Thoracoscopic laser bullectomy: a prospective study with three-month results

Lung transplantation and lung volume reduction surgery

Since the publication of the last edition of the Handbook of Physiology, lung transplantation has become widely available, via specialized centers, for a variety of end-stage lung diseases. Lung volume reduction surgery, a procedure for emphysema first conceptualized in the 1950s, electrified the pulmonary medicine community when it was rediscovered in the 1990s. In parallel with their technical and clinical refinement, extensive investigation has explored the unique physiology of these procedures. In the case of lung transplantation, relevant issues include the discrepant mechanical function of the donor lungs and recipient thorax, the effects of surgical denervation, acute and chronic rejection, respiratory, chest wall, and limb muscle function, and response to exercise. For lung volume reduction surgery, there have been new insights into the counterintuitive observation that lung function in severe emphysema can be improved by resecting the most diseased portions of the lungs. For both procedures, insights from physiology have fed back to clinicians to refine patient selection and to scientists to design clinical trials. This section will first provide an overview of the clinical aspects of these procedures, including patient selection, surgical techniques, complications, and outcomes. It then reviews the extensive data on lung and muscle function following transplantation and its complications. Finally, it reviews the insights from the last 15 years on the mechanisms whereby removal of lung from an emphysema patient can improve the function of the lung left behind.

The National Emphysema Treatment Trial: summary and update

Surgery for severe emphysema involves a cohort of patients who are already at risk for increased perioperative morbidity and mortality. Through the careful screening and selection process, improved intraoperative techniques and rigorous attention to postoperative care, the NETT managed to yield acceptable improvements in survival and functional outcomes in this fragile patient cohort and these benefits were sustained over the long-term. Identification of the characteristics associated with a higher risk of death has provided tangible patient selection criteria for the ongoing application of LVRS. Because the NETT was such a large-scale study, the protocols that were developed had to be standardized across several centers. This produced reliable and reproducible standards for evaluation and treatment that can be applied to the surgical treatment of emphysema. When considering these criteria, although individualized patient selection is important, only patients with upper-lobe predominant disease on chest CT and possibly those with non-upper-lobe predominant disease who also have low baseline exercise capacity are appropriate candidates for LVRS. Expectedly, questions remain regarding the exact mechanism whereby the benefits derived from LVRS are obtained. Additionally, the benefit of LVRS in patients with heterogeneous but non-upper-lobe predominant disease remains to be further elucidated. In spite of the limitations of the study, the NETT, through a tremendous coordinated effort, provided valuable outcomes data, answered the pressing questions regarding lung volume reduc-tion surgery that existed at the time, and provided valuable insight into other facets of emphysema physiology and management through direct observation. Based on the NETT findings, in November 2003, CMS published criteria for expanded coverage for LVRS to include non-high-risk patients who demonstrated either upper-lobe predominant emphysema, or non-upper-lobe predominant emphysema and low baseline exercise capacity and who met the screening guidelines.29 This study not only provided data regarding the clinical efficacy of LRVS, but it was instrumental in determining health policy guidelines for the surgical management of emphysema.

Lung volume reduction surgery: technique, operative mortality, and morbidity

The objective of lung volume reduction surgery (LVRS) is the safe, effective, and durable palliation of dyspnea in appropriately selected patients with moderate to severe emphysema. Appropriate patient selection and preoperative preparation are prerequisites for successful LVRS. An effective LVRS program requires participation by and communication between experts from pulmonary medicine, thoracic surgery, thoracic anesthesiology, critical care medicine, rehabilitation medicine, respiratory therapy, chest radiology, and nursing. The critical analysis of perioperative outcomes has influenced details of the conduct of the procedure and has established a bilateral, stapled approach as the standard of care for LVRS. The National Emphysema Treatment Trial (NETT) remains the world's largest multi-center, randomized trial comparing LVRS to maximal medical therapy. NETT purposely enrolled a broad spectrum of anatomic patterns of emphysema. This, along with the prospective, audited collection of extensive demographic, physiologic, radiographic, surgical and quality-of-life data, has positioned NETT as the most robust repository of evidence to guide the refinement of patient selection criteria for LVRS, to assist surgeons in providing optimal intraoperative and postoperative care, and to establish benchmarks for survival, complication rates, return to independent living, and durability of response. This article reviews the evolution of current LVRS practice with a particular emphasis on technical aspects of the operation, including the predictors and consequences of its most common complications.

Lessons from the National Emphysema Treatment Trial

Medicare coverage for lung volume reduction surgery has been approved recently by the Centers for Medicare and Medicaid Services for the treatment of severe emphysema. The scientific basis for this approval stems largely from findings of the National Emphysema Treatment Trial (NETT). The purpose of this article is to review the contributions of the NETT to the management of chronic obstructive pulmonary disease.

