Harvard Apparatus Model 683 Rodent Ventilator. A ventilator/respirator for use with small animals (rodents, rabbits, guinea pigs). Uses a 0.5-5.0 ml / stroke piston. The piston allows tidal volumes to be set from 0.5 to 5.0 cc in 0.5 cc increments. Features a numerical LED to display the respiratory rate which can be set from 18 to 150 strokes/minute. Volume and rate settings can be adjusted while the ventilator is running. Has four gas inlet and outlet ports. The ventilator exhaust can be attached to a column of water to achieve PEEP (positive end expiratory pressure) when long term animal ventilation is necessary.