Investigating the effect of bilateral quadriceps NeuroMuscular Electrical Stimulation (NMES) on exercise capacity in patients with severe chronic obstructive pulmonary disease

INTERVENTION: Active, NMES to the quadriceps for 30min daily for 6 weeks (frequency 50Hz, pulse width 350µs, duty cycle 11‐50%, amplitude 0‐120mA over 1000O). The proportion of the treatment duration which is active, i.e. the stimulation phase of the duty cycle, will increase on a weekly basis from 11% to 25% to 50%, remaining constant thereafter. Control, Placebo NMES to the quadriceps for 30min daily for 6 weeks using levels of stimulation detectable by the patient but not able to elicit a tetanic muscle contraction (frequency 50Hz, pulse width 350µs, duty cycle 11‐50%, amplitude 0‐20mA). CONDITION: Chronic obstructive pulmonary disease ; Respiratory ; Other chronic obstructive pulmonary disease PRIMARY OUTCOME: Six‐minute walk test (6MWT) at baseline, 6 and 12 weeks SECONDARY OUTCOME: 1. Quadriceps function and size; assessed by quadriceps maximum voluntary contraction and twitch with femoral nerve stimulation, time for twitch to decline to 70% of maximum with repetitive transcutaneous stimulation, rectus femoris cross sectional area with ultrasonography and fat free mass by bioimpedence (kg).; 2. Exercise capacity: assessed by 6MWT distance (m) at 12 weeks; 3. Physical activity level: mean daily step count, up/down transitions and time spent upright; 4. Health‐related quality of life; overall health on EQ5D visual analogue scale (0‐100), St Georges; 5. Respiratory Questionnaire and Chronic Respiratoary Disease Questionnaire; 6. Service utilisation; formal and informal care 12 weeks assessed by Client Service Reciept Inventory; 7. Patients' experiences: semi‐structured interviews in a sub‐group of patients at 6 weeks INCLUSION CRITERIA: 1. >=18 years of age 2. Diagnosis of COPD [ forced expiratory volume in the first one second to the forced vital capacity of the lungs (FEV1: FVC ratio <=70%)] 3. Severe respiratory impairment (GOLD stage III/IV; FEV1 <=50% predicted) 4. Incapacitating breathlessness (MRC dyspnoea score 4/5) 5. Able to provide written informed consent