2004 OPEN FORUM Abstracts
EFFECTS OF POSITIONAL CHANGES ON THE PERFORMANCE OF THE VORTRAN AUTOMATIC RESUSCITATOR
Thomas
Blackson, RRT, Billie Speakman, RRT, Judy Iverson, RRT, Richard
Ermak, RRT, Melani Murphy, RRT, Christiana Care Health Services,
Newark, DE.
Background:
The use of mechanical ventilators designed specifically for
transportation has increased in recent years concomitant with the
increase in both intra- and inter-hospital transport of ventilator
dependent patients. Concerns regarding bio-terrorism and the need to
devise a mass casualty response plan have also increased the need for
inexpensive, portable ventilators. Desirable design features of
transport ventilators (TV) include: small size for ease of transport
and storage, pneumatic power mechanism to avoid the need for
electricity or battery power, low cost, and compatibility for use
with magnetic resonance imaging equipment. One factor that may play
an important role during transportation of ventilated patients or
during emergency ventilation in a pre-hospital setting is the effect
of positional changes on ventilator function.
Purpose: To
evaluate the effect of positional changes on the function of the VAR,
through systematic alteration of modulator position during
ventilation of a test lung model.
Methods: We evaluated the
VAR using a test lung model, (Michigan Instruments, Grand Rapids,
MI). The manufacturer supplied #5 parabolic resistor was used to
simulate airway resistance and lung compliance was set at 0.04 L/cm
H2O for all test conditions. The VAR modulator was
initially positioned with the adjustment controls (C) pointed upward
in a vertical position against a position template (PT). The PT
identified 5 positions drawn on a 180o arc to allow
discrete positional changes of the modulator using the C as the VAR
reference point against the PT. Positions corresponding to, 0o,
(upright, starting position), 45 o, 90 o, 135
o, and 180 o, (inverted), were tested. A CO2SMO
flow sensor, (Novametrix, Wallingford, CT), was placed between the
VAR and the test lung to measure tidal volume (VT),
respiratory rate (RR), minute volume (MV), peak inspiratory flow rate
(PIF), peak airway pressure (PIP) and mean airway pressure (Paw). C
were initially set to provide a PIP: 30 cm H2O and RR: 16
breaths/min. C were not manipulated after initial adjustment.
Ventilation parameters were measured each breath for 1 minute
following each position change. In a separate test, the RR control
function was evaluated with RR:16 breaths/min. and PIP: 25 cm H2O
in the upright position, (0o) followed by inversion,
(180 o), while ventilating the same test lung model.
Results: Data analysis revealed VT, MV, PIP, and
Paw were significantly affected by positional changes (p< 0.01).
VT, MV, PIP, and Paw decreased progressively from the
upright to the inverted position. RR and PIF were unaffected by
changes in modulator position. Apnea, failure to automatically
trigger, was a common, but inconsistent response to modulator
inversion during the independent RR control test.
*p <
0.01
| Condition | VT (L) (±SD) | MV (L/min) (±SD) | PIP (cmH2O) (±SD) | Paw (cmH2O ) (±SD) | RR (B/min.) (±SD) | PIF (L/min.) (±SD) |
| Upright | 1.0 (0) | 16.6 (0.4) | 24.6 (0.1) | 14.2 (0.1) | 16 (1) | 43 (1.4) |
| Inverted | 0.8 (0)* | 11.9 (0.9)* | 14.6 (0.1)* | 10.7 (0.1)* | 15 (0) | 43 (1.4) |
Conclusion:
VAR function was significantly affected by positional changes in this
test lung model. The magnitude of change in VT and MV
experienced in this study may cause clinically significant changes in
ventilation and acid/base balance if encountered clinically in a
patient without a spontaneous drive to breathe. The PIP and Paw
changes demonstrated in this study may adversely affect oxygenation
in susceptible patients. Inversion of the VAR modulator following
initial set-up may result in loss of RR control function and the
potential for apnea under certain combinations of PIP and RR
settings.
Thomas
Blackson, BS, RRT, Billie Speakman, BS, RRT, Judy Iverson, RRT,
Richard Ermak, RRT, Melani Murphy, RRT, Christiana Care Health
Services, Newark, DE.
Presenter: Tom
Blackson, BS, RRT
1215
Stinsford Road
Newark,
DE 19713
Work
Phone: 302-733-3560
Home
Phone: 302-731-8070