The present invention is a diameter expansion cannula apparatus which is used to establish fluid flow to a healthy blood vessel or to a diseased blood vessel. The cannula apparatus has a cannula which is coated with silicone and is formed of a braided construction which provides the cannula with an inherent resilience, yet allows the length of the cannula to become longer and the diameter of the cannula to become narrower when tension is applied along the longitudinal axis of the cannula. A peelable sheath is used to maintain the cannula in its elongated narrow state during insertion into a blood vessel. Removal of the sheath allows the cannula to return to its pre-tensioned diameter, thereby providing a radial force upon any obstruction within the blood vessel. The cannula apparatus is a self-contained unit which includes a sharpened point on the end of a balloon catheter to puncture the blood vessel of a patient and to assist the cannula in returning to its pre-tensioned diameter if any obstruction within the blood vessel prevents the cannula from returning to its pre-tensioned diameter.