Dynamics of venturi jet ventilation through the operating laryngoscope.

Venturi jet ventilation with the oxygen injector needle placed within the lumen of the laryngoscope was studied systematically in two dogs undergoing repeated general anesthesia suspension laryngoscopy. Using a total body plethysmograph, the effect of changes of needle angle, position and its effect on tidal volume delivery were measured. The changes of pressure regulator, flow rate and needle size were correlated with the volume delivery. Intratracheal pressure during Venturi ventilation was measured. Correlation of arterial blood gases and minute ventilation with the system was done. While ventilatory capacity is able to be achieved predictably, there are many variables. Optimal placement of the needle tip for maximum safety and efficiency appears to be at the midthird or lower third of the laryngoscope. It is important to center the needle axis to the laryngoscope axis. Other parameters subject to choice are the selection of needle size, regulator pressure setting and flow rate setting. By first selecting the correct needle size that will hyperinflate the subject, the pressure regulator can then be reduced to achieve ventilatory volumes similar to spontaneous tidal volumes. In prolonged use, the Venturi system was able to provide excellent ventilation safely and predictably.