4. Discussion
The purposes of the study were to develop the respiratory device
training (named TU-Breath Training version II) and examine the effect of
the prototype on cardiorespiratory performance (i.e., respiratory muscle
strength and functional capacity) and rate of dyspnea in hemodialysis
patients. The study reported that use of respiratory prototype program
could improve respiratory muscle strength, functional capacity and rate
of dyspnea in hemodialysis patients. These results are in line with the
previous studies 1, 5-8.
The study was revealed that an improvement in MIP, 6MWD and sensation of
breathlessness were observed in inspiratory muscle training thought
respiratory prototype (TU-Breath Training version II). Dysfunction in
multiple systems (e.g., musculoskeletal, cardiovascular and respiratory
systems) could be found in patients with CRF. The reduction of systemic
protein and skeletal muscle mass leads to loss of muscle mass whether in
type I or type II fibers in cross-sectional areas. Further, the
proportion of show fibers and also in the size of the fast fibers can
been improved inspiratory muscle training 9. Muscle
atrophy in particular type II muscle fibers, results from a reduction of
vascular and capillary blood flow 10. These results
are part of uremic myopathy in relation to skeletal muscles including
the diaphragm and intercostal muscle and may present in muscle weakness
(decreased MIP) and poor functional capacity (i.e., 6-MWT)11. In addition, impaired respiratory muscle by the
uremic neuropathy and myopathy could leads to increases the work of
breathing and also the neuromuscular dissociation 11.
Therefore, neuromuscular dissociation might provoke an increase in
respiratory effort and perceived in breathlessness among patients with
chronic renal failure 12. In addition, weakness of
inspiratory muscle leads to increase respiratory effort during exercise
or physical activity resulting to increase metabolic stress in
respiratory muscle and metaboreflex stimulation 13.
Thus, metaboreflex stimulus and uremic myopathy might partially explain
why respiratory muscle training improved sensation of breathlessness and
cardio-respiratory fitness (i.e., inspiratory muscle strength and
6-MWT).
Regarding to breathlessness, the study found a decrease of dyspnea after
8-week intervention program. Silva et al found an improvement in the
sensation of breathlessness after inspiratory muscle training program in
hemodialysis patients 8. Decreased dyspnea is reported
in IMT, it might be a decreasing dynamic hyperinflation of rib cage and
therefore increasing gas exchange 14. In addition,
increased respiratory muscle strength can be enhancing the pattern of
maximal thoraco-abodminal motion (14). Additionally,
Patessio et al reported the relationship between the sensation of
breathlessness and respiratory muscle strength 15. MIP
less than 80 cmH20 has been defined as inspiratory muscle weakness3,16. In the present study, MIP was an average 68.32
cmH2O which is clinically important inspiratory muscle weakness.
However, after training programme for 8-week, the improvement in
inspiratory muscle rose to 82.55 cmH2O. Therefore, it
might be, in part, inspiratory muscle training improved the inspiratory
muscle strength and thereby decreased sensation of breathlessness.
Some limitations of the present study should be noted. A relative small
sample size with quasi experimental design which is lack of a control
group. Therefore, further study need to explore the effect of
inspiratory muscle training with a large sample size and randomized
control trails. In addition, the training protocol such as intensity,
frequency and duration of the study should be a consideration that might
affect the result of the study.