CARDIAC-OUTPUT DETERMINATION DURING PROGRESSIVE EXERCISE IN CYSTIC-FIBROSIS

Cardiac output (Q) determination using the equilibrium CO2-rebreathe indirect Fick technique (Equil) to estimate mixed venous Pco2 (PvCO2BAR) has been validated during steady state (SS) exercise in subjects with lung disease. A modification of the exponential method using a low concentration of CO2 with an exponential rise in PEtCO2 (Ex) during rebreathing to estimate PvCO2BAR has been validated during nonsteady state exercise. The purpose of the present study was to validate the Ex method in subjects with lung disease. Q was measured by Ex at every second work load during Prog. Q was measured after 5 min of SS exercise by both Ex and Equil. Arterial Pco2 was estimated from PEtCO2. There was no significant difference in the Q-Vo2 relationship during Prog exercise between the combined control and mild (FEV1 >70%) CF subjects or the moderate and severe CF subjects. Q can be determined in the nonsteady state using the exponential CO2-rebreathe indirect Fick technique in subjects with CF, allowing for noninvasive examination of cardiopulmonary interaction during exercise at a wide range of work loads.