Lung Volume Reduction Surgery and the National Emphysema Treatment Trial

by Barry J. Make, M.D.

Print PDF Version

Lung Volume Reduction Surgery (LVRS) ... The National Emphysema Treatment Trial (NETT) ... References

Lung Volume Reduction Surgery and the National Emphysema Treatment Trial

Emphysema is a chronic lung disease in which the air spaces distal to the terminal bronchioles are permanently enlarged, their walls destroyed and without obvious fibrosis. This condition results in reduced surface area for perfusion and the exchange of gases. Emphysema is most commonly caused by cigarette smoking and, in some cases, by a genetic deficiency of the enzyme alpha-1-antitrypsin, a protective antiprotease. In emphysema, there is a progressive decline in respiratory function due to a loss of lung elastic

Barry J. Make, MD Senior Faculty Member, Pulmonary Division, Director of Pulmonary Rehabilitation, Emphysema Program and Respiratory Care, National Jewish Medical and Research Center Professor, Department of Medicine, University of Colorado Health Sciences Center

recoil with a decrease of expiratory flow rates; air-trapping and hyperinflation; enlargement of the lungs and thorax; and, impaired diaphragmatic function. These changes produce the major symptom emphysema patients suffer--dyspnea or shortness of breath.

Current treatments for emphysema include bronchodilators to improve airflow, as well as use of oxygen therapy for patients with chronic hypoxemia. There are also benefits from pulmonary rehabilitation and exercise training, which is indicated for patients with functional limitations and continued dyspnea despite traditional medical therapy.

Lung Volume Reduction Surgery (LVRS)

LVRS recently has received much attention from supporters and critics alike. First introduced in the 1950s, LVRS was initially abandoned due to a high operative mortality and lack of objective statistics to support its continued use. One of the main limitations of the procedure was the difficulty in suturing the remaining lung in an airtight manner after resection. Today, bovine pericardium is used to buttress the staple line and minimize air leaks. Using this procedure, published reports have indicated benefits in some patients.

LVRS downsizes the lungs by resecting badly diseased emphysematous tissue that is functionally useless. Surgeons--removing approximately 20-30% of each lung--capitalize on the heterogeneity of emphysema in which lesions are usually more severe at the apices and less severe at the lung bases. During the course of surgery, one lung is continually ventilated while the lumen of the contralateral lung is clamped. Subsequently, normal areas of lung deflate as blood flows past the alveoli and resorbs oxygen, while emphysematous portions of the lung with less blood flow and reduced surface area remain inflated and are targeted for resection. LVRS is believed to improve function of the lung by restoring pulmonary elastic recoil and correcting over-distention of the thorax and depression of the diaphragm. The result? Some patients experience better respiratory mechanics and relief from severe dyspnea .

The reported benefits of LVRS in some patients include improved airflow, functional capacity and quality of life. It is unclear which patients benefit most from the surgery. As in any major thoracic procedure, there are risks. The duration of the improvement in lung function following resection is not yet completely known, but there is a suggestion that lung function begins to decline two years after LVRS.

Despite optimistic reports, the morbidity, mortality and financial costs associated with LVRS appear to be high, indicating the need for further studies of both short and long term outcomes to truly evaluate the efficacy of LVRS and which patients it benefits the most. The National Emphysema Treatment Trial fills this need.

The National Emphysema Treatment Trial (NETT)

The National Emphysema Treatment Trial is funded and coordinated by the Health Care Financing Administration (Medicare) and the National Heart, Lung and Blood Institute, and is the first controlled, randomized long-term study of the safety, benefits and post-operative costs of LVRS.

Patients--who meet a specific set of criteria--are being enrolled in NETT to determine who will benefit most from LVRS. All patients receive optimal treatment including pulmonary rehabilitation, medications, self-management information and exercise training and are then randomized to receive either continuing medical treatment or continuing medical treatment and LVRS. Follow-up visits are required at 6, 12, 18, 24, 36 and 48 months. The first patient was enrolled at National Jewish Medical and Research Center in October 1997.

The following is a partial list of inclusion criteria for NETT:

• History and physical examination consistent with emphysema
• Non-smoker for four months prior to initial interview with continued non-smoking for duration of screening
• Post-bronchodilator Total Lung Capacity > 110% predicted
• Post-bronchodilator Residual Volume > 150% predicted
• Diffusing capacity < 70% predicted
• High resolution chest CT scan evidence of moderate to severe bilateral, heterogeneous or homogeneous emphysema

• Body mass index > 31.1 kg/m2 (males) or 32.3 kg/m2 (females)
• Unplanned weight loss > 10% of usual weight in prior 90 days
• Pulmonary hypertension (mean PPA greater than or equal to 35 mmHg or peak systolic PPA greater than or equal to 45 mmHg)
• Clinically significant bronchiectasis, i.e., recurrent pulmonary infections with sputum > 3 tablespoons per day
• Previous laser or lung volume reduction surgery
• Previous coronary artery bypass surgery
• Congestive heart failure within six months of interview and ejection fraction < 45%
• Myocardial infarction within six months of interview and ejection fraction < 45%
• Oxygen requirement exceeding 6 L/min to keep saturation > 90% during exercise
• Any disease or condition which may interfere with completion of tests, therapy or follow-up testing

Medical information on potential NETT patients is requested from the referring physician and includes spirometry, chest x-ray, EKG and medical history. Candidates are then required to complete extensive additional testing.

Other NETT clinical centers include Baylor College of Medicine, Brigham and Women's Hospital, Cedars-Sinai Medical Center, Cleveland Clinic Foundation, Columbia University, Duke University Medical Center, Mayo Clinic, Ohio State University, Saint Louis University, Temple University, University of California/San Diego Medical Center, University of Maryland at Baltimore, University of Michigan, University of Pennsylvania Medical Center, University of Pittsburgh, University of Washington and Washington University.

References

Make BJ, Fein AM. Is Volume Reduction Surgery Appropriate in the Treatment of Emphysema? No. Am J Respir Crit Care Med Vol 153:1205-1207, 1996.

Fein AM, Branman SS, Casaburi, R, Irvin CG, Make BJ, Rodarte JR, Solway J. Lung Volume Reduction Surgery. Am J Respir Crit Care Med Vol 154:1151-1152, 1996.

Barry J. Make, M.D.
Senior Faculty Member, Pulmonary Division
Director of Pulmonary Rehabilitation, Emphysema Program and Respiratory Care
National Jewish Medical and Research Center
Professor, Department of Medicine, UCHSC

The Medical Scientific Update, a publication of the Office of Professional Education at National Jewish, provides information to physicians about our clinical and research programs in allergic, respiratory, and immune system disorders. The Web edition of the Medical Scientific Update published by the Gerald Tucker Memorial Medical Library.