Comparison of two noninvasive techniques for estimating cardiac output during exercise

Area of Science:

• Cardiovascular Physiology
• Noninvasive Monitoring Techniques

Background:

• Accurate estimation of cardiac output (Q) is crucial for assessing cardiovascular function.
• Noninvasive methods offer advantages over invasive techniques for monitoring Q.

Purpose of the Study:

• To compare the reliability and efficiency of transthoracic impedance plethysmography (Z) and indirect Fick CO2 rebreathing (RB) for estimating cardiac output.
• To evaluate these techniques at rest and during graded exercise.

Main Methods:

• Paired measurements of cardiac output were obtained using Z and RB methods in 60 male subjects.
• Subjects performed rest and graded cycle ergometer exercise.
• Correlation with oxygen consumption was assessed.

Main Results:

• Both Z and RB techniques showed linear correlation with oxygen consumption (RZ = 0.752, RRB = 0.855).
• A significant linear relationship (R = 0.75) was observed between the Z and RB techniques across all work loads.
• The Z technique demonstrated simpler implementation and comparable reliability to the RB method.

Conclusions:

• Both transthoracic impedance plethysmography and CO2 rebreathing are reliable for estimating cardiac output over a wide range of work loads.
• Transthoracic impedance plethysmography is recommended due to its simplicity and efficiency.
• Lung volume did not affect the cardiac output estimations using the Z technique.