Hyperinflation Therapy - Comprehensive Study Notes

Key Words

Wright's spirometer
EZPAP with mouthpiece
Pressure manometer
V60
Ambu bag mask
HHN (Hand-held nebulizer)
IS (Incentive Spirometry)
Your filter
Test lung
IPPB (Intermittent Positive Pressure Breathing) machine
Saline bullet
Reduced FRC (Functional Residual Capacity)
Barotrauma
Recruitment
Breath hold
Increased WOB (Work of Breathing)
Airway splinting
Collateral ventilation

Goals of Hyperinflation Therapy

Define and describe IS, IPPB, EZPAP, and CPAP therapies:
- Incentive Spirometry (IS): A patient-driven lung expansion therapy that encourages slow, deep breaths to promote alveolar inflation and prevent atelectasis. Patients visually monitor their inspiratory effort to reach a predetermined volume goal.
- Intermittent Positive Pressure Breathing (IPPB): A short-term mechanical ventilation therapy that delivers positive pressure breaths to assist patients with inadequate spontaneous ventilation, improving lung expansion, secretion clearance, and oxygenation.
- EZPAP (EZ-Positive Airway Pressure): A therapy that provides a positive airway pressure during exhalation to stent airways open, recruit collapsed alveoli, and improve removal of secretions, often used as an alternative to IS or in conjunction with nebulizer treatments.
- CPAP (Continuous Positive Airway Pressure): A therapy that maintains a continuous level of positive pressure throughout the breathing cycle (inspiration and expiration) to keep airways open, improve oxygenation, and reduce the work of breathing, commonly used for sleep apnea and respiratory failure.
Develop an understanding of the relationship of pressure, flow, and volume:
- Pressure is the force exerted per unit area ( $P = F/A$ ), crucial for overcoming airway resistance and lung elastance to drive gas into the lungs.
- Flow is the volume of gas moving per unit time (e.g., L/min), determining the speed at which breaths are delivered or inhaled.
- Volume is the amount of gas delivered or inspired (e.g., mL), representing the degree of lung expansion achieved.
- In positive pressure therapies, increasing pressure generally increases the volume delivered, while flow dictates the inspiratory time and how quickly that volume is reached.
Correctly use a pressure manometer and a Wright's spirometer to assess positive pressure and volume:
- A pressure manometer is used to measure the positive airway pressure generated during therapies like IPPB or EZPAP, ensuring pressures are within therapeutic and safe ranges (e.g., monitoring peak inspiratory pressure during IPPB).
- A Wright's spirometer is used to measure exhaled or inspired volumes, such as tidal volume or vital capacity, to assess the effectiveness of lung expansion therapies and monitor patient progress.
Calculate Ideal Body Weight (IBW) and Predicted Body Weight (PBW) to ensure adequate volumes are met: These calculations are foundational in respiratory care to estimate appropriate tidal volumes for mechanical ventilation and other respiratory therapies, ensuring patient safety and optimal lung recruitment based on physiological parameters rather than actual weight.

Goal of Hyperinflation Therapy

Purpose: The primary goal is to inflate lungs to combat atelectasis, which is the collapse of alveoli (small air sacs in the lungs). By expanding the lungs, these therapies aim to re-open collapsed lung tissue, improve gas exchange, and prevent further pulmonary complications.

Definitions

IS (Incentive Spirometry): A therapeutic device used to encourage patients to take slow, deep breaths, hold them, and improve respiratory function by visually measuring inspiratory volumes to prevent and reverse atelectasis.
EZPAP (EZ-Positive Airway Pressure): A form of positive pressure therapy designed to create expiratory positive airway pressure, opening airways and enhancing lung expansion and secretion mobilization by preventing premature airway collapse during exhalation.
IPPB (Intermittent Positive Pressure Breathing): A mechanical ventilatory support technique used to deliver positive pressure breaths, typically for 15-20 minutes every 4-6 hours, to patients with conditions like atelectasis or hypoventilation, improving lung volumes and facilitating cough.
CPAP (Continuous Positive Airway Pressure): A method that maintains a continuous level of positive air pressure throughout the respiratory cycle to keep airways open, improve oxygenation, and reduce the work of breathing, often used in conditions such as obstructive sleep apnea, cardiogenic pulmonary edema, and respiratory distress.

