Lumen

The inside space of a tubular structure

Definition

A lumen is the interior open space or cavity of any tubular or hollow structure, such as blood vessels, intestines, airways, catheters. Lumen size determines flow capacity.

Clinical Significance

Blood vessel lumen: Narrowing (stenosis) → limited flow (PAD, CAD).
Catheter lumen: Larger gauge = smaller number. 16-gauge larger than 22-gauge.
Central line: Single, double, or triple lumen for separate infusions.
Airway lumen: Obstruction by mucus, tumor, edema (stridor, dyspnea).

IV Gauge Selection

14 to 16 gauge: Trauma, rapid transfusions
18 gauge: Blood products, large-volume infusion
20 gauge: Most routine IV therapy, blood
22 gauge: Elderly, children, short-term
24 gauge: Infants, fragile veins

NCLEX Relevance

Larger gauge IV = smaller number = more flow. 18g minimum for blood transfusion.