• cessation of agitation [ Time Frame: 3 hours ]
  
• improvement in the clinical and biological parameters of weaning trial [ Time Frame: 3 hours ]
  

Mechanical ventilation is a life-saving procedure in critically ill patients. This procedure is however not devoid of risks and every effort should be made to shorten its duration. This is best accomplished by the implementation of weaning protocols. Sedation (by opiates and benzodiazepines) is often required in such patients for their comfort and adaptation to the respirator. Withdrawal of sedation in order to allow patients to resume spontaneous breathing may be associated with agitation and confusion that may hinder weaning. In such cases, reinstitution of heavy sedation will prolong ventilator-dependency. It may therefore be interesting to administer a neuroleptic (loxapine) with good anxiolytic properties but that does not notably interfere with spontaneous breathing ability.

Patients will be included when they fail a spontaneous ventilation trial (see inclusion criteria) because of marked agitation. Usual simple clinical (respiratory frequency, P01 measured on the respirator, arterial pressure, cardiac rate) and biological criteria (arterial blood gas determination) and a measurement of sedation/agitation with validated scales (Richmond agitation sedation scale, Ramsay score) will be gathered when a patient is deemed ready for a trial of spontaneous ventilation for weaning. In cases of marked agitation according to validated scales, patients will be given a conventional dose (150 mg) of loxapine by the nasogastric tube and the efficacy of this treatment will be evaluated on the same parameters as above. Demonstration of the facilitation of weaning by this simple strategy would be useful in order to reduce risks associated with mechanical ventilation.