Effects of Neuromuscular Electrical Stimulation on Patients With Prolonged Mechanical Ventilation

Scientific and technologic advances in medicine have resulted in the ability of the medical team to prolong life. One consequence of life-extending advancements in technology is the increasing numbers of patients requiring prolonged mechanical ventilation (PMV). Prolonged mechanical ventilation has been defined as the need for 21 days, of consecutive mechanical ventilation for six hours/day. The interaction of underlying diseases and prolong bedridden result in various complication in patients with PMV. Known complications can include: muscle weakness, atelectasis, and deconditioning. The muscle weakness occurred most commonly in patients with PMV and resulted in increasing time to wean successfully from mechanical ventilation, and longer stay in hospital. Exercise is effective in improving muscle strength and physical function in patients with heart failure and chronic obstructive pulmonary disease (COPD. However, patients with PMV may be too fragile to perform excise. Neuromuscular electrical stimulation (NMES) involves applying a series of stimuli to skeletal muscle, primarily to trigger muscle contraction, and it can be used for the recovery of muscle mass and muscle strength following prolonged immobilization. NMES also improve microcirculation and systemic circulation in patients with cardiopulmonary diseases. In addition, the application of NMES increases oxygen consumption of whole body and elicits physiologic effects that are similar to aerobic exercise. However, the effects of NMES on the PMV population remain unclear. Near-infrared spectroscopy (NIRS) is a recently developed noninvasive method of measuring tissue oxygenation, blood flow, and local tissue metabolism. NIRS combined with a vascular occlusion test is proposed as a tool to assess the microvascular response. Indirect calorimetry (IC) uses the method of breath-bybreath monitoring by pneumotachography to measure oxygen consumption (VO2) and carbon dioxide production (VCO2).

The purposes of this study:

1. to examine the acute effects of NMES on the microcirculation, physiologic response and metabolic demand in patients with PMV.
2. to investigate the training effects of NMES on microcirculation, muscle strength and weaning outcomes in patients with PMV. METHODS: Subjects who have been on ventilator for>= 21 days are recruited form respiratory care center (RCC) and are randomly assigned into NMES (n=20) or control group (n=20).The NMES group receive daily NMES for 30 min/session for 10 days. The assessment of muscle strength and weaning profile were performed before and after intervention. During the first and the last NMES session, the status of microcirculation and local muscle tissue oxygenation will be measured by NIRS, and the metabolic status will be measured by IC. The mechanical ventilator weaning outcomes and length of stay in RCC will be recorded. The results of this study help us to confirm whether the application of NMES is beneficial in the improvement of muscle strength in patients with PMV, and to furtherly understand the mechanisms. The results may provide an alternative options for clinicians functional and hospitalization outcomes in patients with PMV.