Effect of Synchronized Transcutaneous Electrical Diaphragm Stimulation Using Surged Faradic Current Combined With Inspiratory Muscle Training on Diaphragm Function and Clinical Outcomes in Patients With COPD

Effect of Synchronized Transcutaneous Electrical Diaphragm Stimulation Using Surged Faradic Current Combined With Inspiratory Muscle Training on Diaphragm Function and Clinical Outcomes in Patients With COPDEffect of Synchronized Transcutaneous Electrical Diaphragm Stimulation Using Surged Faradic Current Combined With Inspiratory Muscle Training on Diaphragm Function and Clinical Outcomes in Patients With COPDEffect of Synchronized Transcutaneous Electrical Diaphragm Stimulation Using Surged Faradic Current Combined With Inspiratory Muscle Training on Diaphragm Function and Clinical Outcomes

Chronic kidney disease (CKD) is a progressive condition that can be associated with reduced physical capacity, muscle weakness, fatigue, respiratory impairment and frailty. These problems may affect daily activities and quality of life. Exercise-based renal rehabilitation has been increasingly considered as an important part of the management of physical problems in CKD. However, evidence regarding multimodal rehabilitation in frail patients with CKD remains limited. Therefore, the present randomized controlled trial was conducted to evaluate the effect of a 12-week multimodal renal rehabilitation programme on pulmonary function, functional capacity and fatigue in patients with CKD who were classified as frail according to the Fried Frailty Phenotype. Frailty was defined by the presence of three or more of the five Fried criteria.

A total of 54 patients were screened, and 42 eligible participants were included and randomly allocated into two equal groups, with 21 participants in each group. Group A received the multidisciplinary renal rehabilitation, which included aerobic training, resistance training, inspiratory muscle training and multidisciplinary supportive care.

Group B received conventional physiotherapy along with standard medical care. The intervention was provided 3 times a week for 12 weeks. Pulmonary function was assessed using forced expiratory volume in one second, forced vital capacity and FEV₁/FVC ratio. Functional capacity was assessed using the 6-Minute Walk Test (6MWT) and the reported VO₂max measure. Fatigue was assessed using the Daily Fatigue Impact Scale. Assessments were performed before and after the intervention.

At baseline, there were no statistically significant differences between the two groups for pulmonary function, functional capacity or fatigue measures (p>0.05), indicating that the groups were comparable before the intervention. Following the 12-week intervention, significant improvements were observed within Group A for FEV₁, FVC, FEV₁/FVC ratio, 6MWD, VO₂max and D-FIS (p<0.001 for all outcomes). Significant within-group improvements were also observed in Group B for the measured pulmonary function, functional capacity and fatigue outcomes (p<0.001).

The between-group analysis showed statistically significant differences in favour of Group A for FEV₁, FVC, 6MWD, VO₂max and D-FIS (p<0.001). However, the between-group difference in FEV₁/FVC ratio was not statistically significant (p>0.05).

Thus, although both groups demonstrated improvement over time, the multimodal renal rehabilitation group demonstrated significantly greater improvement in most of the measured outcomes compared with conventional physiotherapy along with standard medical care.

The findings suggested that the multidisciplinary renal rehabilitation was effective in

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improving pulmonary function, functional capacity and fatigue in CKD patients with frailty over the 12-week intervention period. The improvement in fatigue was particularly evident from the significant reduction in D-FIS scores in Group A compared with Group B (between-group p<0.001). Similarly, the significant between group improvement in 6MWD and VO₂max (p<0.001) indicated better functional exercise capacity following the rehabilitation programme. The findings were consistent with previous research showing beneficial effects of exercise-based interventions on physical function and fatigue in patients with CKD. However, the study evaluated a combined rehabilitation programme, and therefore the individual contribution of aerobic training, resistance training, inspiratory muscle training and multidisciplinary support could not be determined separately. Other limitations included the relatively small sample size, and limited follow-up period.

Therefore, larger randomized controlled trials with longer follow-up are required to confirm the findings and determine whether the observed improvements are observed over time. Overall, the study concluded that a 12-week multidisciplinary renal rehabilitation may be a useful approach for improving pulmonary function, functional capacity and fatigue in CKD patients with frailty.

