Post MV replacement ventilator dependence

85 yr old female. MV replacement 2002. On and off admissions for dyspnoea. Investigated for weight loss for the last six months. All negative.This admission with ?CAP. Fluid restricted in the ward went in for renal impairment and respiratory failure. Required ventilation and CRRT. ECHO transthoracic dilated left atrium smalll welll contracting ventricle LV. NO pulmonary HT and RV normal. ON CPAP5 with FiO2 0.3 Pressure support of 12. Tracheostomy because of failure to come offf the ventilator. ON Carvedilol,Nepro  feeds because her Urea goes upto 26mmols when she is not on CRRT for 3 days. At present HR 80s,MAP around 65. Bronchoscopy Normal. CT abdomen normal.
Every time tried for spontaneous breathing becomes tachypneic and hypercarbic and hypoxic. On ventilator with above support very comfortable. But for the Urea rise every 3-4 days requiring one day of CRRT all parameters normal.
Is she having Restenosis. Could it be Ottner's syndrome. TOE is organised but cardiologists feel TTE is OK.Could you help me. Patient is with us for nearly 2 weeks