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Background: Monitoring oxygen delivery to the oxygenator of a heart lung machine (HLM) is typically accomplished with an O 2 analyzer connected to the gas inflow line. It is assumed when the FiO 2 is greater than 21% that oxygen is being delivered to the oxygenator. However, this assumption is imperfect because the connection of the inflow line to the oxygenator is downstream from the O 2 analyzer. FiO 2 monitoring will not alert the perfusionist if the inflow line is not actually connected to the oxygenator. Measuring the fraction of expired oxygen (FEO 2 ) is a more reliable way of monitoring O 2 delivery., Methods: An O 2 analyzer was placed on the scavenging line that is attached to the exhaust port of oxygenator (FEO 2 )., Results: Whenever the FiO 2 is greater than 21%, and the inflow line is properly connected, the FEO 2 exiting the oxygenator is greater than 21%. The FEO 2 falls to 21% when the inflow line is not functioning., Conclusion: Monitoring the FEO 2 is a more reliable way to verify O 2 delivery to an oxygenator. An alarm can be set on the FEO 2 monitor to alert the perfusionist if the FEO 2 falls below a predetermined threshold so any issue with O 2 delivery will always be recognized.

A study was performed to evaluate a user-operated patient-side blood gas and chemistry monitor (GEM-STAT, Mallinckrodt Sensor Systems, Ann Arbor, MI) for the first time in a group of infants and children with congenital heart disease undergoing cardiac surgery. Paired blood samples from 18 patients were analyzed by the test instrument and by standard clinical laboratory instruments. One failure of the test instrument, malfunction of a cartridge, occurred during the evaluation. The integrated and external quality control functions gave readings within the manufacturer's tolerance. The differences between the measurements obtained using the GEM-STAT and the standard laboratory instruments for five of the six variables are summarized as follows (mean +/- SD, units of measure, number of samples): pH (-0.017 +/- 0.02, 132), PaCO2 (-1.90 +/- 3.3 mm Hg, 130), hematocrit (-1.3 +/- 2.3%, 129), potassium (-0.17 +/- 0.20 mmol, 112) and sodium (-2.0 +/- 3.3 mmol, 112). The mean difference in the measurements of PaO2 in the clinically important range defined by the upper quality control limit for oxygen tension of 172 mm Hg for the GEM-STAT is: (-0.20 +/- 7.26 mm Hg, 51). The mean difference between the measurements for PaO2s below the lowest quality control point (60 mm Hg) was (-2.3 +/- 5.5 mm Hg, 30). The values for all variables obtained from the GEM-STAT during the trial period, with the exception of the PaO2 less than 60 mm Hg, showed good correlation with the laboratory over the clinically useful range.(ABSTRACT TRUNCATED AT 250 WORDS)