Validation of 2 methods of continuous cardiac output measurement during exercise in patients with chronic heart failure: LiDCO and Physioflow

Patients with chronic heart failure (CHF) suffer from exercise intolerance,
which is caused by abnormal skeletal muscle metabolism and a decrease in
cardiac output during exercise. Information on the cardiac output response
during exercise can lead to a better understanding of the relative contribution
of central and peripheral factors to the exercise capacity of individual CHF
patients. In addition, measuring cardiac output during exercise can be useful
for clinical purposes like measuring effects of therapeutic interventions (e.g.
exercise training, cardiac resynchronization therapy, stem cell therapy) and
predicting the response to exercise training.
Recently, 2 new methods of continuous CO measurement were introduced: LiDCO
(LiDCO Group) and Physioflow (Manatec Biomedical). Since both methods were not
validated during exercise in patients with CHF the aim of the present study is
to compare these methods with the (continuous) direct Fick method and
continuous thermodilution during submaximal and maximal exercise.

The aim of the present study is to compare two methods for measuring continuous
cardiac output (LiDCO and Physioflow) with the direct and continuous Fick
method and continuous thermodilution during submaximal and maximal exercise in
patients with CHF .

First a symptom-limited exercise test and on another day in the same week 2
submaximal constant-load tests (at 30% and 50% of the previously determined
maximal workload) followed by a second symptom-limited exercise test. The
latter tests include cardiac output measurements. Before these tests a 7.5 F
catheter (CCOmbo, Edwards, Irvine, USA) is introduced into the pulmonary artery
through the right or left antecubital vein at the Cardiac catheterization room
(under local anaesthesia); the position of the catheter is verified by
fluoroscopy. In addition, a short catheter is inserted into the radial artery
of the same side.
During the exercise tests LiDCO and Physioflow are compared to a gold standard
method (direct Fick method). LiDCO is based on arterial pulse pressure waveform
analysis and Physioflow is a non-invasive bioimpedance method, based on the
principle that variation in the impedance to flow of a high-frequency,
low-magnitude alternating current across the thorax results in the generation
of a measured waveform from which stroke volume can be calculated.
The direct Fick method is performed by measuring oxygen uptake, mixed venous
and arterial oxygen saturation continuously.

Insertion of pulmonary artery catheter (ventricular arrhytmias, hematoma, local
thrombosis) and radial artery catheter (hematoma, dissection).
Exercising with a pulmonary artery catheter was performed in previous studies
without complications.