The Science Journal of the American Association for Respiratory Care

2002 OPEN FORUM Abstracts

PRIMING EVOLUTION: OCCLUSION OF THE ECMO ROLLER HEAD – VISUAL INSPECTION VERSUS PRESSURE MEASUREMENT

Joseph G.Dwyer BS,RRT, Gary G.Oldenburg BA,RRT, Christina Josephson RRT, Joseph Kohlman RRT.
The Johns Hopkins Hospital, Baltimore Maryland

Introduction: Prior to implementation of pressure monitoring when priming an Extracorporeal Membrane Oxygenator (ECMO) pump, the occlusion maneuver at Johns Hopkins was performed using visual inspection of fluid advancing approximately 1cm/min through a 12? monitoring line post roller head and pre oxygenator. The priming volume of this line measured .7cc. This technique review is to determine variation in flow between the two procedures as well as from person to person, and to show that subjectivity between properly trained specialists does not show significant variance.

Equipment: Stockert SIII occlusive roller head, Medtronic custom tubing pack consisting of class IV tubing, Tygon S65 raceway, Medtronic .8meter squared membrane oxygenator, Medtronic ECMOTherm heat exchanger, Stockert SIII control desk with dual pressure monitors, and Transonics Systems HT110 bypass flow meter.

Methods: A Stockert SIII ECMO system was assembled with the Medtronic custom tubing pack manufactured for Johns Hopkins Hospital. The tubing was then primed through the crystalloid phase. The Stockert roller head was occluded using the pressure readings as described in the equipment procedure manual. Direct flow measurements were taken using the Transonic Systems HT110 Ultrasonic Bypass Flow Meter. The readings were taken on the outflow portion of the tubing pack?s Tygon S65 raceway at pump flow rates of 100, 200, 300, 400, & 500 cc/min (due to the absence of a patient, flows cannot be reported in cc/kg/min). The occlusion process was then repeated using the fluid advance as determined by visual assessment technique for the same flow values. The entire process was then repeated by four different ECMO specialists three times each.

Results: Total # of measurements = 120. Sp1, Sp2, Sp3, Sp4 refers to Specialist #1, etc. V = visual procedure. P = pressure procedure. Var. = variance between ranges in cc?s. All values are representing the averages achieved by each specialist per range. The pump revolutions per minute (rpm) for each flow range measured as follows: 100cc/min = 8rpm, 200cc/min = 15rpm, 300cc/min = 23rpm, 400cc/min = 31rpm, 500cc/min = 38rpm.

cc/min Sp1 V/P Sp2 V/P Sp3 V/P Sp4 V/P Var.V/P=var. total
100 75.7 / 76.7 76.3 / 76.7 74.7 / 74.7 74.3 / 72.7 2.0 / 4.0 = 2.0
200 160.0 / 157.7 159.0 / 157.3 160.3 / 160.7 157.3 / 157.7 3.0 / 3.4 = 0.4
300 239.3 / 238.7 240.7 / 240.0 242.0 / 240.3 239.3 / 238.0 2.7 / 2.3 = 0.4
400 321.3 / 323.0 322.7 / 322.0 324.7 / 324.7 232.3 / 320.7 3.4 / 4.0 = 0.6
500 405.0 / 403.3 402.7 / 404.0 408.0 / 406.0 403.0 / 403.7 5.3 / 2.7 = 2.6

Conclusions: The difference between pressure measurement based values and visual assessment based fluid advancement show minimal variation between all specialists tested. The largest average variance between ranges was 2.6cc. The demonstrated value of this review lies in the confidence that occlusion of a roller head pump can be accurately set in the absence of functional pressure monitoring equipment. This provides a proven mechanism for setting occlusion manually. Recommendations could be made that specialists be trained in both procedures to assure setting of proper occlusion during times when quantitative devices are not functional or available.

OF-02-009

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