Can the length of a catheter change the time to bubble at the tip performing the "Bubble Test"? A bench study.

INTRODUCTION: Intraprocedural tip control techniques are critical during central venous catheter placement. According to international guidelines (INS 2021), intracavitary electrocardiography is the first method of choice to verify it; when this technique is not feasible, it is considered acceptable to use a contrast-enhanced ultrasound-based tip location method, commonly known as "bubble-test" as an effective alternative.

OBJECTIVE: To assess whether the length of the vascular catheter can alter the time between the injection of the contrast media and its appearance at the catheter tip and the injection duration. Differences between operators stratified according to experience were evaluated as secondary endpoints.

METHODS: A bench study was conducted using an extracorporeal circuit. For each catheter length (60, 40, and 20 cm), three injections were obtained by each of the five operators with different levels of experience for a total of 45 measurements. Differences among operators were evaluated using ANOVA, and the impact of catheter length and operator expertise on times was assessed using repeated measurement models.

RESULTS: Hub-to-tip times of 247.33 ms (SD 168.82), 166 ms (SD 95.46), 138 ms (SD 54.48), and injection duration of 1620 ms (SD 748.58), 1614 ms (SD 570.95), 1566 ms (SD 302.83) were observed for 60, 40, 20 cm catheter length, respectively. A significant time variability between operators was observed. Moreover, moving from 60 to 20 cm, hub-to-tip time was significantly longer for 60 cm devices ( p  = 0.0124), while little differences were observed for injection duration.

CONCLUSIONS: Catheter length can change both the time between the injection of the contrast media and its appearance at the catheter tip and the injection duration. Hub-to-tip times obtained with 20 and 40 cm and overall injection duration did not differ significantly; skilled personnel could substantially reduce both values analyzed in this study.