Effect of Neuromuscular Electrical Nerve Stimulation on Quadriceps Muscle Strength and Endurance in Patients With Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) is a respiratory condition that results in a mixture of small airway disease and parenchymal destruction, changes which are characteristic of emphysema. Research showed that COPD is also characterized by persistent airflow limitation, an aspect which some authors noted to be a major cause of morbidity and disease burden worldwide. One in every 8 patients who suffer an exacerbation of COPD requires to be admitted to the hospital. Literature also reported that re-admissions following discharge amounted to more than 20% within the first 20 days and continued to increase to approximately 33% within the first 90 days post-discharge from the hospital. Therefore, given that a high portion of patients will require further hospitalisations, this will impose a financial burden on the health care systems.

It emphasized the fact that apart from the pulmonary changes and respiratory impairments, patients diagnosed with COPD have systemic morphological and biomechanical changes. Morphological changes include a reduction in the cross-sectional area and a reduction in muscle mass. Biochemical changes are primarily due to long-term use of steroids and Chronic Systemic Inflammatory Syndrome (CSIS). Given such changes, more energy is required during activities of daily living (ADLs) by such patients, resulting in shortness of breath (SOB) following minimal exercises.

Due to muscle dysfunction, these patients develop physical deconditioning which is one of the primary symptoms reported. The primary cause of this relates to the ventilatory limitations present.

The severity of the condition and related pathophysiological changes also predict the level of exercise tolerance, with a worse condition resulting in increased levels of muscle atrophy, weakness affecting mostly the lower limbs, and poor oxidative capacity. In 2008, it was noted that the majority of patients with a severe form of COPD were so frail or dyspnoeic, making them unable to tolerate sufficient exercise training intensities required to improve their level of physical activity. Such patients were noted to become dyspnoeic following low-intensity physical activity, resulting in a decreased physical activity to control their SOB, with ultimately one-third of these patients exhibiting quadriceps muscle weakness related to immobility and decreased exercise tolerance.

Deterioration in muscle strength was the most commonly reported symptom characteristic of limb muscle dysfunction in people with COPD. In 2014, Mathur et al. noted that the occurrence of COPD patients experiencing early termination of exercise related to leg fatigue was approximately 40% more common than patients rating of SOB. A further 30% of the population sample reported equal leg fatigue and dyspnoea.