Lung volume reduction surgery for emphysema: What the radiologist needs to know

Imaging plays a pivotal role in the selection of patients for the surgical treatment of emphysema. In this article, the imaging features of emphysema are reviewed along with the surgical options for treatment. Particular emphasis is given to lung volume reduction surgery as this technique has gained wide acceptance within the thoracic surgical community in recent years. Radiologists need to have an understanding of which patients may be potentially suitable for this technique.

Historical perspectives

The history of surgery for emphysema is filled with numerous surgical attempts to improve the disorder. Although many of these procedures have proved to be futile, lung volume reduction surgery has now arrived. This article outlines the progression of procedures and the logic for which they were thought to be of benefit.

Results of lung volume reduction surgery for emphysema

LVRS provides an exciting opportunity for palliation of symptoms and improvement in quality of life for patients who have severe end-stage emphysema. Because no medical therapy has been able to improve pulmonary function or reverse the inexorable decline of breathless patients who have emphysema, this opportunity to improve lung function and quality of life is one of the most innovative additions to thoracic surgery since the first successful lung transplant procedure 20 years ago. Although initial short-term, case-controlled surgeries were criticized because of incomplete and short follow-up care, substantial long-term data now exist to support the use of LVRS for select patients who have severe emphysema. Patients who have upper lobe predominant disease or low exercise capacity are more likely to have a benefit in exercise capacity and quality of life after LVRS. Selected patients who have upper lobe emphysema and poor exercise capacity are also more likely to have improved survival after LVRS. The individual contributions by the large number of investigators pioneering LVRS development, along with the collective contributions of the NETT investigators, have propelled the knowledge surrounding LVRS far beyond that of any similar new technology or procedure in its adolescence.

Patient selection for lung volume reduction surgery

LVRS represents a valid surgical option for a limited number of patients who have symptomatic emphysema. The results of recent controlled studies have provided a realistic view of LVRS outcomes and yielded a validated algorithm for selection of optimal candidates for surgery. Furthermore, the NETT has provided simultaneously collected cost data that have provided a unique view of the costs and benefits of LVRS in patients who have advanced emphysema. Additional data collection will better define the long-term benefits of such surgical intervention in patients who have COPD.

Technical issues and controversies in lung volume reduction surgery

The goal of lung volume reduction surgery (LVRS) is to safely palliate dyspnea in patients suffering from emphysema. Successful LVRS demands attention to the details of patient selection, preoperative preparation, intraoperative anesthetic and surgical technique and multidisciplinary postoperative care. Expertise in and effective communication between pulmonary medicine, thoracic surgery, thoracic anesthesia, pain management services, critical care medicine, respiratory therapy and rehabilitation medicine are vital components to any LVRS program. In experienced centers, bilateral approaches yield nearly twice the physiologic benefit to unilateral LVRS without adversely affecting operative morbidity or mortality. Current practice favors stapled resection over laser ablation to achieve volume reduction. Controversy persists regarding open versus video-assisted operations. The cost-effective need for and choice of materials to buttress staple-lines to reduce the incidence of postoperative air leak have yet to be defined. Ongoing multi-center, randomized, controlled trials should define the utility and durability of LVRS for appropriately selected patients and resolve some of the residual technical controversies. Therapeutic innovations may further reduce the invasiveness of lung volume reduction strategies and allow a more tailored approach to palliate patients with moderate to severe emphysema.

Patients at high risk of death after lung-volume-reduction surgery

BACKGROUND

Lung-volume-reduction surgery is a proposed treatment for emphysema, but optimal selection criteria have not been defined. The National Emphysema Treatment Trial is a randomized, multicenter clinical trial comparing lung-volume-reduction surgery with medical treatment.

METHODS

After evaluation and pulmonary rehabilitation, we randomly assigned patients to undergo lung-volume-reduction surgery or receive medical treatment. Outcomes were monitored by an independent data and safety monitoring board.

RESULTS

A total of 1033 patients had been randomized by June 2001. For 69 patients who had a forced expiratory volume in one second (FEV1) that was no more than 20 percent of their predicted value and either a homogeneous distribution of emphysema on computed tomography or a carbon monoxide diffusing capacity that was no more than 20 percent of their predicted value, the 30-day mortality rate after surgery was 16 percent (95 percent confidence interval, 8.2 to 26.7 percent), as compared with a rate of 0 percent among 70 medically treated patients (P<0.001). Among these high-risk patients, the overall mortality rate was higher in surgical patients than medical patients (0.43 deaths per person-year vs. 0.11 deaths per person-year; relative risk, 3.9; 95 percent confidence interval, 1.9 to 9.0). As compared with medically treated patients, survivors of surgery had small improvements at six months in the maximal workload (P= 0.06), the distance walked in six minutes (P=0.03), and FEV1 (P<0.001), but a similar health-related quality of life. The results of the analysis of functional outcomes for all patients, which accounted for deaths and missing data, did not favor either treatment.

