RELIABILITY OF THE CPX/D NON-INVASIVE CARDIAC OUTPUT BY CO2 REBREATHING APPARATUS 1478

Abstract

The purpose of this study was to determine the reliability of the CPX/D non-invasive cardiac output by CO2 rebreathing (exponential method) in a healthy population. Six healthy females ranging from 18-45 years of age were recruited. A total of 6 tests were performed by each subject, 3 at rest and 3 while exercising. The resting measurements were taken while the subjects were seated comfortably in a chair. The exercise measurements were taken when the subjects begin walking on a treadmill at a zero incline and a speed of 3 mph. The cardiac output was measured when the subjects reached a steady-state by rebreathing 4% CO2 in a closed-circuit for 20 seconds. A repeated measures ANOVA was performed on the data collected and an intraclass correlation ICC(3,k) formula was used to determine an index of reliability of the trials. The test proved to have ICC's at rest =.84 (F=6.349, p =.022) and while exercising=.85 (F = 7.055, p =.017). The mean cardiac output values in L/min for females at rest: R1 = 5.82 (SD =.084), R2 = 6.04 (SD =.241) & R3 = 5.66 (SD =.207) Females exercising in L/min E1 = 9.50 (SD =.255), E2 = 9.92 (SD =.084) & E3 = 9.80 (SD =.274). The data suggests the CPX/D non-invasive cardiac output by CO2 rebreathing apparatus (Medical Graphics) is a reliable instrument at rest and at low intensity exercise.