Application of impedance cardiography during exercise

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Noninvasive Monitoring

Background:

• Impedance cardiography (ICG) has been utilized for over 30 years to measure beat-by-beat stroke volume.
• Previous ICG systems faced limitations with movement artifacts during strenuous exercise.
• Advancements in technology have led to next-generation ICG systems for improved signal acquisition.

Purpose of the Study:

• To evaluate a new noninvasive continuous cardiac output monitor (NCCOM3-R7) at rest and during submaximal exercise.
• To assess the relationships between thoracic impedance (Z(o)), its first derivative (dZ/dt), and posture.
• To compare the NCCOM3-R7 with the Minnesota impedance cardiograph 304B (MIC).

Main Methods:

• Twenty-eight healthy participants underwent ICG measurements in supine, seated, and standing postures.
• Measurements were taken using both the NCCOM3-R7 and MIC devices.
• Cardiac output was assessed at rest and during submaximal upright cycle exercise.

Main Results:

• Thoracic impedance (Z(o)) increased progressively from supine to standing positions with both devices.
• The NCCOM3-R7 reported lower Z(o) and higher dZ/dt values compared to the MIC across all postures.
• Exercise cardiac output estimations were generally reasonable, but accuracy requires further investigation in specific populations.

Conclusions:

• Impedance cardiography provides a reasonable estimate of directional changes in stroke volume and cardiac output during exercise.
• The NCCOM3-R7 shows potential for continuous monitoring, but Z(o) and dZ/dt are influenced by posture, gender, and device characteristics.
• Refined ICG technology is expected to enhance its role in environmental medicine, exercise testing, and sports medicine.