Modeling Intercapillary Distance as a Regulator of Tissue Denitrogenation Rate.

Area of Science:

• Physiology
• Aerospace Medicine
• Biomedical Engineering

Background:

• Breathing 100% oxygen facilitates denitrogenation, crucial for preventing decompression sickness (DCS) during low-pressure exposure.
• DCS risk is significant in aviation and space exploration, necessitating efficient nitrogen removal strategies.
• Tissue denitrogenation is perfusion-dependent, suggesting intercapillary distance (ICD) is a key factor.

Purpose of the Study:

• To develop and evaluate computational models of tissue denitrogenation.
• To investigate the role of intercapillary distance (ICD) in regulating nitrogen washout rates.
• To establish a theoretical framework for predicting denitrogenation efficiency across different tissue types.

Main Methods:

• Five inert gas exchange models were created using a Krogh cylinder model with varying ICD estimates (10-50 µm).
• Nitrogen washout rates were calculated based on ICD and initial tissue nitrogen pressure.
• Model outputs were compared against established whole-body washout functions (Behnke's) to validate predictions.

Main Results:

• The developed models demonstrated a strong correlation (Pearson's r = 1) with benchmark fractional washout curves.
• Calculated nitrogen washout half-times varied significantly, ranging from 5.5 to 90 minutes.
• While ICD and nitrogen solubility affect tissue nitrogen concentration, they do not influence nitrogen pressure.

Conclusions:

• A multicylinder ICD perfusion model, conceptualized as a 'leaky nitrogen reservoir,' provides a valid theoretical basis for denitrogenation rates.
• This modeling approach can enhance the development of strategies to improve perfusion and reduce DCS risk.
• Intercapillary distance is a critical regulator of tissue denitrogenation, offering new avenues for DCS prevention.