Exercise performance and gas exchange after bilateral video-assisted thoracoscopic lung volume reduction for severe emphysema

Exercise Performance of Lowlanders with COPD at 2,590 m: Data from a Randomized Trial

BACKGROUND

Effects of hypobaric hypoxia at altitude on exercise performance of lowlanders with chronic obstructive pulmonary disease (COPD) have not been studied in detail.

OBJECTIVES

To quantify changes in exercise performance and associated physiologic responses in lowlanders with COPD travelling to moderate altitude.

METHODS

A total of 31 COPD patients with a median age (quartiles) of 66 years (59; 69) and FEV1 of 56% predicted (49; 69) living below 800 m performed a constant-load bicycle exercise to exhaustion at 60% of the maximal work rate at 490 m (Zurich) and at an identical work rate at 2,590 m (Davos) in randomized order. Pulmonary gas exchange, pulse oximetry (SpO2), cerebral tissue oxygenation (CTO; near-infrared spectroscopy), and middle cerebral artery peak blood flow velocity (MCAv) by Doppler ultrasound during 30 s at end exercise were compared between altitudes.

RESULTS

With ascent from 490 to 2,590 m, the median endurance time (quartiles) was reduced from 500 s (256; 795) to 205 s (139; 297) by a median (95% CI) of 303 s (150-420) (p < 0.001). End exercise SpO2 decreased from 92% (89; 94) to 81% (77; 84) and CTO from 62% (56; 66) to 55% (50; 60); end exercise minute ventilation increased from 40.6 L/min (35.5; 47.8) to 47.2 L/min (39.6; 58.7) (p < 0.05; all comparisons 2,590 vs. 490 m). MCAv increased similarly from rest to end exercise at 490 m (+25% [17; 36]) and at 2,590 m (+21% [14; 30]). However, the ratio of MCAv increase to SpO2 drop during exercise decreased from +6%/% (3; 12) at 490 m to +3%/% (2; 5) at 2,590 m (p < 0.05).

CONCLUSIONS

In lowlanders with COPD travelling to 2,590 m, exercise endurance is reduced by more than half compared to 490 m in association with reductions in systemic and cerebral oxygen availability.

Association between inspiratory muscle weakness and slowed oxygen uptake kinetics in patients with chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) may have poor inspiratory muscle function, which reduces minute and alveolar ventilation, leading to increased hypoxemia and slow pulmonary oxygen uptake kinetics. However, little is known about the effect of inspiratory muscle weakness (IMW) on oxygen uptake kinetics in patients with COPD. Thus, we tested the hypothesis that COPD patients with IMW have slowed oxygen uptake kinetics. An observational study was conducted that included COPD patients with moderate to severe airflow limitation and a history of intolerance to exercise. Participants were divided into 2 groups: (IMW+; n = 22) (IMW–; n = 23) of muscle weakness. The maximal inspiratory, expiratory, and sustained inspiratory strength as well as the maximal endurance of the inspiratory muscles were lower in IMW+ patients (36 ± 9.5 cm H2O; 52 ± 14 cm H2O; 20 ± 6.5 cm H2O; 94 ± 84 s, respectively) than in IMW– patients (88 ± 12 cm H2O; 97 ± 28 cm H2O; 82.5 ± 54 cm H2O; 559 ± 92 s, respectively; p < 0.05). Moreover, the 6-min walk test and peak oxygen uptake were reduced in the IMW+ patients. During the constant work test, oxygen uptake kinetics were slowed in the IMW+ compared with IMW– patients (88 ± 29 vs 61 ± 18 s, p < 0.05). Our findings demonstrate that inspiratory muscle weakness in COPD is associated with slowed oxygen uptake kinetics, and thus, reduced functional capacity.

Supported and unsupported arm exercise capacity following lung volume reduction surgery: a pilot study

Study Objectives: Lung volume reduction surgery (LVRS) has been shown to improve lung function, leg exercise capacity and quality of life in subjects with severe COPD. This is the first study to examine the effect of LVRS on supported and unsupported arm exercise capacity. Design: Eight subjects with COPD (% pred FEV1 ±SD = 31.1 ± 9.8%) completed testing. At baseline (TI), after eight weeks pulmonary rehabilitation (T2) and four months after LVRS (T3), each subject had tests of lung function, and performed three symptom-limited exercise tests to peak work capacity:supported arm exercise (SAE), unsupported arm exercise (UAE) and leg exercise (LE).Measurements: The FEV1 (% pred) increased from 27.8 ± 7.4 (mean ± SD) at T2 to 36.3 ± 7.1 at T3 (P <0.05). Peak oxygen consumption (VO2) remained similar from TI to T2 for SAE, UAE and LE (all P=1.0) but increased from T2 to T3 (P <0.05) (SAE: T2 = 0.59 ± 0.2 L/min,T3 = 0.72 ± 0.1 L/min; UAE: T2 = 0.45 ± 0.1 L/min, T3 = 0.54 ± 0.1 L/min; LE:T2-0.68 ± 0.2 L/min, T3 = 0.81 ± 0.2 L/min). The ratio of end-expiratory lung volume to total lung capacity was reduced at peak SAE and LE from T2 to T3 (P < 0.01) (SAE:T2 = 81 ± 4.0%, T3 = 76 ± 2.7%; LE: T2-81 ± 5.1%, T3 = 75 ± 3.6%). Conclusion: There was a significant increase in SAE and UAE capacity following LVRS. Dynamic hyperinflation wras reduced during SAE following LVRS.

