DROP DETECTOR HEAD

Typical Number in Hospital:

Cost Bands:

References:

It is now common to control the delivery of intravenous fluids automatically using a pump or automatic controller. The most common method of detecting the quantity of fluid being infused is an optical gate clamped on to the drip chamber on the standard fluid infusion set. The gate consists of a collimated light source on one side of the drip chamber and a photoelectric detector on the other. As the drop falls through the light beam a pulse is presented to the controller and is counted. In the case of the automatic controllers (as opposed to pumps) a valve opens to allow a number of drops fall through. If this exceeds the number allowed in the time which has elapsed, the gate valve closes for a time. The flow is not steady, but the total quantity of fluid infused over several minutes will be correct.

Problems are often experienced with this type of detector head because of the effects of extraneous light (e.g. sunlight) and incorrect positioning on the drip chamber. Some equipment manufacturers insist on a specific type of infusion set being used to minimize this problem. Another problem is that the number of drops in 1 ml of fluid differs for each type of drip set and infusion fluid. Also the fluid used and the temperature, etc. can affect the amount delivered. If the infusion rate rises accidentally until the drops merge into a continuous stream then no pulses will be generated. The same is true if the fluid reservoir is exhausted. Modern infusion pumps include alarm circuits to detect some of these abnormal conditions but none are foolproof.