Hypoxemia after intraluminal oxygen line obstruction during cardiopulmonary bypass

A system for monitoring the delivery of ventilating gas to the oxygenator during cardiopulmonary bypass

Present methods for monitoring delivery of ventilating gas to the oxygenator during cardiopulmonary bypass have not been critically examined despite the occurrence of catastrophic gas flow disturbances. Currently, a flowmeter regulates the delivery of gas into the proximal portion of the gas circuit, and at these institutions, an oxygen (O2) analyzer positioned downstream of the flowmeter monitors oxygen concentration of the flowing gas. However, these devices are incapable of accurately analyzing the flow of gas into the oxygenator housing. In response to this deficiency, the authors developed and evaluated, in a laboratory model, an alternative system for monitoring ventilating gas flow. The system measured quantity of gas flow by pneumotachography, and oxygen concentration of the ventilating gas with a polarographic oxygen analyzer at the gas inlet port of the oxygenator. Five types of disturbances in gas delivery, which have been documented in the medical literature, were created in a laboratory model: (1) O2 concentration variation, (2 and 3) oxygenator gas line disconnection at each of two locations in the gas circuit, (4) a decrease in gas flow to the oxygenator secondary to a leak in the gas circuit, and (5) excess gas flow to the oxygenator. The capability of currently used monitoring devices (flowmeter and "passive" O2 analyzer) with the proposed monitoring system (pneumotachograph and "aspirating" O2 analyzer) was compared for detecting these abnormalities in gas delivery. The currently used devices were only able to satisfactorily detect a change in oxygen concentration. In contrast, the proposed system was able to rapidly detect all types of gas delivery disturbance.(ABSTRACT TRUNCATED AT 250 WORDS)