In this study, we sought to separate the confounding effects of smoking behavior on severity of lung disease in African-American and white patients, and examined the association between race and the extent of emphysema in a specific, well-defined patient population: enrollees of the National Emphysema Treatment Trial (NETT). Severity, distribution, and physiologic impact of emphysema were evaluated by a battery of cardiopulmonary function tests, quantitative CT of the chest, and quality of life questionnaires. The results of this study may help in understanding host factors involved in the development of severe emphysema, and may aid in shaping antismoking policies that target African Americans.
The NETT is a multicenter, randomized clinical trial of optimal medical therapy vs optimal medical therapy plus lung volume reduction surgery in the treatment of severe emphysema. The design and methods of the NETT have been described previously and are summarized below. All analyzed data were obtained from the baseline prerehabilitation assessment during the first or second visit to NETT centers, except for some chest CT scans that were collected after rehabilitation. Here
The inclusion criteria were as follows: FEV1 < 45% of predicted value, and if age > 70 years, FEV1 > 15% of predicted; total lung capacity (TLC) > 100% of predicted; residual volume (RV) > 150% of predicted; Paco2 < 60 mm Hg (< 55 mm Hg in Denver), with patients at rest and breathing room air; Pao2 > 45 mm Hg (> 30 mm Hg in Denver), with patients at rest and breathing room air; ability to walk > 140 m (459 feet) in 6 min; ability to complete 3 min of pedaling on a bicycle ergometer without a load; and abstinence from smoking for 6 months before randomization. Lung function was tested according to the guidelines of the American Thoracic Society. For race adjustment, predicted values of Crapo were used, multiplying by 0.88 for African Americans to correct for their smaller lung volumes. Patients were excluded if they had other medical conditions that made them unsuitable for surgery or prohibited them from follow-up. All patients provided written informed consent, and the study was approved by the institutional review board at each center.