AARC Clinical Practice Guideline Humidification during Mechanical Ventilation HMV 1.0 PROCEDURE: The addition of heat and moisture to inspired gases delivered to the patient during mechanical ventilatory support via an artificial airway HMV 2.0 DESCRIPTION/DEFINITION: When the upper airway is bypassed, humidification during mechanical ventilation is necessary to prevent hypothermia, inspissation of airway secretions, destruction of airway epithelium, and atelectasis.(1-7) This may be accomplished using either a heated humidifier or a heat and moisture exchanger (HME). (HMEs are also known as hygroscopic condenser humidifiers, or artificial noses). The chosen device should provide a minimum of 30 mg H2O/L of delivered gas at 30°C.(8,29) Heated humidifiers operate actively to increase the heat and water vapor content of inspired gas.(11-14) HMEs operate passively by storing heat and moisture from the patient's exhaled gas and releasing it to the inhaled gas.(I5-25)

1. 1

2. 2

3. Ancient man discovered medicinal plants by
observation and experience.
Inhaling the smoke or odors of some plants was a
frequent trial to get pleasure and relief of body
troubles.
Nearly all respiratory troubles were treated by one
form or other of inhalation.
3

4. The highest achievement of progress of inhalation
therapy began at the ninth century.
Arab physicians introduced many therapeutic
agents to inhalation therapy.
The twentieth century witnessed the introduction
of new therapeutic agents and higher
technological devices for inhalation therapy.
4

5. 5

6. Drs. Starkey and Palen, 1888
6

7. Treatment for respiratory
ailments were common
during the late 1800s.
This popular concoction
claimed that it was not a
drug but a “scientific
adjustment to oxygen
and nitrogen.”
7

8. Indications for Compound Oxygen:
 Asthma
 Bronchitis
 Indigestion
 Hay fever
 Headache
 Rheumatism
 Neuralgia
 Diarrhea
…and cured none.
8

9. 9

10. In the 1940s in Chicago, Illinois, a group of oxygen-
tank technicians began meeting with doctors
concerned with lung disease.
This group named itself the Inhalational Therapy
Association in 1946.
They gradually put together a series of classes for
people administering medical gases to patients.
10

11. In December, 1950, 31 members of the Association
were issued certificates for attending 16 lectures.
This was the first certification of Inhalation
Therapists. It was an on-the-job training system
for so-called "oxygen jockies".
They had little formal education, but did have a
desire to do their jobs better and help patients in
the process.
11

12. 12

13. 13

14. In the simplest of terms, humidity is the amount
of water vapor that is present in the air at any
point in time.
This can be expressed as absolute humidity,
relative humidity or specific humidity.
Almost all weather reports generated anywhere
in the world point out the percentage of
humidity that is present in the atmosphere.
14

15. Absolute humidity is the exact amount of water
that is present in a given volume of air.
This gives a precise measurement of the
amount of water present, and thus lets the
experts calculate the percentage of humidity
in the atmosphere.
Absolute humidity calculators specify the
amount of grams of water vapor present in
each cubic meter of air.
15

16. Relative Humidity is the relationship between
absolute humidity and the maximum
humidity which gas can contain, expressed as
a percentage, at a given temperature.
16

17. Absolute humidity is the exact amount of water
that is present in a given volume of air.
This gives a precise measurement of the
amount of water present, and thus lets the
experts calculate the percentage of humidity
in the atmosphere.
Absolute humidity calculators specify the
amount of grams of water vapor present in
each cubic meter of air.
17

18. Specific humidity is the number of grams of
water vapor per kilogram of air.
18

19. The Dew point temperature is the temperature
at which the air can no longer hold all of its
water vapor, and some of the water vapor
must condensate into liquid water.
The dew point is always lower than or equal to
the air temperature.
19

20. The upper respiratory tract is lined by a warm,
viscous mucous membrane.
As air passes over the membrane, heat and
humidity is added to the inspired air before
it reaches the lower airways and lungs.
20

21. This membrane is lined with very small microscopic
cilia which act as an airway protection
mechanism.
The cilia’s constant movement is designed to expel
any inhaled contaminants lodged in the airway.
21

22. When a person exhales, the upper airway traps
most of the heat and moisture in the exhaled
breath so that it can be reused during the next
inhaled breath.
22

23. Your nose is responsible for about two-thirds of
this process.
As the air passes further into your airway, it
becomes warmer and more humid.
By the time air reaches your lungs it is at the
ideal temperature and humidity.
23