CONCLUSIONS

Caution is warranted in the use of lung-volume-reduction surgery in patients with emphysema who have a low FEV1 and either homogeneous emphysema or a very low carbon monoxide diffusing capacity. These patients are at high risk for death after surgery and also are unlikely to benefit from the surgery.

Underestimation of mortality following lung volume reduction surgery resulting from incomplete follow-up

STUDY OBJECTIVES

Incomplete follow-up can bias interpretation of data that are collected in longitudinal studies. We noted that many patients failed to return for follow-up in a study of effect of lung volume reduction surgery (LVRS) on quality of life (QOL). Accordingly, we designed this investigation to determine the reasons patients dropped out, and to assess differences between those who continued in the study (attendees) and those who did not (nonattendees).

DESIGN

Telephone survey.

SUBJECTS

Patients with advanced emphysema who had undergone LVRS and had previously agreed to participate in a longitudinal QOL study.

RESULTS

No differences were found with regard to age, gender, preoperative pulmonary function, or oxygen use between attendees and nonattendees. Long-term mortality in nonattendees (27%) was considerably greater than that seen in attendees (3%, p < 0.05). Distance from the hospital, financial burden, and living out of the region were the most common reasons cited by surviving nonattendees for their failure to return for follow-up.

CONCLUSIONS

Studies reporting the long-term mortality after LVRS can be biased in the direction of underestimating the true value if they are compromised by incomplete follow-up.

Lung volume reduction surgery for emphysema

Over the past decades, extensive literature has been published regarding surgical therapies for advanced COPD. Lung-volume reduction surgery would be an option for a significantly larger number of patients than classic bullectomy or lung transplantation. Unfortunately, the initial enthusiasm has been tempered by major questions regarding the optimal surgical approach, safety, firm selection criteria, and confirmation of long-term benefits. In fact, the long-term follow-up reported in patients undergoing classical bullectomy should serve to caution against unbridled enthusiasm for the indiscriminate application of LVRS. Those with the worst long-term outcome despite favourable short-term improvements after bullectomy have consistently been those with the lowest pulmonary function and significant emphysema in the remaining lung who appear remarkably similar to those being evaluated for LVRS. With this in mind, the National Heart, Lung and Blood Institute partnered with the Health Care Finance Administration to establish a multicenter, prospective, randomized study of intensive medical management, including pulmonary rehabilitation versus the same plus bilateral (by MS or VATS), known as the National Emphysema Treatment Trial. The primary objectives are to determine whether LVRS improves survival and exercise capacity. The secondary objectives will examine effects on pulmonary function and HRQL, compare surgical techniques, examine selection criteria for optimal response, identify criteria to determine those who are at prohibitive surgical risk, and examine long-term cost effectiveness. It is hoped that data collected from this novel, multicenter collaboration will place the role of LVRS in a clearer perspective for the physician caring for patients with advanced emphysema.

Effects of Nd:YAG laser irradiation on morphometry and lung function in elastase-induced emphysema in rats

BACKGROUND & OBJECTIVE

Although thoracoscopic laser ablation therapy has been hailed as an effective surgical treatment for diffuse emphysema, no one has as yet made an in-depth study of the efficacy of this treatment. This investigation was undertaken to research the effects of laser pneumoplasty on an animal model of emphysema.

STUDY DESIGN/MATERIALS AND METHODS

Eight weeks after elastase treatment, the rats' left lungs were irradiated using contact Nd:YAG laser. Pulmonary function tests were performed 4 weeks after irradiation and the lungs were prepared for histologic examination.

RESULTS

Dense fibrous scars beneath the pleura were observed at 4 weeks after irradiation. Although mean linear intercept values of irradiated lungs were not much lower than those in the non-irradiated elastase-treated group, laser irradiation caused a significant decrease in lung volume. While there was no significant difference in quasistatic compliance, elastic recoil pressure of the lung increased to control levels at total lung capacity volume.

CONCLUSION

We conclude that laser therapy does not cause normalization of compliance, or improvement in the deeper part of the emphysematous lung, but rather a peripheral volume reduction and "encasement effect" on the lungs as a result of fibrotic scars.

Short- and long-term results after lung volume reduction surgery

Lung volume reduction surgery (LVRS) is a palliative surgical procedure for patients with severe emphysema. Resection of nonfunctional emphysematous lung tissue has been reported to relieve breathlessness and to improve quality of life for many patients by improving lung elastic recoil, respiratory muscle function, and ventilation-perfusion matching. However, the risks and benefits of LVRS remain controversial, as mainly short-term data are available for carefully selected groups of LVRS patients and no prospective, randomized trials for LVRS with pulmonary rehabilitation versus optimal medical therapy plus pulmonary rehabilitation have been reported. Bilateral staple resection for LVRS appears to be superior to use of a laser or unilateral approach in the short term, but relatively little data exist on long-term outcomes. Additional clinical investigation is required to determine whether LVRS should be a widely accepted therapy for severe emphysema.

