RESPIRATORY DRIVE AND PULMONARY MECHANICS DURING HEMODIALYSIS WITH ULTRAFILTRATION IN VENTILATED PATIENTS

The improvements of respiratory drive and pulmonary mechanics which fo llow haemodialysis with ultrafiltration in mechanically ventilated ren al failure patients seem predictable but have not been studied before. In this study, 14 renal failure patients with stable haemodynamics me chanically ventilated with pressure support ventilation (PSV) were enr olled. Respiratory drive (represented as PO.1), pulmonary mechanics, b reathing pattern, arterial blood gas and haemodynamics were measured a ccording to the time schedule: pre-dialysis (Time 0), and at 60, 120, 180, 240 minutes thereafter. Following the removal of excess lung wate r during haemodialysis, auto-PEEP and patient's work of breathing (WOB p) decreased gradually, PO.1 lessened progressively along with the imp rovement in pulmonary mechanics. The changes in auto-PEEP and WOBp cor related closely to the pre- and post-dialysis decline of PO.1 (Delta P O.1), There was a negative, moderately significant correlation between the amount of fluid ultrafiltrated during dialysis (Delta UF) and the Delta PO.1 (R = -0.54). The breathing pattern remained stable during dialysis, No hypoventilation or hypoxaemia occurred despite the develo pment of metabolic alkalosis induced by bicarbonate dialysate. We have shown that respiratory drive decreases gradually during bicarbonate h aemodialysis, The improvements of pulmonary mechanics, rather than the rapid alkalization of body fluids, responds to the decrease of PO.1 i n renal failure patients ventilated with PSV.