DISCUSSION
In the data analysis of the present study, it was observed that the
inspiratory muscle training protocol, applied to patients at high risk
of pulmonary complications, did not show any significant difference in
relation to the variables of MIP, MEP and 6MWT in patients undergoing
coronary artery bypass grafting.
Pulmonary function is one of the factors that presents changes in the
postoperative period, Barros et al. showed that there is a significant
reduction in ventilatory capacity and muscle strength in patients who
underwent MR. Still, in this same study, it was observed that the IMT
helped to restore the overlapping values evaluated in the preoperative
period14. Similar results have been reported by
Matheus et al. who demonstrated the effectiveness of IMT in recovering
the values of tidal volume and vital capacity found in the
pre-surgical15. In the present study, a reduction in
values was also observed when comparing pre and postoperative in
patients who presented risk factors that may generate PPC, however these
numbers were not significant, both in the control group and in the
intervention group.
Possible justifications may be related to the reduction of ventilatory
mechanics, among which are the presence of drains and pain. Sternotomy
is an aggressive procedure, which causes several dysfunctions and can
cause pain until the fifth postoperative day16. This
symptom is common and can cause restriction of chest expansion, causing
hypoventilation and making IMT difficult.
Cordeiro et al. presented different results and a similar population in
relation to the current study. The researchers investigated the
influence of IMT on inspiratory muscle strength and functional capacity.
They observed a significant reduction in MIP in both groups, but the
intervention group had a higher value for this variable at hospital
discharge, compared to the control group. An analysis of functional
capacity showed an improvement in the 6MWT when comparing the IMT group
to the control group3.
This result is probably related to the researched sample, which was
larger when compared to the present study and included other types of
surgery besides MRI, considered to be large. Therefore, the greater
number of patients, the different inclusion criteria, and, especially,
the risk factors present increase the likelihood of PPC, heterogeneous
characteristics among the studied samples.
With a more prolonged IMT protocol and with progressive load increase,
Praveen et al. they also investigated the effectiveness of IMT in
patients who underwent CABG and showed a reduction in MIP in both groups
both in the short term and over time in the postoperative period. The
group that underwent intervention presented approximate values
preoperatively, however some of them increased significantly at maximum
inspiratory strength17.
In the training mentioned above, patients were stimulated and instructed
to perform IMT from the fourth to the nineteenth postoperative period,
with a load that could increase according to the patient’s resistance.
Unlike the current research, in addition to extending the intervention
period, the fact of starting IMT on the fourth postoperative day can
reduce characteristics such as pain, analgesic effect and the patient’s
concern about sternotomy. Generally, these findings are still present in
the second POD, making it possible to compromise load measurement and
training17.
In this context, it is necessary to emphasize that the barriers found in
the postoperative period are not limited to the restrictions of the
surgical procedure. Predisposing risk factors such as: age, sex,
obesity, smoking, diabetes mellitus, arterial hypertension and
dyslipidemia are aggravating factors that guide the team about possible
complications during or after surgery, directly affecting the recovery
of functional and respiratory capacity, increasing the chance morbidity
and mortality18.
A study carried out Feltrim et al. sustained the benefit of IMT in
high-risk patients with factors similar to the current study and
demonstrated a reduction in pulmonary complications of greater impact,
acting in a protective way, training improved the strength and
resistance of the respiratory musculature8. IMT could
probably decrease complications in the studied population, but the
functional capacity is dependent on other conditions, not influencing
the postoperative risk factors.
Nery et al. also used the 6MWT to assess functional capacity in
individuals who underwent MRI surgery. The patients were divided into a
sedentary and active group, who performed physical exercises and IMT. In
the evaluation, after two years, patients who performed exercises
associated with IMT showed less loss in functional capacity, showing
significant improvement in the distance covered in relation to sedentary
patients. This result may be associated with IMT for a prolonged period
and the performance of exercise19.
Physical exercises are beneficial in wide aspects, considerably improve
hemodynamics and cardiac output. Demonstrating more effective recovery
of the myocardium where they consequently improve muscle fatigue, caused
by the decrease in blood distribution, reducing the feeling of
tiredness. When associated with IMT, patients effectively improve
functional capacity and optimize pulmonary
capacity20-22.
In relation to the 6MWT, researchers evaluated the functional capacity
in patients with risk factors who underwent CABG and noticed an
improvement in the distance covered in older individuals, aged over 75
years, with greater benefit in relation to the distance covered, unlike
the present study that had an average age of 67
years23,24. This is one of the inconstant factors,
however it is understood that when there is an imminent risk in elective
surgeries, it is important to carry out preventive interventions, such
as preoperative training, which can train the muscles and minimize
impacts on MIP and MEP and probably in the distance covered in the
postoperative8.
Our work has some limitations, such as the sample size and the absence
of patients’ effort evaluation (BORG scale), which could have been used
to gradually increase the load. The different study protocols used by
the authors are also characterized as a work limitation.