Lung Mechanics

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Peter G Davis - One of the best experts on this subject based on the ideXlab platform.

Jane J Pillow - One of the best experts on this subject based on the ideXlab platform.

  • High-frequency oscillatory ventilation: mechanisms of gas exchange and Lung Mechanics.
    Critical care medicine, 2020
    Co-Authors: Jane J Pillow
    Abstract:

    Overview of the mechanisms governing gas transport, mechanical factors influencing the transmission of pressure and flow to the Lung, and the measurement of Lung Mechanics during high-frequency oscillatory ventilation (HFOV) in acute respiratory distress syndrome. Studies indexed in PubMed illustrating key concepts relevant to the manuscript objectives. Pressure transmission during HFOV in the adult Lung was simulated using a published theoretical model. Gas transport during HFOV is complex and involves a range of different mechanisms, including bulk convection, turbulence, asymmetric velocity profiles, pendelluft, cardiogenic mixing, laminar flow with Taylor dispersion, collateral ventilation, and molecular diffusion. Except for molecular diffusion, each mechanism involves generation of convective fluid motion, and is influenced by the mechanical characteristics of the intubated respiratory system and the ventilatory settings. These factors have important consequences for the damping of the oscillatory pressure waveform and the drop in mean pressure from the airway opening to the Lung. New techniques enabling partitioning of airway and tissue properties are being developed for measurement of Lung Mechanics during HFOV. Awareness of the different mechanisms governing gas transport and the prevailing Lung Mechanics during HFOV represents essential background for the physician planning to use this mode of ventilation in the adult patient. Monitoring of Lung volume, respiratory Mechanics, and ventilation homogeneity may facilitate individual optimization of HFOV ventilatory settings in the future.

  • high frequency oscillatory ventilation mechanisms of gas exchange and Lung Mechanics
    Critical Care Medicine, 2005
    Co-Authors: Jane J Pillow
    Abstract:

    The mechanisms governing gas flow, gas mixing, and pressure transmission during highfrequency oscillatory ventilation (HFOV) are fundamentally different to ventilation at more conventional respiratory breathing frequencies. They are integrally related to each other through the prevailing mechanical characteristics of the intubated respiratory system and frequency, symmetry, and magnitude of the applied pressure waveform. An appreciation of these mechanisms, and their implications for gas mixing efficiency, and the appropriate selection and matching of ventilator settings to the mechanical properties of the intubated respiratory system represent essential knowledge foundations for the clinician who uses HFOV to treat respiratory disease in the adult. This article aims to summarize the known mechanisms of gas mixing and to discuss the impact of Lung Mechanics on pressure transmission, flow generation, and the efficiency of ventilation and how each of these interact with each other during HFOV. A brief overview of the practical difficulties and progress achieved to date in measuring Lung Mechanics during HFOV is given and the relevance of measuring Lung Mechanics to optimization of clinical application of HFOV in acute respiratory distress syndrome (ARDS) is reviewed.

Stefan Uhlig - One of the best experts on this subject based on the ideXlab platform.

  • recurrent recruitment manoeuvres improve Lung Mechanics and minimize Lung injury during mechanical ventilation of healthy mice
    PLOS ONE, 2011
    Co-Authors: Lucy Kathleen Reiss, Anke Kowallik, Stefan Uhlig
    Abstract:

