 It is common practice in these patients to perform trials of spontaneous breathing while still connected to the ventilator in order to assess their readiness to breathe without assistance. To help with this assessment, new mechanical modes have been incorporated to modern ventilators. A recently developed mode, called Automatic Tube Compensation, is designed for this purpose spontaneous breathing. Whether this method is superior to traditional ones has not been established and the investigators intend to address this question. 