An analysis of pressure-volume characteristics of the lungs

Salazar, Eduardo; Knowles, John H.

doi:10.1152/jappl.1964.19.1.97

Cited by 309 publications

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“…A distributed time-varying pressure load was applied to the surface of the FE lung model. Pressure amplitudes at each breathing phase were evaluated from the parametrized P-V curve 52 and the mean P-V curve 53 shown in Fig. 5.…”

Section: Iib Physiological Respiratory Motion Modelingmentioning

confidence: 99%

“…Though in Fig. 5, the value of volume of tidal volume ͑TV͒ and pressure was used as 500 ml and 10 cm H 2 O for illustration, the pressures at EI are evaluated by the mean P-V curve 53 and the change of scaled pressure over volume are fitted by the parameterized P-V curve. 52 A tumor-bearing lung is modeled as an elastic medium ⍀ consisting of N homogeneous isotropic subdomains in the finite-element model of ABAQUS.…”

Section: Iib Physiological Respiratory Motion Modelingmentioning

confidence: 99%

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Predictive modeling of lung motion over the entire respiratory cycle using measured pressure‐volume data, 4DCT images, and finite‐element analysis

Eom

et al. 2010

Medical Physics

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Purpose: Predicting complex patterns of respiration can benefit the management of the respiratory motion for radiation therapy of lung cancer. The purpose of the present work was to develop a patient-specific, physiologically relevant respiratory motion model which is capable of predicting lung tumor motion over a complete normal breathing cycle. Methods: Currently employed techniques for generating the lung geometry from four-dimensional computed tomography data tend to lose details of mesh topology due to excessive surface smoothening. Some of the existing models apply displacement boundary conditions instead of the intrapleural pressure as the actual motive force for respiration, while others ignore the nonlinearity of lung tissues or the mechanics of pleural sliding. An intermediate nonuniform rational basis spline surface representation is used to avoid multiple geometric smoothing procedures used in the computational mesh preparation. Measured chest pressure-volume relationships are used to simulate pressure loading on the surface of the model for a given lung volume, as in actual breathing. A hyperelastic model, developed from experimental observations, has been used to model the lung tissue material. Pleural sliding on the inside of the ribcage has also been considered. Results:The finite-element model has been validated using landmarks from four patient CT data sets over 34 breathing phases. The average differences of end-inspiration in position between the landmarks and those predicted by the model are observed to be 0.450Ϯ 0.330 cm for Patient P1, 0.387Ϯ 0.169 cm for Patient P2, 0.319Ϯ 0.186 cm for Patient P3, and 0.204Ϯ 0.102 cm for Patient P4 in the magnitude of error vector, respectively. The average errors of prediction at landmarks over multiple breathing phases in superior-inferior direction are less than 3 mm. Conclusions:The prediction capability of pressure-volume curve driven nonlinear finite-element model is consistent over the entire breathing cycle. The biomechanical parameters in the model are physiologically measurable, so that the results can be extended to other patients and additional neighboring organs affected by respiratory motion.

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Section: Iib Physiological Respiratory Motion Modelingmentioning

confidence: 99%

Section: Iib Physiological Respiratory Motion Modelingmentioning

confidence: 99%

Predictive modeling of lung motion over the entire respiratory cycle using measured pressure‐volume data, 4DCT images, and finite‐element analysis

Eom

et al. 2010

Medical Physics

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“…A cannula was inserted and the mice were attached to a ventilator equipped with a pressure and volume (flow) transducer (flexiVent; SciReq). Static compliance measurements were obtained from dynamic pressure volume curves using the Salazar-Knowles equation (34).…”

Section: Measurement Of Lung Functionmentioning

confidence: 99%

Endogenous 4-1BB Ligand Plays a Critical Role in Protection from Influenza-Induced Disease

