Is lung volume reduction surgery effective in the ... - Semantic Scholar

ARTICLE IN PRESS doi:10.1510/icvts.2010.252213

Interactive CardioVascular and Thoracic Surgery 12 (2011) 480–486 www.icvts.org

Best evidence topic - Pulmonary

Is lung volume reduction surgery effective in the treatment of advanced emphysema? Imran Zahida, Sumera Sharifa, Tom Routledgeb, Marco Scarcib,* a Imperial College London, South Kensington Campus, London SW7 2AZ, UK Department of Thoracic Surgery, Guy’s Hospital, Great Maze Pond, London SE1 9RT, UK

b

Received 17 August 2010; received in revised form 16 November 2010; accepted 23 November 2010

Summary A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was whether lung volume reduction surgery (LVRS) might be superior to medical treatment in the management of patients with severe emphysema. Overall 497 papers were found using the reported search, of which 12 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results are tabulated. We conclude that LVRS produces superior patient outcomes compared to medical treatment in terms of exercise capacity, lung function, quality of life and long-term ()1 year postoperative) survival. A large proportion of the best evidence on this topic is based on analysis of the National Emphysema Treatment Trial (NETT). Seven studies compared LVRS to medical treatment alone (MTA) using data generated by the NETT trial. They found higher quality of life scores (45.3 vs. 27.5, P-0.001), improved maximum ventilation (32.8 vs. 29.6 lymin, Ps0.001) and lower exacerbation rate per person-year (0.27 vs. 0.37%, Ps0.0005) with LVRS than MTA. Mortality rates for LVRS were greater up to one year (Ps0.01), equivalent by three years (Ps0.15) and lower after four years (Ps0.06) postoperative compared to MTA. Patients with upper-lobe-predominant disease and low exercise capacity (0.36 vs. 0.54, Ps0.003) benefited the most from undergoing LVRS rather than MTA in terms of probability of death at five years compared to patients with non-upper-lobe disease (0.38 vs. 0.45, Ps0.03) or upper-lobedisease with high exercise capacity (0.33 vs. 0.38, Ps0.32). Five studies compared LVRS to MTA using data independent from the NETT trial. They found greater six-minute walking distances (433 vs. 300 m, P-0.002), improved total lung capacity (18.8 vs. 7.9% predicted, P-0.02) and quality of life scores (47 vs. 23.2, P-0.05) with LVRS compared to MTA. Even though LVRS has a much greater cost per person over five years ($137,000 vs. $100,200, P-0.001), its improved lung function, greater exercise capacity and better quality of life scores make it a preferable treatment option to MTA, with particular indications for patients with upper-lobe-predominant disease and low exercise capacity. 䊚 2011 Published by European Association for Cardio-Thoracic Surgery. All rights reserved. Keywords: Lung volume reduction surgery; Emphysema; Medical management

1. Introduction A best evidence topic was constructed according to a structured protocol. This is fully described in ICVTS w1x.

He complains that he is finding it progressively more difficult to walk short distances. You feel that lung volume reduction surgery (LVRS) may provide a better quality of life and improve exercise capacity than just continued medication use. You carry out a review of the literature.

2. Three-part question In wpatients with severe emphysemax is wLung Volume Reduction Surgeryx superior to wmedical treatmentx in terms of wsurvival, lung function and quality of lifex. 3. Clinical scenario You see a 65-year-old male with heterogeneous, upperlobe-predominant emphysema identified on computed tomography (CT). Over the past six months, he has become more short of breath despite complying with his medication and completing eight weeks of pulmonary rehabilitation. *Corresponding author. Tel.yfax: q44 751 5542899. E-mail address: [email protected] (M. Scarci). 䊚 2011 Published by European Association for Cardio-Thoracic Surgery

4. Search strategy Medline search 2000 to October 2010 was performed using the OVID interface wLVRS.mp OR Lung volume reduction.mpx AND wCOPD.mp OR exp pulmonary disease, Chronic ObstructiveyEmphysema.mp or exp Emphysemay x AND wsurgery.mpx. 5. Search outcome Four hundred and ninety-seven papers were found using the reported search. From these 12 papers were identified that provided the best evidence to answer the question. These are presented in Table 1. In addition, the reference list of each paper was searched.

