The Science Journal of the American Association for Respiratory Care
INTRODUCTION: Traditionally, PVTs have high imposed work of breathing (WOBI). Newer PVTs include flow triggering and PSV to minimize WOBI. We compared the WOBI and response time (RT) of 4 PVTs on a lung model.
Methods: A two-chambered test lung (TTL) was modified to mimic spont breathing. An Evita 4 (Drager) powered the ?drive? lung at 3 volume and flow conditions: 1) 300 ml @ 40 L/min, 2) 500 ml @ 60 L/min, and 3) 800 ml @ 80 L/min. TTL characteristics were C of 50 ml/cmH2O and R of 5 cmH2O/L/sec. PVTs (Achieva, T-Bird, 740, LTV) were attached to ?pt? lung with flow trigger of 2 and set at PEEP/PSV combinations of: 0/0, 0/10, 5/0, and 5/10. Five breaths at each setting were analyzed and data recorded = WOBI, peak negative pressure (PNP), RT and VT.
Results: WOBI was higher with Achieva with PEEP set. Table 1 shows results (mean ± SD) at 0/10 (cond #2). Table 2 shows results at 5/0 (cond #2).
| Table 1. | WOBI (mJ/L) | PNP (cmH2O) | RT (Sec) |
| Achieva | 0.2 ± 0.02 | -0.5 ± 0.03 | 0.12 ± 0.02 |
| LTV 1000 | 0.9 ± 0.2 | -0.9 ± 0.1 | 0.14 ± 0.02 |
| T-Bird | 0.06 ± 0.02 | -0.1 ± 0.03 | 0.14 ± 0.02 |
| 740 | 1.0 ± 0.3 | -1.24 ± 0.06 | 0.17 ± 0.02 |
| Table 2. | WOBI (mJ/L) | PNP (cmH2O) | RT (Sec) |
| Achieva | 67.0 ± 3.0 | 0.41 ± 0.2 | 0.5 ± 0.04 |
| LTV 1000 | 18.0 ± 1.5 | -0.1 ± 0.1 | 0.25 ± 0.02 |
| T-Bird | 13.0 ± 0.2 | 2.30 ± 0.03 | 0.27 ± 0.02 |
| 740 | 8.0 ± 1.3 | 3.6 ± 0.1 | 0.32 ± 0.02 |
CONCLUSION: WOBI on these PVTs is clinically acceptable and may be minimized by adding PSV.
OF-99-148