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VALIDATION OF REPORTED TIDAL VOLUMES
OF THE DRÄGER BABYLOG AND THE BIRD GOLD VENTILATORS IN A NEONATAL BENCH MODEL
Jim Keenan BS, RRT, FAARC,
Ralph A. Lugo, PharmD, Primary Children?s Medical Center, University of Utah
College of Pharmacy, Salt Lake City, Utah.
Introduction: Monitoring
tidal volumes (Vt) in a time-cycled, pressure-limited mode has greatly improved
the management of ventilated neonates, thereby preventing lung injury and possibly
BPD. However, increased reliance upon monitoring Vt requires that the accuracy
of the flow sensors be assessed. We sought to validate Vt reported on the Bird
Gold and Dräger Babylog infant ventilators by comparison with plethysmography,
which is the gold standard for Vt measurement.
Methods: The Vitaltrends body
plethysmograph isolette is designed for infants <3 kg and uses a single screen
(300 mesh stainless steel) low resistance pneumotachometer to measure volume
displaced within a closed system. The Bird Gold and Dräger Babylog ventilators
were compared using a neonatal circuit, a 3.0-mm endotracheal tube, and an IngMar
neonatal test lung. New flow sensors were used for each experiment. Two ventilator
conditions were selected: Condition 1) time-cycled, pressure limited AC, rate
25, pressure 20 cm H2O, Ti 0.3 sec and a flow of 6 LPM; Condition
2) time-cycled, pressure limited AC, rate 20, pressure 30 cm H2O,
Ti 0.4 sec and a flow of 10 LPM. Under each condition, experiments using FiO2 = 0.21 and 1.0, and relative humidity = 21% and 100% were conducted. The plethysmograph
was calibrated prior to each experiment according to manufacturer?s specifications.
Each experiment was conducted using 20 ventilator breaths. The Vt reported for
each ventilator breath was compared to the corresponding Vt measured by plethysmography.
Vt was adjusted for the local altitude of ~5000 ft, according to conversion
factors provided by each ventilator manufacturer. Data were compared using Student?s
t test or Mann Whitney U test.
Results: Vt for both ventilators
and plethysmography are reported and compared in the table.
Conclusion: Ventilator?s accurate
measuring and reporting of tidal volumes is extremely important, as it is often
an integral part of ventilator management. In this study the Dräger reported
the volumes more accurately than the Bird Gold.
| Test Condition One |
Pleth |
Bird |
% Deviation |
Pleth |
Drager |
% Deviation |
21% O2 /
Ambient Humidity |
8.0 (0.21) |
9.9 (0.07)
* |
23.2 ? |
9.5 (0.35) |
9.5 (0.08) |
0.29 |
100% O2 /
Ambient Humidity |
7.4 (0.14) |
9.4 (0.00)
* |
26.2 ? |
9.1 (0.14)
? |
9.0 (0.08) |
1.7 |
21% O2 / 100%
Humidity |
7.8 (0.07) |
8.8 (0.00)
* |
15.8 ? |
9.6 (0.14)
? |
8.9 (0.00) |
6.5 |
100% O2 /
100%
Humidity |
7.7 (0.14) |
8.5 (0.07)
* |
11.7 |
8.4 (0.28) |
9.0 (0.08)
? |
8.5 |
| Test
Condition Two |
21% O2 / Ambient
Humidity |
12.4 (0.28) |
14.5 (0.00)
* |
16.9 ? |
14.2 (0.07) |
14.6 (0.00)
? |
3.2 |
100% O2 /
Ambient Humidity |
12.1 (0.35) |
14.6 (0.07)
* |
20.1 ? |
14.2 (0.42) |
14.4 (0.00) |
0.75 |
21% O2 / 100%
Humidity |
12.8 (0.07) |
13.9 (0.15)
* |
9.5 ? |
14.6 (0.35)
? |
13.5 (0.00) |
6.6 |
100% O2 /
100%
Humidity |
12.4 (0.21) |
13.8 (0.21)
* |
12.6 ? |
14.6 (0.35) |
15.0 (0.08)
? |
2.4 |
* P<0.05,
Pleth vs. BIRD ? P< 0.05, % Deviation, BIRD vs. Drager ? P< 0.05, Pleth
vs. Drager
OF-02-097
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