Constant Oxygen Insufflation (COI) in a Ventilatory Failure Model

We examined the use of a constant insufflation of oxygen into the lungs to assist ventilation in a ventilatory failure model. The model consisted of 12 anesthetized dogs (17 to 32 kg) that were partially paralyzed using intermittent low doses of muscle relaxant; this produced a steady-state mean PaCO2 of 90 +/- 15.8 mm Hg (+/- SD). A catheter (1.5 mm ID) was inserted into each lung to the most distal position possible and withdrawn 1 to 2 cm. The effects of a constant insufflation of oxygen at rates of 5, 10, or 20 L/min were studied at this position (mean distance from the carina = 9 +/- 2 cm); at the carina; and using a single catheter located 2 cm above the carina. The changes in PaCO2 and minute ventilation (VE) due to the insufflation were calculated from the mean steady-state control values. Using the data for all catheter positions and flow rates, the insufflation was associated with a mean decrease in PaCO2 of 31 (+/- 7.6) mm Hg associated with a mean decrease in VE of 48 (+/- 12.9)%. The flow of 20 L/min caused a significantly greater drop in PaCO2 than the flow of 5 L/min (p = 0.02). This technique may prove beneficial for patients with various forms of ventilatory failure that are difficult to treat by conventional means.