Egan Ch 40

What is an aerosol?

A suspension of solid or liquid particles in gas. In the clinical setting, therapeutic aerosols are made with atomizers or nebulizers

What is the general aim of aerosol drug therapy?

Delivery of a therapeutic dose of the selected agent to the desired site of action

Describe how particle size, motion, and airway characteristics affect aerosol deposition.

Answer: Aerosol particle deposition in the respiratory tract is influenced by particle size, shape, motion, and airway characteristics. Key mechanisms include:

• Inertial Impaction: Occurs when moving aerosol particles collide with and deposit on a surface. This is the primary mechanism for larger particles (greater than 5 µm), typically depositing in the upper airway (nose, larynx, trachea). The greater the particle's mass and velocity, the higher its inertia and tendency to continue its path, leading to impaction.

  Gravimetric Sedimentation: Particles settle out of suspension due to gravity, primarily depositing in the lower airways. This is the main mechanism for small particles (1-5 µm) and is enhanced by breath-holding. Larger particles settle faster.

  Brownian Diffusion: The primary deposition mechanism for very small particles (less than 3 µm) deep within the lung parenchyma (alveolar region). Particles between 0.5 and 1 µm are very stable and tend to remain in suspension, often being exhaled.

  Targeting by Size: Particles 5-20 µm MMAD target the upper airway, 2-5 µm target the lower airways, and 1-3 µm target the lung parenchyma (alveolar region). Particles less than 0.1 µm can also reach the parenchyma.

  Other Factors: Deposition is also influenced by inspiratory flow rate, flow pattern, respiratory rate, inhaled volume, I:E ratio, and breath-holding.

List the hazards associated with aerosol drug therapy.

The primary hazard of aerosol drug therapy is an adverse reaction to the medication being administered. Other potential hazards include:

Infection (often due to dirty hands).

Secondhand exposure (e.g., to multidrug-resistant organisms).

Airway reactivity.

Pulmonary and systemic effects.

Eye irritation (particularly with medications like Ipratropium Bromide/Atrovent).

What is the primary sign of bronchospasm when giving an inhaled medication?

Wheezing — especially new or worsening wheezing or increased airway resistance during or immediately after administration.

A drop in peak pressure during mechanical ventilation suggests effective bronchodilation, implying that an increase in peak pressure could be a sign of bronchospasm or airway narrowing. Airway reactivity is also listed as a hazard of aerosol therapy

Describe how to select the best aerosol drug delivery system for a patient.

Selecting the best aerosol drug delivery system for a patient involves considering several factors:

• Patient Ability and Cooperation: Small Volume Nebulizers (SVNs) are less technique-dependent and commonly used in acute care. Dry Powder Inhalers (DPIs) require a sufficiently high inspiratory flow rate (at least 40-60 L/min). DPIs are not recommended for infants, small children, patients unable to follow instructions, or those with severe airway obstruction.

  Age: Pressurized Metered Dose Inhalers (pMDIs) can be used for infants, children, and adults, often with valved holding chambers or masks for younger patients. DPIs are generally not suitable for infants and small children.

  Hand-Breath Coordination: pMDIs require coordination, which can be improved significantly with spacers and valved holding chambers. DPIs do not require hand-breath coordination.

  Medication Type and Formulation: The choice of device often depends on the specific medication to be delivered.

  Desired Deposition Site: Different devices and particle sizes are more effective at targeting specific areas of the respiratory tract (e.g., upper airway, lower airways, alveolar region).

  Clinical Setting: SVNs are more frequently used in acute care settings.

What are characteristics of pMDI inhalers?

Pressurized Metered Dose Inhalers (pMDIs):

• Mechanism: Contain the drug in a volatile propellant within a pressurized canister.

  Actuation: Most are "press and breathe" devices, though breath-actuated versions exist to reduce coordination issues.

  Convenience: Portable, compact, easy to use, and offer multidose convenience.

  Particle Size: Produce particles in the respirable range (MMAD 2-6 µm).

  Deposition: Approximately 80% of the aerosol deposits in the oropharynx, with pulmonary deposition ranging from 10-20% in adults and older children.

  Coordination: Require hand-breath coordination, which can be improved with accessory devices like spacers and valved holding chambers.

  Priming: Must be primed (shaken and sprayed a few times) when new or unused for 24 hours to ensure proper mixing of drug and propellant for an adequate dose.

  Hazards: Potential for eye irritation if sprayed into eyes (especially with anticholinergics like Ipratropium Bromide) and increased risk of oral yeast infections (thrush) with steroid pMDIs. Rinsing the mouth after using steroid pMDIs is recommended.

  Features: All pMDIs are now required to have dose counters.