24. When you exhale your nose conserves water by
recovering about a third of the moisture
present in each exhaled breath.
That moisture is then used to assist in the
humidification of your next breath.
24

25. If you breathe through your mouth, you may
develop a dry throat.
By breathing through your mouth, you bypass your
nose, which is responsible for two-thirds of
humidification.
This means that you've tripled the humidification
workload of your upper airway.
25

26. Even if you're only exhaling through your mouth,
you are still losing valuable moisture.
You are not allowing your nose to recover the
moisture your body invested in the air as you
"inhaled" it.
26

27. The blood in your capillaries meets the air and
picks up the oxygen your body needs.
At the same time, the blood gets rid of the
harmful carbon dioxide that your cells
produce.
Some people think the lungs are just big hollow
bags, but in fact they are more like sponges.
This increases the amount of area inside the
lungs where the blood can meet with the air.
27

28. 28

29. Clinical uses for molecular water (humidity) can be
divided into two broad classes:
1. To humidify dry, therapeutic gases to make
them more comfortable to breathe.
2. To provide near body humidity levels of inspired
gases for patients with artificial airways.
29

30. 1. Administration of medical gases from a
cylinder or pipeline
2. Environmental R.H. < 70% in a patient with
lung disease
3. Patient with known secretions or a disease
that causes secretions
4. Anatomical humidifier is bypassed
30

31. When the upper airway is bypassed,
humidification during mechanical ventilation
is necessary to:
1. Prevent hypothermia
2. Inspissation of airway secretions
3. Destruction of airway epithelium
4. Atelectasis
31

32. This may be accomplished using either a heated
humidifier or a heat and moisture exchanger.
HMEs are also known as hygroscopic condenser
humidifiers or artificial noses.
The chosen device should provide a minimum of
30 mg H2O/L of delivered gas at 30°C.
32

33. Heated humidifiers operate actively to increase the
heat and water vapor content of inspired gas.
HMEs operate passively by storing heat and
moisture from the patient's exhaled gas and
releasing it to the inhaled gas.
33

34. 34

35. “This is to alert you that FDA has several reports of
patient deaths and injuries resulting from
malfunctioning volume ventilators and/or heated
humidifiers.
One incident of fire, in which three patients died, is
believed to have originated in either a Puritan-
Bennett Cascade IA humidifier or in the Puritan-
Bennett 7200 series ventilator to which the
humidifier was attached.”
35

36. Puritan-Bennett
Cascade Humidifier
36

37. The only regulated parameter is the system’s
temperature, not the humidity.
Temperature is used as a proxy for humidity.
37

38. The optimal temperature setting at the proximal
airway is recommended to be 37°C to 40°C (yielding
44 mg H2O/L of inhaled gas), but the scientific basis
for this is debated.
As the gas travels through the circuit, ambient
temperature changes cause the moisture to “rain
out.”
38

39. The condensation that develops presents a challenge
to ventilator operation.
As it accumulates, the condensate must be disposed of
in an aseptic manner.
Disconnecting the circuit to drain the condensate
(“breaking the circuit”) may contribute to VAP and
placement of an inline water trap may be an
acceptable alternative.
39

40. Use of heated wire circuits offers a partial solution
to the condensation problem, as a temperature
gradient is created by increasing the
temperature in the distal aspect of the
inspiratory limb.
Heating the interior of the circuit in this way
greatly minimizes the rainout.
40

41. The cost of a heated wire system is reported as a
drawback to its use. If the circuit does not require
changing, costs will decrease for each day it is
used.
There are, however, operational issues that should
be addressed.
41

42. Temperature gradients:
To maintain optimal humidity delivery, gradients
need to be adjusted as ambient temperature,
ventilator settings, and water reservoir levels
change.
42

43. These settings will need to be changed if the
patient is getting small volume nebulizer
treatments; is in a room where temperature
fluctuates (bedside fans or heating/air-
conditioning problems).
It can be both intellectually challenging and time-
consuming to have to adjust the equipment
based on ambient conditions.
43

44. Unfortunately, the concept of setting and adjusting
negative or positive gradients is difficult for some
to comprehend.
Setting these levels incorrectly with one system
creates a new set of problems.
The alarms package in earlier versions of some
devices was very sensitive, alerting the staff to
problems very quickly.
44

