title: Neural respiratory drive and breathlessness in COPD.
abstract: The aim of this study was to test the hypothesis that neural respiratory drive, measured using diaphragm electromyogram (EMGdi) activity expressed as a percentage of maximum (EMGdi%max), is closely related to breathlessness in chronic obstructive pulmonary disease. We also investigated whether neuroventilatory uncoupling contributes significantly to breathlessness intensity over an awareness of levels of neural respiratory drive alone. EMGdi and ventilation were measured continuously during incremental cycle and treadmill exercise in 12 chronic obstructive pulmonary disease patients (forced expiratory volume in 1 s±sd was 38.7±14.5 % pred). EMGdi was expressed both as EMGdi%max and relative to tidal volume expressed as a percentage of predicted vital capacity to quantify neuroventilatory uncoupling. EMGdi%max was closely related to Borg breathlessness in both cycle (r=0.98, p=0.0001) and treadmill exercise (r=0.94, p=0.005), this relationship being similar to that between neuroventilatory uncoupling and breathlessness (cycling r=0.94, p=0.005; treadmill r=0.91, p=0.01). The relationship between breathlessness and ventilation was poor when expansion of tidal volume became limited. In chronic obstructive pulmonary disease the intensity of exertional breathlessness is closely related to EMGdi%max. These data suggest that breathlessness in chronic obstructive pulmonary disease can be largely explained by an awareness of levels of neural respiratory drive, rather than the degree of neuroventilatory uncoupling. EMGdi%max could provide a useful physiological biomarker for breathlessness in chronic obstructive pulmonary disease.
authors.affiliation: King's College London Division of Asthma, Allergy and Lung Biology, King's College London School of Medicine, King's Health Partners, London, UK. caroline.jolley@kcl.ac.uk.
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Jolley
authors.affiliation: State Key Laboratory of Respiratory Disease, Guangzhou Medical College, Guangzhou, China.
authors.forename: Yuanming M
authors.initials: YM
authors.lastname: Luo
authors.affiliation: King's College London Division of Asthma, Allergy and Lung Biology, King's College London School of Medicine, King's Health Partners, London, UK. Lane Fox Respiratory Unit/Sleep Disorders Centre, Guy's and St Thomas' NHS Foundation Trust, London, UK.
authors.forename: Joerg
authors.initials: J
authors.lastname: Steier
authors.affiliation: King's College London Division of Asthma, Allergy and Lung Biology, King's College London School of Medicine, King's Health Partners, London, UK.
authors.forename: Gerrard F
authors.initials: GF
authors.lastname: Rafferty
authors.affiliation: NIHR Respiratory Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, UK.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.affiliation: King's College London Division of Asthma, Allergy and Lung Biology, King's College London School of Medicine, King's Health Partners, London, UK.
authors.forename: John
authors.initials: J
authors.lastname: Moxham
mesh_terms: D000368:Aged; D000886:Anthropometry; D004417:Dyspnea / Q000503:physiopathology*; D004576:Electromyography / Q000379:methods; D015444:Exercise; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000294:innervation; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012123:Pulmonary Ventilation; D012119:Respiration; D015656:Respiratory Mechanics / Q000502:physiology; D013990:Tidal Volume / Q000502:physiology*; D014797:Vital Capacity