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Neuromuscular electrical stimulation to improve exercise capacity in patients with severe COPD – Authors' reply
Correspondence
St Michael’s Hospital, Toronto, ON, Canada (AA); University of Toronto, Toronto, ON, Canada (SM); Toronto Western Hospital, University Health Network, Toronto, ON, Canada (MS) 1
2
3 4
Maddocks M, Nolan CM, Man WDC, et al. Neuromuscular electrical stimulation to improve exercise capacity in patients with severe COPD: a randomised double-blind, placebo-controlled trial. Lancet Respir Med 2016; 4: 27–36. Shrikrishna D, Patel M, Tanner RJ, et al. Quadriceps wasting and physical inactivity in patients with COPD. Eur Respir J 2012; 40: 1115–22. Seymour JM, Ward K, Sidhu PS, et al. Thorax 2009; 64: 418–23. Marciniuk DD, Goodridge D, Hernandez P, et al. Managing dyspnea in patients with advanced chronic obstructive pulmonary disease: A Canadian Thoracic Society clinical practice guideline. Can Resp J 2011; 18: 69–78.
Authors’ reply We welcome interest in our trial1 and were delighted to discuss the practical implications with Sindhu Mohan and colleagues at the journal club. With respect to recruitment bias, we were assured by the data that this was minimal given the high uptake rate (52 [71%] of 73 patients) and the fact that only two patients reported feeling too unwell to participate (see figure 1 in the published study).1 The Charlson Index score (median 1, IQR 1–2) was calculated without the primary COPD diagnosis and was similar to that of a larger cohort from one recruiting site.2 Common comorbidities were of cardiovascular and musculoskeletal origin. Theoretically, neuromuscular electrical stimulation (NMES) parameters can be set to preferentially induce strength or endurance adaptations in muscle by matching
stimulation frequency to natural firing rates of fast or slow twitch fibres. However, empirical data remain inconclusive.3 In practice, a common determinant of any effect from NMES is whether sufficient load can comfortably be placed on the muscle to cause a training response. We therefore selected wide, high frequency pulses, to achieve sufficient training loads without requiring high stimulation amplitudes, which patients can find uncomfortable.1 Our focus on strength assessment reflected the use of muscle outcomes to provide secondary mechanistic data, balanced against the burden of fatigueinducing endurance tests, which would necessitate additional trial visits. Current evidence supports NMES as an effective form of exercise training to target skeletal muscle dysfunction. We would not advocate routine use solely on the basis of breathlessness, nor regard NMES as a treatment for breathlessness itself. We would, however, consider using NMES as a component treatment within an approach to reduce disability—eg, a breathlessness support service4 or pulmonary rehabilitation.5 These are complex interventions and clinical expertise is needed to select and optimise component treatments for each patient. Therefore, training and practice recommendations for NMES might support more widespread and appropriate use. Nonetheless, we suggest that NMES should no longer be excluded as a component
treatment solely on the basis of insufficient evidence. The authors’ competing interests remain the same as those declared in the original article.
*Matthew Maddocks, Claire Nolan, William D C Man, Michael Polkey, Nicholas Hart, Wei Gao, Gerrard F Rafferty, John Moxham, Irene J Higginson [email protected] King’s College London, Cicely Saunders Institute, Division of Palliative Care, Policy & Rehabilitation, London SE5 9PJ, UK (MM, WG, IJH); NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK (CN, WDCM, MP); Harefield Pulmonary Rehabilitation Team, Harefield Hospital, UK (CN, WDCM); Lane Fox Unit, Guy’s & St Thomas’ NHS Foundation Trust, London, UK (NH); King’s College London, Respiratory Medicine, Division of Asthma, Allergy & Lung Biology, London, UK (NH, GFR, JM) 1
2
3
4
5
If you would like to respond to an article published in The Lancet Respiratory Medicine, please submit your correspondence online at: http:// ees.elsevier.com/thelancetrm
Maddocks M, Nolan CM, Man WDC, et al. Neuromuscular electrical stimulation to improve exercise capacity in patients with severe COPD: a randomised double-blind, placebo-controlled trial. Lancet Respir Med 2016; 4: 27–36. Jones SE, Maddocks M, Kon SS, et al. Sarcopenia in COPD: prevalence, clinical correlates and response to pulmonary rehabilitation. Thorax 2015; 70: 213–18. Sillen MJ, Franssen FM, Gosker HR, et al. Metabolic and structural changes in lower-limb skeletal muscle following neuromuscular electrical stimulation: a systematic review. PloS One 2013; 8: e69391. Higginson IJ, Bausewein C, Reilly CC, et al. An integrated palliative and respiratory care service for patients with advanced disease and refractory breathlessness: a randomised controlled trial. Lancet Respir Med 2014; 2: 979–87. Spruit MA, Singh SJ, Garvey C, et al. An Official American Thoracic Society/European Respiratory Society Statement: key concepts and advances in pulmonary rehabilitation. Am J Respir Crit Care Med 2013; 188: e13–64.
