Effectiveness of Early Mobilization in Prevention and Rehabilitation of Functional Impairment After Myocardial Revascularization Surgery: A Systematic Review

Abstract Introduction Myocardial revascularization surgery is associated with high morbidity and mortality, due to factors like the general anesthesia and the surgical procedure itself. Physiotherapy, combined with early mobilization (EM), can provide the patient with better functional parameters. Objective To review, identify and describe the effectiveness of EM in the prevention and rehabilitation of functional parameters of coronary artery bypass graft surgery. Methodology This is a systematic review conducted between February 2020 and 2021 of randomized clinical trials (RCTs) published in the Cochrane databases Library, LILACS, Scielo and Medline / PubMed. The Physiotherapy Evidence Database (PEDro) scale was used for assessment of the methodological quality of studies included. Results Four studies were reviewed. Two articles assessed functional capacity, one using the cycle ergometer and one with inspiratory muscle training (IMT) together with active exercises and early walking. One article reported a reduction in the incidence of atelectasis and pleural effusion with EM and one article reported improvements in the alveolus-artery gradient and inspiratory muscle power using an inspiratory muscle trainer combined with EM. Conclusion EM is effective in the prevention and rehabilitation of functional parameters after CABG surgery, by improving functional capacity, respiratory muscle power, quality of life and gas exchange, and reducing the incidence of atelectasis and pleural effusion.


Eligebility criteria
The inclusion criteria were randomized clinical trials (RCTs) in English or Portuguese using passive mobilization, active exercises, positioning and progressions, and a cycle ergometer as the EM, combined or not with another technique in the PO period of CABG.There were no restrictions on the time of publication.Exclusion criteria were review articles and clinical trial protocols.
The articles were initially screened by reading the titles and abstracts, and those that met the eligibility criteria were selected for full-text reading.
The selected studies were entered in an Excel spreadsheet, and the outcomes of interest -study design, sample characteristics, intervention and control, analyzed outcomes and results -were extracted.

Assessment of the risk of bias
To assess the methodological quality of RCTs, the Physiotherapy Evidence Database (PEDro) scale was used.The scale is composed of 11 items, with a score of 0-10 (the first item is not included as it refers to external validity).
The titles and abstracts of the articles were evaluated by two independent reviewers and the full texts by one of the reviewers (Figure 1).postoperative (PO) complications and functional limitations in these patients.EM is a simple intervention that reduces the time to wean from mechanical ventilation (MV) and helps in functional recovery of patients with cardiorespiratory instability. 7The programs employ a multidisciplinary approach to progressively increase patient engagement in therapeutic activities such as bed mobility exercises, sitting at the bedside, transfer to the chair, standing position and ambulation. 7,8ercise improves physical function and general health, and postponing its start contributes to aggravate patient's functional decline.Therefore, early intervention is necessary to prevent physical and psychological problems, prolonged hospitalization, and the risks associated with immobilization. 7 combination, EM and exercise may improve overall muscle strength, oxygen saturation (SpO 2 ), 8 and performance in functional tests. 9.In addition, EM has been reported to reduce atelectasis and pleural effusion in patients undergoing CABG . 10 light of the above, the present study aims to systematically review, identify and describe the effectiveness of EM in the prevention and rehabilitation of functional impairments in patients undergoing myocardial revascularization surgery.

Materials and methods
This is a systematic review of the literature conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analysis Protocols (PRISMA-P, 2015).The study was registered at PROSPERO with registration number CRD42020186693.

