Influence of lower limb pneumatic compression on pulmonary artery temperature: Effect on cardiac output measurements

Objectives: To characterize the decreases in pulmonary artery temperature t hat coincide with the inflation cycle of pneumatic calf compression stockin gs and to examine their effects on the thermodilution measurement of cardia c output. Design: Three-part observational study. Setting: University hospital surgical intensive care unit. Patients: Postoperative patients with indwelling pulmonary artery catheters , Intervention: Thermodilution cardiac output measurements with and without p neumatic calf compression. Measurements and Main Results: Phase 1 (n = 18) examined the effects of pne umatic compression on pulmonary artery temperature. There was no effect on pulmonary artery temperature (device off, 37.468 +/- 0.008 degrees C; devic e on, 37.458 +/- 0.014 degrees C), but the difference between the maximum a nd minimum pulmonary artery temperatures was increased (off, 0.031 +/- 0.00 6 degrees C; on, 0.055 +/- 0.012 degrees 0 [p < .001]). Phase 2 (0 = 12) fo und that the mean thermodilution cardiac output with 10 mt of cold (0-5 deg rees C) injectate was unchanged bit pneumatic compression (off, 7.00 +/- 2. 28 L/min; on, 6.89 +/- 2.22 L/min), However, when the compression devices w ere operating, the variability between the individual measurements was incr eased, as reflected by larger coefficients of variation (off, 3.19 +/- 1.96 ; on, 8.72 +/- 6.56 [p < .02]), Similar results were obtained during phase 3 (n = 5), when cardiac output was measured with room temperature Injectate , Conclusions: Intermittent pneumatic calf compression increased lower limb v enous return, causing acute but transient decreases in pulmonary artery blo od temperature. This did not affect the accuracy of thermodilution cardiac output measurements that were made using 10 mt of either cold or room tempe rature injectate.