Corrections Harding E. Progress with endobronchial valves for severe emphysema. Lancet Respir Med 2016; 4: 97— The linked image has been removed because it shows a lung reduction technology that is not associated with this News piece. This correction has been made to the online version as of April 4, 2016. López-Campos JL, Ruiz-Ramos M, Soriano JB. Mortality trends in chronic obstructive pulmonary disease in Europe, 1994–2010: a joinpoint regression analysis. Lancet Respir Med 2014; 2: 54–62. For this Article, the plot for Finland in figure 2 has been corrected. This correction has been made as of April 4, 2016.
www.thelancet.com/respiratory Vol 4 April 2014
e16
St Michael’s Hospital, Toronto, ON, Canada (AA); University of Toronto, Toronto, ON, Canada (SM); Toronto Western Hospital, University Health Network, Toronto, ON, Canada (MS) 1
2
3 4
Maddocks M, Nolan CM, Man WDC, et al. Neuromuscular electrical stimulation to improve exercise capacity in patients with severe COPD: a randomised double-blind, placebo-controlled trial. Lancet Respir Med 2016; 4: 27–36. Shrikrishna D, Patel M, Tanner RJ, et al. Quadriceps wasting and physical inactivity in patients with COPD. Eur Respir J 2012; 40: 1115–22. Seymour JM, Ward K, Sidhu PS, et al. Thorax 2009; 64: 418–23. Marciniuk DD, Goodridge D, Hernandez P, et al. Managing dyspnea in patients with advanced chronic obstructive pulmonary disease: A Canadian Thoracic Society clinical practice guideline. Can Resp J 2011; 18: 69–78.
Authors’ reply We welcome interest in our trial1 and were delighted to discuss the practical implications with Sindhu Mohan and colleagues at the journal club. With respect to recruitment bias, we were assured by the data that this was minimal given the high uptake rate (52 [71%] of 73 patients) and the fact that only two patients reported feeling too unwell to participate (see figure 1 in the published study).1 The Charlson Index score (median 1, IQR 1–2) was calculated without the primary COPD diagnosis and was similar to that of a larger cohort from one recruiting site.2 Common comorbidities were of cardiovascular and musculoskeletal origin. Theoretically, neuromuscular electrical stimulation (NMES) parameters can be set to preferentially induce strength or endurance adaptations in muscle by matching
stimulation frequency to natural firing rates of fast or slow twitch fibres. However, empirical data remain inconclusive.3 In practice, a common determinant of any effect from NMES is whether sufficient load can comfortably be placed on the muscle to cause a training response. We therefore selected wide, high frequency pulses, to achieve sufficient training loads without requiring high stimulation amplitudes, which patients can find uncomfortable.1 Our focus on strength assessment reflected the use of muscle outcomes to provide secondary mechanistic data, balanced against the burden of fatigueinducing endurance tests, which would necessitate additional trial visits. Current evidence supports NMES as an effective form of exercise training to target skeletal muscle dysfunction. We would not advocate routine use solely on the basis of breathlessness, nor regard NMES as a treatment for breathlessness itself. We would, however, consider using NMES as a component treatment within an approach to reduce disability—eg, a breathlessness support service4 or pulmonary rehabilitation.5 These are complex interventions and clinical expertise is needed to select and optimise component treatments for each patient. Therefore, training and practice recommendations for NMES might support more widespread and appropriate use. Nonetheless, we suggest that NMES should no longer be excluded as a component
treatment solely on the basis of insufficient evidence. The authors’ competing interests remain the same as those declared in the original article.
*Matthew Maddocks, Claire Nolan, William D C Man, Michael Polkey, Nicholas Hart, Wei Gao, Gerrard F Rafferty, John Moxham, Irene J Higginson [email protected] King’s College London, Cicely Saunders Institute, Division of Palliative Care, Policy & Rehabilitation, London SE5 9PJ, UK (MM, WG, IJH); NIHR Respiratory Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust and Imperial College, London, UK (CN, WDCM, MP); Harefield Pulmonary Rehabilitation Team, Harefield Hospital, UK (CN, WDCM); Lane Fox Unit, Guy’s & St Thomas’ NHS Foundation Trust, London, UK (NH); King’s College London, Respiratory Medicine, Division of Asthma, Allergy & Lung Biology, London, UK (NH, GFR, JM) 1
2
3
4
5
If you would like to respond to an article published in The Lancet Respiratory Medicine, please submit your correspondence online at: http:// ees.elsevier.com/thelancetrm
Maddocks M, Nolan CM, Man WDC, et al. Neuromuscular electrical stimulation to improve exercise capacity in patients with severe COPD: a randomised double-blind, placebo-controlled trial. Lancet Respir Med 2016; 4: 27–36. Jones SE, Maddocks M, Kon SS, et al. Sarcopenia in COPD: prevalence, clinical correlates and response to pulmonary rehabilitation. Thorax 2015; 70: 213–18. Sillen MJ, Franssen FM, Gosker HR, et al. Metabolic and structural changes in lower-limb skeletal muscle following neuromuscular electrical stimulation: a systematic review. PloS One 2013; 8: e69391. Higginson IJ, Bausewein C, Reilly CC, et al. An integrated palliative and respiratory care service for patients with advanced disease and refractory breathlessness: a randomised controlled trial. Lancet Respir Med 2014; 2: 979–87. Spruit MA, Singh SJ, Garvey C, et al. An Official American Thoracic Society/European Respiratory Society Statement: key concepts and advances in pulmonary rehabilitation. Am J Respir Crit Care Med 2013; 188: e13–64.
Corrections Harding E. Progress with endobronchial valves for severe emphysema. Lancet Respir Med 2016; 4: 97— The linked image has been removed because it shows a lung reduction technology that is not associated with this News piece. This correction has been made to the online version as of April 4, 2016. López-Campos JL, Ruiz-Ramos M, Soriano JB. Mortality trends in chronic obstructive pulmonary disease in Europe, 1994–2010: a joinpoint regression analysis. Lancet Respir Med 2014; 2: 54–62. For this Article, the plot for Finland in figure 2 has been corrected. This correction has been made as of April 4, 2016.
www.thelancet.com/respiratory Vol 4 April 2014
e16