The prone position results in smaller ventilation defects during bronchoconstriction in asthma.

The effect of body posture on regional ventilation during bronchoconstriction is unknown. In five subjects with asthma, we measured spirometry, low-frequency (0.15-Hz) lung elastance, and resistance and regional ventilation by intravenous (13)NN-saline positron emission tomography before and after nebulized methacholine.

Regional pulmonary perfusion, inflation, and ventilation defects in bronchoconstricted patients with asthma.

Rationale: Bronchoconstriction in asthma leads to heterogeneous ventilation and the formation of large and contiguous ventilation defects in the lungs. However, the regional adaptations of pulmonary perfusion (Q) to such ventilation defects have not been well studied.

Methods: We used positron emission tomography to assess the intrapulmonary kinetics of intravenously infused tracer nitrogen-13 ((13)NN), and measured the regional distributions of ventilation and perfusion in 11 patients with mild asthma.

Enhanced parameter estimation from noisy PET data: Part II--evaluation.

Rationale And Objectives: Positron emission tomography (PET) is a minimally invasive imaging modality that provides three-dimensional distribution data for a radioactive tracer concentration within the body. Local functional parameters are estimated from these images by fitting tracer kinetic data with mathematical models. However, in some applications, the reliability of parameter estimates may be hindered by the presence of noise.

Identifying airways responsible for heterogeneous ventilation and mechanical dysfunction in asthma: an image functional modeling approach.

We present an image functional modeling approach, which synthesizes imaging and mechanical data with anatomically explicit computational models. This approach is utilized to identify the relative importance of small and large airways in the simultaneous deterioration of mechanical function and ventilation in asthma. Positron emission tomographic (PET) images provide the spatial distribution and relative extent of ventilation defects in asthmatic subjects postbronchoconstriction.

Self-organized patchiness in asthma as a prelude to catastrophic shifts.

Asthma is a common disease affecting an increasing number of children throughout the world. In asthma, pulmonary airways narrow in response to contraction of surrounding smooth muscle. The precise nature of functional changes during an acute asthma attack is unclear.

Tissue heterogeneity in the mouse lung: effects of elastase treatment.

We developed a network model in an attempt to characterize heterogeneity of tissue elasticity of the lung. The model includes a parallel set of pathways, each consisting of an airway resistance, an airway inertance, and a tissue element connected in series. The airway resistance, airway inertance, and the hysteresivity of the tissue elements were the same in each pathway, whereas the tissue elastance (H) followed a hyperbolic distribution between a minimum and maximum.

Relation between structure, function, and imaging in a three-dimensional model of the lung.

Previous studies have reported morphometric models to predict function relations in the lung. These models, however, are not anatomically explicit. We have advanced a three-dimensional airway tree model to relate dynamic lung function to alterations in structure, particularly when constriction patterns are imposed heterogeneously inspecific anatomic locations.