ARTICLE IN PRESS I. Zahid et al. / Interactive CardioVascular and Thoracic Surgery 12 (2011) 480–486

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Table 1. Best evidence papers Author, date and country, Study type (level of evidence)

Patient group

Outcomes

Key results

Comments

Criner et al., (2009), Chest, USA, w2x

Multicentre randomised control trial involving 503 patients

Max ventilation

32.8 vs. 29.6 lymin (Ps0.001)

LVRS improves lung function during exercise and at rest

Tidal volume

1.18 vs. 1.07 l (Ps0.01)

Prospective cohort study (level 1b)

LVRS ns287 MTA ns216 Patients with unstable angina, SaO2 -80% after 2-min unloaded cycling or history of syncopeydysrhythmia were excluded

Borg dyspnoea score

4.4 vs. 5.2 (Ps0.0001)

Ventilatory limitation to perform max exercise

All patients: ns476 49.5 vs. 71.9% (Ps0.001) Non-upper-lobe disease: ns160 52.3 vs. 68.9% (Ps0.15)

All patients were part of the NETT trial

LVRS is more effective in upper-lobepredominant emphysema LVRS makes patients breathe more slowly and deeply during exercise (Ps0.006) at 12 months postoperative

Upper-lobe disease: ns316 48.2 vs. 73.6% (Ps0.001) Arterial PO2

At rest: 121.6 vs. 110.4 mmHg (Ps0.06) Max exercise: 94.4 vs. 98.6 mmHg (Ps0.54)

Ramsey et al., (2007), Chest, USA, w3x Prospective cohort study (level 1b)

Multicentre randomised control trial involving 1218 patients over five years

Survival at five years

All patients: 62.2 vs. 56.1%

Quality of well-being score

All patients: 0.472 vs. 0.444

LVRS ns531 MTA ns535

Total cost per person over five years

All patients: $137,000 vs. $100,200 (P-0.001) Group 1: $152,400 vs. $99,000 (P-0.001) Group 2: $129,600 vs. $99,900 (Ps0.013)

Patients without Medicare (ns12) were also excluded Patients were subdivided into three groups:Group 1: upper-lobe emphysemaqlow exercise capacity (ns137) Group 2: upper-lobe emphysemaqhigh exercise capacity (ns204)

Group 3: $143,200 vs. $98,400 (Ps0.006) QALYs

LVRS improves quality of life in both upper- and non-upper-lobe emphysema patients LVRS is more cost-effective in patients with a combination of upper-lobepredominant emphysema and low exercise capacity

All patients: 1.899 vs. 1.635 (P-0.001) Group 1: 2.023 vs. 1.337 (P-0.001) Group 2: 2.073 vs. 1.898 (P-0.001) Group 3: 1.530 vs. 1.331 (P-0.001)

(Continued on next page)

Best Evidence Topic

A subgroup of patients was identified as ‘High-risk of mortality’ (ns140) and was excluded

LVRS is a much more costly treatment option than medical treatment alone (MTA) in patients with emphysema

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Table 1. (Continued) Author, date and country, Study type (level of evidence)

Patient group

Group 3: non-upper-lobeq low exercise capacity (ns82)

Outcomes

Key results

Cost effectivenessyQALY gained

All patients: $140,000

Comments

Group 1: $77,000


Group 2: $170,000 Group 3: $225,000

Benzo et al., (2009), Am J Respir Crit Care Med, USA, w4x Prospective cohort study (level 1b)


Median time to composite endpoint (death or )7 point rise in a respiratory questionnaire)


Non-‘High-risk’ group: ns1078 24 vs. 12 months (P-0.0001)

Patients sub-divided into groups based on risk of perioperative mortality, emphysema distribution and exercise capacity All patients were part of the NETT trial

