BIO31: Novel Size-Variable Dedicated Rodent Oxygenator for ECLS Animal Models – Introduction of the “Ratox” Oxygenator and Preliminary In-Vitro Results

Abstract

Introduction: Extracorporeal life support (ECLS) grows in relevance. However, the survival rate of ECLS remains low, overall at around 60 %, mostly due to hemocompatibility issues. Research and development in the field is slow due to several factors, including the lack of sophisticated experimental platforms and models. This publication introduces a rodent–sized oxygenator module (“RatOx”) to enable early and large–scale in–vitro and in–vivo studies, followed by preliminary in–vitro classification tests on gas transfer performance. The oxygenator is designed to allow extensive in–vitro testing with donated human blood as well as economic and reproducible in–vivo testing for fundamental research. Materials and Methods: The novel RatOx’ main feature is the adaptable fiber module size suitable for various rodents like mice, rats, or hamsters. The effective membrane surface area is variable between approximately 10 cm2 and 600 cm2. The priming volume, and hence the hemodilution of the supported small animal, is kept at a minimum. Any type of semipermeable hollow fiber with any surface modification or coating can be mounted. The housing is transparent, hemocompatible, sterilizable and reusable. Oxygen transfer and carbon dioxide transfer over the oxygenator membrane were tested for different blood flows and fiber module sizes according to DIN EN ISO 7199. Similar experiments were conducted by an independent laboratory to test the transferability of the system to other institutions. Results: At the maximum possible amount of effective fiber surface and a blood flow of 100 ml/min, the oxygenator performance has been tested to a maximum of 5.5 ml O2/min and –5.5 ml CO2/min, respectively. For the same operating point, results from the independent laboratory showed transfer rates of 6.27 ml O2/min and –8.2 ml CO2/min, respectively. The priming volume for this the largest fiber module is 5.4 ml, while the smallest possible configuration with a single fiber mat layer has 1.1 ml of priming volume. Discussion, conclusion and outlook: The novel RatOx ECLS system has been evaluated in–vitro to comply to a high degree with all predefined functionality criteria for rodent–sized animal models. The maximum gas transfer efficacy for full-support-scenarios was measured to be approximately 70–80 % of the intended value pre–defined as the demand of a resting Sprague–Dawley rat. The priming volume translates into an oxygenator–caused hemodilution of approximately 25 %. We intend for the RatOx to become a standard testing platform for scientific studies on ECLS therapy and technology. This presentation includes evidence that this system is variable, yet very robust, allowing cross–lab and cross–model testing.