chp 38

Question 1

Define Humidity Therapy

Answer 1

◦ Involves adding water vapor and (sometimes) heat to the inspired gas

Question 2

Primary Role of the Upper Airways

Answer 2

◦ Heat and Moisture exchange

‣ Nose is more effective than mouth

Question 3

ISB (Define, Location, T, RH & AH, Purpose)

Answer 3

◦ 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

Question 4

Factors that shifts ISB deeper into the lungs (4)

Answer 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

Question 5

Indications of Humidification and Warming of Inspired Gases (4)

Answer 5

◦ *Administration of dry medical gases
◦ *Overcoming Humidity deficit
◦ Managing hypothermia
◦ Treatment of bronchospasm cause by cold air

Question 6

Causes of poor humidification (5-6)

Answer 6

◦ Heat and water loss 
◦ Thicker mucus
◦ Damaged cilia and cells
◦ Mucus Plugging
◦ Atelectasis, decreased compliance

Question 7

Dew Point (Define)

Answer 7

◦ When air becomes 100% saturated with water vapor @ given temp, and condensation or dew is formed

Question 8

Absolute Humidity and Relative Humidity (Define, and Units)

Answer 8

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 (%)

Question 9

Recommended Humidity Levels with Nose/Mouth

Answer 9

◦ Nose/Mouth ➔ 20-22 C, 50%, 10 mgH2O/L

Question 10

Recommended Humidity Levels with Hypopharynx

Answer 10

◦ Hypopharynx ➔ 29-32 C, 95%, 28-34 mgH2O/L

Question 11

Recommended Humidity Levels with Trachea

Answer 11

◦ Trachea ➔ 32-35 C, 100%, 36-40 mgH2O/L

Question 12

What’s a Humidifier?

Answer 12

◦ A device that adds molecular water to gas and it occurs by evaporated from a surface

Question 13

Principles Governing Humidifier (4)

Answer 13

Temperature, Surface Area, Contact Time, Thermal Mass

Question 14

Temperature (explanation of relationship)

Answer 14

◦ Temperature ➔ the higher the temperature of the gas, the more water vapor it can hold (increase in capacity) ad vice versa

Question 15

Surface Area (explanation of relationship)

Answer 15

◦ Surface Area ➔ The greater SA of contact between water and gas, the more opportunity for evaporation to occur

Question 16

Contact Time (explanation of relationship)

Answer 16

◦ Contact Time ➔ The longer a gas remains in contact with water, the greater opportunity for evaporation to occur

Question 17

Thermal Mass (explanation of relationship)

Answer 17

◦ 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

Question 18

When would you give a Cool Humidified Gas?

Answer 18

◦ Treatment of upper airways inflammation: Croup, Epiglottis, Postextubation Edema

Question 19

Active vs Passive Humidifier

Answer 19

◦ Active ➔ Actively adding heat and/or water to the device-patient interface
◦ Passive ➔ recycling exhaled heat and humidity from the patient

Question 20

Bubble Humidifier

Answer 20

◦ Breaks an underwater gas stream into small bubbles

Question 21

Passover Humidifier

Answer 21

◦ Directs gas over a water surface

Question 22

Vaporizer

Answer 22

◦ Heats water to the point of expansion as a gas

Question 23

Types of HME

Answer 23

Simple, Hygroscopic, and Hydrophobic

Question 24

Efficiency of Simple, Hygroscopic, and Hydrophobic HME

Answer 24

Simple 50%
Hygroscopic 70%
Hydroscopic >70%

Question 25

Indications of HME (3)

Answer 25

◦ Mechanical Ventilation
◦ Spontaneously breathing patients with an artificial airway
◦ Transport

Question 26

Contraindications of HME (3)

Answer 26

◦ Copious amount of sputum
◦ Patients receiving very small or very large tidal breathing
◦ High Minute Ventilation

Question 27

Low Flow vs High Flow (Flow Rate, RH, and AH)

Answer 27

◦ Low Flow (<15 L/min), 30-40% of AH

◦ High Flow (>15 L/min), 100% RH 44mgH2O/L @ body temp

Question 28

How do you avoid constant refilling (2)

Answer 28

◦ Large water reservoir

◦ Gravity feed system

Question 29

Heated vs Unheated Systems (how much RH does it add)

Answer 29

◦ Heated ➔ add 100% RH to the patient’s @ 24-37

◦ Unheated ➔ adds up to 40% RH