Survival after unilateral versus bilateral lung volume reduction surgery for emphysema

OBJECTIVE

Bilateral staple lung volume reduction surgery (LVRS) immediately improves pulmonary function and dyspnea symptoms in patients with advanced heterogeneous emphysema to a greater degree than do unilateral procedures. However, the long-term outcome after these surgical procedures needs to be critically evaluated. We compare 2-year survival of patients who underwent unilateral versus bilateral video-assisted LVRS in a large cohort treated by a single surgical group.

METHODS

The cases of all 260 patients who underwent video-assisted thoracoscopic stapled LVRS from April 1994 to March 1996 were analyzed to compare results after unilateral versus bilateral procedures. Overall survival was calculated by Kaplan-Meier methods; Cox proportional hazard methods were used to adjust for patient heterogeneity and baseline differences between groups.

RESULTS

Overall survival at 2 years was 86.4% (95% CI 80. 9%-91.8%) after bilateral LVRS versus 72.6% (95% CI 64.2%-81.2%) after unilateral LVRS (P =.001 for overall survival comparison). Improved survival after bilateral LVRS was seen among high- and low-risk subgroups as well. Average follow-up time was 28.5 months (range, 6 days to 46.6 months) for the bilateral LVRS group and 29.3 months (range, 6 days to 45.0 months) for the unilateral LVRS patients.

CONCLUSIONS

Comparison of unilateral versus bilateral thoracoscopic LVRS procedures for the treatment of emphysema reveals that bilateral LVRS by video-assisted thoracoscopy resulted in better overall survival at 2-year follow-up than did unilateral LVRS. This survival study, together with other studies demonstrating improved lung function after bilateral LVRS, suggests that bilateral surgery appears to be the procedure of choice for patients undergoing LVRS for most eligible patients with severe heterogeneous emphysema.

Correlation of unilateral thoracoscopic lung volume reduction with improvement in lung function and exercise performance in patients with severe pulmonary emphysema

This study was conducted to investigate the correlation of thoracoscopic lung volume reduction to changes in pulmonary function and exercise performance in patients with pulmonary emphysema. Unilateral thoracoscopic lung volume reduction treatment was performed in 30 patients with severe pulmonary emphysema. If large bullae were present, they were excised using an endoscopic stapling device, and the emphysematous pleura was contracted by neodymium:yttrium-aluminium-garnet laser to reduce the volume of nonfunctional lung air space. Pulmonary function and incremental exercise tests were performed before and at least 3 months after treatment. Follow-up functional evaluation showed a highly significant improvement in the forced expiratory volume in 1s (FEV1), forced vital capacity, static compliance, and maximal oxygen uptake. The functional residual capacity as measured by the gas dilution method (FRCgas), was unchanged; however, it was found to be decreased significantly when measured by body plethysmograph (FRCbox). Positive correlations existed between the reduction in FRCbox and the increase in FEV1 (r = 0.586, P = 0.0042) and maximal oxygen uptake (r = 0.550, P = 0.018). Pulmonary ventilation and exercise ability in patients with pulmonary emphysema were improved in a volume-dependent manner by thoracoscopic lung volume reduction. These findings indicate that patients with a preoperative trapped gas volume level exceeding 11 would be ideal candidates for thoracoscopic lung volume reduction.

Postoperative gastrointestinal complications after lung volume reduction operations

BACKGROUND

Lung volume reduction operations have been shown to improve the quality of life and functional status of some patients with end-stage emphysema.

METHODS

Because of a perceived increase in the occurrence of postoperative gastrointestinal (GI) complications, we reviewed our experience in 287 patients who had lung volume reduction operations to determine the frequency of GI complications and to identify risk factors.

RESULTS

Using a broad definition of postoperative GI complications (nausea, vomiting, abdominal distension, gastroesophageal reflux, diarrhea, constipation) there were 137 complications in 67 patients (23%). More severe GI complications (bowel ischemia, GI bleeding, perforation, ulceration, ileus, colitis, cholecystitis, pancreatitis) occurred 49 times in 27 patients (9.4%). Seven of the 27 patients required abdominal operations. Risk factors identified as predictive of severe complications include diabetes (p = 0.0003), lower preoperative hematocrit (p = 0.01), steroid use (p = 0.02), and use of parenteral meperidine analgesic (p = 0.002). Stepwise logistic regression demonstrated that diabetes was 7.02 times more likely to produce severe complications. Other risk factors included steroids (2.81), number of different pain medications (2.59), hematocrit decrease of 5% (1.96), and hematocrit decrease of 1% (1.14). In the patients with severe GI complications there were six of 27 (22%) hospital deaths compared with five of 260 (2%) in those without GI complications (p = 0.0001).

