Comprehensive Therapeutics Exam 1 Study Guide: Aerosol and Hyperinflation Therapies

Aerosol Therapy Definitions and Deposition Mechanisms

Aerosol: Suspension of liquid or solid particles carried in a gas mixture.
Bernoulli's Principle: Hydrodynamic principle governing jet nebulizer operation. It states that an increase in the velocity of a stream of fluid (gas flow) results in a concurrent decrease in surrounding pressure.
Deposition: Retention of aerosol particles as they make contact with and deposit into airway tissue.
Residual Volume (Dead Volume): The quantity of medication remaining in the nebulizer at the completion of a treatment.
Mean Median Aerodynamic Diameter (MMAD): Unit of measure used to identify particle diameter corresponding to the most typical settling behavior of an aerosol (including mechanisms such as inertial impaction, gravitational sedimentation, and diffusion).
Inertial Impaction: The primary mechanism of deposition for aerosol particles sized $> 5\,\text{microns}$ .
Gravitational Sedimentation: The primary mechanism of particle deposition within the lower, peripheral airway generations.
- Ideal Particle Size: Particles sized $1 - 5\,\text{microns}$ target gravitational sedimentation in the lower and peripheral airways.

Aerosol Delivery Devices and Operational Techniques

Small Volume Nebulizer (SVN) / Jet Nebulizer:
- Pneumatically powered device.
- Patient instructions: Instruct the patient to breathe normally through the mouth with an occasional deep breath.
Pressurized Metered Dose Inhaler (pMDI):
- Without a Valved Holding Chamber (VHC), high oral deposition occurs.
- Administering with a VHC increases lung deposition to $40\%$ .
- Patient instructions: Instruct the patient to exhale normally, take a slow, deep breath in, and perform a breath hold for up to $10\,\text{seconds}$ if possible.
Dry Powder Inhaler (DPI):
- Flow-driven device with no propellant; requires an inspiratory flow rate $> 60\,\text{L/min}$ .
- Oral deposition is high, with approximately $80\%$ deposition in the oropharynx.
- Cannot be exposed to humidity (cannot be administered inline with a mechanical ventilator).
- Patient instructions: Instruct the patient to exhale away from the device, then perform a FAST, deep inhalation followed by a breath hold up to $10\,\text{seconds}$ if possible.
Inhaled Corticosteroids (ICS):
- Identified by generic medication names ending in "-ide" or "-one".
- Mandatory post-administration requirement: Always rinse the mouth after use to prevent thrush (oral candidiasis, a fungal infection).
Technique Evaluation and Dosing:
- To verify correct patient technique, have the patient execute a return demonstration.
- Medication administration order follows the BMAAS sequence: short-acting bronchodilators must always be administered first.
- Aerosol delivery devices must be selected based on individual patient parameters, including age and physical capability.

Advanced Nebulizer Technologies

Vibrating Mesh Nebulizer (VMN) (e.g., Aerogen):
- Electrically powered.
- Creates particles via electricity vibrating a piezo element that pushes liquid through a vibrating mesh plate, generating particles consistently sized $2 - 3\,\text{microns}$ .
- Operates at a lower frequency than Ultrasonic Nebulizers and does not generate heat.
Ultrasonic Nebulizer (USN):
- Electrically powered device in which a piezoelectric crystal vibrates at a high frequency, generating heat.
- Primary application: Sputum induction. Its high-density aerosol output acts as an irritant to induce coughing.
- Solutions used for sputum induction: Normal saline ( $0.9\%\,\text{NaCl}$ ) or hypertonic saline ( $7\%\,\text{NaCl}$ ).
- Contraindications: Do not use Ultrasonic Nebulizers with suspension medications such as budesonide (Pulmicort).

Aerosol Therapy Troubleshooting and Safety Guidelines

Nebulizer Positioning and Volume:
- The nebulizer acorn must remain upright to aerosolize liquid properly.
- Requires an adequate fill volume of $3 - 4\,\text{mL}$ .
pMDI Priming Protocol:
- Propellant sitting in the metering valve or nozzle fails to mix when shaken and must be expelled prior to patient use.
- Priming steps: Shake the device for $5\,\text{seconds}$ , actuate $1\,\text{puff}$ into the air, and repeat for a total of $4\,\text{puffs}$ (shaking for $5\,\text{seconds}$ prior to each puff).
- When to prime: Before first use, if unused for $7\,\text{days}$ or more, or if the device has been dropped.
Treatment Modification and Cessation:
- Clinicians must verify unit dosing (e.g., albuterol) and contact the prescribing physician to clarify inappropriate orders.
- Adverse reactions occurring during treatment (heart rate increase $\ge 20\,\text{bpm}$ above pre-treatment baseline, sudden onset shortness of breath, or arrhythmias): STOP treatment immediately, stabilize the patient, and notify the physician.
- If a heart rate elevation $\ge 20\,\text{bpm}$ is identified post-treatment, recommend a half-dose of albuterol ( $1.25\,\text{mg}$ ) or levalbuterol (Xopenex) for subsequent administrations if bronchodilator therapy remains indicated.

