Lung volume reduction surgery is currently the subject of a trial in the USA comparing LVRS to medical management, the National Emphysema Treatment Trial NETT. The inclusion criteria are the current accepted indications for LVRS. However, please note an emergency NEJM publication of a high death rate in a high risk subgroup which has led to a change in inclusion criteria.

NETT criteria for lung volume reduction

NETT home page (http://www.emphysemastudy.org/lvrs.html)

NEJM article on high risk patients

The inclusion criteria were as follows:

1. •a forced expiratory volume in one second (FEV1) that was no more than 45 percent of the predicted value14  but that was at least 15 percent of the predicted value among patients who were 70 years of age or older, (see below where 20% is a safer figure)
   

2. •a total lung capacity that was at least 100 percent of the predicted value,15 
   

3. •a residual volume that was at least 150 percent of the predicted value,15 
   

4. •a partial pressure of arterial carbon dioxide of 60 mm Hg or less (55 mm Hg in Denver) while patients were at rest and breathing room air, a partial pressure of arterial oxygen of at least 45 mm Hg (30 mm Hg in Denver) while patients were at rest and breathing room air,
   

5. •an ability to walk farther than 140 m (459 ft) in six minutes,
   

6. •an ability to complete three minutes of pedaling on a bicycle ergometer without a load, and abstinence from smoking for six months before randomization.
   

Changes in criteria (August 2001)

Patients with the following criteria have a 30 day mortality of 16%, after 6 months only 33% had improved exercise capacity (23% no change or decrease, 8% unable to do tests and 35% had died):

1. •Very low FEV1 - less than 20% and 
   

2. •either Carbon monoxide diffusion capacity less than 20% predicted
   

3. •or homogeneous emphysema
   

Patients had to complete a measurement of carbon monoxide diffusing capacity but were not excluded on the basis of the value.16 

Lung function was tested according to the guidelines of the American Thoracic Society.17 18 19 

Patients were excluded if they had other medical conditions that made them unsuitable for surgery or that might interfere with follow-up. All patients provided written informed consent, and the study was approved by the institutional review board at each center.

Severity and distribution of emphysema

1. •High-resolution computed tomographic (CT) scans of the chest obtained during full inspiration.
   

2. •Each lung was divided into three apical-to-basal zones, and each zone was scored visually by a radiologist who had been trained in the study protocol.
   

3. •The extent of emphysema was graded from 0 to 4, with a grade of 0 indicating no emphysema and a grade of 4 indicating the presence of emphysema in more than 75 percent of the lung zone.20 21 22 
   

4. •Heterogeneous emphysema was defined as a difference in scores of at least two among the three zones in one lung; otherwise, the distribution of emphysema was classified as homogeneous.
   

Workup

The initial evaluation included

1. •six-minute walk tests,23 24 
   

2. •lung-function tests,
   

3. •bicycle ergometry to determine maximal exercise capacity,
   

4. •the 77-item Quality of Well-Being questionnaire (scores can range from 0 to 1, and higher scores indicate a better quality of life),25 
   

5. •echocardiography,
   

6. •radionuclide pharmacologic (dobutamine) stress testing,
   

7. •measurement of arterial blood gases, and
   

8. •lung-perfusion scanning.
   

Patients who met the enrollment criteria had to complete 6 to 10 weeks of pulmonary rehabilitation, after which the participating center's pulmonologist and surgeon, in consultation with an anesthesiologist and, if necessary, a cardiologist, had to determine whether the patient was a suitable candidate for lung-volume–reduction surgery. Exercise testing, lung-function testing, the Quality of Well-Being questionnaire, and six-minute walk testing were then repeated. Patients who were randomly assigned to medical therapy continued pulmonary rehabilitation and medical treatment. Patients who were randomly assigned to undergo lung-volume–reduction surgery underwent bilateral surgery by means of either a median sternotomy or video-assisted thoracoscopy; the goal was to resect 20 to 35 percent of each lung. After surgery, patients continued rehabilitation and medical treatment. Pulmonary-function testing, exercise testing, the Quality of Well-Being questionnaire, and the six-minute walk test were repeated six months after randomization.