Evaluation of ventilators used during transport of ICU patients - A bench study

Abstract

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 (VT) of 300 ml, 500 ml, and 800 ml under a normal condition A [resistance (R) 5 cmH2O/l/s and compliance (C) 100 ml/cmH20] and two abnormal conditions B (R 20-C 30) and C (R 50-C 100); 2) trapped volume (expired VT relative to inspired VT 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 Δt, ΔP for two inspiratory efforts at a PEEP of 0 cmH20 and 5 cmH20 in ventilators b, d, f, g, and h. Flow and airway pressure were measured with an independent physiologic recording system. Results: 1) VT. For ventilators a-h, the mean±SD changes of a set VT 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 VT 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.