Baseline measurements will be taken. The NAVA titration study will then be done. The NAVA level will be set at a starting value of 0.1 cm H2O/mcV and systematically increased by 0.5 cm H2O/mcV every three minutes to a maximum of 3 cmH2O/mcV. Once the NAVA titration study has been completed, the patient will be extubated. There will be a stabilization period following extubation (15-30 minutes), and then the NAVA titration study will be repeated.