All patient groups: ns1218 24 vs. 12 months (P-0.0001)

Upper-lobe disease: ns709 24 vs. 12 months (P-0.0001) HR of LVRS to medicine at six months

All patient groups: HRs1.44 (P-0.05)

HR of LVRS to medicine at two years

All patient groups: HRs0.69 (P-0.05)

LVRS group took longer than the MTA group to reach the composite endpoint, especially so in patients with upper-lobe disease and high exercise capacity Hazard ratio (HR) -1 at two years shows that LVRS is superior to MTA in terms of long-term outcome for patients

Non-‘High-risk’ group: HRs0.73 (P-0.05) Upper-lobe disease and high exercise capacity: HRs0.58 (P-0.05) SGRQ score

At two-year for all patient groups: 46.12 vs. 57.72 (P-0.01) At five-year for all patient groups: 50.78 vs. 58.60 (Ps0.10)

Kozora et al., (2005), Chest, USA, w5x Prospective cohort study (level 1b)


Mortality

LVRS 2 MTA 0 Control 0

Psychomotor speed

LVRS 32.7"8.0 MTA 37.0"15.3 Control 27.9"6.0 (Ps0.005)

LVRS ns22 MTA ns24 Healthy controls ns39 Quality of life

LVRS 45.3"27.4 MTA 27.5"15.3 Control 88.5"16.1 (P-0.001)

Mean total BDI score

LVRS 5.1"3.6 MTA 8.9"6.3 Control 4.2"4.9 (Ps0.016)


LVRS produces superior neuropsychological and lung functioning than MTA LVRS leads to a better quality of life and has a lower depression index



483


Krachman et al., (2005), Chest, USA, w6x Prospective cohort study (level 1b)

Patient group

Outcomes

Key results

% Predicted FEV1

LVRS 33.6"2.8 MTA 25.0"2.3 (P-0.0025)

Six-minute walk distance

LVRS 1290"76 m MTA 1370"130 m (Ps0.2706)

Single-centre randomised control trial involving 16 patients

Change in total sleep time (min)

LVRS: 184"111 to 272"126 (Ps0.007) MTA: 236"75 to 211"125 (Ps0.8)

LVRSqmedication ns10 MTA ns6

Change in sleep efficiency

LVRS: 45"26 to 61"26% (Ps0.01) MTA: 60"18 to 52"17% (Ps0.5)


Washko et al., (2008), Am J Respir Crit Care Med, USA, w7x Prospective cohort study (level 1b)

Multicentre randomised control trial involving 1204 patients LVRS ns601 MTA ns603 Patients with incomplete Medicare claims data excluded

Change in FEV1 (% Predicted)

LVRS: 27–36 (Ps0.02) MTA: 30–28 (Ps0.6)

Change in TLC (% Predicted)

LVRS: 121–106 (P-0.001) MTA: 128–130 (Ps0.8)

Change in RV (% Predicted)

LVRS: 215–160 (Ps0.003) MTA: 208–204 (Ps0.8)

Exacerbation rateyperson-year

0.27 vs. 0.37% (Ps0.0005)

Exacerbation free at 600 days postoperative

77 vs. 64% (P-0.0001)

Mean FEV1 at six months postoperative

0.97 vs. 0.78 l (P-0.001)

Mortality

LVRS 283 MTA 324 (Ps0.02)

Probability of death at five years postoperative

All patients: 0.42 vs. 0.49 (Ps0.02)

Comments

Combination of LVRS and medical therapy results in longer and more efficient sleep in patients with severe emphysema LVRS improved nocturnal oxygenation and sleep quality

LVRS reduces rate of COPD exacerbations and improves FEV1 more than medical therapy alone

All patients were part of the NETT trial Naunheim et al., (2006), Ann Thorac Surg, USA, w8x


Group 1: 0.38 vs. 0.45 (Ps0.03)

Patients were subdivided into three groups

Group 2: 0.36 vs. 0.54 (Ps0.003)

