Cardiac output during exercise: A comparison of four methods

• Several techniques assessing cardiac output (Q) during exercise are available. The extent to which the measurements obtained from each respective technique compares to one another, however, is unclear. We quantified Q simultaneously using four methods: the Fick method with blood obtained from the right atrium (Q(Fick-M)), Innocor (inert gas rebreathing; Q(Inn)), Physioflow (impedance cardiography; Q(Phys)), and Nexfin (pulse contour analysis; Q(Pulse)) in 12 male subjects during incremental cycling exercise to exhaustion in normoxia and hypoxia (FiO2=12%). While all four methods reported a progressive increase in Q with exercise intensity, the slopes of the Q/oxygen uptake (VO2) relationship differed by up to 50% between methods in both normoxia [4.9 +/- 0.3, 3.9 +/- 0.2, 6.0 +/- 0.4, 4.8 +/- 0.2L/min per L/min (mean +/- SE) for Q(Fick-M), Q(Inn), Q(Phys) and Q(Pulse), respectively; P=0.001] and hypoxia (7.2 +/- 0.7, 4.9 +/- 0.5, 6.4 +/- 0.8 and 5.1 +/- 0.4L/min per L/min; P=0.04). In hypoxia, the increase in the Q/VO2 slope was not detected by Nexfin. In normoxia, Q increases by 5-6L/min per L/min increase in VO2, which is within the 95% confidence interval of the Q/VO2 slopes determined by the modified Fick method, Physioflow, and Nexfin apparatus while Innocor provided a lower value, potentially reflecting recirculation of the test gas into the pulmonary circulation. Thus, determination of Q during exercise depends significantly on the applied method.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

Keyword

Inert gas rebreathing

impedance cardiography

pulse contour analysis

hypoxia

maximal oxygen

IMPEDANCE CARDIOGRAPH DEVICE

GAS REBREATHING TECHNIQUE

MAXIMAL AEROBIC

EXERCISE

HEART-FAILURE PATIENTS

BLOOD-FLOW

NONINVASIVE MEASUREMENT

RECIRCULATION TIME

ARTERIAL-PRESSURE

STROKE VOLUME

LEG EXERCISE

Sport Sciences

Publication and Content Type

ref (subject category)

art (subject category)