Baile, Elisabeth M., Lu Wang, Lorraine Verburgt, and Peter D. Paré. Bronchial vasodilatory response to ionic and nonionic contrast media. J. Appl. Physiol. 82(3): 841–845, 1997.—It has recently been shown that bronchial arterial injection of conventional contrast medium causes a significant increase in bronchial blood flow (Q˙br) and that this response is partially attenuated after infusion of N ω-nitro-l-arginine (l-NNA). However, the precise mechanism for this increase in Q˙br is unknown. In this study we examined the effect of bronchial arterial injection of conventional ionic as well as nonionic contrast media. We measuredQ˙br in nine anesthetized, ventilated, open-chest sheep. Q˙br was recorded before (baseline) and at the peak response to injection of 0.5 ml of either 0.9% saline (control; isosmolar with plasma), Omnipaque 300 (iohexol; nonionic), Conray 66 (sodium iothalamate; ionic), or 50% dextrose (viscous control).