The effect of diffusion in the respiratory tree on the alveolar amplitude response technique (AART)

Theoretical data for the alveolar amplitude response technique (AART) (J. Appl. Physiol. 41 (1976) 419-424) for assessing lung function was simulated using a single path lung model. This model takes account of stratified inhomogeneities in gas concentrations within the respiratory tree. The data was inserted into previously published parameter recovery techniques that may be used to estimate dead-space volume, alveolar volume and cardiac output. These parameter recovery techniques are based on much simpler mathematical models that do not allow stratified inhomogeneities in gas concentrations. It was found that: (i) recovered dead-space volume depended significantly on the ventilation pattern and on the distribution of volume within of the conducting airways; (ii) alveolar volume was recovered to a good degree of accuracy; and (iii) the recovered value of cardiac output was highly dependent on both the choice of inert gas and parameter recovery technique.