The lung mechanics in emphysema: a comparative study in patients with and without chronic respiratory failure.

A comparative study, emphasizing lung mechanics, was made of the clinical and functional pattern in two groups of emphysematous patients; 8 with and 11 without chronic respiratory failure. Loss of lung elasticity appeared to be the most prominent mechanical abnormality in the group with normal arterial blood gases. Airway obstruction due to expiratory check valving was less marked than in the hypercapnic group where it seemed to be the major difficulty, impairment of lung elasticity being a secondary feature. These and other demonstrated differences, suggested that qualitatively different disease processes were represented in the two groups, possibly centrilobular emphysema in the hypercapnic group as opposed to diffuse emphysema in the group with normal blood gases. In addition, the findings suggested that the chief mechanism producing chronic hypercapnia in emphysema is an inability to compensate for distributional defects by increasing ventilation, due to mechanical restriction of the respiratory bellows