Thermodiluted relative tidal volume estimation using a thermal camera in operating room under spinal anesthesia

Area of Science:

• Physiology
• Biomedical Engineering

Background:

• Estimating relative tidal volume is crucial for monitoring breathing status.
• The link between temperature and respiration volume remains understudied.
• Nasal cavity temperature changes offer a potential indicator for respiration volume.

Purpose of the Study:

• To derive and evaluate a formula for calculating thermodiluted respiration volume from nasal cavity temperature.
• To compare the proposed formula's tidal volume estimations against a reference respiration volume monitor.

Main Methods:

• A formula was derived to calculate respiration volume based on thermodilution principles and nasal cavity temperature variations.
• Thermal data were collected from 8 subjects at 10 Hz.
• Simultaneous recordings from a respiration volume monitor (RVM) served as the reference standard.

Main Results:

• The proposed formula demonstrated strong agreement with the RVM, with a mean ICC of 0.948.
• High R-squared value (0.8962) and linear regression coefficients indicate good model fit.
• Bland-Altman analysis confirmed that 96.01% of measurements fell within 2 standard deviations.

Conclusions:

• A thermodynamic model was developed to correlate thermal energy with respiration volume.
• The thermodiluted model presents a feasible and accurate method for estimating relative respiration tidal volumes.