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).