Obstructive Diseases of the Lung

Asthma is among the more common obstructive diseases of the lung. Nearly 3% of the population of the United States alone has some form of asthma. A number of excellent reviews (McFadden and Austen, 1983 Wilson and McPhillips, 1978 and McFadden and Feldman, 1977) and books 

In mast cells, both preformed mediators and those that are synthesized de novo after antigen challenge are released by a process that is believed to involve IgE-induced activation of a serine-esterase-like enzyme, the activation of methyltransferase activities within the plasma membrane, and an influx of calcium into the cell (Ishizaka, 1983). Inside the cell, calcium is believed to interact with the intracellular calcium-binding protein, calmodu- 

BRONCHOCONSTRICTION VASOCONSTRICTION INCREASED CAPILLARY PERMEABILITY INCREASED MUCUS SECRETION 

DIGESTION OF STRUCTURAL PROTEOGLYCANS AND EPITHELIAL TIGHT JUNCTIONS 

The preformed mediator of greatest familiarity that is released in this fashion from mast cells in human lung is the vasoactive amine histamine. This mediator is capable of inducing bronchoconstriction when administered to man by the aerosol route (Mathe et al., 1973) and has been shown in vitro to initiate mucus secretion (Shelhamer et al., 1980) and alter capillary permeability within the vascular tissue (Northover, 1975). But despite these pharmacological actions, histamine is not believed to be the primary mediator (if a primary mediator exists) in asthma since antihistaminic drugs have not demonstrated great use clinically (Karlin, 1972). 

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In recent years, many new tests have been developed to assess pulmonary function in man. Here are presented the general principles, methodology, and clinical significance of the major lung function tests used in the diagnosis of obstructive and restrictive lung diseases. Obstructive diseases of the lung... 

A second way of looking at forced expiration is with a maximum expiratory flow-volume (MEFV) curve, which describes maximum flow as a function of lung volume during a forced expiration (Fig. 12). In healthy human subjects, flow rates or flow-volume curves reach a maximum and will not increase with additional effort after the lungs have emptied 20-30% of their volume (Fry and Hyatt, 1960). This phenomenon of flow limitation is due to airway compression over most of the lung volume. Thus, flow rate is independent of effort and is determined by the elastic recoil force of the lung and the resistance of the airways upstream of the collapse point. In obstructive diseases of the lung this curve is shifted to the left, whereas restrictive diseases shift the curve in the opposite direction (also shown in Fig. 12). 

Bronchial asthma is defined as a chronic inflammatory disease of the lungs it affects an estimated 9 to 12 million individuals in the U.S. Furthermore, its prevalence has been increasing in recent years. Asthma is characterized by reversible airway obstruction (in particular, bronchospasm), airway inflammation, and increased airway responsiveness to a variety of bronchoactive stimuli. Many factors may induce an asthmatic attack, including allergens respiratory infections hyperventilation cold air exercise various drugs and chemicals emotional upset and airborne pollutants (smog, cigarette smoke). 

Chronic obstructive pulmonary disease (COPD) affects over 5% of the adult population, is the fourth leading cause of death worldwide and is the only major cause of mortality that is increasing worldwide. It is an inflammatory disorder of the lungs, caused mainly, but not exclusively, by cigarette smoking. 15-20% of smokers develop COPD. 

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible. The airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases. The most common conditions comprising COPD are chronic bronchitis and emphysema. 

Smoking leads to respiratory problems other than lung cancer. It causes chronic bronchitis, emphysema, and lower resistance to flu and pneumonia. It worsens asthma symptoms in adults and children. As these problems persist, chronic obstructive pulmonary disease (COPD, airway obstruction) develops. Eighty to 85% of deaths due to COPD are from smoking. The role of nicotine in chronic lung diseases such as COPD, emphysema, and asthma is uncertain. However it is known that nicotine can cause an enzyme to be released which is able to destroy parts of the lungs as is seen in emphysema. 

A 68-year-old man with chronic obstructive pulmonary disease underwent CT examination of the abdomen with intravenous infusion of iomeprol for suspected hepatocellular carcinoma and 2 hours later developed severe dyspnea. A chest X-ray showed bilateral diffuse shadowing of the lungs and the heart shadow was not enlarged. A diagnosis of non-cardiogenic pulmonary edema was made and he improved with glucocorticoids. 

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. 

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