Group 1: non-high-risk patients ns1078 Group 2: upper-lobe emphysemaqlow exercise capacity ns290 Group 3: upper-lobe emphysemaqhigh exercise capacity

Group 3: 0.33 vs. 0.38 (Ps0.32) Improvement in exercise capacity at two years postoperative

All patients: 15 vs. 3% (P-0.001) Group 1: 17 vs. 4% (P-0.001) Group 2: 30 vs. 2% (P-0.001) Group 3: 16 vs. 4% (P-0.001)

LVRS is a superior treatment option to MTA for patients with emphysema For the first year postoperative, LVRS has a greater mortality risk (Ps0.01) but by three years postoperative the risk is equivalent (Ps0.15) and after four years, it has a significantly lower risk (Ps0.06) Patients with upper-lobepredominant emphysema and low exercise capacity preoperative benefited the most from LVRS, achieving sustained


Best Evidence Topic

Randomised control trial (level 1b)





Patient group

Outcomes

Key results

Comments


Improvement in quality of life at three years postoperative

All patients: 20 vs. 8% (P-0.001)

improvements in quality of life and exercise capacity

Group 1: 22 vs. 8% (P-0.001) Group 2: 29 vs. 9% (P-0.001) Group 3: 31 vs. 9% (P-0.001)

Hillerdal et al., (2005), Chest, Sweden, w9x Randomised control trial (level 1b)

Multicentre randomised controlled trial involving 106 patients over three years

Mortality

7 vs. 2 (Ps0.489)

SGRQ score

40.4 vs. 59.5 (P-0.05)

SF-36 score

47 vs. 23.2 (P-0.05)

FEV1

0.89 vs. 0.63 l (P-0.001)

Patients with asthma, pleural disease or radiation treatment were excluded

TLC

7.23 vs. 7.74 l (P-0.05)

Distance walked

320 vs. 182 m (P-0.001)

Single-centre prospective study over two years with 18-month follow-up ns57

% Predicted FEV1

35.3"4.7 vs. 27.0"2.3 (P-0.04)

Reduction in TLC

18.8 vs. 7.9% predicted (P-0.02)

LVRS ns29 Conservative ns28

Reduction in residual volume (RV)

89.2 vs. 32.6% predicted (Ps0.0001)

Both groups underwent six weeks rehabilitation before choosing their preferred treatment option

MMRC dyspnoea score

2.52"0.15 vs. 3.15"0.19 (P-0.0001)

Six-minute walking distance

433"53 vs. 300"47 m (P-0.002)

Mortality

0

FEV1

885 vs. 613 ml (Ps0.017)

TLC

7037 vs. 7543 ml (P-0.001)

RV

4212 vs. 5205 ml (P-0.001)

Six-minute walking distance

1223 vs. 1041 feet (Ps0.019)

Mortality rate at six-month follow-up

5.7 vs. 5.1% (PsNS)

Difference in CRDQ score

1.56 (95% CI 0.80–2.32) (P-0.001)

LVRS ns53 Physical training ns53

Wilkens et al., (2000), Eur Respir J, Germany, w10x Prospective cohort study (level 1b)

Miller et al., (2005), Chest, Canada, w11x Meta-analysis (level 1a)

Two multicentre randomised control trials were identified involving 93 patients LVRSqmedication ns54 MTA ns39

LVRS is an effective treatment option for severe emphysema. It improves quality of life, lung function and exercise capacity superior to conservative treatment

LVRS is superior to conservative treatment in terms of improving lung function (FEV1), reducing hyperinflation (RV and TLC) and reducing symptoms (walking distance and MMRC score) LVRS produced superior outcomes despite the conservative group having lower MMRC dyspnoea score (3.5 vs. 3.1, P-0.04) than the LVRS group at baseline Addition of LVRS to optimal medical treatment improves quality of life and lung function significantly more than just MTA



485


Patient group

Outcomes

Key results

Comments

90-day mortality

176y760 vs. 168y743 (Ps0.66)

Difference in SGRQ score between Groups 1 and 2

13.5 (95% CI 11.84–15.13) (P-0.001)