CONCLUSIONS

Severe GI complications in patients with emphysema who had lung volume reduction operations are not uncommon (9.4%) and influence the perioperative mortality rate. Heightened awareness to identified risk factors will allow earlier recognition, prevention, and perhaps decrease morbidity and mortality rates in these high-risk patients.

Surgical strategy for lung volume reduction surgery

Lung volume reduction surgery (LVRS) has been a popular procedure since the early 1990s. It appears that there has developed a consensus in the literature that the ideal patient is one with evidence of marked hyperinflation and heterogenous disease. In this patient profile, LVRS has produced excellent results with respect to lung function and improved exercise tolerance. General areas of controversy are discussed which include the role of lasers; unilateral versus bilateral procedures; the role of a staged unilateral procedure; and which surgical route is best for patients. The existing literature is reviewed on these issues.

Diffusing capacity limitations of the extent of lung volume reduction surgery in an animal model of emphysema

OBJECTIVE

The purpose of this study was to investigate in an elastase-induced emphysema rabbit model the effects of increasing resection volumes during lung volume reduction surgery on pulmonary compliance, forced expiratory air flow, and diffusing capacity to assess factors limiting optimal resection.

METHODS

Emphysema was induced in 68 New Zealand White rabbits with 15,000 units of aerosolized elastase. Static respiratory system compliance, forced expiratory flow, and single-breath diffusing capacity were measured before the induction of emphysema, after the induction of emphysema, and 1 week after a bilateral upper and middle lobe lung volume reduction operation.

RESULTS

Static respiratory system compliance with 60 mL insufflation above functional residual capacity increased with emphysema induction and then decreased progressively with resection of larger volumes of lung tissue (P =.001 by analysis of variance). Expiratory flow improved after lung resection in the rabbits with large resection volumes. In contrast, diffusing capacity tended to deteriorate with larger resection volumes (P =. 18).

CONCLUSION

Improvements in respiratory system compliance and forced expiratory flow after lung volume reduction operations may account for the improvements seen clinically. Declines in diffusing capacity with extensive lung reduction may limit the clinical benefits associated with greater tissue resection volumes. Future investigations with animal models may reveal other physiologic parameters that may further guide optimal lung volume reduction procedures.

Comparison of staged thoracoscopy and median sternotomy for lung volume reduction

BACKGROUND

Lung volume reduction operations have proved beneficial for emphysematous patients, but questions remain about the role of a unilateral procedure.

METHODS

Fifty patients were prospectively enrolled in a lung volume reduction surgery program for emphysema with staged unilateral video-assisted thoracoscopic procedures (VATS group). These patients were compared with 29 patients having bilateral lung volume reduction procedures by median sternotomy.

RESULTS

The VATS group was slightly older and had shorter 6-minute walk distances, but otherwise the two groups were similar. Hospital stays were shorter for each unilateral VATS procedure, but the total of the two hospital stays was longer than the stay for the sternotomy group (21.1 versus 14.8 days). Complications were comparable, there were no in-hospital deaths, and there was significant difference in the 1-year mortality rate (VATS, 6% versus sternotomy, 13.8%; p = 0.137). Functional test results were comparable between the groups with improvements in percent predicted forced expiratory volume in 1 second (VATS, 41%, and sternotomy, 40%), 6-minute walk distances (VATS, 48%, and sternotomy, 26%), dyspnea scores, and acid base measurements.

CONCLUSIONS

Staged lung volume reduction operations do not appear to offer any measurable advantages over a single hospitalization and bilateral lung volume reduction procedures.

Effect of lung volume reduction surgery on pulmonary diffusion capacity in a rabbit model of emphysema

BACKGROUND

While there is renewed interest in lung volume reduction surgery (LVRS) for treatment of emphysema, many aspects of the operation such as patient selection and surgical end points of excision are uncertain. We studied the effects of LVRS on measured lung volumes and diffusion capacity in an animal model to investigate optimal resection volumes.

METHODS

Emphysema was induced in 32 New Zealand white (NZW) rabbits using aerosolized elastase. Helium dilution lung volumes and single breath DLCO were measured concurrently at baseline, following induction of emphysema (preop), and 1 week postoperatively (postop) following LVRS. Bilateral upper and middle lobe stapled lung resections were performed through midline sternotomies with excision of variable amounts of lung tissue from 1.8 to 5.8 g.

RESULTS

FRC increased following induction of emphysema and decreased postoperatively. DLCO improved with increasing lung tissue resection up to 3 g of tissue and then decreased as even greater amounts were removed (r = 0.54).

CONCLUSIONS

Measured lung volumes increase with development of emphysema and appropriately decrease in response to LVRS in this rabbit model. DLCO improves with moderate resection but then decreases with excessive excision of lung quantities and may help define one physiologic operative end point. In this rabbit model, excision of approximately 30% of lung volume was optimal and prevented further decrease in diffusion capacity.

