An In Vitro Comparison of Micro Air Passage in the Venous Reservoir Bag

_____________ _ The increasing use of membrane oxygenators and collapsable venous reservoir bags (VRB) imposes a concern not associated with bubble oxygenators: Venous line air. Since no defoamer is present, a VRB must rely on flow characteristics or a barrier to remove air from the venous return. The purpose of this study is to determine the air removal efficiency of seven commercially available VRBs. Seven VRBs with clear crystaloid solution were tested for microbubble passage using an ultrasonic bubble detector at the outlet. At 5 LPM flow, 50cc of air was injected into a stopcock in the venous line. Microbubble counts were taken in six trials of each bag, and divided into three size ranges: 10-50~-t, 50-100~-t, and >100~-t. The means and standard deviations are presented below. VRB 10-50~-t 50-100~-t >100~-t BMR1400 208.00±50.29 307.00±82.8 48.83± 18.2 BMR1900 165.83 ± 62.39 1.83± .09 0.00±0 J&JlOOO 147.33±40.75 46.16±19.98 4.33±3.44 SM1300 226.16±55.07 56.00±22.91 11.66±12.64 SM1500 332.33 ± 66.41 116.00 ± 24.30 13.33 ± 10.58 SHILEY1500 110± 18.54 7.33 ± 3.61 0.00±0 TERUMOlOOO 206.00 ± 49.68 49.80 ± 15.66 4.00 ± 5.51 There were significant differences (p<.OOl) between the bags in all three microbubble size ranges. Although the two best VRBs, BMR1900 and Shiley1500 had similar counts, their design is remarkably dissimilar. The BMR1900 contains a 200~-t heparin coated screen and is the only VRB utilizing a barrier in the blood path. Introduction ______________ _ The rapidly increasing use of membrane oxygenators and collapsible venous reservoir bags (VRB) Direct communications to: Charles M. Tyndal, Jr., PSICOR, Inc., 810 East Grand River, Brighton, MI 48116 imposes a concern which is not normally associated with the use of bubble oxygenators: Venous line air. Controversy exists concerning the superiority of membrane or bubble oxygenators. In membrane oxygenators there is no direct blood-gas interface as there is with the bubble oxygenator. This offers the advantage of not creating bubbles in the blood which then have to be removed before the blood is returned to the patient. Since there are persistent questions about the efficiency of defoaming sponges used in bubblers, and indeed their tendency to embolize silicone antifoam material, 1 it can be argued that membrane oxygenators are inherently less likely to transmit microemboli. This, of course, assumes that no air is present in the blood that enters the membrane. For this condition to exist in the absence of a defoaming sponge, the venous reservoir must be able to remove any air which enters through the venous line. The purpose of this study is to determine the air removal efficiency of seven commercially available VRBs. By comparing them in an experimental setting, we were able to establish their relative efficiency in removing air from the venous return. Materials and Methods ________ _ Seven commercially available VRBs: Bentley 1400cc (BMR1400)•, Bentley 1900cc (BMR1900)•, Terumo lOOOccb, J & J 1000ccc, SciMed 1300cc (SM1300)ct, SciMed 1500cc (SM1500)ct, and Shiley 1500cce; were examined to determine their ability to separate air from the venous return. A simple circuit consisting of a VRB, six feet of 3/8" perfusion tubing through a roller pump, a hollow fiber membrane oxygenatorb (HFMO), and six feet of 112" perfusion tubing returning to the vena American Bentley, Irvine, CA 92714 b Terumo, Piscataway, NJ 08854 c J & J Cardiovascular, King of Prussia, P A d SciMed Life Systems, Minneapolis, MN 55441 e Shiley, Irvine, CA 92714 f Cobe Laboratories, Lakewood, CO 80215