What are the characteristics of DPIs?

• Mechanism: Breath-actuated systems where the patient inhales a dose of finely milled dry drug powder.

  Propellants: Do not use chemical propellants.

  Coordination: Do not require hand-breath coordination.

  Inspiratory Flow: Require the patient to generate a sufficiently high inspiratory flow rate (at least 40-60 L/min) to disperse the powder effectively.

  Limitations: Should not be used by infants, small children, patients unable to follow instructions, or those with severe airway obstruction.

  Usage Rule: Patients should not exhale into the device.

  Types: Categorized by dose containers, including unit-dose (e.g., Aerolizer, Handihaler), multiple-unit dose (e.g., Diskhaler), and multiple-dose drug reservoir (e.g., Twisthaler, Flexhaler, Diskus)

What are examples of large volume nebulizers?

Examples of large volume nebulizers include:

• Large Volume Jet Nebulizers.

  HEART (High-Output Extended Aerosol Respiratory Therapy) and HOPE nebulizers.

  Small Particle Aerosol Generator (SPAG).

  Hand-bulb atomizers and nasal spray pumps (used for upper airway aerosols).

  Large Volume Ultrasonic Nebulizers (USNs) (mainly for bland aerosol therapy or sputum induction)

What is the SPAG and when do we use it?

The SPAG (Small Particle Aerosol Generator) is a large volume jet nebulizer system. It features a regulator connected to two flowmeters that independently control the flow to the nebulizer and the flow through a drying chamber. The nebulizer flow should be maintained at approximately 7 L/min, with the total flow from both flowmeters not less than 15 L/min.

Specifically to deliver aerosolized ribavirin — an antiviral medication — most commonly for:

Respiratory Syncytial Virus (RSV) infection in infants and young children, especially those at high risk (e.g., premature, immunocompromised, or with chronic lung/heart disease)

The provided document specifically mentions a problem with caregiver exposure to drug aerosol occurring only when the SPAG is used to deliver ribavirin through a mechanical ventilator circuit. This implies its use in situations requiring ribavirin administration, particularly in mechanically ventilated patients.

When is an SVN used?

Compared with pMDI and DPI delivery systems, use of an SVN is less technique-dependent and is more commonly used in acute care

When are large volume drug nebulizers used?

Large volume jet nebulizers are also used to deliver aerosolized drugs to the lung," and are "Particularly useful when traditional dosing strategies are ineffective in the management of severe bronchospasm". Continuous nebulization for refractory bronchospasm is also mentioned as a special consideration.

Large volume drug nebulizers can be used to provide continuous aerosol delivery when traditional dosing strategies are ineffective in controlling severe bronchospasm

Can SVNs be used to administer bronchodilators, anti-inflammatory agents, and antibiotics?

True for bronchodilators and antibiotics, and likely for anti-inflammatory agents. The document lists common nebulized medications such as Albuterol (a B2 agonist/bronchodilator) and Ipratropium Bromide (an anticholinergic). While "anti-inflammatory agents" are not explicitly stated in conjunction with SVNs, specific nebulizer-drug combinations like Cayston (aztreonam, an antibiotic) are mentioned, indirectly supporting the use of nebulizers for antibiotics.

Which delivery method has the highest respirable drug dose?

The delivery method with the highest respirable drug dose is typically:

Valved holding chambers or a spacer used with pMDIs provide "higher respirable drug dosages" compared to simple spacers.

What info do patients need to know to self-administer drug aerosol therapy for pMDIs?

Flashcards for RCP 200, Exam 2 Review - Chapter 40: Aerosol Drug Therapy 📚

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For pMDIs (Pressurized Metered Dose Inhalers):

• Priming: Patients must shake the device and release 2-4 sprays into the air when it's new or hasn't been used for 24 hours. This mixes the drug and propellant, ensuring an adequate dose.

  Technique: When using the open-mouth technique, the pMDI should be actuated at the beginning of inspiration, held 4 cm in front of an open mouth. Patients should be aware that proper technique is crucial, as many do not use it correctly.

  Rinsing Mouth: Patients should rinse their mouth with water without swallowing after using corticosteroid pMDIs to reduce the risk of oral fungal infections (thrush).

  Using with Valved Holding Chamber: If using a valved holding chamber, it traps and holds the medicine, allowing the patient more time to take a slow, deep breath to inhale all the medicine. This also provides less oropharyngeal deposition and better protection from poor hand-breath coordination.

State the information patients need to know to self-administer drug aerosol therapy properly for DPIs.

For DPIs (Dry Powder Inhalers):

• Inspiratory Flow: Patients must be able to generate a high inspiratory flow rate, at least 40-60 L/min, to produce a respirable powder aerosol.

