Aerosol Therapy and Nebulizers RET 2274 Respiratory Therapy Theory Module 6.2

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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