Laboratory Performance Testing of Venous Cannulae During Inlet Obstruction

Abstract

Venous cannulae undergo continuous improvements to achieve better and safer venous drainage. Several cannula tests have been reported, though cannula performance during inlet obstruction has never been a test criterion. In this study, five different cannulae for proximal venous drainage were tested in a mock circulation that enabled measurement of hydraulic conductance after inlet obstruction by vessel collapse. Values for hydraulic conductance ranged from 1.11 x 10(-2) L/min/mm Hg for a Thin-Flex Single Stage Venous Cannula with an open-end lighthouse tip to 1.55 x 10(-2) L/min/mm Hg for a DLP VAD Venous Cannula featuring a swirled tip profile, showing a difference that amounts to nearly 40% of the lowest conductance value. Excessive venous drainage results in potentially dangerous high-negative venous line pressures independent of cannula design. Cannulatip design featuring swirled and grooved tip structures increases drainage capacity and enhances cannula performance during inlet obstruction.

Hypovolemia in Extracorporeal Life Support Can Lead to Arterial Gaseous Microemboli

“…In long‐term and in short‐term ELS, decreased cardiopulmonary assistance following hypovolemia can be recognized by a drop in mixed venous saturation and deteriorating hemodynamic stability , next to decreasing readouts for supporting pump flow and venous line pressure , concurrently with chattering of the venous line and, as shown in this study, GME. Pump data and pressure measurement, however, have proven less suitable to reveal changes in intravascular volume and patient volume status .…”

“…Next to a severe decrease of support, hypovolemia can lead to a venous line pressure far below atmospheric . Henry's law states that the amount of gas that dissolves in liquid is directly proportional to the partial pressure of that gas within that liquid .…”

The Need of Slanted Side Holes for Venous Cannulae

“…is to be a practical target for improving the efficacy and safety of venous cannulae. In practical medical/animal test cases, doctors frequently suffers from the reduced intake volume to the extracorporeal system due to unstable blood suction through the venous cannulae; here, it should be noted that the side holes contribute to prevention of rupture of blood vessel (obstruction of cannula) during perfusion [1]. For the evaluation of performance of cannulae, the “M-number” (or “catheter number”) has been widely used [2]; the M-number is a single dimensionless number that is based on a Reynolds friction factor correlation and describes the pressure-flow relationship in a cannula.…”

Dynamic filling index: a novel parameter to monitor circulatory filling during minimized extracorporeal bypass

“…In our experiments we made sure that with luxation the cannula tip was not obstructed. Moreover, a previous study on cannula performance revealed high resistance against inlet obstruction for the cannula used in this study [10]. Therefore, the observed changes in DFI are likely to reflect changes in DV, as induced by limiting venous return.…”

“…In previous laboratory studies, we found that the relationship between bypass flow and pump speed in a minimized perfusion setup is modulated by venous return and DV [10,11]. Fig.…”