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Respiratory Skills > Chapter 39 > Flashcards

Chapter 39 Flashcards

1
Q

Humidity Therapy

A

therapy that adds water vapor and sometimes heat to inspired gas

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2
Q

Humidity

A

water in its gaseous or vapor form in the environment (invisible)

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3
Q

Absolute Humidity (AH)

A

amount of water in a given volume of gas (mg/L)

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4
Q

Relative Humidity (RH)

A

ratio between the amount of water in given volume of gas and max amount it is capable of holding at same temperature and pressure

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5
Q

Formula for relative humidity

A

RH = absolute humidity capacity x 100

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6
Q

Aerosol

A

suspension of water particulate, a mist you can visibly see, in gases that can be inhaled (nebulizers)

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7
Q

Nose on inhalation

A
  • warms air and picks up water vapor from moist mucosal lining
  • filters inhaled gases
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8
Q

Nose on exhalation

A
  • exhaled gases transfer back to cooler trachea holding less water vapor
  • condensation occurs on mucosal surfaces
  • liquid water is reabsorbed by mucus (rehydration)
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9
Q

What is BTPS

A

Body Temperature Pressure Saturated

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10
Q

___ relative humidity at 37 C

A

100%

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11
Q

Gas at body temperature and ambient pressure (BTPS) contains ____ mg/L of water vapor

A

43.9 mg/L

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12
Q

Above ISB

A

temperature and relative humidity decrease during inspiration and increase during exhalation

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13
Q

Below ISB

A

temperature and relative humidity remain constant

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14
Q

ISB shifts distally when

A
  • person breathes cold, dry air
  • airway is bypassed (tracheostomy)
  • minute ventilation is higher than normal
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15
Q

Shifts of ISB

A

can compromise body’s normal heat and exchange mechanisms

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16
Q

What is ISB

A

isothermal saturation boundary

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17
Q

Nose and mouth

A

T = 22 C
RH = 50%
AH = 10 mg/L

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18
Q

Larynx/Pharnyx

A

T = 30 C
RH = 95%
AH = 30 mg/L

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19
Q

Lungs

A

T = 37 C
RH = 100%
AH = 43.9 mg/L

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20
Q

Humidity deficit:

A

43.9 mg/L - 10.0 mg/L = 33.9 mg/L

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21
Q

Primary indications for humidification therapy

A
  • humidifying dry medical gases
  • overcoming humidity deficit created when upper airway is bypassed
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22
Q

Secondary indications for humidification therapy

A
  • treating bronchospasm caused by cold air
  • managing hypothermia (reducing body temperature)
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23
Q

Clinical signs and symptoms of inadequate airway humidification

A
  • atelectasis
  • dry, nonproductive cough
  • increased airway resistance
  • increased incidence of infection
  • increased work of breathing
  • patient complaint of substernal pain and airway dryness
  • thick, dehydrated secretions
  • destruction of the airway epithelium
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24
Q

4 Physical principles governing humidifier function

A
  1. temperature
  2. surface area
  3. time of contact
  4. thermal mass
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25
Q

Temperature

A

the higher the temperature of gas, the more water it can hold

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26
Q

Surface area

A

affects rate of evaporation
- greater the surface area of contact between water and gas, more opportunity there is for evaporation to occur

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27
Q

Passover humidifier

A

pass gas over a large surface area of water

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28
Q

Bubble diffusion

A

directs a stream of gas underwater, where it is broken up into small bubbles

29
Q

Wicks

A

use porous water-absorbent materials to draw water (similar to a sponge) into its fine, honeycombed structure by means of capillary action

30
Q

Time of contact

A

evaporation increases as contact time increases
- longer gas remains in contact with water, greater the opportunity for evaporation to occur
- for bubble humidifiers, contact time depends on the depth of water column
- passover and wick-type humidifiers, the flow rate of gas through humidifier is inversely related to contact time
(with high flow rates reducing the time available for evaporation to occur)

31
Q

Thermal mass

A

the greater the amount of water in humidifier, the greater the thermal mass and capacity to hold and transfer heat to therapeutic gas

32
Q

Active humidifier

A

actively adding heat of water or both to the device-patient interface
- bubble humidifiers, passover humidifiers, nebulizers or bland aerosols, and vaporizers

33
Q

Passive humidifier

A

recycling exhaled heat and humidity from the patient
- typical heat and moisture exchangers (HMEs)

34
Q

Bubble humidifiers

A
  • breaks underwater gas stream into small bubbles
  • use of foam or mesh diffuser produces smaller bubbles than open lumen, allowing greater surface area or gas/water interaction
  • usually used unheated with oxygen delivery systems to raise water vapor content of gas to ambient levels
  • includes simple pressure relief valve
  • can produce aerosols at high flow rates
  • unheated bubble humidifiers can provide AH levels b/w approx. 15 - 20 mg/L
35
Q

Passover humidifiers

A
  • directs gas over water surface
    1. simple reservior
    2. Wick type
  • absorbent material increases surface area for dry ir to interface with heated water
    3. membrane type
  • separates water from gas stream by means of hydrophobic membrane
36
Q

Heat-moisture exchangers

A
  • often passive humidifier that has been described as “artificial nose”
  • captures exhaled heat and moisture and returns up to 70% of heat and humidity to patients during next inspiration
  • HMEs do not actively add heat or water to the systems
37
Q

