P1 - inhaled drugs and deposition mechanims in the lung

what are 5 repsiratory diseases where inhaled drugs are indicated

1. asthma

2. COPD

3. influenza

4. cystic fibrosis

5. COVID-19

what 2 systemic indcations for inhaled drugs

1. parkinsons disease - levodopa

2. insulin for diabeties

advantages of inhalation therapy

1. local delivery - directly to site of action, lower doses required

2. systemic delivery - extensive blood supply and large SA postnetial for rapid absorpiton and avoids GI tract and first pass metabolism

what is an aerosol

a relaltivly stable suspension of solid particles or liquid droplets in a gas

in an aerosol what must particles be

small - 0.001um to 100um

small particles = low mass = low gravitational force

so collisions with gas molecules keeps particles suspended

what is dust

solid particles formed by mechanical disintegration of a material

what is smoke

a visible aerosol resultng from incomplete combustion

what is fog/mist

liquid partciles formed by condensation or atomisation

what is particle movment in air controlled by

the interaction with surrounding air molecules and gravity

what do aerodynamic properites depend on

size, shape, density

what are the 3 particle deposition mechanisms

1. intertial impaction

2. sedimentation

3. diffusion

what is amount of interital impaction proportional to

aerodynamic diameter² x velocity

when does intertial impaction commonly occur

large particles when the gas airsteam is fast, changing direction or turbulent

where does inertial impaction tpyically occur

oropharync, larynx, bifurcations

when does gravitational sedimentation typically occur

when air velocity in repsiratory tract is low, so residence time is high - important deposition in bronchioles

whats the typical particle size for gravitational sedimentation

1-4 um

amount of sedimentation deposition is proportional to

aerodynamic diameter² x residence time

less efficent than inertial impaction

what happens in diffusion (Brownian motion)

particles bombarded by air moelcules giving rise to a random walk

important for small particles

where is diffusion important

important depostion in termnal bronchioles and alveolar reigions

high residence time increases diffusion deposition efficency

what is interception

deposition where particles contact wals - important for fibres at airway birfucations

what is electrostatic deposition

charged particles repel - increase in migration towards airway walls - can increase efficency of deposition

whats the deposition particle diameter in trachea

7-10um

whats the deposition particle diameter in bronchi

2-7um

whats the deposition particle diameter in terminal bronchiole/alveolar duct

0.5-2um

what 3 factors control aerosol deposition

1. aerosol properties - particle size

2. mode of inhalation - flow rate, inhaled volume, breath holding pause

3. patient related factors - obstructive airway disease, anatomical and physiology variations

how to due measure the delivered dose

using an impactor