Arterial blood gas analysis assesses the patient's oxygenation and acid-base status and adequacy of ventilation. Venous blood gas samples are more easily obtained, but interpretation is difficult. Arterial blood gas samples are obtained from any palpable artery. Collection sites include the femoral, metatarsal, and auricular (rabbit) arteries. Infiltration of the periarterial area with 1% lidocaine without epinephrine may prevent reflex vasoconstriction.