  Exhalation: Patients should not breathe out into the DPI.

  Suitability: DPIs are not suitable for infants, small children, individuals unable to follow instructions, or patients with severe airway obstruction.

State the information patients need to know to self-administer drug aerosol therapy properly for Nebulizers.

For Nebulizers:

• Inhalation Technique: A slow inspiratory flow optimizes aerosol deposition.

  Delivery Method: The choice between a mask or mouthpiece depends on patient ability, preference, and comfort.

State the information patients need to know to self-administer drug aerosol therapy properly for Infants and Children.

For Infants and Children:

• Crying: Aerosols should never be administered to a crying child, as crying reduces lower airway deposition.

  "Blow-by" Technique: While sometimes tolerated, this technique is associated with poor deposition and should be avoided.

What are accessory devices, spacers, and holding chambers used with and for?

Accessory devices, spacers, and holding chambers are used with pMDIs to reduce oropharyngeal deposition of a drug and to overcome problems with poor hand–breath coordination.

A spacer creates "space" between the mouth and the medicine, reducing velocity. A valved holding chamber, a type of spacer with a one-way valve, does more by trapping and holding the medicine, giving the patient time to take a slow, deep breath to inhale all the medicine. These devices provide "less oropharyngeal deposition, higher respirable drug dosages, and better protection from poor hand-breath coordination than simple spacers".

Why do patients rinse their mouths after some medications?

Patients should rinse their mouths with water without swallowing after using certain medications, particularly steroidal pMDIs (such as those containing corticosteroids like Budesonide and Formoterol in Symbicort). This practice helps to reduce the chance of developing a fungal infection in the mouth or throat, commonly known as thrush.

At what age can we start giving pMDI with mouthpiece?

3 years old (can use a mask with valved holding chamber at any age

MDIs can be used with infants, children, and adults

At what age can we start giving DPI?

5 years old

DPIs should not be used by infants, small children, those who cannot follow instructions, and patients with severe airway obstruction

What liter flow do we need to run a nebulizer?

The required liter flow for a nebulizer can vary by device:

• Typically 6-8 L/min for Jet nebulizer and SVNs

• For LVN often ≥10 L/min

• For the Small Particle Aerosol Generator (SPAG), the nebulizer flow should be maintained at approximately 7 L/min, with a total flow from both flowmeters not less than 15 L/min.

• The Akita smart nebulizer controls inspiratory flow to keep it slow, between 12-15 L/min, to reduce impaction loss in the upper airways.

Why is priming a pMDI important?

Priming a pMDI is important because it involves shaking the device and releasing two to four sprays into the air when the pMDI is new or has not been used for 24 hours. This process:

• Mixes the drug and propellant.

• Is required to provide an adequate dose of medication.

How do we protect caregivers from exposure to aerosolized antibiotic and antifungal drugs?

To protect caregivers from exposure to aerosolized drugs, especially those associated with health risks like Pentamidine and Ribavirin, several strategies are recommended for controlling environmental contamination:

• Use of one-way valves and filters can help contain aerosolized drugs.

• Utilize negative-pressure rooms and treatment booths.

• Personal protective equipment (PPE) is recommended, particularly when caring for patients with diseases spread by airborne routes (e.g., tuberculosis, chickenpox, COVID-19).

• Continuous pneumatic nebulizers produce the greatest amount of second-hand aerosol, highlighting the need for these control measures.

How can we assess patient response to aerosol therapy?

Assessing patient response to aerosol therapy is a key role for respiratory therapists and involves several components:

• Ongoing Patient Assessment: This is fundamental to effective bronchodilator therapy protocols.

  Patient Assessment Components: Includes patient interviewing, observation, measurement of vital signs, auscultation, blood gas analysis, and oximetry.

  Peak Flow Measurement: Can be used to track trends in patient response, provided the same device is used consistently.

  Dose-Response Titration: Can be conducted to determine the optimal dosage for patients with moderate obstruction

• For Mechanically Ventilated Patients:

  • Measure the change in difference between peak and plateau pressures.

  • A drop in peak pressure during mechanical ventilation suggests effective bronchodilation.

  • Automatic positive end-expiratory pressure (PEEP) levels may also decrease in response to bronchodilators.

• For Continuous Nebulization (e.g., for refractory bronchospasm):

  • Patients should be carefully assessed every 30 minutes for the first 2 hours, then hourly.

  • Patients must be observed for adverse drug responses.

  • A positive response is indicated by an

    increase in Peak Expiratory Flow Rate (PEFR) of at least 10% after the first hour of therapy, with a goal of achieving at least 50% of the predicted value.