Lung volume reduction surgery has variable effects on blood gases in patients with emphysema

Most studies of bilateral lung volume reduction surgery (LVRS) report increases in arterial oxygenation (PaO2). Some suggest this results from an increased alveolar ventilation, but others imply that ventilation-perfusion heterogeneity is reduced. We measured arterial blood gases (ABGs) on air before and 3 mo following LVRS in 46 patients (61% of eligible patients), estimate the difference between alveolar and arterial O2 (AaPO2), and correlated the changes observed with preoperative ABGs, and with pre-and postoperative pulmonary function. The mean +/- SD change in PaO2 and AaPO2 was +3 +/- 10 mm Hg (p = 0.058) and +1 +/- 11 mm Hg (p = NS), respectively, and the range of change was large (-17 to +29 mm Hg and -24 to +23 mm Hg, respectively). The mean change in PaCO2 was -3 +/- 5 mm Hg (p < 0.05) and ranged from -11 to +5 mm Hg. Changes in PaO2 and AaPO2 were poorly correlated with changes in PaCO2 or with pre- or postoperative pulmonary function. Although some patients had a marked improvement in ABGs following LVRS, almost as many deteriorated. On average, only minimal effects were seen. Although mean alveolar ventilation improved somewhat, the effect of LVRS on PaO2 primarily resulted from alterations in ventilation-perfusion heterogeneity.

Comparison of Ho:YAG versus Nd:YAG thoracoscopic laser treatment of pulmonary bullae in a rabbit model

OBJECTIVE

To determine the relative efficacy and morbidity of Ho:YAG versus Nd:YAG laser treatment of bullous lung disease in an animal model.

SUMMARY BACKGROUND DATA

Laser coagulation procedures for treatment of emphysematous pulmonary bullae and heterogeneous emphysema continue to evolve. The role of lasers in lung volume reduction surgery remains controversial due to issues of relative efficacy and morbidity. The Nd:YAG laser is most commonly used for these procedures. We hypothesized that the shallower penetration of the Ho:YAG laser may be better suited for laser bullae coagulation and emphysema lung volume reduction with increased efficacy and reduced lung injury.

METHODS

Thirty New Zealand White rabbits (15 normal rabbits; 15 with bullous lung disease) were evaluated with Ho:YAG compared to Nd:YAG laser exposures. Bullae were coagulated by either Ho:YAG or Nd:YAG treatment. In all animals (bullous-induced and normals), unaffected lung tissue in the upper lobes and contralateral lungs were treated with 5 spot exposures of Nd:YAG and Ho:YAG, each to assess depth of lung injury. Animals were sacrificed at Days 0, 7, and 21 and their lungs were examined histologically.

RESULTS

Ho:YAG and Nd:YAG exposures caused equivalent lung injury to normal lung tissue. In the acute phase, parenchymal necrosis depth was similar for both Ho:YAG and Nd:YAG (850 +/- 273 microns vs. 900 +/- 270 microns respectively, p = 0.7). By Day 7, lung necrosis depth was 925 +/- 133 microns Ho:YAG vs. 1225 +/- 235 microns Nd:YAG (p = 0.33), and lung fibrosis depth was 300 +/- 134 microns Ho:YAG vs. 558 +/- 127 microns Nd:YAG (p = 0.11). By Day 21, pulmonary parenchymal necrosis was not seen. Pleural fibrosis depth was maximal at Day 21, reaching 250 +/- 102 microns for Ho:YAG vs. 300 +/- 156 microns Nd:YAG (P = 0.88). Pleural necrosis depth was 67 +/- 42 microns Ho:YAG vs 48 +/- 34 microns Nd:YAG (p = 0.42) on Day 7 and resolved by Day 21. During surgical coagulation procedures, the Ho:YAG laser was dramatically more efficient in coagulating bullae. The Ho:YAG laser required less exposure at equivalent power and resulted in immediate desiccation of bullae, in sharp contrast to the Nd:YAG laser.

CONCLUSIONS

Because the Ho:YAG was more effective and did not result in more acute lung injury than the standard Nd:YAG laser in this study, Ho:YAG lasers may have improved potential for laser treatment of bullae or lung volume reduction surgery (LVRS) compared to Nd:YAG lasers.

Lung volume reduction surgery for emphysema: out on a limb without a NETT

Lung volume reduction surgery (LVRS) has recently been rediscovered and offers the potential of improving the quality of life of patients with advanced emphysema. In this article, we discuss the historical and contemporary versions of LVRS. Although initial enthusiasm has been substantial, existing data seem insufficient to demonstrate the safety and efficacy of the procedure in comparison with conventional medical therapy. Fundamental questions remain regarding the long-term effects of an operation versus medical therapy, the optimal selection criteria, the best measures of efficacy, the mechanisms of improvement, the cost-effectiveness of the procedure, and the optimal surgical technique. Until such questions are answered, advising patients about the best management their emphysema will be difficult. The National Emphysema Treatment Trial will address many of these issues and should be embraced by both health-care providers and patients.

