A pressurized injection/suction system for ventilation in the presence of complete airway obstruction

OBJECTIVETo describe the design and ventilatory characteristics of a new mode of ventilation (pressurized injection/suction ventilation). DESIGNDescriptive and analytical laboratory study. SETTINGLaboratory study. SUBJECTSSimulated lung model and dogs. INTERVENTIONSWe tested the ability to maintain ventilation through a 2.5-mm internal diameter ventilating stylet in the setting of simulated complete airway occlusion. A microprocessor-controlled ventilator mode was used wherein injection of oxygen under high pressure (flow rate 95 L/min) alternates with suction of expired gas (flow rate 18 L/min) through the ventilating stylet. MEASUREMENTS AND MAIN RESULTSIn a lung model, we achieved a maximum minute ventilation of 12.9 L/min. In two dogs, we maintained stable oxygenation (mean Pao2 603 ± 47 torr [80.4 ± 6.3 kPa]) and ventilation (mean Paco2 19 ± 3 torr [2.5 ± 0.4 kPa]) for 15 mins at maximum minute ventilation settings. No clinically important deleterious effects on the tracheal mucosa were observed. The ventilator systemʼs safety-abort feature prevented overinflation or excessive deflation of the dogsʼ lungs in every test of simulated malfunction of the pressure-monitoring mechanism. CONCLUSIONSPressurized injection/suction ventilation can maintain adequate gas exchange in an animal model with near-complete airway obstruction. Further work is needed to develop the safety and clinical applications of pressurized injection/suction ventilation in the management of patients with near-complete airway occlusion. (Crit Care Med 1994; 22:326–333)