Effects Of Chronic Electric Stimulation Using Low And Physiologic Frequencies On Respiratory Function And Quality Of Life In Patients With Stable COPD

Chronic obstructive pulmonary disease (COPD) is a common chronic obstructive airway inflammation in respiratory system and its morbidity and mutilation rate are high. In the past 30 years, the mortality of COPD has been increasing. Because chronic obstructive inflammation of airway severely influences the ventilation and exchange function of COPD patients, the patients have pulmonary over-inflation for a long time. This has not only resulted in dropping and flattening of the diaphragm but also the shortening of early length of the diaphragm. Consequently, the diaphragm is in a disadvantageous position from the mechanical angle, which further caused the decrease of sensitivity of the diaphragm to nervous stimuli and diaphragm fatigue to aggravate the pulmonary over-inflation. As a result, inadequate ventilation appears to cause hypoxemia and hypercapnia and increase in oxygen needs, thus vicious cycle emerges to further restrict patient's respiratory and motor function. In 2001,after summarized the research results of COPD, the World Health Organization (WHO) and the National Heart/Lung and Blood Institute(NHLBI) established the Global Initiative for Chronic Obstructive Lung Disease (GOLD) to propose guidelines for diagnosis and treatment of COPD. In the guidelines, pulmonary rehabilitation was formally proposed as the first non-drug management procedure fro stable COPD patients.The principal goals of pulmonary rehabilitation are to reduce symptoms, improve the quality of life and enhance participation in physical and social activities. In all GOLD guidelines, comprehensive, integral pulmonary rehabilitation programs are based on a multidisciplinary team approach. The team is consisted of physicians, physiotherapists, professional respiratory nurses, occupational therapists, dietetic staffs, social workers and smoking-cessation counselors. The contents include exercise training, education, nutritional advice, and psychosocial and behavioral intervention etc.Previous researches have already confirmed that the COPD patient has the skeletal muscle functional impairment and functional impairment of diaphragmatic muscle is closely related to degradation of exercise tolerance. The diaphragm, a kind of skeletal muscle, is the most important aspiratory muscle. It accounts for 60-80% of the respiratory function. The main reasons for diaphragmatic fatigue are hypoxia, excessive generation of oxygen free radicals, malnutrition, hypercapnia, electrolyte imbalance and mechanical disorders etc. Nowadays, the diaphragmatic fatigue may be prevented and treated by medications for ameliorating diaphragmatic contractility, mechanical ventilation to help diaphragm rest, respiratory muscle exercise and diaphragmatic pacing. Chronic electrical stimulation to diaphragm plays an important role in the rehabilitation of diaphragm in COPD patients because it can enhance respiratory muscle contraction and improve tolerance and force.The use of diaphragmatic pacing is based on the experimental evidence that diaphragmatic muscle, like skeletal muscles, undergoes adaptive changes under electric stimulation. Electric stimulation using various frequencies may cause varying changes in the structure, metabolism and function of skeletal muscles. Diaphragmatic muscle, being skeletal muscle, may undergo adaptive changes similar to those changes of skeletal muscles under chronic electric stimulation. Recent reports indicate that patients with mild to moderate COPD present atrophy in type I and type II diaphragmatic muscle fibers, and that patients with severe COPD manifest increase in the percentage of type I fibers, impairment in the contractile function of diaphragmatic muscle, increase in protein degradation, and reduction in Ca2+ sensitivity and periodic locomotion of cross-bridges. Chronic electric stimulation using physiologic frequency may recruit motor units of atrophic diaphragmatic muscle, enhance the function of various types of muscle fibers, and maintain relatively normal percentages of various types of muscle fibers. Hence, physiologic frequency electric stimulation transforms the type of diaphragmatic muscle fibers in COPD patients, but does not lead to optimal muscle fiber remodeling which is required in clinical perspective, and 40Hz is not the optimal frequency for the rehabilitation of diaphragmatic muscle of COPD patients. In recent years, foreign researchers reported that 10Hz chronic intermittent low-frequency electrical stimulation can transform