Difference in FEV1 between groups

0.28 l (95% CI 0.08–0.37) (P-0.05)

LVRS is an effective method of treating severe emphysema. It is superior to conservative management in terms of quality of life and lung function

Difference in six-minute walking distance between groups

20.85 m (95% CI –9.36 to 51.07) (P-0.001)

Difference in total cost at three years between groups

$36,000 (P-0.001)

Mortality

LVRS 4 MTA 1

% Predicted TLC

133 vs. 150 (P-0.05)

% Predicted RV

191 vs. 236 (P-0.05)

% Predicted FEV1

45 vs. 31 (P-0.05)

Six-minute walk distance

403 vs. 346 m (P-0.05)

CRQ scores

Dyspnoea: 4.90 vs. 3.15 (P-0.0001)

between surgery and non-surgical groups Tiong et al., (2006), Cochrane Database Syst Rev, Australia, w12x Systematic review (level 1a)

Eight randomised control trials involving 1503 patients were reviewed Group 1: LVRS ns760 Group 2: MTA ns743 Patients with giant or bullous emphysema were excluded

Goldstein et al., (2003), Thorax, Canada, w13x Randomised control trial (level 1b)

Single-centre randomised control trial involving 55 patients LVRS ns28 MTA ns27

LVRS increases exercise capacity but is a much more costly treatment option

LVRS is a safe and effective method to treat severe COPD patients. It significantly improves both lung function and quality of life more than MTA

Emotional function: 5.90 vs. 4.55 (P-0.0001)

6. Results Seven studies compared LVRS to medical treatment alone (MTA) using data generated by the National Emphysema Treatment Trial (NETT) trial. Criner et al. w2x demonstrated improved maximum ventilation rate (32.8 vs. 29.6 lymin), tidal volume (1.18 vs. 1.07 l, Ps0.01) and lower Borg dyspnoea score (4.4 vs. 5.2, Ps0.0001) with LVRS than MTA. Patients with upper-lobe-predominant disease (Ps 0.001) showed greater benefits with LVRS than those with non-upper-lobe-predominant disease (Ps0.15). Ramsey et al. w3x randomised patients to undergo LVRS (ns531) or MTA (ns535) and reported higher quality-adjusted life years (QALY) (1.899 vs. 1.635, P-0.001) but greater total costs per person over five years ($137,000 vs. $100,200,

P-0.001) with LVRS. Patients with upper-lobe-predominant disease were most cost-effective ($77,000). Benzo et al. w4x reported improved St. George’s Respiratory Questionnaire (SGRQ) scores (46.12 vs. 57.72, P-0.01) with LVRS compared to MTA. Hazard ratio (HR) of LVRS to MTA changed significantly between six months (1.44, P-0.05) and two years (HR 0.69, P-0.05). Kozora et al. w5x demonstrated greater improvements in psychomotor speed scores (32.7 vs. 37.0, Ps0.005), forced expiratory volume in 1 s (FEV1) (33.6 vs. 25.0% predicted, P-0.0025) and six-minute walking distances (1290 vs. 1370 m, Ps0.2706) with LVRS than MTA. Lower Beck Depression Inventory (BDI) scores (5.1 vs. 8.9, Ps0.016) and higher quality of life scores (45.3 vs. 27.5, P-0.001) were achieved with LVRS. Krachman et al. w6x compared MTA (ns6) to LVRS with continued optimal

Best Evidence Topic

LVRS, lung volume reduction surgery; NETT, National Emphysema Treatment Trial; QALY, quality-adjusted life years; SGRQ, St. George’s Respiratory Questionnaire; BDI, Beck Depression Inventory; FEV1 , Forced expiratory volume in 1 s; TLC, total lung capacity; COPD, chronic obstructive pulmonary disease; MMRC, Modified Medical Research Council; CRDQ, chronic respiratory disease questionnaire; CRQ, chronic respiratory questionnaire; SaO2 , oxygen saturation; PO2 , oxygen partial pressure.



