Cardiac output and end-tidal carbon dioxide

Area of Science:

• Physiology
• Cardiopulmonary Resuscitation (CPR)
• Respiratory Gas Exchange

Background:

• Previous research noted elevated mixed venous carbon dioxide tension (PvCO2) and decreased end-tidal carbon dioxide concentration (ETCO2) during CPR in pigs.
• This phenomenon was hypothesized to result from reduced cardiac output and subsequent pulmonary blood flow.
• The precise relationship between ETCO2 and cardiac output during CPR remained to be fully elucidated.

Purpose of the Study:

• To investigate the correlation between end-tidal carbon dioxide concentration (ETCO2) and cardiac output.
• To determine the utility of ETCO2 as an indicator of cardiac output during cardiopulmonary resuscitation (CPR).

Main Methods:

• Utilized a porcine model of cardiac arrest.
• Monitored ETCO2 and cardiac output in 19 minipigs.
• Analyzed the relationship between these variables before and during CPR.

Main Results:

• A strong, high linear correlation was observed between ETCO2 and cardiac output.
• This correlation was consistent both before cardiac arrest and during CPR.
• Findings support the link between reduced cardiac output and altered CO2 dynamics.

Conclusions:

• The observed increase in PvCO2 and decrease in ETCO2 during CPR are direct reflections of critically reduced cardiac output.
• Diminished cardiac output severely limits alveolar blood flow, impairing the lungs' ability to clear carbon dioxide.
• ETCO2 serves as a valuable, non-invasive indicator of cardiac output and resuscitation effectiveness.