PULMONARY PATHOPHYSIOLOGY IN CYSTIC FIBROSIS

Abstract

Twenty children with pulmonary involvement from cystic fibrosis of the pancreas and 10 normal children were studied by clinical and physiologic means. Clinical severity of disease was numerically scored on the basis of general activity, physical examination, state of nutrition, and roentgenologic findings. Studies of pulmonary function consisted of spirometry, lung volume measurement by both He dilution and body plethysmographic methods, measurements of airway resistance, intrapulmonary gas distribution, arterial blood O2,CO2 and pH, and the single breath CO2 diffusing capacity. The children with cystic fibrosis manifested a wide span of clinical severity, from those who were virtually asymptomatic to those who were within a few months of death from their disease. The group as a whole was found to have a pattern of ventilatory dysfunction characteristic of obstructive pulmonary disease with evidence of increasing airway obstruction paralleling the increase in clinical severity. Arterial CO2 pressure [PCO2] and pH did not reflect increasing functional impairment; this is attributed to anxiety hyperventilation that accompanied the trauma of arterial puncture. In no patient was the CO2 diffusing capacity found to be reduced. The most interesting and significant result was the almost perfect correlation (r = 0.97) between clinical severity and the ratio of residual to total lung volume as determined by the body plethysmographic method. In contrast to the results of conventional (He) lung volume measurement, no patient had a reduced total thoracic gas volume with the body plethysmograph. When a reduced total lung capacity is found by the He method in patients with cystic fibrosis, "trapped gas" is present and more vigorous therapeutic measures for the relief of bronchial obstruction should be tried. No single test of pulmonary function was found to characterize adequately the total functional impairment and functional evaluation should include a battery of such tests.