medication (ns10). Significant improvements in total sleep time (184–272 min, Ps0.007) and sleep efficiency (45– 61%, Ps0.01) were observed postoperative with LVRS but not with MTA (Ps0.5). Higher FEV1 (27–36% predicted, Ps0.02) and lower total lung capacity (TLC) (121–106% predicted, P-0.001) were reported after LVRS. No significant changes in FEV1 (30–28% predicted, Ps0.80) and TLC (128–130% predicted, Ps0.8) were observed with MTA. Washko et al. w7x reported lower chronic obstructive pulmonary disease (COPD) exacerbations per year (0.27 vs. 0.37%, Ps0.0005) and higher FEV1 (0.97 vs. 0.78 l, P0.001) in patients with LVRS than MTA. Naunheim et al. w8x randomised patients to receive LVRS (ns608) or MTA (ns610). Lower mortality rates (283 vs. 324, Ps0.02), greater improvements in exercise capacity (15 vs. 3%, P-0.001) and quality of life scores (20 vs. 8%, Ps0.005) were found with LVRS than MTA. Patients with upper-lobepredominant disease and low exercise capacity (0.36 vs. 0.54, Ps0.003) benefited the most from undergoing LVRS rather than MTA in terms of probability of death at five years compared to patients with non-upper-lobe disease (0.38 vs. 0.45, Ps0.03) or upper-lobe-disease with high exercise capacity (0.33 vs. 0.38, Ps0.32). Five studies compared LVRS to MTA using data independent from the NETT trial. Hillerdal et al. w9x compared LVRS (ns53) to conservative treatment (ns53) and found lower SGRQ scores (40.4 vs. 59.5, P-0.05) and improved 36-item Medical Outcomes Study Short-Form General Health Survey (SF-36) scores (47.0 vs. 23.2, P-0.05). FEV1 (0.89 vs. 0.63 l, P-0.001) and walking distance (320 vs. 182 m, P-0.001) both improved more with LVRS. Wilkens et al. w10x compared LVRS (ns29) and MTA (ns28) and reported lower Modified Medical Research Council (MMRC) dyspnoea scores (2.52 vs. 3.15, P-0.0001) and greater six-minute walking distances (433 vs. 300 m, P-0.002) with LVRS. FEV1 (35.3 vs. 27.0% predicted, P-0.04) was greater, while residual volume (RV) (89.2 vs. 32.6% predicted, P-0.0001) and TLC (18.8 vs. 7.9% predicted, P-0.02) were lower with LVRS. Miller et al. w11x reported greater FEV1 (885 vs. 613 ml, Ps0.017) and lower TLC (7037 vs. 7543 ml) with LVRS compared to MTA. LVRS led to a significant difference in chronic respiratory disease questionnaire (CRDQ) scores (1.56, P-0.001) and improved six-minute walking distance (1223 vs. 1041 feet, Ps0.019). Tiong et al. w12x reported significant differences in SGRQ scores (13.5, P-0.001), FEV1 (0.28 l, P-0.05), six-minute walking distance (20.85 m, P-0.001) and total cost ($36,000, P-0.001) between LVRS and MTA. Mortality rates were equivalent (176 vs. 168, Ps0.66) between the treatment options. Goldstein et al. w13x randomised patients to receive LVRS (ns28) or MTA (ns27) and demonstrated higher FEV1 (45 vs. 31% predicted, P-0.05) and reduced TLC (133 vs. 150% predicted, P-0.05) with LVRS than conservative treatment. Chronic respiratory questionnaire (CRQ) scores (4.9 vs. 3.15, P-0.0001) and six-minute walking distances (403 vs. 346 m, P-0.05) were greater with LVRS.