    Introduction Mechanical ventilation (MV) of mice is increasingly required in experimental studies, but the conditions that allow stable ventilation of mice over several hours have not yet been fully defined. In addition, most previous studies documented vital parameters and Lung Mechanics only incompletely. The aim of the present study was to establish experimental conditions that keep these parameters within their physiological range over a period of 6 h. For this purpose, we also examined the effects of frequent short recruitment manoeuvres (RM) in healthy mice. Methods Mice were ventilated at low tidal volume VT = 8 mL/kg or high tidal volume VT = 16 mL/kg and a positive end-expiratory pressure (PEEP) of 2 or 6 cmH2O. RM were performed every 5 min, 60 min or not at all. Lung Mechanics were followed by the forced oscillation technique. Blood pressure (BP), electrocardiogram (ECG), heart frequency (HF), oxygen saturation and body temperature were monitored. Blood gases, neutrophil-recruitment, microvascular permeability and pro-inflammatory cytokines in bronchoalveolar lavage (BAL) and blood serum as well as histopathology of the Lung were examined. Results MV with repetitive RM every 5 min resulted in stable respiratory Mechanics. Ventilation without RM worsened Lung Mechanics due to alveolar collapse, leading to impaired gas exchange. HF and BP were affected by anaesthesia, but not by ventilation. Microvascular permeability was highest in atelectatic Lungs, whereas neutrophil-recruitment and structural changes were strongest in Lungs ventilated with high tidal volume. The cytokines IL-6 and KC, but neither TNF nor IP-10, were elevated in the BAL and serum of all ventilated mice and were reduced by recurrent RM. Lung Mechanics, oxygenation and pulmonary inflammation were improved by increased PEEP. Conclusions Recurrent RM maintain Lung Mechanics in their physiological range during low tidal volume ventilation of healthy mice by preventing atelectasis and reduce the development of pulmonary inflammation.

Béla Suki - One of the best experts on this subject based on the ideXlab platform.

  • assessment of peripheral Lung Mechanics
    Respiratory Physiology & Neurobiology, 2008
    Co-Authors: Jason H T Bates, Béla Suki
    Abstract:

    The mechanical properties of the Lung periphery are major determinants of overall Lung function, and can change dramatically in disease. In this review we examine the various experimental techniques that have provided data pertaining to the mechanical properties of the Lung periphery, together with the mathematical models that have been used to interpret these data. These models seek to make a clear distinction between the central and peripheral compartments of the Lung by encapsulating functional differences between the conducing airways, the terminal airways and the parenchyma. Such a distinction becomes problematic in disease, however, because of the inevitable onset of regional variations in mechanical behavior throughout the Lung. Accordingly, Lung models are used both in the inverse sense as vehicles for extracting physiological insight from experimental data, and in the forward sense as virtual laboratories for the testing of specific hypothesis about mechanisms such as the effects of regional heterogeneities. Pathologies such as asthma, acute Lung injury and emphysema can alter the mechanical properties of the Lung periphery through the direct alteration of intrinsic tissue Mechanics, the development of regional heterogeneities in mechanical function, and the complete derecruitment of airspaces due to airway closure and alveolar collapse. We are now beginning to decipher the relative contributions of these various factors to pathological alterations in peripheral Lung Mechanics, which may eventually lead to the development and assessment of novel therapies.

  • Sensitivity analysis for evaluating nonlinear models of Lung Mechanics.
    Annals of Biomedical Engineering, 1998
    Co-Authors: Huichin Yuan, Béla Suki, Kenneth R. Lutchen
    Abstract:

    We present a combined theoretical and numerical procedure for sensitivity analyses of Lung Mechanics models that are nonlinear in both state variables and parameters. We apply the analyses to a recently proposed nonlinear Lung model which incorporates a wide range of potential nonlinear identification conditions including nonlinear viscoelastic tissues, airway inhomogeneities via a parallel airway resistance distribution function, and a nonlinear block-structure paradigm. Additionally, we examine a system identification procedure which fits time- and frequency-domain data simultaneously. Model nonlinearities motivate sensitivity analyses involving numerical approximation of sensitivity coefficients. Examination of the normalized sensitivity coefficients provides direct insight on the relative importance of each model parameter, and hence the respective mechanism. More formal quantification of parameter uniqueness requires approximation of the paired and multidimensional parameter confidence regions. Combined with parameter estimation, we use the sensitivity analyses to justify tissue nonlinearities in modeling of Lung Mechanics for healthy and airway constricted conditions, and to justify both airway inhomogeneities and tissue nonlinearities during broncoconstriction. The tools in this paper are general and can be applied to a wide class of nonlinear models. © 1998 Biomedical Engineering Society.

Georg M Schmolzer - One of the best experts on this subject based on the ideXlab platform.

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