TABLE 1.

Interpretation of the ‘bubble test’.

Observation	Interpretation
No bubbles	Negative test: an aberrant or too distal tip
Few bubbles or appearance in > 2 s	Negative test: possible misplacement (probably in SCV or IJV)
Numerous bubbles with turbulent flow from RA within 2 s	Negative test: intra-atrial position
Numerous bubbles with linear flow from SVC within 2 s	Positive test: correct position

Source: Vezzani A, Brusasco C, Palermo S, Launo C, Mergoni M, Corradi F. Ultrasound localization of central vein catheter and detection of postprocedural pneumothorax: An alternative to chest radiography. Crit Care Med. 2010;38(2):533–538. https://doi.org/10.1097/CCM.0b013e3181c0328f

IJV, internal jugular vein; SCV, subclavian vein; RA, right atrium.