Sustained oxygenation without ventilation in paralyzed pigs with high-flow tracheal oxygen

OBJECTIVES: It is generally assumed that ventilation is necessary for oxygenation. This study tested if paralyzed animals without respirations can maintain arterial oxygenation when administered high-flow oxygen delivered by a catheter in the trachea. METHODS: DESIGN: Prospective observational study. SETTING: University research laboratory. PARTICIPANTS: 3 anesthetized/paralyzed swine weighing 29.5 +/- 4.2 kg. INTERVENTIONS/OBSERVATIONS: Pigs were intubated, anesthetized with intravenous tiletamine and a pentobarbital drip. A femoral arterial line was placed to record arterial blood gases and vital signs every 5 minutes. Respiratory paralysis was obtained with vecuronium 150 microg/kg and repeated at any sign of movement. A catheter was placed in the trachea to deliver oxygen at 15 L/min. Outflow gas from the endotracheal tube was analyzed for O2 and CO2. O2 was discontinued at 75 minutes. The institutional animal care and use committee approved the protocol. RESULTS: All pigs survived to 75 minutes. PaO2 was more than 100 mm Hg throughout the study period. Mean PaCO2 was 37.4 +/- 2.8 mm Hg at baseline, 146 +/- 59 at 30 minutes, then rose above 200 mm Hg in all pigs by 45 minutes. Mean arterial pH fell from 7.47 +/- 0.04 at onset to 6.75 +/- 0.06 at 75 minutes. When oxygen was terminated at 75 minutes, PaO2 fell to 16.5 +/- 7.6 mm Hg within 5 minutes, and all pigs were sacrificed within 10 minutes. For outflow gas, O2 was more than 98% and expired CO2 less than 1% throughout the study period. CONCLUSIONS: Paralyzed, unventilated pigs receiving high-flow oxygen via a tracheal catheter remained alive after 75 minutes, although a profound respiratory acidosis developed.