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Volume-cycled decelerating flow. An alternative form of mechanical ventilation.
S A Ravenscraft1, W C Burke, J J Marini
1University of Minnesota, Minneapolis.
Chest
|May 1, 1992
Summary
Mathematical models for volume-cycled decelerating-flow ventilation (VCDF) accurately predict patient pressures. These VCDF models offer theoretical benefits for mechanical ventilation but require careful application to prevent lung injury.
Area of Science:
- Mechanical Ventilation
- Respiratory Physiology
- Biomedical Engineering
Background:
- Volume-cycled mechanical ventilation (VCDF) is a common feature on modern ventilators.
- The linearly decelerating flow waveform offers potential clinical advantages.
Purpose of the Study:
- To develop and validate mathematical models for two forms of VCDF.
- To predict key respiratory outcome variables using clinician and patient inputs.
Main Methods:
- Developed mathematical equations using ventilator settings and patient impedance (resistance and compliance) as inputs.
- Validated models using a mechanical lung analog across a wide range of settings.
- Compared predicted values with observed values from the mechanical lung.
Main Results:
- Models accurately predicted key outcome variables, including mean airway pressure and alveolar pressures (r >= 0.98).
- Excellent correspondence between predicted and observed values across diverse inputs.
- Outcome variables demonstrated sensitivity to specific clinician-chosen settings.
Conclusions:
- Validated mathematical models for VCDF can reliably predict respiratory mechanics.
- VCDF presents theoretical advantages for mechanical ventilation.
- Clinical application requires caution to avoid barotrauma and volutrauma.