Respiratory Therapy Chapter 35 Quiz

Chapter 35: Humidity and Bland Aerosol Therapy

• Learning Objectives:
  • Describe airway heat and moisture exchange.
  • Identify the effects of dry gases on the respiratory tract.
  • Determine when to humidify and warm inspired gas.
  • Explain how various types of humidifiers work.
  • Describe methods to improve humidifier performance.
  • Outline the selection and safe use of humidifier heating and feed systems.
  • Identify indications, contraindications, and hazards of humidification during mechanical ventilation.
  • Describe monitoring techniques for patients receiving humidity therapy.
  • Explain how to identify and resolve common problems with humidification systems.
  • State when to apply bland aerosol therapy.
  • Explain how large-volume aerosol generators function.
  • Identify delivery systems used for bland aerosol therapy.
  • Describe identifying and resolving common problems with aerosol delivery systems.
  • Describe sputum induction techniques.
  • Explain how to select appropriate therapies to condition a patient's inspired gas.

Humidity Therapy

• Physiological Control of Heat & Moisture Exchange:
  • The upper airway (primarily the nose) warms and humidifies inspired gases.
  • The nose also cools and reclaims water from exhaled gases.
  • Body temperature–pressure–saturated (BTPS) conditions are optimal;
    • Body temperature at 37° C;
    • Barometric pressure;
    • Saturated with water vapor (100% relative humidity at 37° C).
  • Isothermic saturation boundary (ISB):
    • Above ISB, temperature and relative humidity decrease during inspiration and increase during exhalation.
    • Below ISB, temperature and relative humidity remain constant.
    • ISB shifts distally when breathing cold, dry air or via an artificial airway.
  • Humidity deficit:
    • Inspired air that is not fully saturated at body temperature.
    • The body's own humidification system corrects the deficit.
    • Humidity deficit = 44 mg/L – absolute humidity.
  • Relative Humidity: Ratio of water in a given volume of gas to the maximum amount the gas can hold at that temperature (%).
  • Absolute Humidity: Amount of water in a given volume of gas (mg/L).

Humidification Levels

• At least 30 mg/L humidity is recommended for intubated patients.
• Humidifiers should provide optimal humidity levels in inspired gas.
• Heat inhaled gas to maintain airway temperatures near 35-37° C.

Equipment (Humidifiers)

• Humidifier: Device that adds water to gas by evaporation from a surface.
  • Physical principles:
    • Temperature: Higher temperature gases hold more water.
    • Surface area: Greater surface area increases evaporation rate.
    • Contact time: Longer contact time increases evaporation.
    • Thermal mass: Larger water quantity increases humidifier's heat capacity.
• Types of Humidifiers:
  • Bubble: Breaks gas into small bubbles for gas-water interaction, can produce aerosols at high flow rates, poses risk of infection.
  • Passover: Gas passes over a water surface (Reservoir/Wick/Membrane). Usually unheated. Advantage is it maintains saturation at high flow rates and has minimal flow resistance.
  • Heat-moisture exchangers (HMEs): Passive humidifiers, often described as "artificial noses." Do not add heat or water to the system; they capture and reuse exhaled heat and moisture.

Heating Systems

• Heat improves water output in bubble and passover humidifiers.
• Primarily used in patients with bypassed airways or those on mechanical ventilation.
• Heating inhaled gas can pose risks such as airway burns.

Reservoir and Feed Systems

• Heated humidifiers can evaporate over 1 L of water per day.
• Gravity feed systems and large water reservoirs are used to refilling devices.
• Manual Systems: Large reservoirs filled manually.

Setting Humidification Levels

Problem Solving & Troubleshooting (Humidity Systems)

• Condensation:
  • Risks to patients and caregivers.
  • Wastes significant water.
  • May block gas flow.
  • Potential for aspiration.
• Cross-contamination:
  • Water in the circuit can be a source of bacterial colonization, so minimizing condensation is crucial to reduce infection risk. Wick-or membrane type passover humidifiers prevent bacteria-carrying aerosols.
  • Proper gas conditioning:
    • Respiratory therapists regularly track FiO2 and check pressure, volume, and flow.
    • Hygrometer/thermometer systems assess inspired gas humidity.
• Bland Aerosol Therapy: Includes liquid particles suspended in gas. Devices include large-volume jet nebulizers and ultrasonic nebulizers. Variety of liquids like sterile saline, hypotonic, isotonic, and hypertonic solution can be used.
• Large-Volume Jet Nebulizers: Most common devices, pneumatically powered and connected to flowmeters. Unheated units typically produce 26-35 mg H2O/L, heated ones, 35-55 mg H2O/L, largely because larger water capacity is increased. The variable air-entrainment port allows for air mixing and adjustments of flow rates and FiO2 levels.
• Ultrasonic Nebulizers: Use piezoelectric crystals that convert radio waves into vibrations to create aerosols. Particle size inversely correlates with signal frequency. Amplitude directly impacts aerosol volume. Flow and amplitude settings influence aerosol density and total water output.
• Airway Appliances: Used with large-bore tubing to limit flow resistance and prevent condensate buildup. Includes aerosol masks, face tents, T-tubes, and tracheostomy masks.
• Enclosures (mist tents and hoods): Deliver aerosolized particles to infants and children but can present problems like heat retention and CO2 buildup, issues handled via manufacturer-specific methods.
• Sputum Induction: Cost-effective, safe method to diagnose pulmonary conditions (TB, Pneumocystis, pneumonia, lung cancer). Uses high-density hypertonic saline aerosol (3-10%) for effective mucociliary clearance.
• Choosing the Correct Therapy: The treatment is selected based on proper patient assessment, including underlying conditions (hypothermia, dry air, thick lung secretions, etc.). The assessment should indicate the need for humidification.

Test your knowledge on humidity and bland aerosol therapy with this quiz. Covering essential concepts such as airway heat and moisture exchange, and the operation of humidifiers and aerosol systems, this quiz will reinforce your understanding of respiratory care principles. Perfect for students and practitioners in the field of respiratory therapy.