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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.