Abstract..........................................................................................................04 Introduction....................................................................................................10 Methods.........................................................................................................14 Financial Support...........................................................................................22 References.....................................................................................................24

1. INTRODUCTION Patients undergoing invasive mechanical ventilation (IMV) have an intense predisposition to the development of muscle weakness in the first hours after the orotracheal intubation process, since they are exposed, among other factors, to sedative drugs, immobilization and properly controlled ventilation (DEMOULE et al., 2016). It is observed that approximately 25% to 50% of patients submitted to ventilatory support have muscle weakness and, of this proportion, 85% to 95% persist with neuromuscular impairment for a period of two to five years.

   In this context, the elderly deserve attention because the demographic transition process has the inversion of the age pyramid as one of its characteristics (WONG et al., 2006). This leads to a higher incidence of admissions of these patients in intensive care units compared to young people and adults, considering that they represent the largest portion of the population.

   Among the muscles affected by permanence in IMV in the general population and especially in the elderly, the diaphragm can be highlighted, which evolves with a reduction in its ability to generate tension due to the atrophy of its muscle fibers. This leads to an alteration called diaphragmatic dysfunction (DD). The mechanisms involved with DD are the reduction in the number of myofibrils (proteins that involve filaments of actin and myosin responsible for the production of muscle contraction), oxidative stress (inducing the activation of the forkhead box O1 protein, involved with the processes of gluconeogenesis and glycogenolysis) and the abnormal activation of a pathway responsible for the proteolysis of adenosine triphosphate, ubiquitin-proteasome.

   Considering the progressive characteristic of DD, some consequences such as increased IMV time, increased risk of respiratory complications and prolonged hospital stay can be observed, if no specific intervention is performed . Therefore, it is necessary to adopt measures that allow the early detection of diaphragmatic weakness, as well as the use of conducts that prevent or treat this clinical condition.

   As for the diagnosis of DD, it can be performed using instruments that measure inspiratory muscle strength, such as the manovacuometer, in addition to imaging tests that show the diaphragmatic thickness (FDI), such as pulmonary ultrasonography (PU) . The variable referring to inspiratory muscle strength in manovacuometry is the maximum inspiratory pressure (MIP), while the thickness of the diaphragm, verified through the PU, is represented by the diaphragmatic thickening index (DTI), obtained through the difference between the diaphragm thickness total lung capacity (DTTLC) and functional residual capacity (DTFRC), divided by DTTLC. The FDI contributes to the initial diagnosis of DD and is also relevant for monitoring the evolution of diaphragm function during the period of hospitalization and ventilatory weaning. According to Goligher et al. (2015), the decrease in FDI is associated with impaired function of the diaphragm and is correlated with low values of MIP in critically ill patients.

   After obtaining variables related to the function of the diaphragm, as previously described, conducts aimed at preventing or treating DD are important in an attempt to minimize possible damage to the critical patient. Within outpatient pulmonary rehabilitation, positive effects have been demonstrated with the use of electrotherapy, specifically through the technique of transcutaneous electrical diaphragmatic stimulation (TEDS) in patients with chronic obstructive pulmonary disease (COPD). This technique consists of placing electrodes on the skin, in places close to the motor points of the diaphragm, transmitting an intermittent current and generating action potentials capable of producing muscle contractions. However, in the literature, there is no evidence on the effects of this therapy on the FDI of elderly critically ill patients, or even to assess the impact of TEDS on the time of mechanical ventilation and hospitalization of this population. In view of the practicality of this treatment, its low cost and the scarcity of evidence on this topic, the objective of the present study will be to assess the influence of TEDS on respiratory muscle strength, diaphragm thickness and duration of mechanical ventilation in critically ill patients under care intensive.

2. METHODS

   2.1. Study Design and Recruitment

   The present study will be a controlled randomized clinical trial. It will also be registered in the Clinical Trials.

   All research participants will be submitted to the assessment of respiratory muscle strength (manovacuometry) and diaphragm thickness (PU), and only EG patients will be exposed to an intervention through the use of TEDS.

   2.2. Sample

   The sample will consist of participants of both sexes, over the age of 60, who have undergone IMV. The research participants will be divided into a control group (CG) and an experimental group (EG) and will carry out the same evaluation steps during the spontaneous breathing test after weaning from mechanical ventilation, with only the EG undergoing TEDS. The details of the intervention will be exposed later.

   2.3 Proposed Procedures / Methods

   The evaluation of the research subjects will take place in the Adult Intensive Care Units (I and II) of the Hospital e Maternidade Therezinha de Jesus - Juiz de Fora.

   2.3.1. Distribution of Participants, Evaluation and Intervention

   The research participants will be submitted to the evaluation of the FDI through the PU, as well as of the respiratory muscle strength, through the manovacuometry, immediately after the ventilatory weaning. It is worth noting that weaning and extubation will be carried out following an institutional checklist (Appendix I) for greater patient safety.

