Calibration of a bubble evolution model to observed bubble incidence in divers

Area of Science:

• Physiology
• Biophysics
• Diving Medicine

Background:

• Decompression sickness (DCS) is a risk in diving, involving bubble formation in tissues.
• Accurate modeling of bubble evolution is crucial for predicting and preventing DCS.
• Existing models require calibration against empirical data for improved reliability.

Purpose of the Study:

• To calibrate a probabilistic bubble evolution model using real-world diver data.
• To assess the model's ability to predict bubble formation and growth.
• To refine parameters for inert gas exchange and bubble dynamics in divers.

Main Methods:

• Maximum likelihood estimation was used to calibrate the model against 2,064 chamber dives (air and heliox).
• Bubble data (Kisman-Masurel code) were compared to model-predicted maximum bubble radius (Rmax).
• Multinomial statistics and a linear inert gas exchange rate were employed.

Main Results:

• The model was best calibrated using a three-tiered bubble grade (none, low, high) and a single tissue compartment.
• Key parameters estimated include tissue volume (0.00036 cm3), surface tension (5.0 dyne/cm), and gas time constants for nitrogen (27.9 min) and helium (9.3 min).
• Model predictions showed reasonable agreement with temporal bubble grade recordings.

Conclusions:

• The calibrated bubble evolution model provides a more accurate prediction of bubble formation and size in divers.
• This refined model can enhance understanding of DCS pathophysiology and inform decompression strategies.
• The study highlights the importance of empirical data in validating and improving physiological models for diving safety.