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Lung volume reductionReviewer: Andrew Maslow, MD
Reviewer: Feroze Mahmood, MD
Emphysema causes obstruction to expiratory flow, air-trapping, increased ratio of residual volume to total lung capacity, and reduced exercise capacity.1 This limits the function of more normal lung tissue and reduces pulmonary reserve. Although rehabilitation and cessation of tobacco abuse benefits all patients, many require more aggressive interventions, including lung transplantation. Due to lack of available donors, or ineligibility for lung transplantation, Lung Volume Reduction Surgery (LVRS) has garnered significant interest. Resection of 20-30% of the most abnormal lung tissue potentially allows remaining lung tissue room to expand and function more normally. Initial enthusiasm was tempered by poor outcomes, high mortality, and increased costs. The National Emphysema Treatment Trial (NETT) assessed the benefits of LVRS in a randomized study, which included 1,218 patients from 17 surgical centers.2-4 All patients were evaluated at baseline and throughout a two-three year followup using health related questionnaires, six minute walk tests (6MWT), energy expenditure (W), pulmonary function tests, arterial blood gas analysis, computed tomography, and ventilation and perfusion scans. Rehabilitation included behavioral modifications, improvements in nutrition, adjustment of medical therapies, and exercise. After completion of rehabilitation, patients were randomized to continue rehabilitation alone, or in combination with LVRS. In 2003, the results of the NETT study were reported.3-5 Of the 1,218 patients enrolled in pulmonary rehabilitation and subsequently evaluated, 608 were randomized to surgical therapy and 610 to medical therapy alone. Of the surgical group, 406 underwent median sternotomy and 174 video-thoracoscopy. Twenty-one declined surgery and seven were found unsuitable. Thirty-three patients in the medical group underwent LVRS outside the study, and 15 received lung transplantation. Air leaks greater than seven days (45.2%) was the most common postoperative problem.6 Seven percent of patients required reintubation.6 No significant outcome differences were found between median sternotomy and video-thoracoscopy, although the total hospital and six month costs were lower for thoracoscopy patients.4 The 90-day mortality for surgical and medical groups was 7.9% and 1.3%, respectively.3 At two and one-half years, mortality was similar. For survivors, exercise capacity at six, 12, and 24 months was significantly better (approximately 400 meters versus 340 meters) for surgical patients. When 140 high-risk patients were excluded from the data, the 30 and 90-day surgical mortality was 2.2% and 5.2% compared to 0.2% and 1.5% for medical patients. For survivors, quality of life questionnaires and exercise capacity after two years were significantly better for surgical patients. Subsets, depending on preoperative distribution of emphysematous lung (upper versus lower lobes, homogenous versus heterogenous distribution), and preoperative exercise capacity (high versus low), experienced different outcomes. Low exercise capacity was defined as workloads less than 25 W for women and less than 40 W for men. Across all subsets, patients with heterogenous distribution of emphysema had better outcome than patients with homogenous patterns. Patients with upper lobe disease distribution and low exercise capacity had superior outcome and greater functional improvement than patients with upper lobe distribution and higher exercise capacity, which was in turn better than non-upper lobe distribution and lower exercise capacity. For patients with non-upper lobe distribution and higher exercise capacity, there was an increased mortality associated with surgery. In 2001, the NETT identified patients with an FEV1 less than 20% of predicted and either non-heterogeneous distribution of emphysema, or a DLCO less than 20% as high-risk. These patients experienced a 16% 30-day mortality compared to 0% for the non-surgical group, and little functional improvement six months after surgery.2 Outcome differences persisted until 48 months after, at which time surgical and medical groups were similar. However, Meyers et al, separately, reported on 20 patients with an FEV1 less than 20% of predicted, DLCO less than 20% of predicted, and heterogenous distribution of emphysema.7 There was one perioperative death. Short and long term function, and outcome, were significantly improved (FEV1 0.46L (17%) to 0.78L (32%); DLCO 16% to 27%; RV 6.33L (305%) to 4.26 L (205%); Pa02 55 mmHg to 64 mmHg). Improvements were comparable to non high-risk patients and persisted three-four years after randomization, suggesting that high-risk patients with heterogenous disease may benefit from LVRS.7 Patients with a-1 Antitrypsin Deficiency (ATD) are more likely to exhibit homogenous distribution of emphysema. However, it is unnecessary to blanketly exclude all patient with ATD, since many have similar heterogenous upper lobe distribution consistent with "smoker's emphysema". In one study of 21 patients with ATD,13 had heterogenous patterns, while five displayed a mixed pattern, and three had homogenous distribution.8 The two and three and one-half year survival was 66% and 33%, respectively. For the survivors, there were significant benefits, which persisted for two-three years. Improvement, however, was isolated to those with heterogenous patterns of emphysema. The costs of medical and surgical therapies were also compared initially, at three years, and then projected to five and 10 years.9 Cost analysis included costs of each treatment, medications, subsequent hospitalizations, and cost of evaluations and treatment. While initial costs and costs six months after randomization were significantly greater for the surgical group, these differences were minimal, if not better, for the surgical group at two years. The cost of the second year was lower for surgical patients. Three years after randomization, there were no cost differences between the two groups. Costs were significantly better for surgical patients with upper lobe distribution of emphysema and lower preoperative exercise capacity. Long-term benefits of LVRS, via median sternotomy, were also evaluated.6 Survival at one, three, and five years was 94%, 84%, and 68%, respectively. More than 50% of deaths were due to respiratory failure. Functional capacity was improved for the surgical group three years out, but returned toward baseline and was comparable to the non-surgical group between three and five years. In summary, LVRS shows significant benefits for patients with heterogenous distribution of emphysema primarily located in the upper lobe, and preoperative low exercise capacity. Whether or not a low DLCO (less than 20%), when combined with an FEV1 less than 20% is prohibitive or not remains controversial. However, the combination of a homogenous pattern and a low FEV1 may predict an excessive surgical mortality, without apparent clinical benefit. The experience of several centers strongly encourages the use of preoperative pulmonary rehabilitation in order to improve functional status, which is especially important prior to surgery. Finally, the benefits after LVRS may not last greater than two to three years, however, during this time, select patients may experience significant clinical benefits, and allow safe bridging toward lung transplantation, if necessary. References
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