Week 3 Leture Admin of Aerosol Agents

ADMINISTRATION OF AEROSOLIZED AGENTS

• Course: RC110 - WEEK 3

OBJECTIVES

• Ethical responsibilities of clinicians regarding medication delivery.

• Physical properties of inhaled aerosol drugs.

• Types of aerosol devices for drug delivery.

• Clinical applications of aerosol delivery devices.

AEROSOL THERAPY

• Delivery of aerosol particles to the respiratory tract.

• Three main uses:

  • Humidification: Adding moisture to the airways.

  • Improved mobilization and clearance: Assisting in mucus clearance from the lungs.

  • Drug delivery: Direct delivery of medications to the lungs.

TERMS TO KNOW

• Aerosol: Suspension of liquid or solid particles between 0.001 and 100 μm in diameter in a carrier gas.

• Stability: Tendency of particles to remain in suspension.

• Penetration: Depth within the lungs reached by aerosol particles.

• Deposition: Process where aerosol particles deposit in the lungs.

ADVANTAGES OF AEROSOLIZED MEDICATIONS

• Immediate/rapid onset of drug action.

• Reduced systemic side effects.

• Targeted drug delivery to the lungs.

• Smaller doses required compared to systemic delivery.

• Patients can self-administer the medication.

• Treatment is painless and convenient.

DISADVANTAGES OF AEROSOLIZED MEDICATIONS

• Difficulty in determining the exact amount of drug delivered.

• Delivery can be affected by:

  • Patient's breathing pattern.

  • Type of nebulizer used.

  • Patient's willingness and coordination.

  • Ability to take deep breaths and hold at end of inspiration.

• Risk of oral fungal infections (thrush) - recommend rinsing after use.

PARTICLE SIZE

• Main factor in lung penetration.

• Particle size distribution:

  • 10-15 microns: Deposited in mouth and nose.

  • 5-10 microns: Upper airway and trachea deposits.

  • 1-5 microns: Lower airways and alveolar region (optimal).

• Micron definition: 1 micron = 1/1,000,000 meters.

PARTICLE SIZE AND LUNG DEPOSITION

• Nasal delivery removes particles > 10 μm.

• Mouth delivery removes particles > 15 μm.

• 5-10 μm effective for nasal spray.

• 1-5 μm effective for bronchoactive medications like Albuterol.

FACTORS AFFECTING DEPOSITION

• Inertial impaction: Larger particles (> 5 microns) do not penetrate deeper.

• Sedimentation: Larger particles "fall out" due to gravity (1-5 microns).

• Brownian diffusion: Small particles (< 3 microns) diffuse and may reach alveoli.

EFFECT OF TEMPERATURE AND HUMIDITY

• Aerosols generated under dry conditions increase in size when humidified in the airway.

• Medications can increase in aerosol size by a micron in moist conditions, leading to less deposition in lower airways.

AEROSOLIZED MEDICATION DELIVERY DEVICES

Types of Devices

• Small volume nebulizers (SVN)

• Small particle aerosol generators

• Metered dose inhalers (MDI)

• Dry powder inhalers (DPI)

SMALL VOLUME NEBULIZERS (SVN)

• Converts liquid drug solutions to aerosol.

• Powered by compressed gas or electricity.

• Delivers dose over 60-90 breaths.

• Effectiveness not lost due to one ineffective breath.

Factors Affecting SVN Treatments

• Dead volume: Amount left in nebulizer after treatment.

• Filling volume: Recommended 3-5 mL.

• Flow rate: 6-10 L/min maximizes effectiveness.

• Patients should breathe slowly and deeply, holding their breath to improve deposition.

TYPES OF SMALL VOLUME NEBULIZERS

• Jet (pneumatic) with reservoir tube, with collection bag.

• Breath-enhanced.

• Manual & mechanical breath-actuated.

• Mesh nebulizers.

• Ultrasonic nebulizers (USN).

JET NEBULIZERS WITH RESERVOIR TUBE

• Most traditional and widely used; economical.

• Low inhaled dose (10-20%) due to loss in environment during use.

SVN DEAD VOLUME

• Remaining solution that is not nebulized; issue is that a minimal volume (0.5 - 1.0 mL) will not aerosolize.

• Corrected by adding diluent;

• If not rinsed, subsequent treatments may have higher doses.

BREATH-ENHANCED JET NEBULIZER

• Releases more aerosol during inspiration.

• Utilizes one-way valves to minimize loss.

• Decreases output during exhalation or breath hold.

MESH NEBULIZERS

• Uses a plate or mesh to produce aerosol.

• Efficient with minimal dead volume.

• Types include active vibrating mesh and passive mesh.

ULTRASONIC NEBULIZER

• Converts medications into mist using piezoelectric principle.

• Generates smaller particles at higher frequencies but dissipates energy as heat.

• Drug solution effectiveness should be tested prior to use.

CLINICAL APPLICATION OF AEROSOL DELIVERY DEVICES

• Traditional devices have only 10-15% drug delivery efficiency.

• MDI and DPI lost in mouth and stomach; SVN has dead volume losses.

AGE GUIDELINES FOR USE

• SVN: <= 2 years.

• MDI: > 5 years.

• MDI with reservoir: > 4 years.

• Breath-actuated MDI: > 5 years.

• DPI: >= 5 years.

PATIENT-DEVICE INTERFACE GUIDELINES

• Face masks appropriate for infants or unresponsive patients but increase tremor risk.

• Endotracheal tube (ETT) administration reduces aerosol delivery but can use both MDI and SVN.