aerosol therapy and nebulizers ret 2274 respiratory therapy theory module 6.2

Aerosol Therapy and Nebulizers

RET 2274

Respiratory Therapy Theory

Module 6.2


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


Aerosols Medical aerosols are intended to deliver a

therapeutic dose of the selected agent to the desired sit of action, e.g., bronchioles


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


Aerosols Deposition

Inertial Impaction – the primary deposition mechanism for particles larger than 5 µm Tend to be deposited in the oropharynx and

hypopharynx


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


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


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


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


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


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


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


Aerosols Indications – AARC Clinical Practice Guideline

The need to deliver an aerosolized beta-adrenergic, anticholinergic, antiinflammatory, or mucokinetic agent to the lower airway


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



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



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


Aerosols Patient Assessment

Patient interview Respiratory history Level of dyspnea

Observation Signs of increased work of breathing

Tachypnea, accessory muscle usage Restlessness Diaphoresis Tachycardia


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

aerosol therapy and nebulizers ret 2274 respiratory therapy theory module 6.2

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