抄録
A high-frequency ventilator was designed using a loudspeaker as a piston, driven by a power-amplifier. A sine-wave signal was introduced into the amplifier from an electronic oscillator. The mechanical and gas exchange characteristics of the ventilator were studied in vitro and in dogs.
The volume output per stroke, when open to air, was between 100 and 200ml up to 7Hz, then gradually decreased as the frequency increased. A Wright respirometer appeared to measure the volume flow fairly accurately up to 14Hz. The pressure output against a closed volume of 1.1 liters achieved a maximum of 29mmHg at 7Hz. It gradually decreased as the frequency was changed from 7Hz. The loudspeaker worked in such a way that the volume output decreased considerably when it was forced to move against a closed space to generate pressure.
Adequate ventilation was achieved in all dogs from 1.4 to 10Hz. At 14Hz, the results were variable, and at 20Hz and above, gross hypoventilation always resulted. The P ao 2, values were always over 440mmHg when 0.8 liter/(kg·min) of oxygen was supplied into the respiratory circuit.
A speaker ventilator has the advantage of easy assembly and the possibility of applying various flows by electrical control. Its disadvantages are a lack of power and the difficulty in establishing ventilatory volumes without actual measurement.
