Final answer:
A patient's IV bottle or bag should be hung higher than the level of the injection site to enable gravity to push the fluid into the vein, overcoming the blood pressure in the vein which is above atmospheric pressure. The minimum height for an IV bag to just allow fluid into the arm is typically 0.24 meters, but it may be as high as 1.61 meters to create sufficient pressure for infusion. This ensures the fluid enters the vein effectively, following the principles of gravity and pressure.
Step-by-step explanation:
A patient's IV bottle or bag should be hung higher than the level of the injection site. The reason for this is due to the principles of gravity which help in administering the intravenous fluid. For the fluid to just enter the vein, it needs to exert a pressure that is higher than the blood pressure in the vein which is above atmospheric pressure.
For example, if the blood pressure in the vein is 18 mm Hg above atmospheric pressure and the density of the fluid being administered is 1.00 g/ml, the IV bag must be placed at an appropriate height that creates enough pressure. If we convert 18 mm Hg to pascal which is the SI unit of pressure (1.0 mm Hg = 133 Pa), we can determine the necessary height. As noted in examples, an IV bottle with the surface of the saline solution as high as 1.61 meters above the needle entry point, can create a sufficient pressure gradient, assuming minimal pressure drop in the tubing. However, the minimum practical height to just allow fluid into the arm is 0.24 meters above the injection site.
It's essential to note that in contrast, bags used for blood collection are placed below the donor's arm to facilitate blood flow from the arm to the collection bag, which relies on the same gravity-driven principles but in the opposite direction of flow.