The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

MEMBRANE OXYGENATOR EXHAUST CAPNOGRAPHY TO MONITOR PUMP ARTERIAL CARBON DIOXIDE DURING ECMO

Roy Ramirez RRT-NPS, Cindy Smith RN, BSN, John Cleary MD. Children's Hospital Of Orange, CA.

BACKGROUND: With the initiation of ECMO, it is possible to expose the patient to low levels of PCO2 which have been associated with leukomalacia and adverse developmental outcome. Due to that fact, it is crucial to monitor the pump arterial PCO2 during Extracorporeal Membrane Oxygenation (ECMO). In addition, problems with delivery of sweep gas or Carbair during ECMO are well described. During the weaning phase, accurate PCO2 monitoring would also be useful. Conflicting reports of the utility of exhaust capnography during operative CPB have been published (1, 2). We are investigating the use of oxygenator capnography to continuously monitor pump arterial PCO2 during ECMO.

METHODS: A Cosmos + (Respironics Carlsbad Ca.) capnograph monitor with a neonatal adaptor was attached to the exhaust port of the membrane oxygenator. The first patient has a history of Meconium Aspiration Syndrome (MAS) PPHN on Veno-Arterial ECMO. The second patient has a history of PPHN (unknown etiology). A total of 68 pump and patient blood gasses were obtained q 6 hours and p.r.n. Capnograph readings were recorded at the time of blood gas draw. Comparisons were made using descriptive statistics.

RESULTS: On the first patient a total of 26 pump arterial blood gas samples were compared with readings from the capnograph. No significant difference was seen between pump and capnograph CO2. For the second patient, 42 pump arterial gas samples were compared with readings from the capnograph. There was a noted widening of the gap between pump arterial PCO2 and Capnograph readings. The gap narrowed significantly after the ECMO circuit change.

First patient Pump CO2 Capnograph CO2
Mean =/- S.D. 38 +/-2 38 +/-3
Range 32-54 33-54
Second patient Pump CO2 Capnograph CO2
Mean =/- S.D. 39+/-5 32+/-6
Range 21-48 15-42
Second patient After change of circuit Pump CO2 Capnograph CO2
Mean =/- S.D. 41+/-1.1 37+/-1.3
Range 37-45 33-42

CONCLUSION: Initial experience suggests utility of membrane oxygenator exhaust capnography during ECMO. Further studies are needed to explore what factors affect the lung function.

References:

1. Ptger KC, McMillan D, Southwell J, Dando H, J Extra Corporeal Technology. 2003 Sep; 35(3):

2. O'Leary MJ, MacDonnell SP, Ferguson CN. British Journal of anesthesia. 1999 Jun; 82(6): 843-6.

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