   The EG, immediately after the 24-hour period on VMI, will be submitted to TEDS, twice a day, with an interval of six hours between therapies to prevent respiratory muscle fatigue. Initially, it will be performed with the patient in assisted-controlled ventilation mode and well adapted to ventilation. The sensitivity parameter will be adjusted to the value necessary so that the contractions produced by electrical stimulation do not trigger the mechanical ventilator, preventing episodes of asynchrony. After the suspension of drugs with a sedative effect (such as benzodiazepines and endogenous opioids) and the ventilatory drive is resumed, TEDS will continue to be used in EG patients until extubation, in spontaneous ventilation, following the same protocol, however with the sensitivity readjusted to the standardized values to prevent muscle fatigue. The procedures will be detailed below.

   2.3.2. Pulmonary Ultrasound

   Ultrasonography is a simple, safe and relatively low-cost procedure that, when using exact equipment and standardized techniques applied by trained professionals, provides relevant information on the respiratory system that has been demonstrated over the last few years (DEMI et al., 2014).

   The patient will position himself in the supine position and there will be the use of the linear transducer to evaluate the superficial structures and the cardiac transducer to evaluate the deep ones. There is a wide range of techniques to be employed, but the eight-zone assessment is practical and quick to perform in emergency assessment and in intensive care patients. The latter consists of the scanning of four areas by hemithorax, namely: zones 1 and 2 indicate the upper anterior chest wall and the lower anterior one respectively, and zones 3 and 4 indicate the upper lateral chest wall as well as the lower lateral wall, respectively.

   The equipment used to perform all pulmonary ultrasound exams will be the GE LogiqE (Logiq-E GE 2014, Contagem, MG, Brazil), from the Ultrasonography Sector of the Hospital and Maternidade Terezinha de Jesus, Juiz de Fora (MG).

   2.3.3. Assessment of Respiratory Muscle Strength

   According to the American Thoracic Society (2002), the appropriate protocol for obtaining the measurements related to respiratory muscle strength (MIP) must respect the following characteristics: a) environment with a temperature of approximately 21ºC; b) previous calibration of the manovacuometer; c) patient in a sitting posture (head elevated by 90 °); and d) execution of a maximum inspiration starting from the residual volume (RV) to reach the total lung capacity (TLC). The procedure must be repeated two more times, with an interval of two minutes between repetitions (prevention of muscle fatigue) and the measures of MIP and maximum expiratory pressure (MEP) considered will be the highest recorded. The equipment used will be brand M120, with a scale of 4 cmH2O, with variation of +/- 120 cmH2O.

   2.3.4. Transcutaneous Electrical Diaphragmatic Stimulation

   The TEDS protocol will consist of the following parameters: a) frequency of 30 Hz; b) pulse width of 0.4 ms; c) respiratory rate of 15 irpm; d) holding time of 1 s; e) rise time of 1 s; f) 2 s descent time; and g) 2 s non-stimulus time. Phrenics equipment (Dualpex 961, Quark®, SP, Brazil) will be used. The positioning of the electrodes will be performed according to a study by Cancelliero et al. (2012), who proposed the placement of two electrodes in the right and left paraxiphoid regions, and two others in the direction of the axillary midline, over the seventh intercostal space, also on the right and left sides. The duration of the procedure will be 30 minutes, twice a day, with a six-hour interval between applications, until the patient undergoes the extubation process. As long as it does not have a level of consciousness, is not in spontaneous ventilatory mode and without the use of drugs with a sedative effect, the sensitivity of the ventilator will be adjusted in a way that does not trigger the equipment, to avoid episodes of asynchrony. Immediately after recovering the level of consciousness, resuming the ventilatory drive and suspending sedative drugs, the patient during TEDS will be stimulated to inhale after the perception of the arrival of the electric current, in spontaneous mode, and with the sensitivity adjusted to the baseline values.

   2.3.4. Scratchs

   There are chances of hemodynamic decompensation and respiratory distress during the use of TEDS in EG patients, including changes in heart rate, blood pressure, as well as respiratory rate and synchronization with the mechanical ventilator. If the events described occur, the TEDS procedure will be stopped immediately. Ventilatory adjustments will be made by the researcher according to the demands presented and the doctor on duty will be informed to adopt conducts aimed at the patients' hemodynamic recovery, regarding medication adjustments. There will be supervision by the responsible researcher and the rest of the multidisciplinary team.

   2.3.5. Benefits

   Benefits may be generated for the study participants, including the reduction in the time of mechanical ventilation, hospitalization, in addition to the probable rapid reintegration of patients into activities of daily living after discharge, since diaphragmatic muscle weakness contributes substantially to the delay in the process of recovering functionality.

3. FINANCIAL SUPPORT

The equipment used in the research is available at the Therezinha de Jesus Hospital and Maternity Hospital in the city of Juiz de Fora, state of Minas Gerais.

Inclusion Criteria:

• Patients aged ≥ 60 years who underwent IMV.

Exclusion Criteria:

• Recent surgical scar and/or open lesion in the regions where the electrodes would be placed
• Severe hemodynamic instability
• Patient-ventilator asynchrony not reversible with adjustments or optimization of sedation
• Hypoglycemia < 60 mg/dL
• Presence of a cardiac pacemaker
• Undrained pneumothorax
• Use of increasing doses of vasoactive drugs.

The study has a double blind characteristic. Neither the researcher nor the research subject is aware of his group.