The Science Journal of the American Association for Respiratory Care

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


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