Criteria for surgery:
(1) severe dyspnea
(2) severe airflow obstruction on spirometry
(3) evidence of hyperinflated lungs and flattened diaphragm on chest radiographs
(4) presence of emphysema on CT scanning of the chest
Relative contraindications to surgery:
(1) severe concurrent illness such as myocardial infarction
(2) pulmonary artery hypertension (pulmonary artery systolic blood pressure > 45 mm Hg, or mean pressure > 35 mm Hg)
(3) pleural scarring
(4) use of excessive doses of glucocorticoids (> 10 mg of prednisone per day)
(5) failure to complete preoperative rehabilitation program
Definition of a positive response to surgery:
(1) an increase in Forced Expiratory Volume at 1 second (FEV1) >= 0.2 liters
(2) an increase of FEV1 at least 12 percent above baseline values
A preoperative inspiratory resistance of 10 cm water per liter per second was used as the decision level for identifying patients likely to benefit from surgery
(1) Patients with inspiratory resistance <= 10 cm of water per liter per second showed benefit.
(2) Patients with inspiratory resistance > 10 cm of water per liter per second did not show sufficient increase in FEV1.
Predicted change in FEV1 at 6 months following surgery (Figure 1, page 1183):
(1) intercepts based on line shown: inspiratory lung resistance = 0, change FEV1 = 0.6; inspiratory lung resistance = 25, change FEV1 = -0.4
(2) line predicted with slope (-0.04) and x-axis intercept 0.6
predicted change in FEV1 in liters at 6 months following surgery =
= ((-0.04) * (inspiratory lung resistance in cm of water per liter per second)) + 0.6
