[A blind point of vent catheter: air aspiration]

We experienced a case of saphenous vein air embolism after coronary artery bypass graft, in which case we used vent catheter kept in the left atrium. Though it was considered that air bubbles were never aspirated through vent catheter, we speculated that the origin of air bubbles must be the vent catheter. And we made an experiment on the motion of air in the vent catheter using a model of left heart composed with soft reserver (atrium) and pulsatile pump (ventricle). When the pulsatile pump was arrest, the air bubbles were never aspirated from the vent catheter to the soft reserver even if we vented with strong negative pressure. But, when the pulsatile pump was in motion and the left atrium was vented with some negative pressure, some leaks of air bubbles were recognized. So we must pay much more attention to the degree of venting when the heart is in motion. Sometimes we use overpressure safety valve composed with vent catheter, but measured left atrial pressure showed that decreased left atrial pressure was only 2 mmHg. So its use should be restricted in the patients with good ventricular function.