Diaphragm Strength: In addition to routine pulmonary function testing, eight patients also had measurement of maximal transdiaphragmatic pressure before and 3 months after LVRS. Transdiaphragmatic pressure (Pdi) was measured, as previously described, by two balloon-tipped catheters placed into the distal esophagus (endoesophageal pressure [pleural pressure]) and stomach (gastric pressure), and connected to pressure transducers (100 ± 5 cm H2O) [Validyne; Ventura, CA]. The pressure waveforms were continuously displayed on a strip-chart recorder (ES 1000; Gould; Dayton, OH). Pdi was calculated as the difference in end-inspiratory and end-expiratory values.
Pdi during maximum static inspiratory effort (sniff maneuvers) (Pdimax sniff) was determined by having each patient perform three to six maximal sniff maneuvers. After each patient could reproducibly perform several maximal efforts, a total of three values, all within 5%, were averaged and reported. All measurements were performed from functional residual capacity (FRC) by monitoring the endoesophageal pressure waveform, with patients seated in the upright position. Canadian Family Pharmacy
LVRS was performed via median sternotomy with biapical and upper lobe stapling resection in all but three patients who had only lower lobes operated on. The goal of resection was to remove 20 to 40% of the volume of each lung. High-resolution chest CT and quantitative ventilation-perfusion scans were used preoperatively to target lung regions with the worst emphysema (ie, areas of greatest gas trapping with poorest perfusion). At the end of the operation, chest tubes were placed and managed in the conventional manner.
Rib Cage Dimensions: Rib cage dimensions were measured by using two methods: plain AP and lateral CXRs, and chest CT scans. These studies were performed within 3 weeks before LVRS and 3 months after LVRS. Seven patients had undergone CXRs previously, within a year of their preoperative evaluation, and 10 patients underwent CT scans 1 year after surgery.