2004 OPEN FORUM Abstracts
Evaluation of portable automatic resuscitators under changing impedance conditions: A lung model study.
Richard
D. Branson, MS, RRT, Kenneth Davis MD, Jay A. Johannigman MD.
University of Cincinnati, 231 Albert Sabin Way; Cincinnati, OH
45267-0558)
Background:
The concern about bio-terrorism, biochemical warfare, and mass
casualty situations has left many US cities wondering what would
happen if multiple patients required mechanical ventilation
simultaneously. Cost of reliable portable ventilators prohibits
stockpiling hundreds of ventilators in every municipality. Portable
and even disposable low cost automatic resuscitators (AR) have been
introduced as a potential answer. We studied the performance of two
of these AR in a lung model study.
Method:
The Vortran VAR and Oxylator EM-100 were studied. Both devices
were set according to manufacturer instructions. The VAR was
operated with and without the venturi at flow rates of 20 – 40
L/min and pressure of 30 and 40 cm H2O. The EM-100 was attached to a
regulator at 50 psig and peak pressure was set at 30 and 40 cm H2O.
Both devices were connected to an Ingmar ASL 5000 test lung (Ingmar,
Pittsburgh, PA). The test lung was programmed to vary compliance and
resistance on a minute to minute basis to evaluate the response of
each device to changing lung conditions. Volume, flow, and airway
pressures were measured continuously. All tests were accomplished in
triplicate. Conditions are shown below.
| Condition | Compliance (ml/cm H2O) | Resistance (cm H2O/L/s) |
| 1 | 100 | 5 |
| 2 | 50 | 5 |
| 3 | 10 | 20 |
| 4 | 100 | Insp. 10 / Exp 20 |
Results:
Both devices demonstrated significant decreases in delivered VT
with a decrease in compliance. As compliance fell, both devices also
demonstrated significant increases in respiratory rate. Auto-PEEP was
present during all cases, with increases seen as higher airway
resistances. (Auto-PEEP range of 1.2 – 4.6 cm H2O). Airway
pressures were controlled within 3 cm H2O of set pressure and flow
remained constant. Table 2 demonstrates changes in VT(L) and RR
(b/min) at each of the conditions at a set peak pressure of 30 cm
H2O.
| Device | Condition | |||
| #1 | #2 | #3 | #4 | |
| Vortran VT (L) | 1.18±0.05* | 0.48±0.01 | 0.39±0.06 | 0.98±0.08 |
| EM-100 VT (L) | 1.18±0.07* | 0.44±0.02 | 0.39±0.03 | 1.5±0.13 |
| Vortran RR b/min | 11±1.1* | 15±2.6 | 32±4.1 | 15±1.3 |
| EM-100 RR (b/min) | 9±3.1* | 12±2.7 | 26±4.5 | 6±13 |
All
data are mean ± SD. * p<0.01 vs. other conditions.
Compared using ANOVA for repeated measures.
Conclusion:
Use of AR results in unpredictable changes in RR and VT as lung
conditions change. This has implications for use of such devices
unattended and unmonitored.