Influência da atuação fisioterapêutica no processo de ventilação mecânica de pacientes admitidos em UTI no período noturno após cirurgia cardíaca não complicada

Este estudo pretendeu verificar se a presenca do fisioterapeuta influencia no processo de ventilacao mecânica de pacientes submetidos a cirurgia cardiaca nao complicada e admitidos em UTI cardiologica no periodo noturno. Trata-se de estudo documental retrospectivo com pacientes adultos submetidos a cirurgia cardiaca e admitidos na UTI no periodo noturno nos meses de novembro de 2010 a outubro de 2011, com assistencia fisioterapeutica por 12 horas (n=51) e entre novembro de 2011 e outubro de 2012, periodo com assistencia fisioterapeutica por 24 horas (n=43), no Hospital Universitario da Universidade Federal do Maranhao. Para analise estatistica, foram utilizados os testes qui-quadrado, t de Student e G, sendo os dados considerados estatisticamente significantes quando p<0,05. A duracao da ventilacao mecânica foi menor quando ocorreu assistencia fisioterapeutica no periodo noturno (6,7±3,7 horas vs. 8,7±3,1 horas, p=0,02). Nesse mesmo periodo, o numero de pacientes extubados em tempo inferior a seis horas tambem foi significativamente maior (53,4% vs. 27,4%, p=0,0182), assim como o numero de extubacoes programadas (79% vs. 43,1%, p=0,009). A atuacao fisioterapeutica influenciou o processo de ventilacao mecânica de pacientes submetidos a cirurgia cardiaca nao complicada e admitidos na UTI no periodo noturno, reduzindo o tempo de ventilacao mecânica e aumentando o numero de extubacoes em tempo inferior a seis horas e o numero de extubacoes programadas durante a noite.


INTRODUCTION
Cardiac surgery is a complex procedure that involves the alteration of several physiological mechanisms, the contact with medicines and materials that may be harmful to the organism, as well as the imposition of a high organic stress, requiring thus intense postoperative care for the maintenance of the patient's healthy recovery 1 .
The use of anesthesia is one of the factors that causes ventilation-perfusion mismatch, probably associated with secondary atelectasis and with the closing of distal airways.The postoperative pain and the presence of drains imply low lung volumes.Considering that this case of pulmonary dysfunction is related to cardiac surgery and its possible repercussions, physiotherapy has been required as an attempt to reverse or reduce such conditions, avoiding pulmonary complications 2 .
In Brazil, physical therapists are increasingly present in the Intensive Care Units (ICU).This insertion was initiated in 1970 and its assurance as part of the intensive care team has been progressive.The reflection on this subject could generate guidelines and goals to provide recommendations of therapeutic practices, standardization of the administrative structure, technical and managerial training, definitions of labor relations, health and cost effectiveness, and qualified remuneration, with more efficient results along with the population of critical patients 3 .
Physiotherapy in the pre-and postoperative (PO) period is part of the treatment of patients who underwent cardiac surgery.Physiotherapeutic care encompasses a variety of techniques, including breathing pattern exercises, early ambulation, kinesiotherapy, positioning, and stimulus to cough.Respiratory physiotherapy, following the arrival in the ICU, contributes a lot to the proper ventilation and to the success of the extubation 4 .
Mechanical ventilation (MV) is a resource used therapeutically in ICU, aiming at the maintenance of gas exchange, replacement of spontaneous breathing, reversal or prevention of respiratory muscle fatigue, decreased oxygen uptake, and application of specific therapies 5 .Recent studies show that 33% to 46% of the patients admitted to these units use MV sometime during the hospitalization 6,7 .Currently, most patients submitted to mechanical ventilatory support can be quickly removed from the ventilator, as soon as the condition responsible for their hospitalization has been treated and/or stabilized 8 .
The patients in the postoperative period of cardiac surgery are usually extubated immediately after the anesthesia effect; however, approximately 3 to 6% of them may require prolonged MV, due to the complexity of the cardiovascular pathology, pulmonary dysfunction or other systemic changes.The amount of material and financial resources used by these patients are high, therefore, strategies to reduce such costs are necessary 9 .
In clinical or general ICU units it remains controversial whether full-time physiotherapeutic care is able to reduce the time of mechanical ventilatory support 10,11 .On the other hand, studies showed that a reduction in the time of mechanical ventilation is one of the main clinical benefits of the implementation of the night practice of physiotherapy in ICU, especially in postoperative units 12,13 .
The aim of this study was to verify if physical therapists influence the mechanical ventilation process of patients who underwent non-complicated cardiac surgery admitted to the Cardiac ICU overnight.

