Objectives: To evaluate portable ventilators.
Design and settings: Bench study.
Materials and methods: Five portable ventilators used for transporting ICU patients [Osiris 1, (ventilator a), Osiris 2, (ventilator b), Oxylog 1000, (ventilator c), Oxylog 2000, (ventilator d), AXR1a, (ventilator e)] and three ICU ventilators which can be used for this purpose [Horus, (ventilator f), T-Bird, (ventilator g), and SV 300, (ventilator h)] were compared using a test lung regarding: 1) their capability to maintain set tidal volumes (V(T)) of 300 ml, 500 ml, and 800 ml under a normal condition A [resistance (R) 5 cmH(2)O/l/s and compliance (C) 100 ml/cmH(2)0] and two abnormal conditions B (R 20-C 30) and C (R 50-C 100); 2) trapped volume (expired V(T)relative to inspired V(T)at 0.7 s, 1 s, and 1.4 s), an estimate of the expiratory resistance of both circuit and valve; and 3) the triggering system assessed from the measurements of Delta t, Delta P for two inspiratory efforts at a PEEP of 0 cmH(2)0 and 5 cmH(2)0 in ventilators b, d, f, g, and h. Flow and airway pressure were measured with an independent physiologic recording system.
Results: 1) V(T). For ventilators a-h, the mean+/-SD changes of a set V(T)of 300 ml were -2.6+/-0.2%, -9.7+/-0.2%, 0+/-0%, -6.1+/-0.2%, 1.0+/-0.3%, -2.1+/-1.7%, 0.3+/-0%, and -1.3+/-0.1% ( P<0.001), respectively, during condition B relative to A. Similar results were obtained for a V(T)of 500 ml and 800 ml and during condition C relative to A; 2) Trapped volume. For ventilators a-h, trapped volume averaged 1+/-1%, 20+/-0%, 30+/-0.4%, 20+/-1%, 1+/-0%, 19+/-0%, 15+/-0%, and 14+/-0% at 0.7 s ( P <0.001) and 0.6+/-0%, 5+/-0%, 0.5+/-0%, 0+/-0%%, 0+/-0%, 0.6+/-0%, 0+/-0%, and 0+/-0% at 1.4 s ( P=NS); and 3) the triggering system of Oxylog 2000 was poor whereas it was of good quality for Horus, T-Bird, SV 300, and Osiris 2.
Conclusions: The small portable ventilators presently investigated varied between each other and were less accurate than ICU ventilators.