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Expiratory asynchrony in proportional assist ventilation
Hong-Lin Du1, Mikiya Ohtsuji, Masaki Shigeta
1Clinical Research Department, Newport Medical Instruments Inc., Newport Beach, California 92658, USA. HLDu@nmitkb.com
Summary
Proportional Assist Ventilation (PAV) may cause expiratory asynchrony due to control-system delays. This study modeled delays, finding they can prolong ventilator inspiratory time, impacting patient-ventilator synchrony.
Area of Science:
- Biomedical Engineering
- Respiratory Physiology
Background:
- Proportional Assist Ventilation (PAV) is designed for patient-ventilator synchrony.
- Clinical observations suggest PAV can lead to prolonged inspiratory time and "runaway" phenomenon.
Purpose of the Study:
- To investigate the impact of control-system delay on expiratory synchrony in PAV.
- To develop a computer model incorporating control-system delay for PAV simulation.
Main Methods:
- A computer model of PAV was developed.
- The model included a parameter for control-system delay time.
- Simulations were run to assess expiratory synchrony under various conditions.
Main Results:
- Significant expiratory asynchrony was observed in the model with control-system delay.
- Ventilator flow termination lagged patient inspiration by up to 0.33 seconds.
- Delay time was proportional to control-system delay, respiratory time constant, and assist gain.
Conclusions:
- Unavoidable control-system delays in ventilators may be an inherent cause of expiratory asynchrony with PAV.
- This finding challenges the assumption of perfect expiratory synchrony with PAV.
- Further research may be needed to mitigate this effect.