Clinical background

Bronchodilators are used to open up the airways of patients suffering from airway constriction. Through administration of these compounds the lung function can be improved where often the forced expiratory volume in one second or FEV1 is used to quantify the changes in the respiratory system. This parameter, however, regards the respiratory system as a black box and correlations with the patient’s clinical condition are often weak. There is a need for additional, more sensitive parameters that describe the changes in the respiratory system.

Question

Can imaging and CFD provide additional information on the bronchodilation after the administration of a long acting beta2 agonist using Chiesi’s Modulite technology?

Imaging and CFD

In this study a total of 14 mild to moderate asthmatic patients was included. All patients received a low-dose CT scan at baseline after full inhalation. Out of the 14 patients, 10 patients received the bronchodilating compound. The scan was repeated four hours after the administration of the product. In addition to the CT scan also spirometry and bodyplethysmography was performed. Based on the CT scans, the airway tree was segmented and used to determine changes in airway volume. The resulting 3D model was subsequently used for flow simulation to determine changes in airway resistance.

The results clearly showed the increase in airway volume of the smaller airways, generation 3 onwards. The trachea and larger airways showed virtually no change. The resistance consequently reduced in the smaller airways. A significant correlation was found between the changes in imaging parameters and the changes in the parameters from the lung function tests. This indicate that whatever happens in the computer model also occurs in the clinical practice.

When assessing the sensitivity of the different parameters it can be seen that the imaging parameters and in particular the CFD-based resistance is much more sensitive to detect changes compared to the classic lung function. This would imply that fewer patients are needed to achieve the same power for this study.

Conclusions

Imaging and CFD is capable of detecting acute bronchodilation in asthmatic patients. Both changes in airway volume and resistance are parameters that correlate well with lung function, however their sensitivity to detect changes is considerably larger. In future studies this parameter could be used to detect clinically relevant changes in the respiratory system following an intervention.

Publication

Computational fluid dynamics can detect changes in airway resistance in asthmatics after acute bronchodilation.
De Backer JW, Vos WG, Devolder A, Verhulst SL, Germonpré P, Wuyts FL, Parizel PM, De Backer W.
J Biomech. 2008;41(1):106-13