Final answer:
The force used in venipuncture should be just enough to puncture the vein and is achieved through skill rather than measurable force. Pressure calculations come into play when determining the height of an IV bag to ensure fluid pressure exceeds venous blood pressure.
Step-by-step explanation:
The force needed during venipuncture is not measured in conventional units like Newtons as it is a gentle art more than a precise science. The force should be just enough to puncture the vein and should be done with steady and confident hand movements. Considering the pressure, when dealing with the IV system, the physics behind it involves ensuring that the pressure of fluid being administered is sufficient to overcome the blood pressure in the patient's vein.
For example, if the blood pressure is 18 mm Hg above atmospheric pressure, the pressure from the IV must be greater than this. To convert the blood pressure into SI units, we use the conversion that 1.0 mm Hg equals 133 Pa. When inserting the needle, the force applied is minimal and controlled, aimed at inserting the needle smoothly rather than applying measurable pressure.
In the context of fluid dynamics and pressure, as in the calculation of an IV setup, it is critical to calculate the height at which an IV bag should be placed. However, the force required when inserting a needle in venipuncture is achieved by the skill of the healthcare provider rather than by a calculated pressure.