chp 38 Flashcards
Define Humidity Therapy
◦ Involves adding water vapor and (sometimes) heat to the inspired gas
Primary Role of the Upper Airways
◦ Heat and Moisture exchange
‣ Nose is more effective than mouth
ISB (Define, Location, T, RH & AH, Purpose)
◦ Isothermic Saturation Boundary: Right below the carina, homeostasis where the water vapor is heated to body temp (37 C) at 100% RH = 44 mgH2O/L
Factors that shifts ISB deeper into the lungs (4)
◦ Mouth breathing rather than nose
◦ Breathing cold and dry air
◦ When upper airway is bypassed (artificial airways)
◦ When minute ventilation is higher than normal
Indications of Humidification and Warming of Inspired Gases (4)
◦ *Administration of dry medical gases
◦ *Overcoming Humidity deficit
◦ Managing hypothermia
◦ Treatment of bronchospasm cause by cold air
Causes of poor humidification (5-6)
◦ Heat and water loss ◦ Thicker mucus ◦ Damaged cilia and cells ◦ Mucus Plugging ◦ Atelectasis, decreased compliance
Dew Point (Define)
◦ When air becomes 100% saturated with water vapor @ given temp, and condensation or dew is formed
Absolute Humidity and Relative Humidity (Define, and Units)
AH: Actual amount of water vapor in 1 L of gas (mgH2O/L)
RH: Relationship between AH and the Maximum Humidity at a particular temp (%)
Recommended Humidity Levels with Nose/Mouth
◦ Nose/Mouth ➔ 20-22 C, 50%, 10 mgH2O/L
Recommended Humidity Levels with Hypopharynx
◦ Hypopharynx ➔ 29-32 C, 95%, 28-34 mgH2O/L
Recommended Humidity Levels with Trachea
◦ Trachea ➔ 32-35 C, 100%, 36-40 mgH2O/L
What’s a Humidifier?
◦ A device that adds molecular water to gas and it occurs by evaporated from a surface
Principles Governing Humidifier (4)
Temperature, Surface Area, Contact Time, Thermal Mass
Temperature (explanation of relationship)
◦ Temperature ➔ the higher the temperature of the gas, the more water vapor it can hold (increase in capacity) ad vice versa
Surface Area (explanation of relationship)
◦ Surface Area ➔ The greater SA of contact between water and gas, the more opportunity for evaporation to occur
Contact Time (explanation of relationship)
◦ Contact Time ➔ The longer a gas remains in contact with water, the greater opportunity for evaporation to occur
Thermal Mass (explanation of relationship)
◦ Thermal Mass ➔ The greater the mass of water or the core element of the humidifier, the greater is its capacity to hold and transfer heat
When would you give a Cool Humidified Gas?
◦ Treatment of upper airways inflammation: Croup, Epiglottis, Postextubation Edema
Active vs Passive Humidifier
◦ Active ➔ Actively adding heat and/or water to the device-patient interface
◦ Passive ➔ recycling exhaled heat and humidity from the patient
Bubble Humidifier
◦ Breaks an underwater gas stream into small bubbles
Passover Humidifier
◦ Directs gas over a water surface
Vaporizer
◦ Heats water to the point of expansion as a gas
Types of HME
Simple, Hygroscopic, and Hydrophobic
Efficiency of Simple, Hygroscopic, and Hydrophobic HME
Simple 50%
Hygroscopic 70%
Hydroscopic >70%
Indications of HME (3)
◦ Mechanical Ventilation
◦ Spontaneously breathing patients with an artificial airway
◦ Transport
Contraindications of HME (3)
◦ Copious amount of sputum
◦ Patients receiving very small or very large tidal breathing
◦ High Minute Ventilation
Low Flow vs High Flow (Flow Rate, RH, and AH)
◦ Low Flow (<15 L/min), 30-40% of AH
◦ High Flow (>15 L/min), 100% RH 44mgH2O/L @ body temp
How do you avoid constant refilling (2)
◦ Large water reservoir
◦ Gravity feed system
Heated vs Unheated Systems (how much RH does it add)
◦ Heated ➔ add 100% RH to the patient’s @ 24-37
◦ Unheated ➔ adds up to 40% RH
