English to Slovak Medical Medical: Instruments syringe/needle

in a syringe/needle; a medical practitioner needs to know whether to account for any "dead space" when administering a medication to be able to determine a precise dosage.
I would like to verify whether to translate this term as "mrtvy priestor" or "prazdny priestor". There is a "mrtvy priestor" in Slovak but I've heard it only in relation with respiratory diseases.