Hyperinflation Therapy and Atelectasis

Hyperinflation Therapy

Overview

  • Also known as Lung Expansion Therapy.
  • Purpose:
    • Prevent or reverse atelectasis.
    • Mobilize secretions.
    • Promote cough.

Types of Lung Expansion Therapy

  • Incentive Spirometry (IS): Encourages prolonged inhalation to improve lung function.
  • Intermittent Positive Pressure Breathing (IPPB): Delivers positive pressure to aid inhalation.
  • Intrapulmonary Percussive Ventilation (IPV): Uses rapid pulses of air to enhance lung expansion.
  • Continuous Positive Airway Pressure (CPAP): Maintains continuous airway pressure to prevent airway collapse.
  • Positive Expiratory Pressure (PEP): Maintains pressure in the airways during exhalation (e.g., TheraPEP, EZ PAP).

Atelectasis

Definition

  • Derived from Greek, meaning “without air.”

Susceptible Patients

  • Postoperative or debilitated patients.
  • Individuals unable to take deep breaths.
  • Patients with retained secretions or mucus plugging.
  • Those with restrictive lung defects.

Types of Atelectasis

1. Resorption Atelectasis

  • Occurs due to:
    • Obstruction of bronchus by tumor, mucus, or foreign body.
    • Oxygen distal to the obstruction diffuses into pulmonary blood, causing alveoli to shrink and collapse.
    • It is more pronounced with high FiO₂.
    • Therapy is directed at the cause of obstruction.

2. Compression Atelectasis

  • Results from fluid, tumor, blood, or air filling the pleural cavity.

3. Contraction Atelectasis

  • Caused by local or generalized fibrotic changes preventing full lung expansion.

Passive Atelectasis

Definition

  • Failure to intermittently stretch alveoli via deep breathing, sighing, or yawning.
  • Associated with low tidal volumes leading to alveolar collapse.
  • Common in postoperative patients.
  • Management includes repositioning, deep breathing, IS, and IPPB.

Adhesive Atelectasis

Definition

  • Results from surfactant deficiency.
  • Common in conditions like ARDS and in premature neonates.

Candidates for Lung Expansion Therapy

  • Patients with:
    • Neuromuscular diseases (e.g., myasthenia gravis, Guillain-Barré syndrome).
    • Restrictive lung diseases.
    • Heavy sedation (narcotics, barbiturates, anesthetics).
    • Upper abdominal or thoracic surgery (risk increases closer to the diaphragm).
    • Spinal cord injury.
    • Bedridden or immobile individuals (e.g., due to stroke, Alzheimer’s disease, coma).
    • Abnormal preoperative spirometry results.

Post-operative Risks

General Anesthesia Impacts

  • Leads to rapid shallow breathing due to pain, decreased surfactant production, and lower Functional Residual Capacity (FRC).
  • Dependent lung segments show decreased ventilation/perfusion (V/Q), potentially leading to hypoxemia.
  • Splinting effects and reduced tidal volume due to pain inhibit coughing and clear mucosal secretions.

Definitions

  • Dependent: Refers to the lowest point or area of the body affected by gravity, influencing perfusion and ventilation dynamics based on body position.

Signs and Symptoms of Atelectasis

  • Rapid shallow breathing.
  • Increased tactile fremitus.
  • Dullness to percussion.
  • Fine, late inspiratory crackles, bronchial or diminished breath sounds.
  • Abnormal voice sounds, tachycardia, fever, and hypoxemia.

Diagnostic Imaging (CXR) Findings of Atelectasis

  • Increased opacity over affected lung regions.
  • Elevation of the diaphragm on the affected side.
  • Displacement of fissures and mediastinal shift towards the affected side.
  • Crowding of ribs on the affected side, with compensatory hyper-expansion of surrounding lung areas.

Physiologic Basis of Hyperinflation Therapy

  • Objective: Facilitate lung expansion by increasing the transpulmonary pressure gradient (PL).
  • Formula: PL = P{alv} - P{pl}
    • Methods of Increasing PL:
    • Decrease pleural pressure (Ppl) using IS.
    • Increase alveolar pressure (Palv) using IPPB, PEP, CPAP, IPV.
  • Decreasing Ppl is generally more physiologically aligned with normal breathing practice.

Spontaneous Inspiration Mechanism

Pressure Changes During Inspiration

  • Spontaneous inspiration increases the transpulmonary pressure gradient by lowering pleural pressure (Ppl).
  • Barometric Pressure Example:
    • P_B = 761 ext{ mm Hg}
    • Changing pressures throughout the respiratory cycle shown in the context of gas flow and transpulmonary pressure dynamics.

