New metabolic lung simulator: development, description, and validation

Area of Science:

• Biomedical Engineering
• Physiology
• Respiratory Medicine

Background:

• Indirect calorimetry measures airway carbon dioxide elimination (VCO2) and oxygen uptake (VO2) to assess tissue metabolism.
• Validating indirect calorimetry instruments is challenging due to the lack of a reference standard and difficulty achieving steady-state conditions in patients.

Purpose of the Study:

• To develop and validate a practical metabolic lung simulator for generating accurate, adjustable, and stable reference values of VCO2 and VO2.
• To provide a reliable tool for the calibration and validation of indirect calorimetry methodology and clinical monitoring devices.

Main Methods:

• A metered alcohol combustion system precisely delivered ethanol to generate reference VCO2 and VO2.
• A circular circuit with a mechanical lung simulated mammalian gas kinetics, including ventilation waveforms and non-steady-state conditions.
• Reference gas generation was validated against independent measurements of gas flow and fractions.

Main Results:

• The system demonstrated high accuracy, with average errors for VCO2 and VO2 within +/- 4.86% across different ventilation modes.
• Complete and pure combustion was confirmed by low levels of ethanol vapor and carbon monoxide.
• The simulator successfully generated a wide range of stable reference values for VCO2 and VO2.

Conclusions:

• The developed metabolic lung simulator offers a robust solution for calibrating and validating indirect calorimetry.
• This technology can significantly improve the accuracy of patient monitoring in critical care and anesthesia.
• The study provides a foundation for future research in metabolic gas exchange analysis.