Lumbar Transcutaneous Electrical Nerve Stimulation to improve exercise performance in COPD patients

Muscle group III (Aδ fibres) and IV (C fibres) sensory afferents are involved in the cardiorespiratory adaptation to exercise [1, 2]. Their inhibition with intrathecal fentanyl in the dorsal horn of spinal cord to block their cortical projections decreases high intensity constant workload endurance performance in healthy athlete subjects because of a blunted cardiorespiratory response to exercise. In this condition with high metabolic demand, any decrease in ventilation or hemodynamics would compromise performance because of a nearly maximal solicitation without any possibility for a compensatory strategy. At the opposite, Gagnon et al . have published that the use of spinal anesthesia with fentanyl with the goal of inhibiting muscle group III and IV fibres in COPD patients improved dyspnea and endurance capacity [3]. This improvement was due to the blunted ventilatory response to exercise which improved physiological dead space, ventilatory efficiency and in turn, dyspnea. Moreover, at this relatively lower external workload compared with healthy subjects, cardiac output and peripheral oxygen extraction were not maximal and any mitigation in cardiac output (if any) would be overcome by an increase in peripheral muscle oxygen extraction [3]. High frequency (HF) or low frequency (LF) transcutaneous electrical nerve stimulation (TENS) is a less invasive alternative that also activate opioid receptors, especially those located in the dorsal horn of the spinal cord [1, 4, 5]. This approach deserves to be studied during exercise and over a course of pulmonary rehabilitation in these patients. We performed a randomised double-blind study (clinicaltrials.gov; [NCT03312322][1]) aimed to assess whether either HF or LF lumbar TENS could improve endurance exercise capacity in patients with COPD. Secondary objectives were to assess the influence of lumbar TENS on perceived exertion, ventilatory pattern and muscle oxygenation. We hypothesised that endurance capacity would be improved with lumbar TENS due to a blunted response in exercise ventilation which would contribute to improve ventilatory efficacy and reduce exercise dyspnoea. On the other hand, we hypothesised that any mitigation in cardiac output (if any) would be compensated by an increase in peripheral muscular oxygen extraction. Footnotes This manuscript has recently been accepted for publication in the European Respiratory Journal . It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article. Conflict of interest: Dr. Bonnevie has nothing to disclose. Conflict of interest: Dr. Gravier has nothing to disclose. Conflict of interest: Dr. Prieur has nothing to disclose. Conflict of interest: Dr. Combret has nothing to disclose. Conflict of interest: Dr. Debeaumont has nothing to disclose. Conflict of interest: Dr. Patout reports grants from B&D Electromedical, personal fees from ResMed , personal fees from Philips Respironics, grants and non-financial support from Fisher & Paykel, non-financial support from MSD, non-financial support from Asten, grants from ADIR Association, during the conduct of the study. Conflict of interest: Dr. Lamia has nothing to disclose. Conflict of interest: Dr. Muir has nothing to disclose. Conflict of interest: Dr. Medrinal has nothing to disclose. Conflict of interest: Dr. Cuvelier has nothing to disclose. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT03312322&atom=%2Ferj%2Fearly%2F2019%2F09%2F02%2F13993003.00784-2019.atom