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Variations in tidal volume with portable transport ventilators.
E K McGough1, M J Banner, R J Melker
1University of Florida College of Medicine, Gainesville.
Respiratory Care
|March 1, 1992
Summary
Portable transport ventilators show significant variation in delivering consistent tidal volume (VT) when lung mechanics change. The P7 ventilator maintained VT best, while the Bird transport ventilator showed the largest decreases, risking patient hypoventilation.
Area of Science:
- Mechanical Ventilation
- Respiratory Care
- Biomedical Engineering
Background:
- The increasing use of portable transport ventilators for patient transport necessitates reliable performance.
- Transport ventilators must maintain consistent tidal volume (VT) despite variations in lung-thorax compliance (C) and airways resistance (R).
Purpose of the Study:
- To evaluate the impact of changing compliance and resistance on tidal volume delivery in eight commercial transport ventilators.
Main Methods:
- Eight time-cycled transport ventilators were tested using a calibrated pneumotachograph and test lung.
- Simulated normal adult compliance (C=100 mL/cm H2O) and resistance (R=2 cm H2O.s/L) were used, with a target VT of 1,000 mL.
Main Results:
- Tidal volume delivery varied significantly across ventilators as compliance and resistance were altered.
- The P7 ventilator demonstrated the least reduction in VT, while the Bird transport ventilator exhibited the greatest decrease.
Conclusions:
- Inconsistent VT delivery by transport ventilators can lead to patient hypoventilation, hypercapnia, and acidemia.
- Factors such as internal pressure-limiting valves, venturi flow devices, and circuit compression volume influence VT.
- Continuous VT monitoring during transport is crucial, especially when pulmonary mechanics are unstable.