Experimental ablation of emphysematous rat lung with Nd: YAG laser: lung changes studied by histopathology and SEM

Laser ablation has been employed as a therapeutic measure for chronic pulmonary emphysema. As yet, however, its effect is not understood on firm pathological basis. We aimed to study, both histopathologically and using Scanning Electric Microscopy (SEM), the changes produced by irradiation with contact Neodymium-yttrium aluminum garnet laser (Nd: YAG laser) in rat lungs with experimentally induced emphysema. Emphysema was produced in 34 rats by instilling elastase via airways. Eight weeks after the instillation, the emphysematous left lung was irradiated under thoracotomy with contact Nd: YAG laser at a power of 5 watts. The animals were sacrificed in acute as well as chronic phase for histopathological observation of lung and scanning electron microscopy. Laser caused necrotic and inflammatory changes in the subpleural zone of lung. Immediately after irradiation, the alveolar septa were destroyed as visualized by SEM, only leaving the elastic skeleton. In a chronic phase, the necrotic zone was collapsed and replaced with a thick fibrous scar which seemed to serve more or less to keep the organ from being excessively inflated. In this model, irradiation induces subpleural dense scarring, which, by "encasing" an emphysematous lung, is expected to more or less normalize the excessive compliance.

Lung volume reduction surgery: answering the crucial questions

Emphysema and other forms of COPD are not only common, but also have a poor prognosis. Mortality with severe COPD may be as high as 60% at 5 years and is associated with a significant degree of disability and cost to the health-care system. Building on Dr. Otto Brantigan's experience in the 1950s, when multiple-wedge resections of emphysematous lung were performed to decrease lung volume, thereby improving airflow and reducing hyperinflation, recent investigators, utilizing improved surgical and anesthetic technique, have redeveloped a surgical approach to the treatment of emphysema. The operations used to treat emphysema include excision of large bullae (bullectomy) and resection of diffusely emphysematous lung and are variously known as lung volume reduction surgery (LVRS), pneumectomy, and reduction pneumoplasty. These operations aim for a 20 to 30% reduction in lung volume and may be performed by stapler or laser resection, or both. The mechanisms of benefit have been attributed to enhanced elastic recoil, correction of ventilation perfusion mismatch, improved efficiency of respiratory musculature, and improved right ventricular filling. Questions that remain to be answered include duration of benefits, safety, and cost of LVRS. The National Heart, Lung, and Blood Institute and the Health Care Financing Administration have responded to the demand for more access to and information about LVRS by organizing both a national registry and controlled clinical trial of these procedures over a 7-year period. This multicenter trial intends to enroll patients with end-stage emphysema to compare methods of bilateral LVRS to maximal medical therapy.

Preoperative and postoperative imaging in the surgical management of pulmonary emphysema

For patients with emphysema, imaging studies have been useful for diagnostic purposes and for preoperative patient selection for surgical intervention, such as bullectomy, lung transplantation, and LVRS. Chest radiography is useful in evaluating hyperinflation. Inspiratory and expiratory films are used to estimate diaphragmatic excursion and air-trapping. CT scan is used to evaluate the anatomy and distribution of emphysema throughout the lungs, providing information clinically unobtainable by other means. Both imaging techniques are useful for detecting other disease processes. Radionuclide lung scanning also provides an estimate of target areas, volume occupying but nonfunctioning lung. Cohort studies utilizing these imaging techniques have demonstrated associations between preoperative characteristics and postoperative outcome. The imaging studies, especially the chest radiograph, have also played an important role in postoperative management. Many other imaging options are available, such as HRCT scan, quantitative CT scan, and single photon emission CT scan. Other techniques, such as MR imaging, may play a future role as well.

Surgical options for patients with advanced emphysema

Since the early 1900s, a variety of operations have been suggested for emphysema but, with the exception of giant bullectomy, an option in only a small fraction of patients, none has proven effective. Data collected by a number of academic medical centers indicate that LVRS may ameliorate symptoms and improve pulmonary physiology, function, and quality of life in appropriately selected patients with emphysema. Accordingly, LVRS may provide an opportunity to intervene in a rapid, effective, and, possibly, cost-effective manner in a debilitating, chronic disease. That is an extraordinarily attractive proposition for both patients and physicians alike. But a number of questions remain: (1) What is the effect of LVRS compared with maximal medical therapy? (2) What is the duration of any beneficial effect of LVRS? (3) What is the best operative approach? (4) What patient characteristics predict good and bad outcomes? (5) What is the role of pre- and, possibly, postoperative pulmonary rehabilitation? (6) Does LVRS adversely affect the rate of loss of lung function over time, as some have suggested? (7) What is the cost of LVRS compared with standard medical therapy? (8) Can the procedure be performed safely in nontransplant centers? (9) What is the effect on disease-specific quality of life? (10) Does it affect mortality? A prospective, randomized controlled trial involving 18 selected centers will begin in the fall of 1997 under the sponsorship of the Health Care Financing Corporation (the administrators of Medicare) and the National Institutes of Health. We strongly support the creative, collaborative approach that has been taken by those two government agencies to stimulate this study. The need for controlled trials of new therapies cannot be overstated; only with such trials can the questions enumerated above be answered with certainty.

