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J Thorac Cardiovasc Surg 2004;127:829-835
© 2004 The American Association for Thoracic Surgery
General thoracic surgery |
a Division of Cardiothoracic Surgery, Department of Surgery,, Washington University School of Medicine, St Louis, Mo, USA
b Division of Pulmonary and Critical Care Medicine and the Division of General Medical Sciences,, Washington University School of Medicine, St Louis, Mo, USA
c Department of Internal Medicine, Washington University School of Medicine, St Louis, Mo, USA
d Jacqueline Maritz Lung Center at Barnes-Jewish Hospital, St Louis, Mo, USA
Read at the Eighty-third Annual Meeting of The American Association for Thoracic Surgery, Boston, Mass, May 4-7, 2003.
Received for publication April 26, 2003; revisions received August 26, 2003; accepted for publication September 9, 2003.
* Address for reprints: Bryan F. Meyers, MD, One Barnes-Jewish Plaza, 3108 Queeny Tower, St Louis, MO 63110, USA
meyersb{at}msnotes.wustl.edu
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Abstract |
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METHODS: We reviewed 280 patients who underwent bilateral lung volume reduction surgery at our institution between January 1993 and December 2001. All patients met our selection criteria, including heterogeneous distribution of emphysema. Of these 280 patients, 20 patients had both a preoperative forced expiratory volume in 1 second and a diffusing capacity of carbon monoxide of less than or equal to 20% of the predicted normal values, thus meeting one National Emphysema Treatment Trial criterion for high risk. Outcomes of the 20 patients were assessed through 5 years after the operation. The survival of the 20 patient cohort was compared with that of the 260 patients not meeting the National Emphysema Treatment Trial high-risk criterion.
RESULTS: Ninety-day operative mortality included 1 (5%) patient. In all patients the forced expiratory volume in 1 second increased from 0.46 L (17%) to 0.78 L (32%), a 73% change; the diffusing capacity of carbon monoxide increased from 16% to 27%, a 70% improvement; residual volume decreased from 6.33 L (305%) to 4.26 L (205%), a 33% improvement; and room air arterial partial pressure of oxygen increased from 55 mm Hg to 64 mm Hg. Kaplan-Meier 5-year survivals did not differ between the high-risk and non–high-risk groups.
CONCLUSIONS: Patients with a forced expiratory volume in 1 second and a diffusing capacity of carbon monoxide of 20% or less of predicted value might experience improvements in lung function, exercise tolerance, and quality of life with acceptable morbidity and mortality after lung volume reduction surgery.
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| See related editorial on page 631.
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The concept of lung volume reduction as a therapy to reduce dyspnea in patients with emphysema is credited to Brantigan and Mueller.1 Although the initial procedure failed to gather acceptance by surgeons, it was rediscovered and resuscitated by Cooper and colleagues2 nearly 4 decades later. There are now long-term results available on a substantial number of patients, and the conclusion has been that tangible benefit with acceptable risk is available to well-selected patients.3 There has been no shortage of controversy associated with this operation since its reintroduction in 1995. Because of high risks and costs associated with the widespread application of the operation in 1995, Medicare funding for the operation was stopped as of 1996. The National Heart, Lung, and Blood Institute of the National Institutes of Health was tasked with devising a clinical trial to evaluate the benefit of the procedure. The result of this effort, the National Emphysema Treatment Trial (NETT), began enrolling patients in 1999.4 The NETT investigators provided a preliminary report describing their identification of a high-risk subset of patients for whom a high risk of surgical intervention seemed to outweigh a low functional benefit.5
The NETT high-risk subgroup consisted of patients with a very low forced expiratory volume in 1 second (FEV1) in combination with a very low diffusing capacity for carbon monoxide (DLCO), a diffuse pattern of emphysema on chest computed tomography, or both. The high mortality seen in such patients in the NETT prompted a modification of the protocol to exclude from randomization any patients meeting these criteria. As a direct result of the publicity surrounding the NETT report of the high-risk cohort, we reviewed our own results in patients meeting the NETT high-risk criteria. Because we had excluded patients with diffuse emphysema from lung volume reduction surgery (LVRS) from the beginning, the NETT high-risk classification criterion that applied to our patients was the combination of an FEV1 of not more than 20% of predicted value and a DLCO of not more than 20% of predicted value. The specific objective was to assess the appropriateness of excluding patients with both FEV1 and DLCO of not more than 20% of predicted value from receiving LVRS.
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Methods |
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Details of the selection process have been reported previously.12 Critical selection criteria are marked hyperinflation of the chest and sufficient regional variation in the severity of the emphysema to provide target areas of useless lung accessible to surgical resection. The degree of regional parenchymal destruction is analyzed by using standardized computerized tomography of the chest, and the regional distribution of function is assessed by means of radionuclide ventilation-perfusion lung scanning. Thoracic distention is evaluated by means of chest radiography, and lung volumes are determined with plethysmography. No special screening was applied to the patients in this report because this cohort of 20 patients was identified retrospectively on the basis of NETT high-risk criteria.5
The initial evaluation includes physical examination, pulmonary function testing, arterial blood gas analysis (at rest with room air), 6-minute walk testing, and questionnaires assessing quality of life and dyspnea. Fifty percent of more than 800 on-site evaluations were excluded from surgical intervention. The most common reason for exclusion was lack of target areas for surgical resection (76%).3 Patients judged suitable for surgical intervention were enrolled in a preoperative pulmonary rehabilitation program, usually for 3 months (median, 97 days). Medical therapy was optimized, and dietary regimens were prescribed.
