Performances of ventilator at simulated altitude

Introduction

We have assessed the ability of three ventilators to deliver to a normal lung model a set tidal volume (V_t) at different simulated cabin altitudes. We studied the performance of the LTV-1200 (Viasys Healthcare, USA), the Elisée 350 (Resmed, Australia) and the Medumat transport (Weinmann, Germany).

Methods

We used a decompression chamber to mimic the hypobaric environment at a range of simulated cabin altitudes of 2,438 and 3,657 m (8,000 and 12,000 feet). Ventilators were tested with a set fraction of inspired oxygen of 50% and V_t set at 450. Respiratory rate was 12 breaths/minute. Comparisons of preset to actual measured values were accomplished using a t test for each altitude. The protocol included 36 measurements for each V_t set at each simulated altitude. A significant difference was defined by P < 0.05.

Results

Figure 1 summarizes the data. Comparisons of actual delivered V_t in altitude and set V_t demonstrated a significant difference for the three ventilators.

Figure 1

Conclusion

The LTV-1200 showed a very significant increase in V_t delivered with increasing altitude (suggesting a lack of efficacy of altimetric correction in hypobaric conditions), whereas the Elisée 350 and Medumat transport delivered respectively a stable and a rather stable V_t.