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Imposed work of breathing during ventilator failure
Paul N Austin1, Robert S Campbell, Jay A Johannigman
1Department of Nurse Anesthesia, Graduate School of Nursing, Uniformed Services University of the Health Sciences, Silver Spring, Maryland 20910, USA. paustin@usuhs.mil
Respiratory Care
|May 31, 2002
Summary
Mechanical ventilators have an anti-asphyxia valve for backup breathing. This study found that spontaneous breathing during ventilator failure can create significant work of breathing, potentially hindering airflow.
Area of Science:
- Critical care medicine
- Respiratory physiology
- Biomedical engineering
Background:
- Mechanical ventilators are equipped with an anti-asphyxia valve to permit spontaneous breathing of ambient air if the ventilator fails.
- This study investigates the work of breathing and pressure-time product imposed by this valve during simulated spontaneous breathing in ventilator failure.
Purpose of the Study:
- To quantify the imposed work of breathing and pressure-time product for critical care and portable ventilators during simulated spontaneous breathing.
- To assess the inspiratory pressure and timing characteristics associated with the anti-asphyxia valve's function during simulated ventilator failure.
Main Methods:
- A laboratory simulation utilized a test lung to mimic spontaneous breathing with specific tidal volume and peak inspiratory flow.
- Proximal airway measurements included flow (via pneumotachograph) and pressure.
- Calculations involved imposed work of breathing, pressure-time product, and anti-asphyxia valve parameters like cracking pressure and negative inspiratory pressure.
Main Results:
- Imposed work of breathing varied significantly across ventilators, ranging from 213.07 mJ/L to 969.60 mJ/L.
- Pressure-time product values ranged from 2.67 cm H(2)O x s/L to 16.70 cm H(2)O x s/L.
- Both critical care and portable ventilators demonstrated substantial imposed work and pressure-time product.
Conclusions:
- Spontaneous breathing through the anti-asphyxia valve during mechanical ventilator failure can impose a work of breathing comparable to physiological levels.
- This significant imposed work may impede effective breathing via the anti-asphyxia valve.
- Findings underscore the critical need for vigilant patient monitoring, reliable backup power, and manual ventilation strategies during mechanical ventilation.