Functional differences in bi-level pressure preset ventilators

The performance of four bilevel positive pressure preset ventilators was co mpared. The ventilators tested were; BiPAP ST30 (Respironics); Nippy2 (B+D Electric al); Quantum PSV (Healthdyne); and Sullivan VPAP TI ST (Resmed). A patient simulator was used to determine the sensitivity of the triggering mechanism s and the responses to a leak within the patient circuit, and to changes in patient effort. Significant differences (p < 0.05) between the devices were seen in the tri gger delay time and inspiratory trigger pressure. When a leak was introduce d into the patient circuit, the fall in tidal volume (VT) was less than ten per cent for each ventilator, The addition of patient effort produced a nu mber of changes in the ventilation delivered, Patient efforts of 0.25 s ind uced a variable fall in VT, An increase in VT was seen,vith some ventilator s with patient efforts of 1 s but the effect was variable. Trigger failures and subsequent falls in minute volume were seen with the BiPAP and the Nip py2 at the highest respiratory frequency, Differences in the responses of the ventilators are demonstrated that may i nfluence the selection of a ventilator, particularly in the treatment of br eathless patients with ventilatory failure.