Aerosol Drug Delivery - Class 9 Intro

AEROSOL DRUG DELIVERY Hess – Chapter 15  AEROSOL DRUG DELIVERY “3 Articles to Consider” In BlackBoard Under the “Articles / Publications” Folder… Aerosol Guides for HCP, RTs, & Patients  KEY CONCEPTS ◼ Include: ◼ Aerosol ◼ Output and Density...

AEROSOL DRUG DELIVERY Hess – Chapter 15  AEROSOL DRUG DELIVERY “3 Articles to Consider” In BlackBoard Under the “Articles / Publications” Folder… Aerosol Guides for HCP, RTs, & Patients  KEY CONCEPTS ◼ Include: ◼ Aerosol ◼ Output and Density ◼ Particle size ◼ Deposition ◼ Aging. An aerosol is a suspension of solid or liquid particles in gas  Aerosol Output The rate that aerosol is generated is a key parameter in aerosol administration. Aerosol output is defined as the mass of fluid or drug contained in aerosol produced by a nebulizer.  PARTICLE SIZE ◼ Aerosol particle size depends on the substance being nebulized, the nebulizer chosen, and the method used to generate the aerosol. ◼ The particle size is measured by a method called the mass median aerodynamic diameter (MMAD).  MMAD ◼ MMAD is defined as the diameter at which 50% of the particles by mass are larger and 50% are smaller. ◼ It is used to describe those particle sizes for which deposition depends chiefly on inertial impaction and sedimentation.  Site of Deposition ◼ The site of deposition in the respiratory tract varies with the size of the particle. Use of nebulizers that produce particles in a specific size range improves the targeting of aerosols for deposition to a desired site in the respiratory tract, as follows: Measurement of Aerosol Particles  DEPOSITION Deposition: - The process by which aerosol particles are deposited on solid surfaces. Key mechanisms causing aerosol deposition include : ◼ Inertial impaction, ◼ Sedimentation ◼ Brownian diffusion  INERTIAL IMPACTION ◼ Occurs when particles in motion collide with a surface. This is the primary deposition. ◼ A major concern is the mechanism for large, high mass particles (>5 um). ◼ The property of inertia tells us that the greater the mass the greater its tendency to continue moving along its set path. GOOD EASY Proven to go deeper in AW FAST UNEVEN FLOW Does not go very deep Laminar Flow in the AW GOOD Flow Allows Medication to go DEEPER Transitional Airway: Affects of flow in the airways with aerosol delivery  EFFECT OF MASS ON PARTICLE SIZE. ◼ Large particles are more susceptible to the force of gravity than smaller particles, which are more affected by the bombardment of molecules, deposited by diffusion. EFFECT OF MASS ON PARTICLE SIZE.  BROWNIAN DIFFUSION ◼ Brownian diffusion is the primary mechanism for deposition of small particles (< 3 um), mainly in the alveolar region. In this area, bulk gas flow ceases and aerosol particle inertia is very low. ◼ In alveolar region most remaining aerosol particles have very low mass and are easily bounced around by collisions with carrier gas molecules.  SEDIMENTATION ◼ Occurs when aerosol particles settle out of suspension due to gravity. The greater the mass of the particle, the faster it settles ◼ Sedimentation is the primary mechanism for deposition of particles in the 1 to 5 um range, occurring mostly in the central airways. ◼ A 10-second breath hold can increase aerosol deposition 10% and increase the ratio of aerosol deposited in lung parenchyma to central airway by fourfold.  RULE OF THUMB ◼ A particle’s depth of penetration into the respiratory tract varies inversely with its size. ◼ Therefore, it is possible to target aerosols for delivery to the respiratory tract by using nebulizers that produce particles in the size range where most deposition will occur.  AGING ◼ Therapeutic aerosols are dynamic suspensions, with particles constantly growing, shrinking, or falling out of suspension. ◼ The process by which an aerosol suspension changes over time is called aging.  