Ethical clearance was obtained from the Institutional Ethics Committee before commencement of the study. A total of 54 CKD patients were screened, of whom 42 participants fulfilling the eligibility criteria were included in the study. Written informed consent was obtained from all participants. Baseline assessment was performed using Pulmonary Function Tests (FEV₁, FVC and FEV₁/FVC ratio), 6-Minute Walk Test (6MWD, VO₂max) and Daily Fatigue Impact Scale (D-FIS).

The 42 participants were randomly allocated into two equal groups of 21 participants each.

Group A - Renal Rehabilitation :

Participants received a structured renal rehabilitation programme consisting of aerobic training, resistance training and inspiratory muscle training for 3 days per week for 12 weeks.

Each session started with 5-10 minutes of warm-up, followed by the training programme and ended with 5-10 minutes of cool-down.

• Aerobic Training: Aerobic exercise included cycle ergometer. Exercise intensity was maintained at approximately 40-60% of maximum heart rate and RPE 11-13. Aerobic exercise was initially performed for approximately 20-30 minutes and progressively increased by 5 minutes every 2 weeks according to tolerance, up to a maximum of 60 minutes.

• Resistance Training: Exercises were performed for major upper- and lower-limb muscle groups using free weights. The initial resistance was approximately 50% of 10RM, with 10 repetitions per set. Exercises included functional lower-limb and upper-limb strengthening such as sit-to-stand, knee extension, heel raises, biceps curls and shoulder exercises. Rest intervals of approximately 1-2 minutes were provided between exercises/sets. Resistance was progressively increased according to the participant's tolerance and ability to complete the prescribed repetitions with proper technique.

• Inspiratory Muscle Training: IMT was performed using a Threshold Inspiratory Muscle Trainer. Participants performed 5 sets of 10 breaths per session, with 1minute rest between sets. Training intensity was progressively increased according to MIP: 50% MIP during weeks 1-3, 60% during weeks 4-6, 70% during weeks 7-9 and 80% during weeks 10-12, as tolerated.

During all sessions, exercise intensity was individualized according to vitals stability, patient tolerance and clinical condition. Heart rate, blood pressure, SpO₂, fatigue and symptoms were monitored throughout the intervention.

Group B - Conventional Physiotherapy with standard medical care :

Group B received conventional physiotherapy with standard medical care, consisting of general upper- and lower-limb mobility exercises, diaphragmatic breathing exercises, stretching and active range-of-motion exercises for 30-40 minutes per session, 3 days per week for 12 weeks.

Multidisciplinary Care

• Nephrologist: Conducted the initial CKD assessment, staging, medication review, blood pressure assessment and medical clearance before starting rehabilitation (Week 1). Medical review was repeated at Week 4, Week 8 and Week 12, or earlier if clinically indicated, to assess medical problems and exercise safety.
• Renal dietitian: Provided individualized renal dietary counselling at Week 1, including appropriate protein and energy intake, sodium, potassium, phosphorus and fluid management according to CKD stage and laboratory findings. Dietary follow-up was conducted at Week 4, Week 8 and Week 12 to reinforce dietary adherence and modify recommendations when required.
• Nurse: Monitored vital signs and exercise-related symptoms during every rehabilitation session throughout Weeks 1-12. The nurse also provided patient education, reinforced adherence to the exercise programme and coordinated with the rehabilitation team. Additional monitoring was performed whenever clinically required.

At the end of 12 weeks, all participants were reassessed using the same outcome measures. Pre- and post-intervention data were recorded and statistically analyzed to determine the effect of renal rehabilitation on pulmonary functions, functional capacity and fatigue.

Inclusion Criteria:

- Participants were medically diagnosed with moderate COPD (GOLD stage II-III) and were 40-70 years of age. Eligible participants included both males and females who were clinically stable, had the ability to understand and follow study instructions, and had a maximal inspiratory pressure (MIP) below 60 cmH₂O in males or below 50 cmH₂O in females

Exclusion Criteria:

• Patients were excluded if they had an acute COPD exacerbation, a cardiac pacemaker, unstable cardiovascular disease such as recent myocardial infarction or unstable angina, uncontrolled hypertension, or recent fractures.