Types of HMEs

A
  • simple condenser humidifiers
  • hygroscopic condenser humidifiers
  • hydrophobic condenser humidifiers
38
Q

Simple condenser humidifiers

A
  • contain a condenser element with high thermal conductivity, usually consisting of metallic gauze, corrugated metal, or parallel metal tubes
39
Q

Hygroscopic condensor humidifiers

A

Absorbs moisture from air by using materials that:
- incorporate condensing element of low thermal conductivity (helps retain more heat)
- impregnating this material with a hygroscopic salt (helps capture extra moisture from exhaled gas)

40
Q

Hydrophobic condenser humidifiers

A
  • use a water-repellent element with a large surface area and low thermal conductivity
    • on exhalation the condenser temp increase to 25C and provides evaporation of water
      - on inhalation cool gas and evaporation reduce the condenser temp at 10C which causes more uptake of evaporated water
41
Q

HMEs add ____ ml of dead space

A

5 - 90 ml

42
Q

Active HMEs

A

add humidity or heat or both to inspired gas by chemical or electrical means

43
Q

Humid-heat

A
  • absorbs expired heat and moisture and releases it into inspired gas
  • consists of supply unit with microprocessor, water pump, and humidification device
44
Q

HME booster

A
  • designed for patients with minute volumes of 4-20 L
  • no appropriate for pediatric patients with infants
  • consists of T-piece containing electrically heated element
45
Q

Heat ____ water output of bubble and passover humidifiers

A

improves

46
Q

When are heated humidifiers primarily used?

A

primarily used for patients with bypassed upper airways and those receiving mechanical ventilation

47
Q

Types of heating elements that require energy source

A
  • hot plate
  • wraparound type
  • yolk, or collar element
  • immersion type heater
  • heated wire
  • thin-film, high-surface area broiler
  • servo-controlled heating system that monitors temp. at or near patients airway using thermistor probe
48
Q

Manual systems

A
  • simple large reservoir systems are manually opened and refilled with sterilization or distilled water; cross- contamination can occur
  • small inlet can be attached to gravity-fed intravenous bag and line allows refilling without interruption
49
Q

Automatic systems

A
  • avoid need for constant checking and manual refilling
  • flotation valve controls can be used to maintain humidifier reservoir fluid volume
50
Q

At least ____ of humidity is recommended for intubated patients

A

30 mg/L

51
Q

Some experts recommend heating inhaled gas to maintain airway temperature near _____ to _____

A

35C to 37C

52
Q

AARC guidlines reccomends ___C, wishing ___C, with a minimum of ____of water vapor

A

33C, 2C, 30mg/L

53
Q

What occurs due to temperature difference across the system

A

condensation

54
Q

Factors influencing the amount of “rain out”

A
  • temp. difference from humidifier to airway
  • ambient room temp.
  • gas flow
  • set airway temp.
  • length, diameter, thermal mass of breathing circuit
55
Q

Risks for rain out

A
  • can waste a lot of water
  • can occlude gas flow through circuit
  • can be aspirated
  • condensate may be colonized with bacteria
56
Q

Avoid cross-contamination

A
  • water in circuit can be source of bacterial colonization
  • minimizing condensation
  • heated-wire circuits
  • wick or membrane passover humidifiers
  • frequently change circuits is NOT needed to reduce chance of nosocomial infection
57
Q

ensure proper conditioning of inspired gas received by patients by:

A
  • regularly measuring patients FiO2 levels
  • providing ventilatory care and monitoring selected pressures, volume, flows
  • using hygrometer- thermometer system
58
Q

aerosol generators include:

A

large volume jet nebulizers and ultrasonic nebulizers

59
Q

Indications of bland aerosol therapy

A
  • presence of upper airway edema
  • laryngotracheobronchitis
  • subglottic edema
  • postextubation edema
  • postoperative management of upper airway
  • presence of a bypassed upper airway
  • need for sputum
60
Q

Contradictions of bland aerosol therapy

A
  • bronchoconstriction
  • history of airway hyperresponsiveness
61
Q

Hazards and complications of bland aerosols therapy

A
  • wheezing or bronchospasm
  • infection
  • overhydration
  • patient discomfort
  • caregiver exposure to airborne contagions
  • edema of the airway wall
62
Q

What is the most common device used for bland aerosol therapy

A

Large volume jet nebulizers

63
Q

Unheated LVN can produce ___ to ___ mg H2O/L

A

26 to 35

64
Q

Heated LVN can produce ___ to ___ mg H2O/L

A

35 to 55

65
Q

what device is electrically powered that uses piezoelectric crystal to generate aerosols

A

ultrasonic nebulizer

66
Q

Crystal transducer converts radio waves into high-frequency mechanical vibrations that produce aerosol

A

ultrasonic nebulizer

67
Q

Types of airway appliances

A
  • aerosol mask
  • face tent
  • t-tube
  • tracheostomy mask
68
Q

Problems with bland aerosol therapy

A
  • cross-contamination and infection
  • environmental exposure
  • inadequate aerosols output
  • overhydration
  • bronchospasm
  • noise
69
Q

Key considerations of selecting appropriate therapy

A
  • gas flow
  • presence or absence of an artificial tracheal airway
  • character of pulmonary secretions
  • need for and expected duration of mechanical ventilation
  • contraindications to using an HME

Respiratory Skills (3 decks)

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