HAZARDS OF AEROSOL THERAPY ◼ The primary hazard of aerosol drug therapy is an adverse reaction to the medication being administered. ◼ Other hazards include: ◼ Infection ◼ Airway reactivity ◼ Systemic effects of bland aerosols, and ◼ Drug re-concentration.  INFECTION ◼ Aerosol generators can cause nosocomial infections by spreading bacteria by the airborne route. ◼ The most common sources of bacteria include contaminated solutions (including multiple-dose drug vials), caregiver's hands, and the patient’s own secretions.  HAZARDS OF AEROSOL THERAPY - Bronchospasms ◼ Medication such as acetylcysteine, antibiotics, steroids, cromolyn, ribavirin, and distilled water have been associated with increased airway resistance and bronchospasm during aerosol administration. ◼ Administration of bronchodilators prior to administration of these agents may reduce risk of increased airway resistance.  DRUG RECONCENTRATION ◼ During the baffling and recycling of drug solutions undergoing jet or ultrasonic nebulization, solute concentration may increase. ◼ This can expose the patient to increasingly higher concentrations of the drug agent over the course of therapy. This problem is greatest when medications are nebulized over long periods, as occurs with continuous aerosol drug delivery. Small Volume Nebulizer ◼ AKA: ◼ Acorn, nebs, SVN, med neb, mini neb, BAN (breath actuation nebulizer) ◼ Powered by air or oxygen ◼ Powered by Pulmo-Aide nebulizer  SMALL-VOLUME JET NEBULLZERS ◼ Powered by a high-pressure stream of gas directed through a restricted orifice (the jet). The gas stream leaving the jet passes by the opening of a capillary tube immersed in solution. ◼ The high jet velocity produces low lateral pressure at its outlet (Bernoulli Effect), it draws the liquid up the capillary tube (Capillary Action) and into the gas stream, where it is sheared apart into droplets by hitting a baffle. Demonstration of the Bernoulli Effect ◼Air pressure forces the cans to roll toward each other. Capillary Action SideStream Nebulizer  SMALL-VOLUME JET NEBULLZERS ◼ Residual volume also depends on the position of the SVN. Some SVNs stop producing aerosol when tilted as little as 30 degrees from vertical. ◼ Most SVNs are run continuously until they go dry. Some SVNs provide a mechanism for intermittent nebulization. ( you’ll see this with Ventilators) ◼ Running flow for a SVN is ~ 7 to 8 L/M. https://www.youtube.com/watch?v=BI5Rh 54xj5I  Therapy Mnemonic ◼ O – G – P – A – E – R & WASH ◼ O = Orders ◼ G = Gather the required equipment ◼ P = Prepare Equipment and Pt ◼ A = Assess the pt ◼ E = Evaluate the Therapy / Tx ◼ R = Record and Report ◼ Wash Hands before and after all pt contact. Intentionally Left Blank  METERED-DOSE INHALERS ◼ The metered-dose inhaler (MDI) is the most commonly prescribed method of aerosol delivery in the United States. ◼ MDIs are used to administer bronchodilators, anticholinergics, and steroids. More formulations of these drugs are now available for use by MDI than for use with other nebulizers.  METERED-DOSE INHALERS ◼ The output volume of MDIs varies. ◼ Approximately 60% to 80% by weight of this spray consists of the propellant's, with only about 1% being active drug  METERED-DOSE INHALERS TECHNIQUE ◼ The successful administration of aerosol drugs by MDI is highly technique-dependent. ◼ As many as two thirds of both patients and health professionals who teach MDI use do not perform the procedure properly. ◼ Various “Boxes” in Ch. 15 outline the recommended steps for self-administering a bronchodilator by simple MDI.  METERED-DOSE INHALERS ◼ Common hand-breath coordination problems include actuating the MDI before or after the breath. Some patients, especially infants, young children, the elderly, and patients in acute distress may not be able to use a simple MDI. ◼ In addition, some patients exhibit a “cold Freon effect,” which occurs when the cold aerosol plume reaches the back of the mouth, and the patient stops inhaling.  