Positive Pressure Inspiration Mechanism

  • Positive pressure inspiration increases the transpulmonary gradient by raising alveolar pressure (Palv).

Incentive Spirometry Description

  • Functionality: Mimics the natural sighing. Encourages slow, deep inhalations.
  • Provides visual cues to monitor the patient’s progress.

Sustained Maximal Inhalation (SMI)

  • Basic maneuver of Incentive Spirometry.
  • Requires a slow, deep inhalation from Functional Residual Capacity (FRC) to Total Lung Capacity (TLC) followed by a 5-10 second breath hold.
  • This action increases the PL gradient by decreasing Ppl.

Indications for Incentive Spirometry

  • Pre-existing conditions predisposing to atelectasis:
    • Upper abdominal and thoracic surgeries.
    • Patients with COPD undergoing surgery.
    • Presence of existing atelectasis.
    • Restrictive lung defect associated with neuromuscular dysfunction.

Goals of Incentive Spirometry

  • Achieve:
    • Absence of or improvement in signs of atelectasis.
    • Improved vital signs and breath sounds.
    • Normalized radiograph results.
    • Enhanced oxygenation metrics (SpO₂, PaO₂, PaCO₂).
    • Restoration of preoperative lung capacities.
    • Improved inspiratory muscle performance.

Planning for Incentive Spirometry

  • Identify explicit goals based on patient’s capabilities
  • Assess baseline measures, especially for patients scheduled for upper abdominal or thoracic surgery.
  • Establish a postoperative goal for inspiratory capacity using preoperative data.
  • Consider IPPB if postoperative vital capacity (VC) is < 10 ml/kg or inspiratory capacity (IC) is < 1/3 predicted.
  • Contraindications:
    • Uncooperative patients, unconscious patients; alternatives include IPPB or CPAP.

Example Case Evaluation

  • Evaluation of a patient (5’11”, VC 500 mL) with post-operative atelectasis.
  • Consideration of the predicted IC of 2700 mL against the current IC of 950 mL to determine candidacy for Incentive Spirometry.

Hazards Associated with Incentive Spirometry

  • Potential complications include:
    • Hyperventilation leading to dizziness, numbness, paresthesia, fainting.
    • Discomfort related to inadequate pain control.
    • Risk of pulmonary barotrauma.
    • Possible exacerbation of bronchospasm.
    • Patient fatigue and hypoxia from interruptions in oxygen therapy.
    • Ineffective unless supervised or properly performed.

Advantages of IS Over IPPB

  • More effective as a preventative therapy, especially for patients who can take deep breaths.
  • Greater frequency of therapy sessions.
  • Reduced personnel time and costs associated with administration.
  • Lower risks of complications such as barotrauma compared to IPPB.

Types of Incentive Spirometers

Volume Oriented Incentive Spirometry

  • Measures volume during inspiration; the bellow rises as air is drawn through the breathing hose.

Flow Oriented Incentive Spirometry

  • Equivalent to volume measurements based on duration of inhalation:
    ext{Flow} imes ext{Time} = ext{Volume}
  • Example: Inhaling at 100 ml/sec for 3 seconds yields a total inhaled volume of 300 ml.

Tri-Flow Incentive Spirometer

  • A flow-oriented breathing trainer with color-coded balls giving visual feedback on inhaled volume.
  • Specifications include spirometer lung capacities of 600 ml/sec, 900 ml/sec, and 1,200 ml/sec.

Administration of Incentive Spirometry

  • Set realistic goals requiring moderate effort.
  • Instruct the patient to inhale slowly and deeply, with a breath-hold of 5-10 seconds.
  • Advise resting 30-60 seconds to prevent hyperventilation after each attempt.
  • Patients should aim for 10 breaths per hour to mimic normal sighing.

Monitoring Incentive Spirometry

  • Track:
    • Frequency of sessions, number of breaths per session, volume goals achieved, and maintenance of breath holds.
    • Evaluate effort and observe compliance periodically.
    • Ensure IS device is within arm's reach for patient convenience.
    • Data charting example: Predicted goal of 3500 mL, achieved volume of 1500 mL for 10 breaths.

Troubleshooting the Incentive Spirometer

  • If an obstruction or leak is present, the ball or bellow will not rise.
  • Recommend clearing obstructions, sealing leaks, or replacing the unit to ensure proper functioning.