Variable airflow obstruction

These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment. The inflammation also causes an associated increase in the existing bronchial hyperresponsiveness to a variety of stimuli. 

Airway inflammation, and probably its effects on airway structure (airway remodeling), are considered to be responsible not only for the acute but also the longterm changes in airway function in asthma such as persistent airway responsiveness and variable airflow obstruction (56-59). 

The major characteristics of asthma include a variable degree of airflow obstruction (related to bronchospasm, edema, and hypersecretion), BHR, and airway inflammation. 

Yellowlees PM, Alpers JH, Bowden JJ, et al Psychiatric morbidity in patients with chronic airflow obstruction. Med J Aust 146 305-307, 1987 Yeragani VK, Pohl R, Berger R, et al Decreased heart rate variability in panic disorder a study of power-spectral analysis of heart rate. Psychiatry Res 46 89-103,... 

Asthma is a respiratory illness characterized by variable and reversible airflow obstruction. Over 100 years ago. Osier, in his influential Textbook of Medicine (Osier, 1892), concluded that airway wall edema, bronchoconstriaion and mucus plugging are responsible for the airflow obstruction in asthma. Since that time, edema of the airway mucosa has been assumed to be one of the central features of asthma, but comparatively few studies have addressed the issue directly. Therefore, there is litde information about the onset, duration, magnitude, location, mechanism, consequences and management of mucosal edema in asthma. 

Distribution of ventilation Single and multiple breath nitrogen washout Homogeneity of ventilation in lungs - airflow obstruction and gas trapping causes greater variability of ventilation... 

The pattern of deposition of inhaled particles in a normal lung is dependent on particle size, flow rate, and airway anatomy (branching). There are also patient specific variables that influence aerosol deposition. These include respiratory rate, tidal volume, and other anatomical features. The presence of airflow obstruction characteristic of some lung diseases will affect deposition. 

FIGURE 25-4. A. Flow-volume loop depicting mild obstruction characterized by decrease flow at low lung volumes. B. Moderate airflow obstruction characterized by a more concave curve. C. Variable intrathoracic obstruction in which peak flow is decreased at higher lung volumes with normalization of curve at lower lung volumes. D. Restrictive lung disease with a curve that is decreased in width but with a normal shape. 

The major characteristics of asthma include a variable degree of airflow obstruction (related to bronchospasm, edema, and hypersecretion), BHR, and airways inflammation (Fig. 26-1). Evidence of inflammation arose from the studies of nonspecific BEIR, bron-choalveolar lavage (BAL), bronchial biopsies, and induced sputum, as well as from postmortem observations of patients with asthma who died from an attack of asthma or from other causes. To understand the pathogenetic mechanisms that underlie the many variants of asthma, it is critical to identify factors that initiate, intensify, and modulate the inflammatory response of the airways and to determine how these immunologic and biologic processes produce the characteristic airways abnormalities. Immune responses mediated by IgE antibodies are of foremost importance. 

IV. Diagnosis requires a careful occupational history. Pulmonary function testing may document an obstructive deficit or may be normal. Variable airflow or changing measures of airway reactivity (methacholine or histamine challenge) temporally linked to exposure strongly support the diagnosis of isocyanate-induced asthma. 

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