Modelflow underestimates cardiac output in heat-stressed individuals

Area of Science:

• Physiology
• Cardiovascular Research
• Thermoregulation

Background:

• The Modelflow method estimates cardiac output from arterial pressure waveforms.
• Its accuracy during whole body heat stress is not well-established.
• Whole body heat stress significantly impacts cardiovascular function.

Purpose of the Study:

• To test if Modelflow accurately tracks thermodilution-derived cardiac outputs during whole body heat stress.
• To evaluate Modelflow's performance under normothermic and heat-stressed conditions with varying cardiac outputs.

Main Methods:

• Cardiac output was measured using Modelflow (arterial cannulation and Finometer) and thermodilution.
• Lower-body negative pressure (LBNP) was used to induce acute changes in cardiac output.
• Nine healthy normotensive subjects were studied under normothermic and heat-stressed conditions.

Main Results:

• Modelflow and thermodilution showed similar cardiac output measurements in normothermic conditions.
• During heat stress, Modelflow significantly underestimated cardiac output compared to thermodilution.
• Modelflow also attenuated the reduction in cardiac output during LBNP under heat stress.

Conclusions:

• The Modelflow method underestimates cardiac output during whole body heat stress.
• Accuracy is compromised in both direct arterial and Finometer-derived waveforms during heat exposure.
• Thermodilution remains a more reliable method for measuring cardiac output in heat-stressed individuals.