Regional Lung Mechanics in Pulmonary Disease.

Recent studies in this laboratory have shown that one lobe of the lung may be used as a tonom-eter to measure pressure variations within the human thorax (1). These studies demonstrated that negative pressure swings were greater in the intrapleural "space" about the lower lobe than about the upper lobe, and the pressure swings about the upper lobe were in turn greater than those surrounding an esophageal pressure tap. In normal subjects these differences increased with lung volume. Lobar compliance was similar in upper and lower lobes. In the "diffuse obstructive pulmonary syn-drome" (DOPS or clinical emphysema), the overall distensibility of the lungs is increased when measured as a static function (2-4). The so-called "dynamic compliance," however, is rate dependent, as might be expected, and is decreased in the obstructive airway syndrome (3, 4-6). The compliance of individual lobes as well as the pressure relationships about them is unknown in this condition. Lungs with pulmonary fibrosis might be expected to have a decreased compliance (7) but have accentuated pressure differences about the fibrotic portion. Herein reported are the values for lobar compliance and the distribution of pressures within the thorax in patients having pulmonary disease. Methods The subjects were patients having routine broncho-spirometry who volunteered for additional studies. They were classified according to their functional state as outlined in Table I. Normal subjects (N) were less than 40 years of age, without known disease now or in the past in the lung under study. These patients had a maximal breathing capacity (MBC) greater than predicted and a vital capacity greater than 80% of predicted (8). Their maximal expiratory flow rates (MEF) were greater than 260 L per minute for the males and 210 L per minute for the females (9). A group of older subjects (O ± D) were mixed in character. Three subjects in this group had mild DOPS with an MEF between 200 and 240 L per minute and an MBC ranging from 76% to 100% of predicted. None of these subjects had symptoms referable to their obstructive airway disease; none had significant disease in the lung under study. Two had normal flow rates. All members of the group labeled DOPS (D) had an MEF less than 170 L per minute, an air velocity index (AVI) less than 0.8 (10), and hyperlucency of the lung fields on X ray. There was no productive (fibrotic) disease within the lung …