A new ventilator for physiologic studies during high-frequency ventilation.

Research in the field of high frequency ventilation (HFV) has been hampered by the difficulty of collecting and analyzing expired gas, uncontaminated by gas of inspiratory composition, at ventilatory frequencies in the relevant range. A new mechanical ventilator is described, which has been designed to facilitate studies on the respiratory physiology of small animals during HFV. Ventilation is controlled by a single rotary valve, which alternately switches the airway to an approximately constant-flow gas source during inspiration, and to gas measurement and analysis apparatus during expiration, which takes place passively. Theoretical and experimental studies, using the techniques of mechanical and mathematical modelling, are used to measure the performance of the ventilator and to demonstrate that it allows the quantitative collection of expired gas during ventilation at rates up to at least 20 Hz. The advantages and limitations of this approach are discussed.