Results
Initially, 116 articles were retrieved.After removing duplicates, 96 articles were screened for titles and abstracts, and 82 were excluded.To assess eligibility, 14 articles were selected for full-text reading, of which seven were excluded because they did not meet the inclusion criteria (Figure 1).Thus, seven 7 RCTs were included in the review.
Table 1 presents the characteristics of the studies, and description of the intervention and of methodological quality assessed using the PEDro scale.The years of publication ranged from 2012 to 2020; the study populations were adults and elderly men and women aged from 18 to 75 years undergoing CABG, 10,,11,13-16 -.
A total of 697 participants were included, 350 in the intervention group (IG) and 331 in the control group (CG); the studies were conducted in Australia, 11 Iran, 10 Egypt, 12 Brazil, 13,15 China 14 and Germany. 16nctional capacity was assessed using different methods and measurements, including stationary cycling, 11 inspiratory muscle training (IMT) and early ambulation, 13 the six-minute walking (6MW) test, timedup-and-go (TUG) test 15 and -the MacNew questionnaire, 16 and respiratory muscle strength combined with oneminute sit-to-stand test and intensive care unit (ICU) length of stay. 15An article reported a reduction in the incidence of atelectasis and pleural effusion by EM, 10 and another study showed improvements of IMT and alveolar-arterial gradient by using a threshold load inspiratory muscle trainer (POWERbreathe) and EM resulted in improvement of inspiratory muscle power,   and oxygen saturation. 12A study reported reduction in PO length of hospital stay and improvements in physiological and psychological symptoms with early ambulation. 14st-traumatic stress disorder in patients undergoing CABG submitted to early ambulation (was lower (P < 0.001) compared to controls, 14 and significant improvements in functional capacity, TUG and quality of life of patients awaiting elective CABG undergoing anexercise-based prehabilitation program. 15'Also, patients receiving protocols combining active physical exercises and early walking experienced a more effective recovery of functional capacity, both before hospital discharge and 30 days after discharge. 13On the other hand, there was no difference between the cycle ergometer and supervised walking in the recovery of functional capacity. 11Most training programs were carried out twice a day, in the PO period until hospital discharge.The beginning of the interventions varied from the first PO day , 14,15 the second PO day 10,12,13 to the third PO day, 11 and from baseline to the end of cardiac rehabilitation. 16sults of analysis of the methodological quality of the articles, using the PEDro scale, are shown in Table 2.The scores of all included studies were equal to or greater than five.