Patients at Risk for Atelectasis

Patients post-surgery: Especially after abdominal or thoracic surgery, due to pain, opioids (which depress respiratory drive), shallow breathing, and immobility. This leads to reduced diaphragmatic excursion and surfactant dysfunction.
Patients with neuromuscular diseases: Conditions like muscular dystrophy or ALS weaken respiratory muscles, leading to ineffective deep breaths and cough, causing alveolar collapse and secretion retention.
Smokers: Chronic irritation and inflammation of airways reduce mucociliary clearance and can lead to increased mucus production, small airway obstruction, and eventually atelectasis.

Breath Sounds Associated with Atelectasis

Crackles (also known as “rales”): Often heard upon inspiration and are indicative of collapsed alveoli popping open as air enters them. They can be fine or coarse depending on the size of the airways involved.
Diminished breath sounds: Occur over areas of atelectasis because less air is moving into (or out of) the collapsed lung regions, reducing the sound transmission.
Bronchial breath sounds: Typically heard over the trachea, but if heard over peripheral lung fields, they suggest consolidation or atelectasis where lung tissue is dense and transmits sounds from larger airways more clearly.

Contribution of Oxygen Therapy to Atelectasis Development

High concentrations of oxygen therapy (FiO $_{2}$ greater than 0.50) can lead to absorption atelectasis. Nitrogen, which normally acts as a “splint” to keep alveoli open, is washed out by pure oxygen. When oxygen is absorbed into the bloodstream from the alveoli, if ventilation is obstructed (e.g., by secretions or shallow breathing), the alveoli can collapse as oxygen is absorbed more quickly than it is replaced. This can also lead to decreased respiratory drive, potentially causing shallow breathing and subsequent atelectasis if the patient does not take deep breaths.

Incentive Spirometry (IS) Instructions

Frequency of use: Instruct a patient to use IS every hour (Q1hr) while awake, completing 10 breaths per session intensely to maximize lung expansion.
Breath count: Patients should perform approximately 3 IS breaths within a period of 30-45 seconds, allowing for adequate rest between breaths to prevent hyperventilation.
Example volumes noted:
- 2,500 mL
- 2,250 mL
- ~2,500 mL

Setting Initial Volume Goals for the Patient

Prevent and treat atelectasis: By encouraging deep inhalation and breath holding, IS helps to expand collapsed lung units and ensures adequate ventilation to all lung segments.
Increase lung volumes: Specifically, IS aims to increase inspiratory capacity (IC) and vital capacity (VC), which can be reduced in patients at risk for atelectasis, thereby improving overall lung function.
Enhance recruitment of collapsed alveoli: The sustained maximal inspiration generated by IS helps to overcome the surface tension in collapsed alveoli, forcing them open and improving gas exchange.

Contraindications for IS Therapy

Specific contraindications:
- Pneumothorax: Patients with an untreated pneumothorax (collapsed lung due to air in the pleural space) should not use IS, as the deep breaths could worsen the air leak and further expand the pneumothorax.
- Trauma: Patients with recent thoracic or abdominal surgery, especially those with unhealed surgical sites or rib fractures, may experience severe pain or further injury with deep breaths.
- Untreated tension pneumothorax or barotrauma risk are absolute contraindications.

Common Hazards of IS Therapy

Most common hazard: Light-headedness or dizziness. This often occurs due to hyperventilation (exhaling too much $CO_{2}$ ) during repeated deep breaths.
To prevent: Ensure the patient is safely seated during therapy and coach them through the breathing process, emphasizing slow, sustained inhalations with adequate rest periods (30-45 seconds) between sets of breaths to allow $CO_{2}$ levels to normalize.

