surfactant function in isolated fetal rat lung epithelial cells, fibroblasts and human A549 cells

Pollard¹,

Shaw²,

Sowa³

et al. 2013

OJPed

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Moulds, notably Stachybotrys chartarum (atra), are constant contributors to air pollution particularly to air quality in buildings. The spores themselves or their volatile organic products are present in variable amounts in almost all environments, particularly in buildings affected by flooding. These moulds and products can account for the sick building syndrome and have been tied to such occurrences as the outbreak of pulmonary hemosiderosis and hemorrhage in infants in Cleveland, Ohio. The present study was designed to investigate the effects of S. chartarum extracts on surfactant protein expression, surfactant quality and cell survival in the developing lung. S. chartarum extracts were incubated with cultures of several cell types; isolated fetal lung type II cells and fetal lung fibroblasts, and human lung A549 cells, a continuously growing cell line derived from surfactant producing type II alveolar cells. MTT formazan assays were employed to test cell viability. The synthesis and release of the predominant surfactant protein A (SP-A), which is involved in the regulation of surfactant turnover and metabolism, and surfactant protein B (SP-B) involved in shuttling phospholipids between surfactant subcompartments was also assessed. Antibodies to these proteins and western blotting results were used to assess the quantity of protein produced by the various cell types. A novel approach utilizing captive bubble surfactometry was employed to investigate the quality of surfactant in terms of surface tension and bubble volume measurements. Electron microscopy was used to examine changes in cellular structure of control and S. chartarum-treated cells. Results of the study showed that exposure to the S. chartarum extracts had deleterious effects on fetal lung epithelial cell viability and their ability to produce pulmonary surfactant. S. chartarum extracts also induced deleterious changes to the developing fetal lung cells in terms of expression of SP-A and SP-B as well as to the surface tension reducing abilities of the pulmonary surfactant. Ultrastructurally, spore toxin associated changes were apparent in the isolated lung cells most notably in the lamellar bodies of fetal rat lung alveolar type II and human A549 cells. This study has demonstrated the potential damage to surfactant production and function which may be induced by inhaling S. chartarum toxins.

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“…As the breathing pattern stabilises, respiratory elastance slowly decreases to a specific minimum at that PEEP level as shown in Figure 2 for one representative subject. Decrease of elastance over time to a specific minimal can be described by recruitment and/or the lung's viscoelastic properties, which cause hysteresis [22,23].…”

Section: Recruitment Maneuver -Phasementioning

confidence: 99%

Model-based respiratory mechanics to titrate PEEP and monitor disease state for experimental ARDS subjects

Drunen

Chiew

Chase

et al. 2013

2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

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Modelling the respiratory mechanics of mechanically ventilated (MV) patients can provide useful information to guide MV therapy. Two model-based methods were evaluated based on data from three experimental acute respiratory distress syndrome (ARDS) induced piglets and validated against values available from ventilators. A single compartment lung model with integral-based parameter identification was found to be effective in capturing fundamental respiratory mechanics during inspiration. The trends matched clinical expectation and provided better resolution than clinically derived linear model metrics. An expiration time constant model also captured the same trend in respiratory elastance. However, the assumption of constant resistance and a slightly higher fitting error results in less insight than the single compartment model. Further research is required to confirm its application in titrating to optimal MV settings.

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The effect of tissue elastic properties and surfactant on alveolar stability

Cited by 30 publications

References 43 publications

Expiratory model-based method to monitor ARDS disease state

Expiratory model-based method to monitor ARDS disease state

<i>Stachybotrys chartarum</i> (<i>atra</i>) spore extract alters surfactant protein expression and surfactant function in isolated fetal rat lung epithelial cells, fibroblasts and human A549 cells

Model-based respiratory mechanics to titrate PEEP and monitor disease state for experimental ARDS subjects

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The effect of tissue elastic properties and surfactant on alveolar stability

Cited by 30 publications

References 43 publications

Expiratory model-based method to monitor ARDS disease state

Expiratory model-based method to monitor ARDS disease state

&lt;i&gt;Stachybotrys chartarum&lt;/i&gt; (&lt;i&gt;atra&lt;/i&gt;) spore extract alters surfactant protein expression and surfactant function in isolated fetal rat lung epithelial cells, fibroblasts and human A549 cells

Model-based respiratory mechanics to titrate PEEP and monitor disease state for experimental ARDS subjects

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<i>Stachybotrys chartarum</i> (<i>atra</i>) spore extract alters surfactant protein expression and surfactant function in isolated fetal rat lung epithelial cells, fibroblasts and human A549 cells