An automatic sigh feature for animal ventilators.

A device is described that provides a reliable automatic deep breath to an animal being ventilated with a typical laboratory ventilator. The deep breath is provided by closing a solenoid valve in the expiratory tubing causing the animal to inspire two, three, or four consecutive tidal volumes without expiration. The interval between deep breaths is selected to be every 1, 2, 4, 6, 8, or 10 min. Control of this interval is provided by simple integrated circuits. Total parts cost of this device is approximately $90.