Incidence of lung nodules found in patients undergoing lung volume reduction

BACKGROUND

The risk of lung cancer is increased with cigarette smoking and obstructive lung disease. Patients having a lung volume reduction operation represent a high-risk population for cancer.

METHODS

Between March 1994 and December 1996, 281 patients underwent a lung volume reduction operation. All had severe obstructive lung disease with hyperinflation. The incidence of lung nodules and their management were addressed.

RESULTS

Of the 281 patients, 39.5% had at least one lung nodule identified. Fifty-two nodules had typical benign calcification patterns. Of the remaining nodules, 78 were resected and 20 were followed up. Seventeen nodules resected were cancerous, of which 13 were primary lung cancers. Of the resected nodules there were 28 nodules not identified by the preoperative radiologic evaluation.

CONCLUSIONS

Nodules are frequently seen in patients undergoing lung volume reduction operations. The overall incidence of cancer was 6.4%, with several only identified in the pathologic examination. Survival at short follow-up has been excellent for those with primary lung cancer. Nodules seen in this group of patients should be aggressively diagnosed and managed.

Evaluation and preoperative management of lung volume reduction surgery candidates

The efficacy of lung volume reduction surgery has been demonstrated by improvements in functional status, dyspnea, pulmonary function, alveolar gas exchange, and exercise tolerance. However, surgery has a significant morbidity, mortality, and cost. Surgical outcome is dependent on the clinical, anatomical, and physiological features of the patients and their emphysema. Therefore, the patient evaluation process and the preoperative optimization of medical therapy are crucial for success. Through understanding mechanisms for improvement have added insight to the selection process, patient selection needs further clarification.

Effect of bovine pericardial strips on air leak after stapled pulmonary resection

BACKGROUND

Surgical procedures for emphysema have been proposed and in many settings resulted in significant improvement in dyspnea and function. The most prevalent surgical problem in all series is prolonged postoperative air leak.

METHODS

One hundred twenty-three patients undergoing stapled thoracoscopic unilateral lung volume reduction operation were prospectively randomized to receive either no buttressing of their staple lines or buttressing of all staple lines with bovine pericardial strips.

RESULTS

The two groups were comparable in preoperative risks and in the severity of their emphysema. Postoperative complications were identical in the two groups with respect to pneumonia, empyema, and wound infection; however, there was a significant difference in the duration of postoperative air leaks. Those having the pericardial strips used to buttress their staple lines had chest tubes removed 2.5 days sooner and were discharged from the hospital 2.8 days sooner as a result. The cost data revealed that because of the cost of the pericardial sleeves, the overall hospital charges were almost identical for the two groups ($22,108 bovine, $22,060 no bovine) in spite of the shortened hospital stay.

CONCLUSIONS

The use of bovine pericardial sleeves to buttress the staple lines in thoracoscopic unilateral lung volume reduction operation results in a shorter duration of postoperative air leaks. Total hospital charges were comparable in the two groups as the 2.8 days saved in the hospital were offset by the cost of the pericardial sleeves.

Early and long-term functional outcomes following lung volume reduction surgery

In the past 3 years, lung volume reduction surgery has become the most controversial topic in the clinical management of patients with emphysema. Although literature has added to the understanding of the procedure, many important issues remain unclear. This article emphasizes functional and basic physiologic changes that occur following lung volume reduction surgery in patients with emphysema.

Lung reduction surgery in chronic obstructive lung disease

In the 1960s the promise of the Brantigan lung reduction surgery was shattered when it was shown that the improvement in airway conductance drifted back towards the preoperative value over a period of 12 to 18 months. Since then there has been a marked improvement in our understanding of emphysema, its pathology, and techniques for obtaining images of the lung. In addition, reliable automated cardiopulmonary and physiologic testing, advances in critical care medicine, and new pharmacologic agents have improved patient care. Surgical techniques now allow better control of air leaks and access to anatomic regions not previously accessible. The combination of all of the above makes lung reduction surgery worth re-examining as a palliative procedure for severely symptomatic patients. Clearly, it is not a panacea but can in some cases produce dramatic improvements in symptomatology and quality of life. This article presents the available data describing potential mechanisms of improvement and clinical outcomes following lung reduction surgery. It also outlines areas that need further work, such as patient selection and surgical techniques.