Q Are there any guidelines for withdrawing fluid through a filter straw?

A Paula Lusardi, RN, PhD, CCRN, CCNS, and Alex Smith, MS, RD, reply:

There are a number of variables that factor into aspiration pressure (the size of the syringe used and the aggressiveness of the person aspirating the fluid through the filter being the most noteworthy). Therefore, an exact pressure cannot be stated for each occasion. The filter straws do meet the required product specifications, namely, 20 mL of distilled water must be aspirated at a vacuum pressure of 26 inches of Hg in 5 to 40 seconds. The recommendation on using these, or any filter device, is that an effort should be made not to create an excessive vacuum within the syringe, that is, between the plunger and the fluid.

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