Capnographic trend curve monitoring can detect 1-ML pulmonary emboli in humans

Research paper by Gilbert C. Carroll

Indexed on: 01 Apr '92Published on: 01 Apr '92Published in: Journal of Clinical Monitoring and Computing


To evaluate the potential of trend monitoring of end-tidalPco2 (Petco2) to detect pulmonary embolization, the capnograms of 24 mechanically ventilated patients were monitored during simulation of 1-ml pulmonary embolization by inflation of the balloons of their pulmonary artery catheters. Within 1 minute of balloon inflation,Petco2 showed an exponential decrease to a new equilibrium. This response is characteristic of a CO2 wash-out curve produced by a step increase in dead space. Because of a steady baseline, the depression of the trend line during balloon inflation was apparent to a naive reader repeatedly in 20 of the 24 patients (sensitivity, 85%; specificity, 94%; positive predictive value, 98%; negative predictive value, 89%), despite a small mean decrease inPetco2 (2±1.97 mm Hg). ThePetco2 trend curve did not reliably allow detection of balloon inflation in 4 patients whose capnograms were poorly formed. In conclusion, during constant ventilation,Petco2 trend curve monitoring might provide clinically useful “on line” information regarding pulmonary embolization.

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