Is Optimal Minute Ventilation a Predictor of Weaning in Patients With Prolong Mechanical Ventilation?

Investigators will preform this study at our respiratory care center. Initially, Investigators collected all physiological parameters and baseline characteristics of patients with prolong mechanical ventilator. Investigators use Gold-Galileo ventilator and patients use adaptive support ventilation mode. In adaptive support ventilation, the clinician enters a target minute volume , using a parameter called minute ventilation percentage. The minute ventilation percentage setting be initially set at 100% (the 100%minute ventilation setting), which provides a target minute ventilation of 0.1 L/min/kg of ideal body weight . Investigators observed respiratory frequency of patients, the minute ventilation percentage was increased every 5 min until the mandatory breath began to appear and spontaneous rate is zero. If the minute ventilation percentage had exceeded 250%, but patients do not have mandatory rate appeared, the optimal minute ventilation of the patient is means above 250%. Investigators also measure other weaning parameters. Finally, Investigators analyze the prediction of optimal minute ventilation as a weaning parameter.