The initial evaluation included 6-min walk distance; post-bronchodilator pulmonary function tests; maximal exercise capacity during cycle ergometry while receiving 30% oxygen; echocardiography; radionuclide pharmacologic (dobutamine) cardiac stress testing; arterial blood gas measurement; and lung perfusion scanning. Patients also responded to a battery of general and disease-specific self- administered quality of life scales: the Quality of Well-being (QWB) scale, the Short Form-36, St. George’s Respiratory Questionnaire (SGRQ), and the University of California, San Diego Shortness of Breath Questionnaire. Other collected variables included demographics, medications, and smoking habits (type, debut, duration, amount, quit age). сanadianhealthcaremallinc.com
Diagnostic Imaging Studies:
The severity and distribution of emphysema were determined from CT scans of the chest obtained during full inspiration. Spiral CT scans were acquired with a collimation ranging from 3 to 10 mm, with the majority of the centers having a slice collimation < 5 mm. Data were evaluated using the standard reconstruction kernel but were not complete for all patients because of early archiving problems, not meeting a set of minimum criteria for matching the prescribed scanning protocol, or missing images from the data sets. Image analysis was done using a custom-built software package (Pulmonary Analysis Software Suite; University of Iowa; Iowa City, IA) after segmenting and dividing the lung according to previously reviewed methods for defining upper, middle, lower, core, and peel regions.
Once segmented, the lung was divided into three equal apical-to-basal regions (upper, middle, lower) and, in the implementation used for this study, the peel consisted of the outer 1.5 cm of lung identified in three-dimensional space. The image voxels within the lung field were then labeled as being emphysema-like based on their reconstructed image gray scale representing the radiograph attenuation coefficient or Hounsfield Unit (HU); the HU of air is – 1,000, of blood is approximately 55, and that of water is 0. Because lung is largely composed of only two densities (air and tissue), the voxel density within the lung field can be translated into a percentage of air and percentage oftissue value. The distribution of the number of voxels at each HU within lung fields has been termed the density histogram and is traditionally plotted with number of voxels on the y-axis, with HU values < 950 corresponding to severe emphysema. HU values of — 910 and – 850 have approximately corresponded to moderate and mild emphysema regions, respectively.