Lin

Sedgmen

Moraes

et al. 2009

The Journal of Immunology

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A critical issue during severe respiratory infection is whether it is the virus or the host response that does the most damage. In this study, we show that endogenous 4-1BBL plays a critical role in protecting mice from severe effects of influenza disease. During mild respiratory influenza infection in which virus is rapidly cleared, the inducible costimulatory receptor 4-1BB is only transiently induced on lung T cells and 4-1BB ligand (4-1BBL) is completely dispensable for the initial CD8 T cell response and mouse survival. In contrast, during more severe respiratory influenza infection with prolonged viral load, 4-1BB expression on lung CD8 T cells is sustained, and 4-1BBL-deficient mice show decreased CD8 T cell accumulation in the lungs, decreased viral clearance, impaired lung function, and increased mortality. Transfer of an optimal number of naive Ag-specific T cells before infection protects wild-type but not 4-1BBL-deficient mice from an otherwise lethal dose of influenza virus. T he CD8 T cells are important mediators of protective immunity to viruses (1). Indeed a strong CD8 T cell response to influenza offers the hope of cross-protective immunity to diverse influenza strains (2, 3). However, there is a concern that too strong an immune response in the lung will cause immune pathology and a worse outcome (4 -6). Upon initial encounter with Ag, T cells commit to programmed expansion, which occurs independently of the continued presence of Ag (7,8). How then does the immune system provide the appropriate level of T cell stimulation for a particular infection? T cells regulate their level of response by integrating signals from the Ag-specific receptor as well as from costimulatory, coinhibitory, and cytokine receptors which in turn influence the initiation, duration, and differentiation of the response (9 -12). The initial activation of T cells requires costimulatory signals from CD28, expressed on resting T cells. In addition, during an on-going immune response, other costimulatory receptors and ligands are up-regulated on the T cells and APCs (13-15). The question arises as to why so many costimulatory receptor ligand pairs have accumulated in the mammalian immune system. Here we provide evidence that the expression of one such costimulatory receptor, 4-1BB, is sustained in response to severe as compared with mild respiratory infection with influenza virus, thereby allowing the immune system to maintain a level of CD8 T cell response appropriate for the severity of the infection.The receptor 4-1BB (CD137) is a member of the TNFR family expressed on Ag-receptor activated T cells (14, 16 -18). In vivo with nonreplicating immunogens, 4-1BB is rapidly and transiently up-regulated on T cells upon immunization, before the first cell division and concomitantly with the expression of the early activation marker CD69 (19). Evidence that 4-1BB can play a role early in the response comes from systemic administration of agonist anti-4-1BB Abs, which can enhance initial antitumor and antiviral T cell responses wi...

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“…(2) Equation (2) included total lung capacity (TLC) and was designed to fit the whole range of lung volumes, whereby former models fitted data only for lung volumes above functional residual capacity [5]. Originally, TLC is the amount of gas in the lungs after a voluntary maximal inspiration.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Sigmoidal Equations To Describe the Pulmonary Pressure- Volume Curve in Acute Respiratory Distress Syndrome~!2008-09-18~!2008-10-27~!2008-12-05~!

Orfao¹,

Hochhausen²,

Kuhlen³

et al. 2008

TOCCMJ

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Pulmonary pressure-volume curves (P-V curves) of patients with acute lung injury are commonly analyzed using a parametric algorithm with symmetrical properties. Some of the aspects observed after performing nonlinear regression for two models capable of fitting symmetric, respectively asymmetric data are discussed.One analyzed aspect was the algebraic complexity of the asymmetric model that does not allow for an estimation of the boundaries of the zone of maximal compliance directly from the parameter estimates in contrast to the symmetric model. Moreover, mathematical evidence is provided.Using a sigmoid equation for analysis of P-V curves a systematic deviation caused by asymmetrical distribution was encountered, leading to non-robust definitions of lower and upper inflection points. Increasing the number of parameters to fit asymmetric data does not increase physiological expression.We conclude that some of the drawbacks in using P-V curves may be attributed to imprecise analysis tools. To increase the value of P-V curves other forms of mathematical analysis should be investigated.

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An analysis of pressure-volume characteristics of the lungs

Cited by 309 publications

References 0 publications

Predictive modeling of lung motion over the entire respiratory cycle using measured pressure‐volume data, 4DCT images, and finite‐element analysis

Predictive modeling of lung motion over the entire respiratory cycle using measured pressure‐volume data, 4DCT images, and finite‐element analysis

Endogenous 4-1BB Ligand Plays a Critical Role in Protection from Influenza-Induced Disease

Analysis of Sigmoidal Equations To Describe the Pulmonary Pressure- Volume Curve in Acute Respiratory Distress Syndrome~!2008-09-18~!2008-10-27~!2008-12-05~!

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