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Continuous positive airway pressure in new-generation mechanical ventilators: a lung model study
Muneyuki Takeuchi1, Purris Williams, Dean Hess
1Department of Anesthesia and Respiatory Care, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Anesthesiology
|December 26, 2001
Summary
New mechanical ventilators impose minimal work for triggering continuous positive airway pressure (CPAP). However, most ventilators offer some pressure support and create an expiratory workload, with pressure triggering requiring slightly more effort than flow triggering.
Area of Science:
- Mechanical Ventilation
- Respiratory Physiology
- Critical Care Medicine
Background:
- Numerous microprocessor-controlled mechanical ventilators have emerged recently.
- The capacity of these devices to deliver continuous positive airway pressure (CPAP) without patient effort has not been assessed.
Purpose of the Study:
- To evaluate the work of breathing imposed by new mechanical ventilators during CPAP.
- To compare pressure and flow triggering mechanisms in these ventilators.
Main Methods:
- Six different mechanical ventilators were tested using a spontaneously breathing lung model.
- The model simulated specific compliance and resistance, with varying peak inspiratory flows at 10 cm H2O CPAP.
- Both pressure and flow triggering responses were evaluated.
Main Results:
- Increased peak flow led to higher tidal volumes and pressure changes across all ventilators.
- Peak flow did not significantly affect trigger delay times or expiratory workloads.
- Ventilator performance varied significantly, with pressure triggering demanding slightly more effort than flow triggering (4.48 vs. 3.74 cm H2O).
Conclusions:
- Most tested ventilators impose minimal inspiratory effort for triggering CPAP.
- However, they provide some pressure support and create an expiratory workload.
- Pressure triggering necessitates a slightly higher pressure threshold compared to flow triggering.