7. Clinical bottom line Lung volume reduction is becoming increasingly recognised as an effective treatment option for severe emphysema. Currently, no consensus is in place on which patients should be considered for surgery. The studies above have shown that LVRS improves lung function, exercise capacity and quality of life more than conservative treatment with additional benefits for patients with upper-lobe-predominant disease and low exercise capacity. However, its greater cost and higher peri-treatment mortality rates assert caution to its use in patients with multiple co-morbidities or homogenous disease. References w1x Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: best BETS. Interact CardioVasc Thorac Surg 2003;2:405–409. w2x Criner GJ, Belt P, Sternberg AL, Mosenifar Z, Make BJ, Utz JP, Sciurba F, National Emphysema Treatment Trial Research Group. Effects of lung volume reduction surgery on gas exchange and breathing pattern during maximum exercise. Chest 2009;135:1268–1279. w3x Ramsey SD, Shroyer AL, Sullivan SD, Wood DE. Updated evaluation of the cost-effectiveness of lung volume reduction surgery. Chest 2007; 131:823–832. w4x Benzo R, Farrell MH, Chang CC, Martinez FJ, Kaplan R, Reilly J, Criner G, Wise R, Make B, Luketich J, Fishman AP, Sciurba FC, NETT Research Group. Integrating health status and survival data: the palliative effect of lung volume reduction surgery. Am J Respir Crit Care Med 2009; 180:239–246. w5x Kozora E, Emery CF, Ellison MC, Wamboldt FS, Diaz PT, Make B. Improved neurobehavioral functioning in emphysema patients following lung volume reduction surgery compared with medical therapy. Chest 2005;128:2653–2663. w6x Krachman SL, Chatila W, Martin UJ, Nugent T, Crocetti J, Gaughan J, Criner GJ, National Emphysema Treatment Trial Research Group. Effects of lung volume reduction surgery on sleep quality and nocturnal gas exchange in patients with severe emphysema. Chest 2005;128:3221– 3228. w7x Washko GR, Fan VS, Ramsey SD, Mohsenifar Z, Martinez F, Make BJ, Sciurba FC, Criner GJ, Minai O, Decamp MM, Reilly JJ, National Emphysema Treatment Trial Research Group. The effect of lung volume reduction surgery on chronic obstructive pulmonary disease exacerbations. Am J Respir Crit Care Med 2008;177:164–169. w8x Naunheim KS, Wood DE, Mohsenifar Z, Sternberg AL, Criner GJ, DeCamp MM, Deschamps CC, Martinez FJ, Sciurba FC, Tonascia J, Fishman AP, National Emphysema Treatment Trial Research Group. Long-term followup of patients receiving lung-volume-reduction surgery versus medical therapy for severe emphysema by the National Emphysema Treatment Trial Research Group. Ann Thorac Surg 2006;82:431–443. w9x Hillerdal G, Lo ¨fdahl CG, Stro ¨m K, Skoogh BE, Jorfeldt L, Nilsson F, Forslund-Stiby D, Ranstam J, Gyllstedt E. Comparison of lung volume reduction surgery and physical training on health status and physiologic outcomes: a randomized controlled clinical trial. Chest 2005;128:3489– 3499. w10x Wilkens H, Demertzis S, Ko ¨nig J, Leitnaker CK, Scha ¨fers HJ, Sybrecht GW. Lung volume reduction surgery versus conservative treatment in severe emphysema. Eur Respir J 2000;16:1043–1049. w11x Miller JD, Berger RL, Malthaner RA, Celli BR, Goldsmith CH, Ingenito EP, Higgins D, Bagley P, Cox G, Wright CD. Lung volume reduction surgery vs medical treatment: for patients with advanced emphysema. Chest 2005;127:1166–1177. w12x Tiong LU, Davies R, Gibson PG, Hensley MJ, Hepworth R, Lasserson TJ, Smith B. Lung volume reduction surgery for diffuse emphysema. Cochrane Database Syst Rev 2006;18:CD001001. w13x Goldstein RS, Todd TR, Guyatt G, Keshavjee S, Dolmage TE, van Rooy S, Krip B, Maltais F, LeBlanc P, Pakhale S, Waddell TK. Influence of lung volume reduction surgery (LVRS) on health related quality of life in patients with chronic obstructive pulmonary disease. Thorax 2003; 58:405–410.