• José A L Calbet and Robert Boushel.
• Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, Las Palmas de Gran Canaria, Spain; Research Institute of Biomedical and Health Sciences, IUIBS, University of Las Palmas de Gran Canaria, Canary Island, Spain; Copenhagen Muscle Research Center, Heart & Circulatory Section, Department of Biomedical Sciences, University of Copenhagen, and Department of Anaesthesia, Bispebjerg Hospital, Copenhagen, Denmark; and lopezcalbet@gmail.com.
• J. Appl. Physiol. 2015 Jan 1;118(1):1-10.

AbstractThe accuracy and reproducibility of transpulmonary thermodilution (TPTd) to assess cardiac output (Q̇) in exercising men was determined using indocyanine green (ICG) dilution as a reference method. TPTd has been utilized for the assessment of Q̇ and preload indexes of global end-diastolic volume and intrathoracic blood volume, as well as extravascular lung water (EVLW) in resting humans. It remains unknown if this technique is also accurate and reproducible during exercise. Sixteen healthy men underwent catheterization of the right femoral vein (for iced saline injection), an antecubital vein (ICG injection), and femoral artery (thermistor) to determine their Q̇ by TPTd and ICG concentration during incremental one- and two-legged pedaling on a cycle ergometer and combined arm cranking with leg pedaling to exhaustion. There was a close relationship between TPTd-Q̇ and ICG-Q̇ (r = 0.95, n = 151, standard error of the estimate: 1.452 l/min, P < 0.001; mean difference of 0.06 l/min; limits of agreement -2.98 to 2.86 l/min), and TPTd-Q̇ and ICG-Q̇ increased linearly with oxygen uptake with similar intercepts and slopes. Both methods had mean coefficients of variation close to 5% for Q̇, global end-diastolic volume, and intrathoracic blood volume. The mean coefficient of variation of EVLW, assessed with both indicators (ICG and thermal) was 17% and was sensitive enough to detect a reduction in EVLW of 107 ml when changing from resting supine to upright exercise. In summary, TPTd with bolus injection into the femoral vein is an accurate and reproducible method to assess Q̇ during exercise in humans.Copyright © 2015 the American Physiological Society.

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