Comparison of pressure and volume preset nasal ventilator systems in stable chronic respiratory failure.

Nasal intermittent positive pressure ventilation (NIPPV) has been widely used in the treatment of chronic respiratory disease. Ventilators may be volume or pressure preset; each type has theoretical advantages, but to date there has been no formal comparison. We wanted to assess the efficacy on blood gas changes that may be achieved and overall acceptability of four nasal ventilators (two pressure preset: Respironics bilevel positive airway pressure (BiPAP) and the Thomas NIPPY; and two volume preset: BromptonPac and Monnal-D) in patients with stable chronic respiratory failure. Median age was 59 yrs (range 48-71 yrs), mean (SD) arterial oxygen tension (PaO2) 7.16 (0.21) kPa, arterial carbon dioxide tension (PaCO2) 7.02 (0.35) kPa, forced expiratory volume in one second (FEV1) 0.76 (0.24) l, and forced vital capacity (FVC) 1.58 (0.49) l. All had previously used NIPPV. There were significant changes in blood gases at 2 h with each ventilator: mean change (95% confidence interval); BiPAP PaO2 +1.52 (0.95-2.09) kPa, PaCO2-1.04 (1.55-0.54) kPa; NIPPY PaO2 +1.63 (0.85-2.41) kPa, PaCO2, -1.1 (1.86-0.34) kPa; BromptonPac PaO2 +1.22 (0.75-1.67) kPa, PaCO2 -1.14 (1.52-0.76) kPa; Monnal-D PaO2 +1.14 (0.42-1.84) kPa, PaCO2 -1.19 (2.14-0.23) kPa. Analysis of variance showed no significant differences in the efficacy of volume or pressure preset equipment, and all ventilators proved equally acceptable to the patients studied. We conclude that all four of the volume or pressure preset ventilators examined are suitable for the delivery of nasal intermittent positive pressure ventilation in patients with stable chronic respiratory failure.