Reducing Risk of Pulmonary Complications (IS)

Besides taking deep breaths, patients should engage in ambulation (walking) to help reduce the risk of pulmonary complications. Ambulation promotes deeper breathing, improves circulation, helps mobilize secretions, and prevents stasis in the lungs, synergistically working with IS to prevent atelectasis and pneumonia.

Technique for Performing IS Breaths

Example Volumes Recorded:
- IS breath with perfect technique: 2,500 mL
- IS breath inhaling rapidly: 1,800 mL
Analysis: There may be a significant difference in recorded volumes due to the effects of inhalation technique on airflow dynamics and lung expansion. A perfect technique involves a slow, deep, sustained inhalation followed by a breath hold (5-10 seconds), which allows for optimal alveolar filling. Rapid inhalation causes turbulent flow, leading to premature airway collapse or uneven distribution of air, resulting in a lower measured volume, even with the same inspiratory effort.

Intermittent Positive Pressure Breathing (IPPB)

Identifying Pressure: It is crucial to monitor both positive pressure (during inspiration, ensuring appropriate breath delivery and patient comfort) and negative pressure (indicating patient inspiratory effort or baseline during expiration) on the manometer. This feedback helps adjust settings to patient needs and avoids barotrauma.
Adjust flow settings: Considerations for the proper IS breath/ inspiration to expiration (I:E) ratio are vital. A longer inspiratory time (lower flow) allows for better distribution of gas, especially in patients with obstructive disease, while a shorter inspiratory time (higher flow) is used for patients with reduced compliance or those who cannot tolerate longer inspiratory phases. An I:E ratio of 1:2 to 1:4 is commonly targeted.
Volume Measurement: Use a Wright's Spirometer to measure volumes produced during IPPB to verify that the desired tidal volume is being achieved, ensuring the therapy is effective in expanding the lungs.

Case Study: Post-operative Patient Management

Patient description: Post-operative patient experiencing shortness of breath with shallow respiratory efforts, SpO $_{2}$ levels 86% on room air, improving to 94% on 4 L/min nasal cannula. These vitals indicate significant hypoxemia and respiratory compromise, making them a good candidate for IPPB to improve lung expansion and oxygenation.
IPPB Settings:
- Pressure = 15 cmH $_{2}$ O (This pressure aims to provide sufficient positive pressure to inflate atelectatic lung regions while minimizing the risk of barotrauma. It's a common starting point.)
- Flow = 15 L/min (This flow rate delivers the breath at a moderate speed, allowing for adequate inspiratory time to recruit alveoli without causing excessively rapid inflation that could lead to discomfort or turbulent flow.)

Test Lung Setup

Attach IPPB circuit to a test lung using two outside springs engaged (indicating a patient with atelectasis/reduced lung compliance). The engaged springs simulate stiff lungs, requiring higher pressure to achieve desired volumes.
Record volumes produced with Wright's Spirometer:
- Volumes at 15 cmH $<em>{2}$ O: 500 mL (With reduced compliance, 15 cmH $</em>{2}$ O might yield a moderate volume.)
- Increase pressure to 20 cmH $<em>{2}$ O: Record new volumes = 700 mL (Increasing pressure by 5 cmH $</em>{2}$ O leads to a noticeable increase in volume, demonstrating the direct relationship between pressure and volume in the absence of significant airway resistance).

Patient Progress Over Days

Observation of patient improvement: Able to ambulate more easily, experiencing less shortness of breath, reduced oxygen requirements, and a strong cough for secretion clearance. These are all positive indicators of improved lung function, increased lung volumes, and better gas exchange.
Adjustment Effects:
- When adjusting pressure: Increasing the pressure (e.g., from 15 to 20 cmH $_{2}$ O) typically leads to an increase in volume delivered to the lungs, assuming compliance remains constant. This is because a greater pressure gradient forces more air into the lungs, improving lung expansion and recruiting more alveoli. Conversely, decreasing pressure would reduce delivered volume.
- When adjusting lung compliance (removing a spring): Removing a spring from the test lung simulates an increase in lung compliance (lungs become less stiff). For the same applied pressure, an increase in compliance will result in a larger volume measured by the spirometer, as the lungs are easier to inflate.

