SHORT-TERM EFFECTS OF NASAL PROPORTIONAL ASSIST VENTILATION IN PATIENTS WITH CHRONIC HYPERCAPNIC RESPIRATORY INSUFFICIENCY

Proportional assist ventilation (PAV) has recently been proposed as a mode of synchronized partial ventilatory support, This study evaluates the short-term effects of nasal PAV on arterial blood gases in stable patients with chronic hypercapnia, Forty two patients (30 with chroni c obstructive pulmonary disease (COPD) and 12 with restrictive chest w all disease (RCWD) due to kyphoscoliosis) underwent a 1 h run of nasal PAV. Randomly, two levels of assistance were performed: 1) PAV was se t at a level corresponding to volume assist (VA) and how assist (FA) a t 80% of the individual values of elastance (Ers) and resistance (Rrs) obtained with the ''runaway'' method; and 2) VA and FA were set at a value corresponding to the difference between the patients' individual Ers and Rrs and normal values of Ers and Rrs, Arterial blood gases an d dyspnoea (by visual analogue scale (VAS)) were evaluated in all pati ents during unsupported ventilation and 60 min of PAV, PAV was well to lerated and resulted in significant improvement in arterial oxygen ten sion (Pa,O-2), arterial carbon dioxide tension (Pa,CO2) (6.8+/-0.8 to 7.4+/-1.4 and 7.2+/-0.9 to 6.8+/-0.9 kPa, respectively) and VAS (29+/- 23 to 20+/-18%). The effects of PAV were not different in the two grou ps of diseases nor in the two groups of settings, Different settings o f nasal proportional assist ventilation are well tolerated and may imp rove gas exchange and dyspnoea in patients with stable hypercapnic res piratory insufficiency.