Protocol-directed Weaning From Mechanical Ventilation in Neurological Patients: a Controlled Trial

Protocol Patients will be included in the study if they meet the following conditions: no or minimal sedation (Propofol ≤1miligram per kilogram per hour (mg/kg/h) o Midazolam ≤0,1mg/ kg/h), with a spontaneous ventilatory stimulus, absence of intracranial hypertension, Glasgow Coma Score > 9 (with a motor score > 4 points), Noradrenaline ≤ 0,2mcgr/kg/min, fraction of inspired oxygen ≤ 0.5, positive end-expiratory pressure of 5 centimeters of water (cmH20), no scheduled surgery in the next 48 hours, maximal inspiratory pressure < -20 cmH20 (means occlusion pressure test) and a airway occlusion pressure at 0.1 sec (P0.1) >6 millimeters of mercury (mmHg) with a support pressure of 7 cmH20 and 0 cmH20 of positive end-expiratory pressure.

Protocol study (study group). Spontaneous Breathing Trial (SBT). The patient will be connected to mechanical ventilation in a pressure support ventilation mode, which one will be gradually reduced (until a level de pressure support of 10 cmH20 above 5 cmH20 of positive end-expiratory pressure). After, the patient will be disconnected from the ventilator and a spontaneous breathing trial will begin through the connexion of the patient to a T-tube and a source of oxygen. Hemodynamic parameters [systolic blood pressure, heart rate], and breathing parameters [respiratory rate, partial pressure of oxygen, partial pressure of carbonic anhydrid, partial pressure of oxygen to fraction of oxygen ratio, and pH through blood gas analysis and saturation of oxyhemoglobin by pulse oximetry], and neurological (means by Glasgow Coma Score) will be collected during final period of pressure support ventilation (before disconnection) and at onset (5 minutes) and final (between 30 to 120 minutes) of spontaneous breathing trial. A once daily spontaneous breathing trial will be stablished in all the patients until they were extubated. Unsuccessful spontaneous breathing trial will be considered with more than 2 criteria: partial pressure of arterial oxygen of 50-60mmHg with fraction of inspired oxygen ≤ 0.5 (or transcutaneous pulse oximetry <90%), partial pressure of carbonic anhydride > 50 mmHg, pH <7.35, respiratory rate > 35breath per minute, heart rate > 140 beats per minute, systolic blood pressure > 180mmHg, cardiac arrhythmias during spontaneous breathing trial, dyspnea, and increased use of accessory muscles. If the SBT fails, the patient will reconnect to mechanical ventilation. A successful spontaneous breathing trial is defined as absence of whatever of variables above defined.

Airway Patency. Otherwise, if the spontaneous breathing trial is successful, the ability to maintain airway will be analyzed by the following variables: Number of aspirations of secretions/ nursing shift (No aspiration-0, 1 aspiration-1, 2 aspiration-2, ≥ 3 aspiration-3), cough capacity (Strong -0, Mild-1, Weak-2, Absent-3), Appearance and color of secretions: [Viscosity (liquid-0, frothy-1, thick-2, dry-3) and color (clear- 0, brown- 1, yellow-2, green-3)] and the presence of gag reflex (strong- 0, moderate- 1, weak- 2, absent- 3). A score ≤8 is considered as adequate to keep the permeability of airway. Then the patient will be extubated and connected to oxygen mask with fraction of inspired oxygen of 0.4. In case of extubation failure, the patient will be reintubated. The use of non-invasive ventilation is not considered in this study (neither prevention of extubation failure nor in case of extubation failure).

Conventional weaning (control group). Patients in the control group will receive weaning from mechanical ventilation according to the usual procedure, by reducing level of pressure support ventilation. Then a spontaneous breathing trial will be performed through a T-tube (the same parameters as protocol study will collected) and subsequent extubation of the patient if there is a successful spontaneous breathing trial. The criteria for spontaneous breathing trial failure and for extubation failure are the same than in the study group. In case of extubation failure, non-invasive ventilation will be not considered, but it left to the discretion of the attending physician.