Lung deflation and oxygen pulse in COPD: results from the NETT randomized trial

BACKGROUND

In COPD patients, hyperinflation impairs cardiac function. We examined whether lung deflation improves oxygen pulse, a surrogate marker of stroke volume.

METHODS

In 129 NETT patients with cardiopulmonary exercise testing (CPET) and arterial blood gases (ABG substudy), hyperinflation was assessed with residual volume to total lung capacity ratio (RV/TLC), and cardiac function with oxygen pulse (O(2) pulse=VO(2)/HR) at baseline and 6 months. Medical and surgical patients were divided into "deflators" and "non-deflators" based on change in RV/TLC from baseline (∆RV/TLC). We defined deflation as the ∆RV/TLC experienced by 75% of surgical patients. We examined changes in O(2) pulse at peak and similar (iso-work) exercise. Findings were validated in 718 patients who underwent CPET without ABGs.

RESULTS

In the ABG substudy, surgical and medical deflators improved their RV/TLC and peak O(2) pulse (median ∆RV/TLC -18.0% vs. -9.3%, p=0.0003; median ∆O(2) pulse 13.6% vs. 1.8%, p=0.12). Surgical deflators also improved iso-work O(2) pulse (0.53 mL/beat, p=0.04 at 20 W). In the validation cohort, surgical deflators experienced a greater improvement in peak O(2) pulse than medical deflators (mean 18.9% vs. 1.1%). In surgical deflators improvements in O(2) pulse at rest and during unloaded pedaling (0.32 mL/beat, p<0.0001 and 0.47 mL/beat, p<0.0001, respectively) corresponded with significant reductions in HR and improvements in VO(2). On multivariate analysis, deflators were 88% more likely than non-deflators to have an improvement in O(2) pulse (OR 1.88, 95% CI 1.30-2.72, p=0.0008).

CONCLUSION

In COPD, decreased hyperinflation through lung volume reduction is associated with improved O(2) pulse.

Video-assisted thoracoscopic surgery

Video-assisted thoracoscopic surgery is finding an ever-increasing role in the diagnosis and treatment of a wide range of thoracic disorders that previously required sternotomy or open thoracotomy. The potential advantages of video-assisted thoracoscopic surgery include less postoperative pain, fewer operative complications, shortened hospital stay and reduced costs. The following review examines the surgical and anesthetic considerations of video-assisted thoracoscopic surgery, with an emphasis on recently published articles.

Lung volume reduction surgery as a bridge to lung transplantation

Lung volume reduction surgery (LVRS) improves lung function, exercise capacity, and quality of life in patients with advanced emphysema. In some patients with emphysema who are candidates for lung transplantation, LVRS is an alternative treatment option to lung transplantation, or may be used as a bridge to lung transplantation. Generally accepted criteria for LVRS include severe non-reversible airflow obstruction due to emphysema associated with significant evidence of lung hyperinflation and air trapping. Both high resolution computed tomography (CT) scan of the chest and quantitative ventilation/perfusion scan are used to identify lung regions with severe emphysema which would be used as targets for lung resection. Bilateral LVRS is the preferred surgical approach compared with the unilateral procedure because of better functional outcome. Lung transplantation is the preferred surgical treatment in patients with emphysema with alpha1 antitrypsin deficiency and in patients with very severe disease who have homogeneous emphysema pattern on CT scan of the chest or very low diffusion capacity.

Management of COPD: surgical options

Dyspnoea on exertion and exercise intolerance are the hallmarks of chronic obstructive pulmonary disease (COPD); the primary causes appear to be respectively, increased airway resistance with reduced maximal ventilatory capacity and peripheral skeletal muscle dysfunction with early onset of anaerobic metabolism. Patients with end-stage COPD usually show little or no benefit from conventional medical treatment. Physical training is capable of ameliorating exercise tolerance, but improvement is usually modest in the advanced disease state. Two surgical options are generally accepted for carefully selected patients with emphysema: resection of large bullae, when identified, and lung transplantation. Transplantation, the only effective cure for advanced COPD, is of limited use primarily because of age, comorbidity, limited availability of organs and cost. A different approach for severe emphysema, lung volume reduction surgery (LVRS), has been increasingly utilized during the past several years. In carefully selected emphysematous patients, LVRS improves lung volumes and mechanics, and reduces exertional dyspnoea. Unfortunately, surgical mortality still remains high and some patients show no measurable improvement after surgery. There is an urgent need for data on long-term effects of LVRS; the results of large, randomized trials will soon be forthcoming. The aim of this brief review is to summarize the available knowledge on the effects of LVRS, the criteria for patient selection, short- versus long-term effects and, finally, to propose future directions in this field.

