An inflatable blanket for a forced air convection system for use in covering a patient during cardiac surgery on a patients heart, for example, the inflatable blanket having at least one separable seal line within the blanket. The separable seal line may be separated to form a slit. A patients femoral artery may be accessed through the slit, and an elongate medical instrument is passed through the slit, and through the femoral artery toward the patients heart. Cardiac surgery is performed with the elongate medical instrument, and the elongate medical instrument may be withdrawn from the femoral artery through the slit.