skeletal muscle type IIB fibers into the IIA, and with the corresponding MHC isoforms of change. Our animal experiments have proved that, in the chronic electric stimulation using low and physiologic frequencies (10 +40 Hz), the strength and speed of diaphragm contraction of emphysema rabbit can be increased, the ability of fatigue resistance be enhanced and time for fatigue recovery be shortened.Objective:To determine whether chronic electric stimulation using low and physiologic frequencies (10 +40 Hz) can improve the quality of life in patients with COPD by improving the respiratory function through enhancing the respiratory muscle strength and intensity to provide a new method of treatment.Methods:I Establishment of rabbit models of emphysema and animal models of chronic electric stimulation1. Rabbit models of emphysema were established by caroid aerosol inhalation.2. Animal models of chronic electric stimulation were established by using the portable, frequency-adjustable and in vitro diaphragmatic muscle pacemaker developed by the author(s).3. Changes in the mechanic properties of diaphragmatic muscle were assayed by the Rm6240 multi-channel physiological signal collecting and processing system.â…¡Effects of chronic electric stimulation using low and physiologic frequencies on respiratory function and quality of life in patients with stable COPDAccording FEV1 classification, 35 patients with stable COPD were divided into two groups based on severity. Twenty-six patients belonged to group A have the mild - moderate COPD while the left 9 in Group B have severe - very severe COPD. All the patients were given EDP at the frequency of 10 +40 Hz and pulse rate of 70-100 V to stimulate the diaphragm at the frequency of 14 beats / min for 30 min. The stimulation was performed once a day for 20 d.All the patients did not accept the professional guide for nutrition and medication as well as socio-psychological and health education during the rehabilitation.Results:1. Pathological study demonstrated characteristic manifestations of emphysema in rabbit models such as sparse lung tissue, thinning of alveolar septum, compression of capillaries in alveolar septum, disruption and loss of some alveolar septa, and alveolar fusion-induced bullae etc.2. Following chronic electric stimulation using 10+40Hz, diaphragmatic muscle twitch tension (Pt) and titanic tension (Po) were significantly increased in rabbits with emphysema, time-to-peak tension(TPT) and half-relaxation time (1/2Rt) were significantly reduced, and fatigue index (FI) and fatigue recovery index (FRI) were significantly decreased (P<0.01).3. As compared with the pulmonary function before the rehabilitation, the values of FVC, FEV1/FVC (%), FEV1/pre (%), MMEF were higher after the rehabilitation. They significantly increased in group A (P<0.05) but not in group B(P>0.05).4. Change of Respiratory muscle tolerance Compared with pro-rehabilitation, the patients' 6MWD and MVV had elevation. Significant difference was found in group A (P<0.05) but not in group B(P>0.05).5. Change of respiratory muscle strength Compared with pro-rehabilitation, Patients'MIP and MEP have elevation. Marked difference was found in group A (P<0.05) but not in group B(P>0.05).6. Changes in the SGRQ scores In group A, very significant improvement was observed in the activity score, the impact score and the total score of the SGRQ after 20 days of treatment (P<0.001). In group B, significant improvement were observed in the activity score, the impact score and the total score of the SGRQ after 20 days of treatment (P<0.05)7. Changes in arterial blood gas Compared with pro-rehabilitation, Patients' PO2 had somewhat elevation and reached statistical significance (P<0.05). The patients' PCO2 had somewhat decrease, but there was no significant difference(P>0.05).8.The impact of nutritional status on rehabilitation Compared with pro-rehabilitation, significant improvement was observed in static pulmonary function, respiratory muscle tolerance and strength in group A. Patients with normal body mass index had statistical significance (P<0.05). Those with low body mass index had somewhat improvement, but there was no significant difference(P>0.05).Conclusions:1. Chronic electric stimulation using low and physiologic frequencies can improve the ventilation function and strength and tolerance of respiratory muscle in patients with COPD.2. Chronic electric stimulation using low and physiologic frequencies can improve the quality of life in patients with COPD. 3. The nutritional status of patients with COPD can affect the effectiveness of rehabilitation therapy.