Discussion
The present systematic review demonstrated that EM techniques were effective in promoting rehabilitation and preventing functional decline of patients in the PO period of CABG surgery.Improvements in functional capacity, respiratory muscle power, quality of life, changes of arterial gases and in the alveolus-arterial gradient, and reductions in the incidence of atelectasis and pleural effusion and in hospital stay were reported in the studies included in the review.
Hirschhorn et al. 11 showed that both stationary cycling and moderate walking exercise were effective in recovering functional capacity in the immediate PO period of CABG.There was no difference in hospital discharge compared between groups in the 6MW test (P = 0.803) and in the 6-minute cycle work (P = 0.798).However, when compared to preoperative data, all patients obtained a significant reduction in the 6MWA and 6MCA tests (P < 0.001).
Regarding the subjective perception of effort, EM activities, according to BORG scale were between easy and slightly tiring, which is in accordance with the guidelines of the American college of sports medicine. 17his may partially explain the positive results of EM on functional capacity.The level of effort perceived must be within acceptable levels to promote the best results, without presenting risks to patients.
Zanini et al. 13 evaluated different rehabilitation protocols after CABG.The CG that only received conventional pulmonary therapy, despite showing less recovery in functional capacity, obtained longer 6MW distance, reaching values similar to the preoperative ones.Interestingly, this study 13 did not assess subjective perception of effort during EM, which may have contributed to underestimating exercise capacity of patients, who were submitted to an amount of exercise that was less than necessary.In addition to the intensity, other exercise prescription parameters were not clear, such as time, and whether the active training of limbs included resistance / calisthenic exercises focused on improving the resistance of patients (e.g., exercises with low load and greater number of repetitions).
In the study by Moradian et al., 10 EM reduced the incidence of atelectasis and pleural effusion.This fact is relevant, as these conditions compromise gas exchange, reducing uptake and consequently the maximum oxygen consumption (VO2máx.), in addition to increasing dyspnea. 18In fact, the mean PaO2 was 95 ± 2.5 mmHg in the IG and 93.5 ± 3 mmHg in the CG (P value = 0.01), with SaO2 of 92/3 versus 91% respectively (P value = 0.03).It is known that oxygenation, together with VO2max, is directly proportional to exercise capacity, and its elevations often correspond to an increase in the distance covered in tests such as the 6MW test. 17rroborating with these findings, Hanada et al. 19 evaluated, in a retrospective study, the effectiveness of EM in preventing pulmonary complications in a group composed of 118 PO patients undergoing video-assisted thoracoscopic surgery.All participants underwent preoperative physiotherapy and EM in the PO period in the form of walking and activity of daily living without the assistance of the physiotherapist.The results showed a decrease in the incidence of PO pulmonary atelectasis (P <0.001).
Turky and Afify 12 (2017) evaluated changes in the arterial alveolus gradient and respiratory muscle power with IMT in the preoperative period and IMT and EM after surgery .After extubation, there was a progressive increase in the alveolar-arterial gradient , followed by a gradual decrease 24hrs (P <0.005), 48hrs (P <0.004) and at the end of the study (P = 0.02).The IMT through positive end-expiratory pressure provided the patient with alveolar expansion, improved gas exchange, oxygenation, right ventricular afterload , and in CABG, it may promote alveolar recruitment, reducing the incidence of atelectasis caused by prolonged time of extra-bodily circulation, surgical trauma and anesthesia. 20Also, EM significantly improved respiratory muscle power measured by PImax, one day after extubation (P <0.001) and at the end of the study (P <0.001).Corroborating this, in a controlled study, Bonorino used the same IMT protocol (2x daily 3 series of 10 breaths) in the IG and found that preoperative training increased Plmax , resulting in a lower incidence of pulmonary complications.
A recently published clinical trial 14 showed significantly shorter hospital stay and faster physiological and psychological functional return in older adults after CABG, as well as better levels of arterial oxygenation with an accurate mobilization program.Exercise intensity was individualized based on age-predicted maximal heart rates.The use of these physiological parameters, compared with the CG (routine rehabilitation) allowed most of the intervention participants to complete the low-intensity exercises in a controlled manner, resulting in a lower incidence of post-surgical complications such as hypotension and orthostatic intolerance. 21This allows greater safety for these older patients, considering that these complications have a significant positive association with falls. 22wever, the study has low statistical power for secondary outcomes due to the small sample size, clinical limitations in early ambulation, high risk of bias due to the inclusion criteria of age and type of surgical procedure, and lack of blinding participants and therapists.This limits generalization or results to other hospitals that do not adopt the same interventions after CABG difficult.
Steinmetz et al. 15 aimed to determine the impact of an exercise-based pre-rehabilitation program (exercise bike and gymnastics), in the pre-and post-CABG on functional capacity and quality of life of elderly patients.The CG did not perform this program in the preoperative period and both groups performed cardiac rehabilitation in the PO period.The results of the pre-and post-CABG tests demonstrated that the individualized pre-rehabilitation program was efficient in improving functional capacity of the IG, in addition to positively influencing the cardiac rehabilitation in the PO period, even without affecting cardiopulmonary capacity.
The aforementioned results corroborate previous pilot studies that showed a significant difference in functional capacity with tests conducted before and after myocardial revascularization surgery, in addition to a reduction in the length of hospital stay (in the PO period) in patients who underwent pre-rehabilitation protocols before procedure. 23,24ndmoller et al. 16 evaluated the effects of two therapeutic interventions on rehabilitation of individuals in the PO period of cardiac surgery.One intervention was a standardized and progressive exercise protocol, which consists of an individualized physical therapy program.This protocol was compared with a new References intervention that combined physical exercises in a cycle ergometer with continuous positive airway pressure (CPAP) and showed that the latter was safer and decreased the ICU length of stay.This result suggests a significant impact of the physical therapy intervention on hospital costs and on functional capacity of the individuals.
Although the two protocols presented in this study have shown benefits for the patients, the second has led to additional improvements.However, studies comparing the effects of the physical training on a cycle ergometer alone and the combination of this training with CPAP are still needed.Furthermore, this study had two main limitations, first, it was not possible to blind the subject or the physiotherapist for the type of treatment and, second, it was not possible to evaluate the subject in the immediate PO period to compare the outcomes between the pre-and post-periods.
The results of the present study corroborate those of the systematic review by Silva et al. 25 aimed to systematize EM in the ICU.The authors concluded that EM prevented neuromuscular disorders associated with a long length of stay in the ICU, and improved functional capacity, quality of life, and functional parameters such as peripheral and respiratory muscle strength.Although the populations of the two studies were different, we can somehow extrapolate the study result to patients with CABG, as both groups of patients (ICU and CABG) are exposed to the effects of immobilization during hospitalization.
It should be noted that EM provides the patient with significant gains in terms of functionality, quality of life, overall muscle strength, ICU length of stay and hemodynamic variables in the PO period.When administered and monitored by the physiotherapist, kinesiotherapy and cycle ergometer exercise are safe and can reduce the incidence of adverse effects.The presence of a multidisciplinary team is essential to make EM possible. 8though the articles included had a PEDro scale score ≥ 5, the total number of articles is relatively small.This is a reflection of the low number of studies addressing EM alone in the PO period of CABG.

Conclusion
EM is effective in the prevention and rehabilitation of functional parameters after CABG.Especially when combined with other techniques, EM promoted an improvement in functional capacity, respiratory muscle power, gas exchange and quality of life, and a reduction in the incidence of atelectasis and pleural effusion.

Table 1 -Characteristics of included studies Author and year Study design Pedro scale Sample Intervention Control Analyzed outputs Main results
RCT: