To assess the role of chest radiography in the differential diagnosis of bronchiolitis obliterans organizing pneumonia (BOOP) and usual interstitial pneumonia (UIP), records of 34 patients with biopsy-proved BOOP (16 patients) or UIP (18 patients) were reviewed. Chest radiographs taken before biopsy were available in 26 patients, clinical information in 33, and pulmonary function data in 22. These data were reviewed independently, without knowledge of the pathologic diagnosis. The clinical symptoms of BOOP were similar to those of UIP, although the duration of symptoms was longer in UIP (P less than .05), and the prevalence of systemic symptoms was higher in BOOP (P less than .025). The physical findings were similar except that finger clubbing was more common in patients with UIP than in those with BOOP (P less than .01). There was no significant difference in lung volumes, flows, or diffusing capacity between BOOP and UIP. The chest radiograph showed distinguishing features between UIP and BOOP in 23 of 26 patients. The most characteristic radiologic finding in BOOP was the presence of patchy areas of air-space consolidation (eight of 11 patients).

1. A rapid method for the analysis of CO in expired air has been developed, which is suitable for use in studies of smoking. 2. The Bohr equation has been used to calculate the mean alveolar CO partial pressure (PA,CO). 3. The values of PA,CO obtained are highly correlated with direct measurements of venous carboxyhaemoglobin (r = 0-96). 4. The method will distinguish between populations of smokers and non-smokers, and can allow the changes of CO in a smoker throughout a 12 h period to be followed. It provides a measure of the dose of cigarette smoke (vapour phase) that results from smoking a single cigarette.

We investigated the effect of obvious emphysematous lesions and the mean airspace size in the lung surrounding these lesions on the exponential constant K of the lung pressure-volume curve. The severity of the centrilobular emphysematous (CLE) lesions was determined in resected lung specimens, and the mean linear intercept (Lm) was measured on random histologic sections taken from regions without obvious emphysema. The exponential constant K was determined by fitting lung pressure-volume data obtained from the patient just prior to resection to the equation V = A - Be-KP. This allowed us to compare patients with little or no emphysema that had either normal (0.16 +/- 0.03 SD; n = 12) or increased (0.27 +/- 0.04 SD; n = 12) K to other patients that had severe emphysema but either normal (0.17 +/- 0.01 SD; n = 10) or increased (0.25 +/- 0.03 SD; n = 10) K. In subjects without emphysema, K was significantly related to Lm, suggesting that K is a measure of mean alveolar size. In the subjects with emphysema, a lower value for K was associated with more severe airway dysfunction and gas trapping. We conclude that K reflects airspace size except when airway closure subtracts the contribution of lung units from the deflation pressure-volume curve.

ABSTRAcr The standard plethysmographic method of measuring total lung capacity (TLC) has been reported to result in spuriously high estimates in patients with severe airway obstruction. The helium-dilution method is known to underestimate TLC in the same patients. To determine the magnitude of these possible errors we measured TLC by four methods in 20 patients with varying degrees of chronic obstructive lung disease and in 11 normal subjects. TLC was measured by (1) helium dilution (TLCHe); (2)

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