Aerosol Therapy and Nebulizers

1. Aerosol Therapy and Nebulizers RET 2274 Respiratory Therapy Theory Module 6.2

2. Aerosol Therapy and Nebulizers • Aerosols • Particulate matter suspended in a gas • Aerosols occur in nature as pollens, spores, dust, smoke, smog, fog, and mist • In the clinical setting, medical aerosols are generated with atomizers, nebulizers, and inhalers – physical devices that disperse matter into small particles and suspend them into a gas

3. Aerosol Therapy and Nebulizers • Aerosols • Medical aerosols are intended to deliver a therapeutic dose of the selected agent to the desired sit of action, e.g., bronchioles

4. Aerosol Therapy and Nebulizers • Aerosols • Deposition • Only a portion of the aerosol generated from a nebulizer (emitted dose) man be inhaled (inhaled dose) – a smaller fraction of fine particles may be deposited in the lung (respirable dose) • Not all aerosol delivered to the lung is retained, or deposited – a significant percentage of inhaled drug may be exhaled

5. Aerosol Therapy and Nebulizers • Aerosols • Deposition • Inertial Impaction – the primary deposition mechanism for particles larger than 5 µm • Tend to be deposited in the oropharynx and hypopharynx

6. Aerosol Therapy and Nebulizers • Aerosols • Deposition • Sedimentation – the primary mechanism for deposition of particles in the 1 – 5 µm range • The greater the mass of a particle, the faster it settles • Tend to be deposited in the central airways • Breath holding after inhalation of an aerosol increases enhances sedimentation

7. Aerosol Therapy and Nebulizers • Aerosols • Deposition • Brownian Diffusion – is the primary mechanism for deposition of small particles <3 µm – bulk gas flow ceases and aerosol particles reach the alveoli by diffusion • Particle size is not the only determinant of deposition • Inspiratory flow rate, flow pattern, respiratory rate, inhaled volume, I:E ration, and breath-holding all influence deposition

8. Aerosol Therapy and Nebulizers • Aerosols • Quantification of Aerosol Delivery • At the bedside, quantification of aerosol delivery is based on the patient’s clinical response to the drug • Pulmonary function; peak flow, forced expiratory volumes or flow • Physical changes; reduced wheezing, shortness of breath, or retractions • Side effects; tremors, tachycardia

9. Aerosol Therapy and Nebulizers • Aerosols • Hazards • Adverse reaction to the medication being delivered • Infection caused by contaminated solution (multi-dose vials), caregiver’s hands, the patient’s own secretions

10. Aerosol Therapy and Nebulizers • Aerosols • Hazards • Airway reactivity • Cold and high-density aerosols can cause bronchospasm and increased airway resistance • Medications, e.g., acetylcysteine, antibiotics, steroids, cromolyn sodium, ribavirin, and distilled water have been associated with increased airway resistance and wheezing during aerosol therapy • Administration of bronchodilators before or with administration of these agents may reduce the risk of increased airway resistance

11. Aerosol Therapy and Nebulizers • Aerosols • Hazards • Pulmonary and Systemic Effects • Overhydration from excessive water • Hypernatremia from excess saline solution • Drug Reconcentration • During evaporation, heating, baffling, and recycling of drug solutions undergoing jet or ultrasonic nebulization, solute concentrations may increase – exposing patients to increasingly higher concentrations of drug therapy. Increase in concentration usually time dependent, the greatest effect occurring when medications are nebulized over extended periods, as in continuous aerosol drug delivery

12. Aerosol Therapy and Nebulizers • Aerosols • Delivery Systems • MDI – Metered Dose Inhalers • DPI – Dry Powder Inhalers • Pneumatic (Jet) Nebulizers • Large volume • Small volume • Ultrasonic Nebulizers • Large volume • Small volume • Hand-Bulb Atomizers

13. Aerosol Therapy and Nebulizers • Aerosols • Indications – AARC Clinical Practice Guideline • The need to deliver an aerosolized beta-adrenergic, anticholinergic, antiinflammatory, or mucokinetic agent to the lower airway

14. Aerosol Therapy and Nebulizers • Aerosols • Selection of Aerosol Delivery Device • MDI – preferred method for maintenance delivery of bronchodilators and steroids to spontaneously breathing patient – effectiveness is highly technique dependent • Accessory devices; e.g., spacer and holding chambers are used with MDI to reduce oropharyngeal deposition of drug and overcome problems with poor hand-breath coordinaiton

15. Aerosol Therapy and Nebulizers • Aerosols • Selection of Aerosol Delivery Device • DPI – does not require hand-breath coordination, but does require high inspiratory flows • Most patients in stable condition prefer DPI delivery systems • SVN – less technique and device dependent and are the most useful in acute care

16. Aerosol Therapy and Nebulizers • Aerosols • Selection of Aerosol Delivery Device • Large volume drug nebulizers provide continuous aerosol delivery when traditional dosing strategies are ineffective in controlling severe bronchospasm • Small Volume USN – used to administer bronchodilators, antiinflammatory agents, and antibiotics

17. Aerosol Therapy and Nebulizers • Aerosols • Patient Assessment • Patient interview • Respiratory history • Level of dyspnea • Observation • Signs of increased work of breathing • Tachypnea, accessory muscle usage • Restlessness • Diaphoresis • Tachycardia

18. Aerosol Therapy and Nebulizers • Aerosols • Patient Assessment • Expiratory airflow measurements • FVC, FEV1, PEFR • Vital signs • Auscultation of breath sounds • Increase or decrease in wheezing and intensity of sounds • Blood gas analysis • Oximetry