A LABORATORY COMPARISON OF 4 POSITIVE PRESSURE VENTILATORS USED IN THE HOME

Four brands of ventilator used for noninvasive positive pressure venti lation in the home were assessed to determine their performance on a p atient simulator. We tested the tidal volume (VT) preset Companion 280 1 (Puritan Bennett), minute volume preset Monnal D (Taema), and two pr essure preset ventilators, the Nippy (Friday Medical) and the Bilevel Positive Airway Pressure (BiPAP) (Respironics). A patient simulator wa s employed to investigate the relationships between VT, peak ah-way pr essure (PAP) and mean airway pressure (MAP), the responses to an addit ional leak in the circuit and patient effort of a variable duration, w hich was modelled using a negative pressure pump. For equivalent VTs, >300 mL, the Monnal D and Nippy generated it PAP up to 100% greater th an the Companion 2801 and BiPAP. When an additional leak was introduce d to the circuit, the VT of the Companion 2801 and Monnal D felt by >5 0%, while the Nippy and the BiPAP responded by increasing flow and mai ntained VT close to the level achieved with no leak. When the ventilat ors were triggered by a simulated patient effort of 0.25 s duration wi th a frequency 33% greater than that of the ventilator, the minute vol ume increased by 41% for the Companion 2801, by 18% for the Monnal D ( no change expected), and by 17% for the Nippy (less than expected), an d fell by 7% for the BiPAP due to irregular triggering. When patient e ffort was prolonged to 1.5 s, a similar length to the inspiratory time of the ventilators, there was no further change in the minute volume of the Companion 2801 and Monnal D, while that of the Nippy and of the BiPAP increased by 38 and 71%, respectively, compared to baseline. Th ese results show that distinct brands of ventilator respond to changes in the patient and patient circuit in different ways, which are not a lways predictable from a simple description of their operating princip les. This should be borne in mind when choosing a positive pressure ve ntilator for noninvasive ventilation.