Exercise training in COPD: how to distinguish responders from nonresponders

PURPOSE

Pulmonary rehabilitation programs consistently have improved exercise capacity, quality of life, and symptoms over the past decade. Although training has been shown to be an essential component of the rehabilitation program, individual patients do not always benefit to the same extent. The present study was designed to investigate which patients were achieving significant benefit of exercise training.

METHODS

Forty-nine stable outpatients with moderate to severe COPD (FEV1 37 (15)%pred) were evaluated before and after 12 weeks of exercise training (3 times per week). Responders in exercise capacity were defined as having 15% increase in maximal workload and/or 25% increase in walking distance, while responders in quality of life showed an improvement of at least 10 points on the chronic respiratory disease questionnaire. With multivariate discriminant analysis, responders were distinguished from nonresponders based upon their initial characteristics.

RESULTS

Thirty-two patients were responders in terms of improved exercise capacity. Ventilatory reserve (VE/MVV), inspiratory muscle strength (Plmax), and peripheral muscle strength (handgrip force and quadriceps force) were significant predictors of the training response (P < 0.05) (accuracy 80% P < 0.001). Although the explained variance was modest, patients that were clearly ventilatory limited and had normal skeletal muscle strength were not likely to benefit from exercise training in terms of exercise capacity. No physiologic variables predicted whether a patient would increase quality of life after exercise training.

CONCLUSION

Patients with reduced exercise capacity who experience less ventilatory limitation to exercise and more reduced respiratory and peripheral muscle strength are more likely to improve with exercise training. Improvements in quality of life after exercise training were significant but remained unpredictable with variables included in the present trial.

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.

Reduction pneumoplasty versus respiratory rehabilitation in severe emphysema: a randomized study. Pulmonary Emphysema Research Group

BACKGROUND

The purpose of the study was to determine in a prospective randomized trial the independent short-term physiologic impact of reduction pneumoplasty (RP) on respiratory rehabilitation (RR).

METHODS

Sixty patients eligible for RP were randomly selected by computer to receive either RP (n = 30) or comprehensive RR (n = 30). Pulmonary function tests, analysis of blood gas levels, measurement of respiratory muscle strength (maximal inspiratory and expiratory pressures), 6-minute walk test (6MWT), and incremental treadmill test (ITT), were performed at baseline and at 3 and 6 months.

RESULTS

Two treatment-related deaths occurred after RP and one after RR. At 6 months dyspnea index, maximal inspiratory pressure, 6MWT, ITT, and PaO2 were significantly improved in both groups whereas forced expiratory volume in 1 second and residual volume were significantly improved only in the surgical arm. In addition at 6 months, dyspnea index, 6MWT, maximal ITT, and PaO2 improved significantly more after RP than after RR.

CONCLUSIONS

In our study short-term improvements in dyspnea index, oxygenation, inspiratory muscle strength, and exercise capacity occurred after either RP and RR. However dyspnea index, PaO2, and exercise capacity improved more after RP than after RR whereas pulmonary function improved only after RP.

Lung volume reduction surgery: a survey on the European experience

STUDY OBJECTIVE

To evaluate the activity and evolution in the field of lung volume reduction surgery (LVRS) performed at surgical centers in Europe.

BACKGROUND

LVRS is a novel surgical therapy with the potential to improve lung function, exercise performance, and quality of life in selected patients suffering from severe pulmonary emphysema.

METHODS

Questionnaire addressed to 75 European thoracic surgical centers presumed to perform LVRS, and review of the literature.

RESULTS

Of 45 responding centers, 42 centers in 17 countries covering a population of 423 million reported performing LVRS. Until the end of 1998, 1,120 patients were reported to have undergone LVRS, corresponding to 2.6 patients/million inhabitants. Thirty-one of 40 centers (78%) perform the operation bilaterally. Most centers (83%) evaluate their activity prospectively. The average perioperative mortality rate of 4.1% is moderate. The most commonly utilized technique is video-assisted thoracoscopy, which is most frequently performed bilaterally. Two thirds of the centers treat patients with alpha(1)-antitrypsin deficiency, and half of the centers will consider patients with homogenous morphology of emphysema on CT scan for LVRS. Half of the centers also perform lung transplantation. The five largest centers have operated on 49% of all LVRS patients assessed by this survey.

CONCLUSIONS

LVRS is performed at few thoracic surgical centers throughout Europe, with a large variation in the operative activity between different regions. Half of the centers also perform lung transplantation. Between 1995 and 1997, the number of LVRS procedures performed per year nearly tripled but has reached a plateau since then. As five centers perform nearly half the total number of operations, an optimal exchange of knowledge with smaller centers seems important.

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.