Pulmonary function tests were performed with a Medgraphics System 1085 (Medical Graphics Corp, St Paul, Minn) before and after administration of aerosolized albuterol, and the best values for forced vital capacity and FEV1 were chosen for the data analysis. Lung volumes were determined by means of plethysmography, and diffusion capacity for carbon monoxide (DLCO) was measured by using the single-breath technique. During the 6-minute walk test, supplemental oxygen was administered through a nasal cannula as needed to maintain the arterial oxygen saturation at 90% or better.
Quality of life was assessed by using the Medical Outcomes Study 36-Item Short-Form (SF-36) Health Survey. We specifically report the SF-36 Physical Component Summary Scale (PCS) and the SF-36 Mental Component Summary Scale (MCS), the Physical Functioning (PF) scale, and the response to a single question about health now compared with 1 year prior. The PCS, MCS, and PF scores can range from 0 (worst) to 100 (best). The PCS and MCS scores are standardized so that the general population has a mean ± SD score of 50 ± 10. A 10-point change in the PF score and a 3-point change in the PCS score are considered clinically important. Patients were asked to assess their own satisfaction with the operation on the basis of how they felt at present to measure preoperative patient satisfaction. There are 5 possible responses: poor, fair, good, very good, and excellent. All tests were performed during periods of clinical stability.
A complete battery of pulmonary function tests was performed at our institution during the postoperative follow-up periods; an abbreviated battery of tests (FEV1 and RV) from other institutions was also used. Follow-up evaluation also included arterial blood gases on room air, a 6-minute walking test, and completion of dyspnea and quality-of-life questionnaires.
Surgical technique
All procedures were performed through a median sternotomy. The operative technique has evolved very little since our initial experience. In 1 of 20 patients in this report, lobar destruction and complete fissures led to a complete lobectomy rather than wedge excision of lung tissue. Two chest tubes were placed on each side. The pleural space was closed bilaterally before closure of the sternotomy. The chest tubes were brought out through the upper abdomen in a subxiphoid position.
All patients were extubated in the operating room or shortly thereafter in the postanesthesia recovery area. One patient required immediate reintubation and spent the night attached to a ventilator, with successful extubation on the following morning. The surgical, anesthetic, and postoperative care techniques have been previously described.2,9,13
Statistical analysis
Descriptive statistics were expressed as means ± SD unless otherwise specified. Categorical data were expressed as counts and proportions. Kaplan-Meier estimates were used to depict survival. The log-rank test was used to compare survival between groups. Patients who had lung transplantation after LVRS were censored for all observations at or beyond the time of transplantation. All data analysis was performed with Systat (Systat 10.0 for Windows; SPSS Inc, Chicago, Ill).
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1-antitrypsin deficiency emphysema, and one patient had lower-lobe predominance with lower-lobe target areas. Seven of the 20 patients used chronic oral corticosteroids before the operation (Table 1).
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Discussion |
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20% of the predicted normal values) patients might experience improvements in lung function, exercise tolerance, and quality of life with acceptable morbidity and mortality after LVRS. There have been many published reports describing the outcomes after lung volume reduction, with the majority describing a postoperative mortality of 3% to 8%. The health technology assessment report that led to the cessation of reimbursement by the Health Care Financing Administration reported a mortality of 6%.14 It is typically accepted that properly selected patients will experience a perioperative mortality risk of less than 10%, with many high-volume centers reporting mortality clustered in the 4% to 6% range.2,15-19
Randomized controlled trials (RCTs) have advantages over individual case series by avoiding selection and reporting bias. An important contribution to knowledge about a procedure takes place when an RCT is interrupted or altered because of findings by a data and safety monitoring board. Two such trials have reported the need to restrict enrollment criteria during the trial because of an excessive observed mortality. The Geddes trial changed the enrollment criteria after 15 enrolled patients exhibited excessive risk of death. The trial subsequently excluded 2 groups: patients with DLCO values of less than 30% of predicted value and patients unable to achieve a specified minimum threshold in a pre-enrollment exercise evaluation.20 The second RCT to adjust enrollment criteria occurred when the NETT trial acknowledged an excessive mortality in 2 subgroups of patients randomized to surgical intervention: patients with a very low FEV1 and homogeneous emphysema and patients with a very low FEV1 and a low DLCO.5
The findings in both of those trials corroborated observations from the early LVRS experience, and the statistically sound nature of a prospectively randomized trial has added additional weight of evidence to the belief that such patients were poor candidates. Because we have excluded patients with a homogeneous pattern of emphysematous destruction, our series cannot address the issue of whether homogeneous destruction is an absolute or relative contraindication. The NETT high-risk article identified 140 (13.6%) of 1033 patients as belonging to the high-risk group. Close analysis of the NETT data shows that 46 (66%) of 70 patients randomized to surgical intervention and 48 (69%) of 70 patients randomized to medical therapy were classified as having homogeneous emphysema and would therefore not be representative of patients in our series. Furthermore, the deaths reported in the NETT article for patients with LVRS with heterogeneous emphysema and both FEV1 and DLCO values of not more than 20% of predicted value are 3 (12.5%) deaths in 24 patients. This death rate is not significantly different from that presented in the current article. The relative risk of early death in comparable patients in the NETT article versus our own results is 1.08 (95% confidence interval, 0.91-1.30). It seems that the apparent differences in outcome between the NETT high-risk patients and our own patients declared high risk by using the NETT criteria disappear when the patients with homogenous emphysema are excluded from the analysis.