EZPAP Therapy

Instructions for Patient Breathing:
- Instruct the patient to breathe normally during inspiration.
- Breath holding is required for 1-3 seconds after expiration to maximize lung expansion and allow the positive expiratory pressure to effectively stent airways open and facilitate collateral ventilation.
Setup Procedure:
- 1. Connect the filter to the EZPAP device. This filter ensures that the air being delivered to the patient is clean and free of particulate matter.
- 2. Connect the small-bore tubing from the EZPAP device to the correct port on the device and then to the flowmeter. This tubing delivers the gas flow from the flowmeter to the EZPAP device.
- 3. Attach a pressure manometer to the pressure port on the EZPAP circuit. This allows for real-time monitoring of the positive expiratory pressure (PEP) being generated.

Flow Adjustment and Pressure Recording

Initiate flow at different rates and record expiratory (resistance) pressures:
- At 5 L/min: Pressure = 5 cmH $_{2}$ O
- At 7 L/min: Pressure = 9 cmH $_{2}$ O
- At 10 L/min: Pressure = 13 cmH $_{2}$ O (As observed, increasing flow directly increases the expiratory pressure generated by the EZPAP device).
Therapeutic PAP Pressure Range: Review literature to identify range = 10-20 cmH $_{2}$ O. The specific target pressure often depends on the patient's condition and tolerance, aiming for effective lung expansion without discomfort or adverse effects.

Observations During EZPAP Use

Experience during EZPAP use at 7 L/min flow: "Nothing happens" indicates further investigation and adjustment may be needed. This could mean the pressure is too low to be therapeutically effective for the patient's condition, the patient's technique is incorrect (e.g., not holding breath), or there is an equipment malfunction (e.g., leak in the circuit or improper seal).
Mask Utilization: Yes, an Ambu bag mask can be used for EZPAP therapy. It provides a proper seal over the patient's nose and mouth, allowing for effective delivery of positive airway pressure when the EZPAP device is connected to the mask port.

Combining Therapies: EZPAP and HHN Treatment

If only one oxygen flowmeter and one air flowmeter are available, contingency plans for oxygen delivery and HHN treatment can include:
- Sequential therapy: Administer the HHN treatment first using the available oxygen flowmeter, then disconnect and use the flowmeter for the EZPAP therapy (potentially with supplemental oxygen if needed).
- Blender/Aerosol setup: If an air flowmeter and an oxygen flowmeter are available, a blender can be used to mix gases to achieve a precise FiO $_{2}$ for the HHN, then the EZPAP can be connected to the patient interface. If the EZPAP requires its own dedicated flow source, the HHN might need to be administered first or via a different method if the patient's oxygenation needs are critical.
- Using a Y-connector (with caution): A Y-connector could be used to split the gas flow, but this often compromises the pressure and flow delivery to each device, making accurate therapeutic delivery challenging and potentially ineffective for both.
Discuss implications of having only one oxygen flowmeter for therapy provision: Having only one oxygen flowmeter severely limits the ability to simultaneously provide multiple oxygen-dependent therapies. It necessitates prioritizing therapies based on the patient's most critical need (e.g., oxygen for hypoxemia vs. nebulized bronchodilators vs. lung expansion therapy). It also requires constant switching between devices, which can be time-consuming, interrupt treatment continuity, and potentially lead to periods of untreated hypoxemia or delayed therapy.
Key Relationship: The relationship between flow and pressure in EZPAP therapy reflects that increasing flow leads to increased pressure, and fluctuations in either parameter can significantly affect therapeutic efficacy. Specifically, higher flow rates overcome expiratory resistance more effectively, generating higher PEP. Maintaining a consistent flow is critical to achieve and sustain the desired therapeutic pressure range, thereby optimizing airway splinting and alveolar recruitment.