Eli5: why does an IV drop into that capsule that’s half full of iv and half air?
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It’s so that whoever’s monitoring the IV knows it’s flowing. It’s hard to tell in a clear tube if the clear fluid is moving or not. Also a lot of hospitals use pumps now to regulate the flow instead of the old plastic clip style ones. Said pumps will also sound an alarm if the flow is blocked so no need for the drip thingy.
A few reasons.
It allows any gas that may be suspended in the liquid a chance to bubble out.
It allows the nurses to see that the IV is flowing. If the line is obstructed, the bag won’t drip.
It allows them to monitor the rate of flow independently of what the machine is telling them.
Suppose you have a bag of IV fluid and just an unbroken line into the patient. How do you adjust the speed at which the fluid enters the patient? How do you even *know* how quickly it is flowing? You don’t!
To figure that out you will want to have some kind of device to make the flow visible, like a container where the IV can drip at a rate you can time and adjust your flow valve as desired. That is your half-air capsule.
To stop air bubbles in the IV. Since Air floats, it will rise up into the little air/IV compartment, while only IV will go down the tube into your arm.
This lets us calculate how fast it is being administered. Typically every 10 drops is 1 ml of fluid. We call that a macro drip. We also have micro drip sets that vary with some being 20 or even 60 drops to 1 ml. Those can be used for more concentrated medications but nowadays we would typically just use a pump that is more accurate for those medications.
This is so that we can see if the IV is flowing. There are some instances where you will have multiple IV’s flowing all attached to each other in a configuration called piggy-back. Add to this that sometimes there are multiple pumps administering meds. The drop falling is an easy way to see that this particular line is flowing.
Another thing, though not so common in hospitals, but more in the field is that depending on your drip-set, usually 10 drops per ml or 60 drops per ml for a microset, you can control dosing. By counting the drops, you can calculate how many milligrams or micrograms of a med a person is getting per minute.
We need to see the drops to know the line is flowing. Sometimes we use the drops to determine the rate of flow.
In a standard line, 15 drops is one milliliter. In a microdripper line, 60 drops is one milliliter.
If I have a drug (say phenylephrine diluted to 40 micrograms per milliliter) running on a microdripper line, and I see one drop per second, I can calculate and document the rate of drug delivery as 40 mcg/min.
A pump is a better solution, but it is not always available.
That’s a drip chamber. Let’s us know that the IV is running, but also at what rate. Most pumps are programmable nowadays but if you don’t have a fancy little machine you can set the drip rate to the proper ml/hr with some calculations. You’ll notice on the line there’s a slidey clamp looking thing. That’s how you adjust the rate or clamp it all together.
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Before IV pumps nurses used that to control how fast or slow the infusion happens. There’s a calculation based on how many drips per minute and the volume of each drip.
Now that there are IV pumps that do that for you it just tells you if it’s running or not.
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