Pre-clinical background
Inhalation medication is delivered to the patient by means of an inhalation device. In the majority of the cases this device is either a metered dose inhaler (MDI) with a propellant gas or a dry powder inhaler (DPI) where the patient inhales the powder without the use of a propellant. The design of the device has an influence on the deposition patterns.
Question
Can imaging and CFD be used to assess the aerosol deposition patterns for specific patients? Can the inhaler geometry be taken into account?
Imaging, CFD and aerosol deposition
To address this question, a commercially available inhaler was selected and converted into a computer model. the latter was done by CT scanning the device and segmenting the air parts from the CT images.
Segmentation of the scanned inhaler geometry
The segmented inhaler was subsequently coupled with a patient specific model of the respiratory system of an asthmatic patient. Computational fluid dynamics was used to calculate the flow inside the coupled models generated by the personalised inhalation profile generated by the patient. Aerosol deposition patterns were determined by solving the force mass balance on the discrete particles. Whenever a particle hit the wall it was trapped at that location.
Coupled model (left), aerosol deposition in respiratory system (middle) and deposition efficiency as a function of particle size
Conclusions
Segmentation and CFD simulations can be used to assess the aerosol deposition behaviour in the airways of specific patients. The influence of several parameters such as inhaler design, inhalation profile, particle size, etc can be investigated.
Publication
Aerosol deposition in patient-specific models using computational fluid dynamics (CFD)
De Backer JW, Vos WG, Verhulst SL, De Backer W.
RDD 2010, Orlando