Case Studies in the Human Respiratory System - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 282

Table 8.9 Variables related to
the actuation of a nasal spray

Consumer variables Parameter affected

Increased/Decreased inhalation Air flow rate

Nostrils opened (one or two) Air flow pattern

Head tilt back/forward Insertion angle inwards

Spraying away from septum walls Insertion angle sideways

Strength of actuation Particle size and velocity

Speed of actuation Particle size and velocity

Insertion location Surrounding geometry

results are presented and the implementation of such data into a CFD simulation is
shown.
Nasal particle deposition delivered by a spray device has been performed by
Cheng et al. (2001) using a multi-sectional nasal airway replica model, and they
found deposition patterns from four different nasal spray pumps. The results
showed that particles deposited mainly in the anterior and turbinate regions and that
deposition in the anterior region increased with an increase in spray cone angles and
larger particles. Suman et al. (2002) investigated deposition patterns in relation to
in-vitro measurements of two different nasal spray pumps having different perfor-
mance characteristics. It was found that spray characteristics, such as spray angle and
plume geometry, did not affect the distribution of droplets in the nose. The discrep-
ancy between the two correlations may be attributed to the numerous variations that
exist in nasal spray applications that are hard to quantify experimentally (Table 8.9 ).

8.4.1 Nasal Spray Atomization Experimental Images

CFPD simulations of nasal drug delivery often neglect the initial spray particle condi-
tions (e.g. particle velocity) and instead introduce particles entrained with the inhaled
airflow into the nasal cavity. This section presents some experimental images which
provides qualitative insight and improved understanding into the physical behaviour
of nasal spray delivery. Firstly a steady stream of water is passed through a nasal
spray that is placed in a perspex test chamber. A schematic of the setup is given
in Fig. 8.40 which shows both the pressurised water supply and the visualisation
system. An upstream pressure of 500 kPa was used to force water through the nasal
spray. The transparent perspex test chamber encloses a nasal spray nozzle that is
pointed downwards. Using high speed shadow lighting photography techniques with
lasers, high resolution images in the near nozzle spray region can be captured to
allow a better understanding of the physical behaviour of the spray. Initial measure-
ments are made with the spray pointing downwards to avoid any interference from
gravitational settling of droplets which is unavoidable if the nasal spray were to be
directed upwards.
The nasal spray device was sliced open at the nozzle and a scan electron micro-
scope (SEM) was used to determine the type of atomizer used. Figure 8.41 shows
the 80X image SEM magnification of the internal atomizer which is a pressure swirl