Name a blood collection method used for adults when venipuncture is not feasible.

Capillary blood sampling is indeed the correct method used for blood collection in adults when venipuncture is not feasible. This technique typically involves puncturing the skin, often on a fingertip or heel, to collect a small sample of blood. It is particularly useful in situations where venous access is difficult due to conditions such as dehydration, obesity, or other medical issues that make finding a vein challenging.

Capillary sampling is also advantageous because it requires minimal equipment, can be performed quickly, and is less invasive than venipuncture. It is commonly used for routine tests, such as glucose monitoring in diabetic patients, and can provide adequate samples for many laboratory tests, although some specialized tests may still require venous blood.

While arterial blood sampling is a valid method for obtaining blood, it is generally reserved for specific scenarios like assessing arterial blood gases, and it is not commonly used when venipuncture is not feasible. Similarly, venous blood sampling requires accessing a vein, which defeats the purpose when venipuncture is not possible. A peripheral blood smear is a laboratory technique used to examine blood cells under a microscope and is not a method for blood collection by itself.