Respiratory Pharmacology and Specialty Aerosols

Auscultation and Airway Assessment:
- Wheezing is a key clinical sign of bronchospasm and an indication for bronchodilator administration.
- Auscultation must evaluate overall air exchange quality alongside wheezing:
  - An increase or improvement in air exchange indicates clinical improvement.
  - A decrease in air exchange indicates clinical deterioration.
Standard Pharmacologic Agents:
- Albuterol: Beta-2 agonist (adrenergic, sympathomimetic bronchodilator). Nebulized unit dose is $2.5\,\text{mg}$ . Fluid volume is calculated from ordered dose in milligrams. Causes expected heart rate elevation via secondary Beta-1 stimulation; an increase $\ge 20\,\text{bpm}$ is an adverse reaction requiring treatment termination.
- Ipratropium (Atrovent): Anticholinergic/muscarinic antagonist. Nebulized unit dose is $0.5\,\text{mg}$ .
- Beta-2 Agonist Tachycardia: Beta-2 agonists (albuterol, levalbuterol, racemic epinephrine) induce tachycardia due to cross-reactivity with Beta-1 receptors.
Specialty Aerosol Delivery Systems:
- Pentamidine (Nebupent):
  - Indication: Treatment/prophylaxis of Pneumocystis jiroveci pneumonia (PCP).
  - Delivery device: Respirgard II nebulizer system.
  - Pre-treatment requirement: Pre-treat with albuterol (a bronchodilator) before administering pentamidine.
  - Safety requirements: Clinicians must wear an N95 respirator and administer the medication inside a negative pressure room.
- Ribavirin (Virazole):
  - Indication: Severe Respiratory Syncytial Virus (RSV).
  - Delivery device: Small Particle Aerosol Generator (SPAG).
  - Safety requirements: Clinicians must wear an N95 respirator and administer the medication inside a negative pressure room.

Hyperinflation and Lung Expansion Therapy

Pathophysiology of Atelectasis:
- A secondary restrictive condition characterized by the collapse of previously expanded alveoli.
Hyperinflation Therapy Principles:
- Functions to expand lung volumes through simple deep breathing, sustained maximal inhalations, or positive pressure applications (PEP, EzPAP, CPAP).
Therapeutic Modalities:
- Incentive Spirometry (IS): Mimics a sigh breath to encourage long, slow, deep breathing to prevent atelectasis.
- Intermittent Positive Pressure Breathing (IPPB): Delivers positive pressure breaths via mask or mouthpiece to deliver large tidal volumes.
- Positive Expiratory Pressure (PEP) Therapy (TheraPEP, EzPAP): Provides $10 - 20\,\text{cmH}_2\text{O}$ of positive expiratory pressure.
- Refractory Hypoxemia: Inadequate arterial oxygenation ( $PaO_2$ or $SaO_2$ ) despite optimal levels of inspired oxygen ( $FiO_2$ ).
  - Etiology: Caused by intrapulmonary right-to-left shunting (perfusion is present, but alveoli are unventilated) due to collapsed alveoli (atelectasis) or fluid-filled alveoli (pulmonary edema, pneumonia).
  - Therapeutic rule: Hypoxemia is refractory to oxygen therapy alone (does not respond to supplemental oxygen); the patient requires positive pressure therapy.

$Summary of atelectasis, hyperinflation modalities, and refractory hypoxemia definitions$

Incentive Spirometry Protocol and Clinical Decision-Making

Sustained Maximal Inspiration (SMI) Technique:
- Deep breathing and coughing exercises performed alone are as clinically beneficial as IS therapy.
- IS provides visual feedback cues to incentivize deep breathing while measuring inspiratory capacity (IC).
- SMI Technique: Starting from the end of a normal exhalation, the patient forms a tight seal around the mouthpiece and executes a slow, deep, maximal inhalation.
Target Volume Determination:
- $2 \times$ normal tidal volume ( $V_T$ ; average adult $V_T \approx 500\,\text{mL}).\n * 15\,\text{mL/kg} $Ideal Body Weight (calculate IBW in kg and multiply by$ 15).\n* **Device Classification**:\n * Flow-oriented devices (utilizing floating balls) vs. Volume-oriented devices.\n* **Assessment & Patient Education**:\n * Pre-operative assessments establish baseline post-operative targets.\n * Educate patients on the critical role of deep breathing and coughing during periods of surgical pain or immobility.\n* **IS Troubleshooting Checklist**:\n * If the volume indicator fails to rise during inhalation:\n * Verify that the patient has a proper mouth seal and is not breathing through the nose.\n * Confirm that the patient is inhaling rather than exhaling into the mouthpiece.\n * Inspect the device for physical cracks or system air leaks.\n* **Indications and Support Escalation**:\n * Indicated for the prevention or treatment of atelectasis.\n * Escalation Criteria: If Vital Capacity (VC) < 10\,\text{mL/kg} $IBW (Predicted Body Weight) or Inspiratory Capacity (IC)$ < 33\% of predicted, Incentive Spirometry is insufficient. Patients meeting these criteria require higher levels of positive pressure support (such as IPPB or CPAP) and may require full ventilatory assistance.\n\n# Contraindications, Hazards, and Safety Precautions\n\n* **Contraindications for Incentive Spirometry**:\n * Patient is unable to be instructed or supervised to assure appropriate use.\n * Patient is unable to cooperate, follow instructions, or effectively use a mouthpiece.\n * Patient is unable to take a deep breath or generate adequate inspiratory volume.\n* **Contraindications for Positive Pressure Therapies (PEP, EzPAP, CPAP)**:\n * Acute sinusitis.\n * Increased intracranial pressure (ICP > 20\,\text{cmH}_2\text{O} is critically high).\n * Hemodynamic instability.\n* **Hazards and Complications**:\n * **Hyperventilation / Respiratory Alkalosis**:\n * Clinical manifestations: Lightheadedness, dizziness, and numbness or tingling in the extremities.\n * Management: Instruct the patient to slow their breathing rate and take rest breaks between maneuvers.\n * **Hypoxemia**: Discontinue therapy, administer supplemental oxygen, and evaluate for pneumothorax during positive pressure administration.\n * **Therapy Cessation Guidelines**: Discontinue therapy immediately upon development of severe tachycardia (\ge 20\,\text{bpm}$$ increase over baseline) or sudden onset of shortness of breath (suggestive of pneumothorax).