Comparison the work of breathing between healthy and obese by thermodynamic analysis

Abstract

Introduction: Respiratory muscle can be regarded as a thermodynamic machine that converts chemical energy into mechanical work during each breathing cycle.

Aims and Objectives: Aim of the study is to determine the glucose consumption, exergy destruction and entropy generation of healthy, obese and Obesity-hypoventilation Syndrome (OHS) subjects by thermodynamic analysis of the work of breathing (wob).

Methods: In this study, a human respiratory system was modelled thermodynamically using the first and second laws of thermodynamics. Mass, energy, exergy and entropy balances are performed around the respiratory muscles to calculate the glucose consumption, exergy destruction and entropy generation as a function of the second law efficiency.

Results: As a result of the thermodynamic analysis of the wob performed by the healthy, obese and OHS subjects, exergy destruction was calculated as 6.41x10-3 (kJ/min), 4.85x10-2 (kJ/min) and 6.16x10-2 (kJ/min), respectively. Entropy generation by the healthy, obese and OHS individuals through the breathing cycle were 2.15x10-5 (kJ/K)/min, 1.63x10-4 (kJ/K)/min and 2.07x10-4 (kJ/K)/min, respectively. Glucose consumed for wob of healthy, obese and OHS individuals were calculated as 0.20, 1.06 and 1.59 mmol/min, respectively. Obese and OHS patients consume approximately 5 and 8 times more glucose, respectively, than their healthy counterparts to do the same breathing activity.

Conclusions: The obese and OHS patients have significantly increased glucose consumption, exergy destruction and entropy generation. As a conclusion, thermodynamic analysis of the respiratory muscles in obese population may provide additional information in case of respiratory problems.