2. Materials and Methods
The Research has been approved from the Ethics Committee on Human Subject of Thammasat University and the Ethics in Human Research Committee of the Thammasat University Hospital, according to the principles of the Declaration of Helsinki 1975.
Participants were adults aged 30-75 years old both males and females. Further, those had been diagnosed end stage renal failure at stage 5 and receiving hemodialysis more than three months, undergoing hemodialysis three times a week for 3-4 hours per day. The exclusion criteria were participants who had been resting systolic blood pressure greater than 200 mmHg and/or diastolic blood pressure greater than 120 mmHg, had neurological problems (e.g., stroke, had musculoskeletal problems (e.g., severe osteoarthritis, ambulation), uncontrolled pulmonary disease, mental health problems (diagnosis from doctor or psychiatrist) and cognitive impairment.
Prior to the training program, the participants were explained the objective and methodology of the study. Next, participants were asked to sign the informed consent and fill in a questionnaire, such as medical history, duration of hemodialysis, history of drinking and smoking. Participants performed respiratory muscle strength testing. Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were measured by a mouth pressure meter (Micromedical generation, micro DL no.2, Carefusion company). Participants were asked to sit on a chair comfortably and the noseclip was attached. After that, individuals were requested to take a deep breath near to residual volume and inhale deeply with hold on 1.5 seconds this could be defined as MIP. Next, for the MEP, participants take a deep breath near to total lung capacity and exhale fast and then hold on 1.5 seconds. Participants were requested to repeat the tests for three to five times and maximal value was recorded3. Participants rest for five minutes or rest until heart rate recovery. Prior to the functional capacity testing (i.e., the 6-minute walk test: 6MWT), the participants were recorded blood pressure, heart rate, rate perceived exertion (RPE: modified Borg scale 0-10) and oxygen saturation Participants performed the 6MWT which is long level corridor 30 meters and walk within six minutes4. Blood pressure, heart rate, RPE and oxygen saturation were re-assessed after 6MWT. The perception of breathlessness is rated on a Likert scale between 1 (very difficult to breath) and 5 (not difficult to breath). Participants were asked to complete how difficult breath during the past month.
The respiratory muscle training program was used by the prototype of respiratory muscle training version II (TU-breathe V. 2); see Figure 1. The system composes an air resistive respiration training device including a respiration sensor. The pressure sensor is connected to the respiratory sensor and it is sent the pressure value via Bluetooth which has been installed by a smartphone. The pressure sensor and system have been described in detail elsewhere 2.
The participants were asked to take a deep breath in deeply and the maximal pressure value was shown and recorded. After that, the participants were required to take deep breath in for 40% of maximal inspiration, 15 times/ sets for 3 sets, interval 60 seconds. Respiratory muscle strength was reassessed after 4-week intervention for adjusting respiratory loading. Functional capacity and respiratory muscle strength were performed after 8-week intervention program.
The data analysis was calculated with SPSS program version 20. The statistically significance is set p value less than 0.05. Kolmogorov - Smirnov (Goodness of fit) test was used for test of distribution data. Paired t-test was performed to evaluate the effect of breathing training on respiratory muscle strength, functional capacity and sensation of breathlessness in pre and post training program (before vs. after 8-week intervention).