MDI ACCESSORY DEVICES ◼ Accessory devices have been developed to overcome the two primary limitations of these systems: ◼ Problem: Hand-breath coordination problems and high oropharyngeal deposition. ◼ Solution: Devices include flow-triggered MDIs, spacers and holding chambers. MDI ALONE MDI with Spacer  METERED-DOSE INHALERS ◼ In the United States, the Autohaler is only available with pirbuterol (MAX AIR), a bronchodilator that is quite similar to albuterol. Current data indicate that the device does indeed reduce pharyngeal impaction and enhance lung deposition.  METERED-DOSE INHALERS ◼ Spacers and Holding Chambers. Spacers and holding chambers are MDI accessory devices designed to both reduce oropharyngeal deposition and the need for hand-breath coordination. ◼ These devices also can reduce the bad taste of some medications and eliminate the cold Freon effect. Intentionally Left Blank Turbuhalers  DRY, POWDER INHALERS ◼ Newer multidose DPIs, such as the Turbohaler, store from 60 to 200 separate drug doses in channels or blisters, which are opened by rotating a grip or thumb wheel. Intentionally Left Blank THIS IS INCORRECT  DRY, POWDER INHALERS ◼ A dry powder inhaler (DPI) is a breath-actuated metered-dosing system. With a DPI, the patient creates the aerosol by drawing air though a dose of finely milled drug powder. ◼ DPIs are relatively inexpensive, do not need propellants and do not require the hand-breath coordination required of MDIs.  DRY, POWDER INHALERS ◼ In terms of both lung deposition and drug response, DPIs are at least as good as MDIs. In addition, some patients prefer DPIs over MDIs.  DRY, POWDER INHALERS ◼ Infants, small children (younger than 5 years old), and those not able to follow instructions cannot develop flows this high, DPIs cannot be used ◼ Any patient experiencing severe airway obstruction may not be able to achieve these flows (COPD). ◼ DPIs should not be used when treating acute bronchospasm.  DRY, POWDER INHALERS ◼ Hand-breath coordination is not as important with DPIs, however, exhalation into the device can result in loss of drug delivered to the lung. ◼ High humidity can also affect DPI drug availability. The Hygroscopic powders will clump if exposed to high humidity, creating larger particles which are not as effectively inhaled.  KEY CONCEPTS ◼ Include: ◼ Aerosol ◼ Output and Density, ◼ Particle size, ◼ Deposition, ◼ Aging. An aerosol is a suspension of solid or liquid particles in gas Measurement of Aerosol Particles GOOD EASY Proven to go deeper in AW FAST UNEVEN FLOW Does not go very deep Laminar Flow in the AW GOOD Flow Allows Medication to go DEEPER  SEDIMENTATION ◼ Occurs when aerosol particles settle out of suspension due to gravity. The greater the mass of the particle, the faster it settles ◼ Sedimentation is the primary mechanism for deposition of particles in the 1 to 5 um range, occurring mostly in the central airways. ◼ A 10-second breath hold can increase aerosol deposition 10% and increase the ratio of aerosol deposited in lung parenchyma to central airway by fourfold.  HAZARDS OF AEROSOL THERAPY ◼ The primary hazard of aerosol drug therapy is an adverse reaction to the medication being administered. ◼ Other hazards include infection, airway reactivity, systemic effects of bland aerosols, and drug reconcentration.  DRUG RECONCENTRATION ◼ During the baffling and recycling of drug solutions undergoing jet or ultrasonic nebulization, solute concentration may increase. ◼ This can expose the patient to increasingly higher concentrations of the drug agent over the course of therapy. This problem is greatest when medications are nebulized over long periods, as occurs with continuous aerosol drug delivery.  r t s t a t a j u s is h is T