Pulmonary Hemodynamics, Gas Exchange, and the Severity of Emphysema as Assessed by Quantitative CT Scan in Chronic Bronchitis and Emphysema

We have used the CT transthoracic scan to measure regional lung density in vivo, as our previous studies have shown that this correlates with the increase in size of distal air spaces, which is a defining characteristic of emphysema. We have studied 32 patients with chronic airflow limitation (FEV1 15 to 68% predicted) caused by chronic bronchitis and emphysema (synonym, COPD), with a wide range of arterial Po2 (38 to 90 mm Hg) and Pco2 (32 to 63 mm Hg) while breathing air at rest. We could find no significant relationships between the extent of emphysema (as assessed in vivo by the EMI number defining the lowest fifth percentile of the CT density histogram of the lung fields) and either arterial blood gas tensions, mean pulmonary arterial pressure, cardiac output, or calculated total pulmonary vascular resistance while at rest (n = 32) or during supine leg exercise (n = 29). We conclude that the extent of emphysema does not correlate with the clinical or pathologic features of the “pink and puffing” (i.e...