METHODOLOGY
Documentary and retrospective study developed in a university hospital, after approval by the Research Ethics Committee, under opinion no.428,632, according to Resolution CNS/MS no.466/12.
The population of the study consisted of adult patients who underwent cardiac surgery admitted to the Cardiac ICU overnight from November 2010 to October 2011 (with physiotherapeutic care only during the day) and from November 2011 to October 2012 (with physiotherapeutic care 24 hours).This ICU offers 10 beds, with one physical therapist for every 10 beds in both moments of the research.
We included all adult patients submitted to myocardial revascularization surgery and valve replacement (aortic and/or mitral valve) with the use of cardiopulmonary bypass (CPB) in the periods proposed, they were extubated within 12 hours after admission to the ICU.This time is considered, because the need for prolonged mechanical ventilation after cardiac surgery is usually associated with the occurrence of postoperative complications, such as metabolic acidosis or excessive bleeding.
We excluded individuals with lung or neurological disease, the ones who underwent associated or emergency surgeries, and those who died in the perioperative period, before the weaning from the ventilatory support.
The necessary data for the study were taken from the Physiotherapeutic Evolution of the Cardiac ICU Form.In this unit, the physical therapist conducts the mechanical ventilation process, since the hospitalization until the interruption or weaning, which was shared with the medical team.
All patients used the mechanical ventilator Evita 2 dura (Dräger Medical, Lübeck, Germany).They were admitted to the Cardiac ICU according to the protocol established in the volume-controlled mode, with the following parameters: tidal volume between 6 and 8 ml/ kg; positive end expiratory pressure (PEEP) of 8 cmH 2 O; respiratory rate equal to 14 ipm; inspiratory flow from 8 to 10 times the volume; inspiratory time of 1 second, and inspired oxygen fraction of 40%.In the period in which there were only 12 hours of physiotherapeutic care, the mechanical ventilators were programmed by the physical therapist of the afternoon shift, according to the patients' characteristics, previously passed by the surgical center.
As soon as the patients showed satisfactory clinical conditions, such as hemodynamic stability, absence or minimal bleeding; Glasgow Coma scale >10, the spontaneous breathing trial was initiated (SBT) according to the routine of the sector, in the pressuresupport mode (PS=7cmH 2 O, PEEP=5cmH 2 O, FiO 2 <40%), being conducted the extubation after 30 minutes to 2 hours, as long as the patient did not show any sign of intolerance to SBT.
The collected data were subjected to statistical analysis using the program Stata/SE 11.1 (Statacorp, College Station, Texas, USA).Quantitative data are expressed through mean and standard deviation, and their differences were verified using the Student's t-test.The qualitative variables were expressed in the form of proportions and the association was tested through G or Chi-square test, using the Yates correction.The results were considered statistically significant when p<0.05.

RESULTS
Ninety four patients were included in this survey, 51 of the first period, with physiotherapeutic care during the day (Group 12), and 43 of the second, with 24 hours of physiotherapeutic care (Group 24).Table 1 shows the demographic and clinical characteristics, and Table 2 shows the surgical characteristics.The groups were homogeneous regarding these variables, which may suggest that there is no difference in the severity of patients from both periods studied.The average time of mechanical ventilation was 7.8±3.5 h, being lower when physiotherapeutic care occurred at night (6.7±3.7 h vs. 8.7±3.1 h, p=0.02) (Figure 1).In this same period, the number of patients extubated in less than six hours was also significantly higher (53.4% vs. 27.4%,p=0.0182), as well as the number of scheduled extubations (79% vs. 43.1%,p=0.009) (Table 3).

