Correlation and level of agreement between echocardiography and a new inert gas rebreathing technique in estimating cardiac output

Pregnancy induces major maternal cardiovascular changes, which are necessary
for the normal course of pregnancy. The hyperdynamic circulation of pregnancy
develops in early gestation, but the increase in cardiac output continues up to
the end of pregnancy.
However, most of these studies are performed with echocardiography, but
although Doppler ultrasound is a non-invasive and safe method to measure
cardiac output, there are some theoretical and practical constraints to Doppler
cardiac output estimations. Recently, a new foreign gas rebreathing technique
is developed, which seems to be a fast and easy way of measuring cardiac
output. Due to the use of minor concentrations of N2O and SF6, this method can
safely be used.
Yet, a comparison between echocardiography and the rebreathing technique seems
te be a logical next step.

We would like to perform a study in which first the level of agreement and the
correlation between echocardiography and the new rebreathing technique in
estimating cardiac output will be determined.

To determine the correlation and level of agreement between cardiac output
measured by the rebreathing technique and by echocardiography, 20 female
non-pregnant patients will be subjected to both techniques. All women will be
recruited from the postpartum follow-up, who will normally receive
echocardiography as part of the postpartum evaluation after a vascular
complicated pregnancy.

The concentrations of the gases inspired during the Innocor measurements are
completely safe in a non-pregnant situation.However, it should be emphasized
that there is an interval of 5 minutes between the measurements, to prevent an
accumulation of gases in the pulmonary blood stream. Additionally, we try to
create a quiet and comfortable environment during the measurements.