A model of neonatal oxygenation covering the dynamics of the alveoli -

Abstract

It is observed clinically that wide-band pressure oscillations enhance oxygenation of blood flow in pulmonary capillaries. One application of this phenomenon is to impose pressure oscillations on the inhaled air to ventilate ill infants with respiratory distress syndrome. The objective of this research is to study the effect of these oscillations on the alveolar gas exchange. This study is based on modeling the alveolus and the gas exchange across alveolar membrane. The proposed model that takes as its input wide-band oscillatory pressure signal, predicts the dynamic oxygenation of blood flowing through the pulmonary capillaries while accounting for (i) pressure dependent change in the alveolar volume, (ii) viscoelastic nature of the alveolar membrane, (iii) surface tension of the tissue-air interface and its dependence on surfactant secretion (alveolus volume dependent), and (iv) change in thickness of the alveolar membrane as the alveolus shrinks or expands. We focus in particular on the interplay between the air pressure signal time scale, oxygen diffusion time scale, tissue relaxation time scale, and blood pressure oscillation time scale. This research provides a robust model that examines the concentration of oxygen from the point the oscillatory air enters the alveolus to the point the pulmonary capillaries get oxygenated. We expect this model to shed more light on the physics underlying the enhancement of the oxygenation process due to a wide-band pressure signal.