The NETT high-risk patients fell into 2 subgroups, both of which had an FEV1 of less than or equal to 20% of predicted value. The first group had a homogeneous pattern of emphysematous destruction (n = 94), and the second group had a DLCO of less than or equal to 20% of predicted value (n = 87). However, when the outcomes were reported as survival curves, the results of each subgroup were displayed without emphasizing the substantial overlap (n = 41) of patients who met all 3 criteria. Rather, 2 overlapping groups of patients were displayed: all patients with FEV1 values of not more than 20% and homogeneous emphysema and all patients with DLCO and FEV1 values both not more than 20%. In the overlap group patients with all 3 characteristics are reported twice because they appear in each of the previous groups. The true 2-factor groups were never described apart from the very high-risk patients in the overlap group.
We do agree that patients with severe functional impairment, as reflected by both an FEV1 and a DLCO of 20% or less of predicted value might still represent relatively high-risk patients. The small number of patients presented here makes the mortality estimate of 5% susceptible to large fluctuations in the event of 1 or 2 deaths in future patients meeting this criterion. The median hospital stay was 3 days longer for the patients in this current report than for the recently reported larger cohort from which they were drawn.3 It is also important to point out that the rates of prolonged air leak and pneumonia were higher in these patients than in the larger cohort, although these differences do not reach statistical significance. It is our habit to give thorough counseling to such patients about the possibility of lung transplantation as an alternative to lung volume reduction. Patients with severe destruction and homogeneous emphysema are steered preferentially toward transplantation because of our bias that LVRS requires heterogeneous target areas to be effective.
The DLCO determination does have limitations in its role as an exclusionary criteria for LVRS. One such limitation is the fact that many physiologic processes can lead to a low DLCO. For instance, it might result from combinations of extensive loss of diffusing surface caused by emphysematous destruction of alveolar walls and capillaries, thickening of the alveolar-capillary interface, reduction of red cells in capillaries, and marked hypoventilation of potentially functional pulmonary parenchyma. It has been the authors' belief that in heterogeneous emphysema compression of the spared lung by the diseased areas leads to focal hypoventilation and underestimation of the DLCO. Recruitment of capillaries after LVRS might account for an increase in DLCO after resection of 20% to 30% of the lung parenchyma.
Another limitation of the DLCO is the problem of reproducibility. To evaluate the test-to-test variability of measuring the DLCO, we performed an exploratory analysis of our preoperative patients before and after pulmonary rehabilitation. In the initial evaluations of 280 patients undergoing LVRS, 63 (23%) had FEV1 values of less than 20%, and 34 (12%) had DLCO values of less than 20%, with 13 (5%) patients meeting both criteria. However, after rehabilitation and immediately before the operation, 69 (25%) patients had FEV1 values of less than 20%, and 40 (14%) had DLCO values of less than 20%, with 20 (7%) patients meeting both criteria. The fact that the cohort described in this article could vary from 13 to 20 patients on the basis of measurements taken a few weeks apart suggests that a fixed cut-off point of DLCO or FEV1 applied to the selection criteria for LVRS would be inappropriate.
A limitation of this study is the retrospective nature of the analysis. We did not collect a full set of initial data on all patients referred for consideration for LVRS, and as a result, we have no ability to estimate what fraction of all patients with the criteria in question (FEV1 and DLCO 20% of predicted value) were actually selected for surgical intervention. Presumably, as one or more relative contraindications are encountered, there must be other favorable criteria, such as youth or motivation, that tip the decision toward acceptance for LVRS. We performed an exploratory analysis to see whether the patients undergoing LVRS in our series had some evidence of selection bias in the form of favorable measurements on other known risk factors, such as sex, age, and exercise capability. These data (not shown) suggested an overrepresentation of female patients but did not otherwise support the hypothesis that the patients in this report had favorable observations on other covariables to explain their selection or their favorable outcome. Furthermore, there are no data about patients selected with such criteria who might have embarked on the preoperative rehabilitation and either failed to complete it or declined during that period to the extent that they were rendered unacceptable for the risk of surgical intervention.
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