Effects of anatomy and particle size on nasal sprays and nebulizers

Abstract

Objective: To study the effects of nasal deformity on aerosol penetration past the nasal valve (NV) for varying particle sizes using sprays or nebulizers.

Study design: Computed mathematical nasal airway model.

Setting: Department computer lab.

Subjects and methods: Particle deposition was analyzed using a computational fluid dynamics model of the human nose with leftward septal deviation and compensatory right inferior turbinate hypertrophy. Sprays were simulated for 10 µm, 20 µm, 50 µm, or particle sizes following a Rosin Rammler particle size distribution (10-110 µm), at speeds of 1, 3, or 10 meters per second. Nebulization was simulated for 1, 3.2, 6.42, or 10 µm particles. Steady state inspiratory airflow was simulated at 15.7 liters per minute.

Results: Sprays predicted higher NV penetration on the right side for particle sizes >10 µm, with comparable penetration on both sides at 10 µm. Nearly 100% deposited in the nasal passages for all spray characteristics. Nebulizer predictions showed nearly 100% of particles <6.42 µm and more than 50% of 6.42 µm bypassing both sides of the nose without depositing. Of the nebulized particles that deposited, penetration was higher on the right at 10 µm, with comparable penetration on both sides at 6.42 µm. Spray penetration was highest at 10 µm, with more than 96% penetrating on both sides at 1 and 3 meters per second. Nebulization penetration was also highest at 10 µm (40% on the left, >90% on the right).

Conclusion: In the presence of a septal deviation, sprays or nebulizers containing 10-µm particles may have good penetration beyond the NV. Nebulized particles <10 µm are likely to be respirable. Additionally, spray speeds above 3 meters per second may limit penetration.

Keywords: aqueous spray; computational fluid dynamics; nebulizer; particle deposition; particle size; septal deviation.

FIGURE 1

1. Coronal view showing leftward septal deviation.

2. Sagittal view of the left lateral wall of the nasal cavity reconstruction showing regions used for tracking particle deposition (blue, anterior; green, middle; purple, posterior).

FIGURE 1

1. Coronal view showing leftward septal deviation.

2. Sagittal view of the left lateral wall of the nasal cavity reconstruction showing regions used for tracking particle deposition (blue, anterior; green, middle; purple, posterior).

FIGURE 2

Particle penetration past the naval valve area as predicted by varying the spray, and nebulizer characteristics.

FIGURE 3

Escaped particles as predicted by varying the spray, and nebulizer characteristics.

FIGURE 4

Lateral and Septal walls “difference to sum” penetration ratio. A positive LSWDR value indicates higher deposition on the lateral wall.

FIGURE 5

1. Simulated spray deposition pattern on the affected side using RRPSD released at a speed of 1m/s.

2. Simulated spray deposition pattern on the right (unaffected) side using RRPSD released at a speed of 1m/s.

3. Simulated nebulized particle deposition pattern on the deviated side, 10µm particles released from the left nostril.

4. Simulated nebulized particle deposition pattern on the unaffected side, 10µm particles released from the right nostril.

FIGURE 5

1. Simulated spray deposition pattern on the affected side using RRPSD released at a speed of 1m/s.

2. Simulated spray deposition pattern on the right (unaffected) side using RRPSD released at a speed of 1m/s.

3. Simulated nebulized particle deposition pattern on the deviated side, 10µm particles released from the left nostril.

4. Simulated nebulized particle deposition pattern on the unaffected side, 10µm particles released from the right nostril.

FIGURE 5

1. Simulated spray deposition pattern on the affected side using RRPSD released at a speed of 1m/s.

2. Simulated spray deposition pattern on the right (unaffected) side using RRPSD released at a speed of 1m/s.

3. Simulated nebulized particle deposition pattern on the deviated side, 10µm particles released from the left nostril.

4. Simulated nebulized particle deposition pattern on the unaffected side, 10µm particles released from the right nostril.

FIGURE 5

1. Simulated spray deposition pattern on the affected side using RRPSD released at a speed of 1m/s.

2. Simulated spray deposition pattern on the right (unaffected) side using RRPSD released at a speed of 1m/s.

3. Simulated nebulized particle deposition pattern on the deviated side, 10µm particles released from the left nostril.

4. Simulated nebulized particle deposition pattern on the unaffected side, 10µm particles released from the right nostril.