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Pulmonary ventilation and gas exchange in bronchiectasis

The subdivisions of the lung volume, pulmonary mechanics, and resting steady state pulmonary transfer factor were measured in 31 patients with bronchographically proven bronchiectasis. In seven patients the process of gas exchange was further investigated by fractionating the total alveolar-arterial oxygen tension gradient into diffusion, distribution, and true shunt components. A restrictive type of ventilatory defect with varying degrees of airway obstruction was observed in a majority of the patients; the airway obstruction was partially reversed by a bronchodilator. Dynamic compliance was usually decreased and the pulmonary resistance increased. Pulmonary transfer factor was decreased in proportion to the number of segments involved. Vital capacity, maximum breathing capacity, and dynamic compliance bore a less significant correlation with the extent of disease. The degree of airway obstruction, as judged by pulmonary resistance, was independent of the extent of disease. All the patients were hypoxaemic and some had hypercapnia as well. The alveolar-arterial oxygen tension gradient was widened primarily because of distributional abnormalities and, to some extent, by the presence of true right-to-left shunts. The latter amounted to 13·6% of the total cardiac output. Surgical resection of the affected lobe or segments resulted in a further deterioration of all the parameters of pulmonary function tested.