DISCUSSION
This study observed average time of mechanical ventilation of approximately 8 hours and showed that the increase of physiotherapeutic care overnight, for a total of 24 hours, provided significant clinical benefits: reduction in the time of mechanical ventilation and greater number of extubations in less than 6 hours after surgery.These benefits were achieved mainly by the great number of extubations carried out at night.
According to Mendez-Tellez and Needham 14 , early rehabilitation interventions for mechanically ventilated patients are safe and viable.These authors cite, as benefits of this practice, the improvement of the functional status and the reduced duration of mechanical ventilation and hospitalization.
In historical controlled trial with 501 patients, Malkoç et al 15 found that the group that received respiratory physiotherapy had a significant reduction in  the time of mechanical ventilation and hospitalization in the ICU when compared with a control group, reinforcing the importance of this professional in the intensive care unit.Lima 16 evaluated the profile of patients submitted to myocardial revascularization with physiotherapeutic care only during the day (12 hours) and observed average time of mechanical ventilation of 10 hours, a result similar to this research.Ribeiro and Santana 17 studied the same practice and showed high mechanical ventilation time (16 hours) in patients who underwent surgery using cardiopulmonary bypass for more than 90 minutes (an average of 100 minutes), little more than the one verified in this research.Also, the authors consider that the absence of the physical therapist at night lengthens the time of mechanical ventilation, since this professional, along with the medical team, is responsible for the processes of weaning from the ventilatory support and extubation.
In this context, Nunes 18 conducted a study that verified the view of the multidisciplinary team on the participation of the physical therapist in the weaning and extubation processes in the ICU with physiotherapy care for 12 or 24 hours, and found that most (>75%) professionals consider the mechanical ventilatory weaning the responsibility of doctors and physical therapists.The author also noted that the physical therapist has greater autonomy in handling the mechanical ventilation in the 24-hour care when compared with the 12-hour practice.Confirming these findings, Nozawa et al. 3 outlined the profile of physical therapists who work in Brazilian intensive care units and showed that most of them (80%) declared to carry out the procedures of mechanical ventilation weaning and extubation.
International research 19 and national 13,20,21 studies corroborate the findings of this research, indicating the decrease in the time of mechanical ventilation as the main result of the implementation of physiotherapeutic care at night.
Study conducted in Cingapura 19 showed a case of patient admitted to the ICU with physiotherapeutic care (24 hours) due to acute respiratory failure, the individual was subjected to six sessions on the first day and five on the second, which resulted in improved arterial oxygenation with radiographic resolution, being avoided the endotracheal intubation and the invasive mechanical ventilation.For the author the possibility of 24-hour access to physiotherapy reduces the chance of pulmonary complications.
Davidson and Velloso 13 surveyed two hospitals that performed cardiac surgery and showed that the full-time presence of the physical therapist on the team was one of the factors that accelerated the process of mechanical ventilation weaning and the discharge of the patient from the ICU, reinforcing the results of this study.
Castro et al. 20 conducted a bicentric study aiming to assess the differences between a hospital where patients received physiotherapeutic care 24 hour per day and another hospital with only 6 hour per day; the conclusion was that the presence of the physical therapist full time (24 hours) in the intensive care unit contributes to the early recovery of the patient, reducing the length of stay in the mechanical ventilation and hospitalization, as well as the incidence of respiratory infection and mortality, which corroborates the findings of this research.
In similarity to this research, Silva 12 conducted another one in a general postoperative unit comparing the results before and after the implantation of overnight physiotherapy.Although the patients with full-time care were older, had greater number of comorbidities, higher frequency of intraoperative complications, higher incidence of dialytic acute renal failure, and moderate to high-risk of surgery, in comparison with patients with partial care, they showed better clinical outcomes, characterized by shorter time of mechanical ventilation (4 days vs. 6 days) and less time in ICU (10 days vs. 15 days), endorsing this study.
Fernandes and Esbell 21 conducted a retrospective study involving six months before and six months after the implementation of the 24-hour intensive physiotherapeutic care.Data were collected from medical records of adult patients admitted to the ICU of the General Hospital of Roraima and they observed a reduction in the number of deaths and reduced length of stay in the ICU.This study did not examine these variables, which limits the comparison with the outcomes mentioned above.
Teixeira 10 did not observe reduced time of mechanical ventilatory support when the overnight physiotherapy, of 24 hours, was implemented; however, when the patients with neurological diseases were separated, the time of mechanical ventilation was lower.Methodological differences explain this divergence.The author conducted the research in a general clinical-surgical unit with patients on mechanical ventilation for more than 72 hours, and she also compared the results obtained after 18 hours (three physiotherapeutic sessions) and 24 hours (four physiotherapeutic sessions).
In contrast to this study, Santos et al. 11 also did not verified reduction of time of mechanical ventilation and hospitalization in comparison with the results of both physiotherapy practices in ICU (12 h vs. 24 h), however, the research shows methodological limitations due to the differences involving the classification of the ICU, number of beds, number of exclusive physical therapists, physical therapist/number of beds relation, and epidemiological profile of the patients in both hospitals.
The research described above seems to demonstrate the reduction of time in mechanical ventilation as the main clinical benefit from the implementation of the overnight practice of physiotherapy in ICU.This outcome is particularly achieved in postoperative units, as demonstrated by Silva 12 and Davidson and Velloso 13 , as well as by this research.In clinical or general units, however, it remains controversial if full-time physiotherapy (24 hours) is able to reduce the time of mechanical ventilatory support, as shown by Teixeira 10 and Santos et al. 11 The lack of assessment of secondary outcomes (permanence in the ICU, cardiac and pulmonary complications, mortality, and costs) can be considered a limiting factor of this research.

CONCLUSION
The physiotherapeutic practice influenced the mechanical ventilation process of patients who underwent non-complicated cardiac surgery admitted to the ICU overnight, reducing the time of mechanical ventilation and increasing the number of extubations in less than six hours, as well the number of extubations scheduled during the night.

Figure 1 .
Figure 1.Duration of the mechanical ventilation of patients who underwent cardiac surgery according to the periods with physiotherapeutic care for 12 and 24 hours

Table 1 .
Demographic and clinical characteristics of patients according to the periods with physiotherapeutic care for 12 and 24 hours c BMI -Body Mass Index; ASA -American Society of Anesthesiologists; SH -systemic hypertension; AMI -acute myocardial infarction; CRF -chronic renal failure.a Chi-square test; b Student's t-test; c G test

Table 2 .
Surgical characteristics of patients according to the periods with physiotherapeutic care for 12 and 24 hours