45. The audible alarms sound so frequently that there
is a great temptation to either adjust the heater
to a level that could be subtherapeutic or just
turn it off.
Newer systems use compensatory algorithms to
make these adjustments automatically, but in
one study the devices produced humidity levels
lower than advertised.*
*Lellouche F, Taille S, Maggiore SM, et al. Influence of ambient and ventilator
output temperatures on performance of heated-wire humidifiers.
Am J Resp Crit Care Med. 2004;170(10):1073-9.
45

46. Condensation from the patient circuit should be
considered infectious waste and disposed of
according to hospital policy using strict
Universal Precautions.
46

47. 47

48. 48

49. June 2005
Respiratory Care Journal
“HMEs should be used in all patients in whom there is no
contraindication.”
Richard D. Branson MSc RRT FAARC
49

50. 50

51. The first heat/moisture exchanger, which was
made of corrugated aluminum, was presented
by a group of Swedish professors in the early
1960’s.
Due to its weight, the device never became
widely used.
The market breakthrough for the artificial nose
did not occur until the beginning of the 1970’s.
51

52. The aluminum was replaced with a special
paper in a corrugated structure with a large
capacity for absorbing and giving off
moisture.
Over the years the “noses” have been gradually
developed and the design has been refined.
52

53. 53

54. Heat and Moisture Exchanger
 Natural physical properties only
Hygroscopic Condenser Humidifier
 Enhancement of the natural physical properties
Calcium Chloride, Condensation, etc.
54

55. There are 6 types of passive humidifiers.
55

56. HME
• heat and moisture exchanger
• least amount of moisture returned
HMEF
• filtered heat and moisture exchanger
• second lowest amount of moisture returned
HCH
• hygroscopic condensing humidifier
• second highest amount of moisture returned
HCHF
• filtered hygroscopic condensing humidifier
• highest amount of moisture returned
56

57. Bypass; BHME / BHCH
• Gas flow may be altered
Active; AHME / AHCH
• Heat and water is added
57

58. “The chosen device should provide a minimum of
30 mg H2O/L of delivered gas at 30°C”.
58

59. 59

60. The patient has humidity and heat within their
lungs. When the air or gas is forced out of the
lungs, the PH collects or conserves that heat and
humidity.
When this breath is exhaled, the gas passes
through the PH and the heat and humidity or
moisture is transferred to the PH.
When the second breath from the ventilator passes
through the PH, it picks up heat and humidity
from the PH and delivers it back to the patient’s
lungs and so on.
60

61. This continues and the patient’s moisture needs
are meet.
Many products fail to meet the patient’s needs
resulting in adverse events such as:
high pressure alarms, spontaneous
pneumothorax, thick secretions, endotube
occlusions, plugged airways, death and
more.
61

62. 62

63. 63

64. “Charging” is a function used by many
manufactures to explain why their devices
drain moisture from the patient’s breath.
“Coring” is the result from the charging process
and the drying of the patient – the yellow
spot on a cigarette filter is similar.
The longer you use this type PH, the more
problems you will encounter.
64

65. 65

66. 30/30
?
66

67. INDICATIONS:
 Humidification of inspired gas during mechanical
ventilation is mandatory when an endotracheal
or tracheostomy tube is present.
67

68. CONTRAINDICATIONS:
 Patients with preexisting pulmonary disease
characterized by thick, copious, or bloody
secretions should not use PH.
 Use of an PH is contraindicated for patients with
an expired tidal volume less than 70% of the
delivered tidal volume.
68

69. “The chosen
device should
provide a
minimum of
30 mg H2O/L of
delivered gas
at 30°C”.
30mg + 14mg = 44mg
69

70. 30/30
70

71. Filter
Design Cost
Dead space Resistance
Moisture
output
71

72. HME HMEF HCH HCHF
lowest highest
72

73. 73

74. Most product literature today is misleading.
 Resistance – wet? dry? first hour of use? last
hour of use?
 Does the device weight increase the longer it
is used?
 Does the moisture return remain constant
over 24 hours of use?
 Mg returned at what minute volume?
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77. 77

78. 78

79.  Third party, third party, third party - but who
funds the study?
 Does the investigator have a financial interest?
 In house studies are like calling your own balls
and strikes.
79

80. 80

81. Any patient on a ventilator shall have
30mg of moisture delivered at 300 C.
81

82. Spun Polypropylene/plastic - coated with CaCl-
82

83. This is a question that all RCPs should ask
themselves. It has certainly been asked by
researchers.
Regardless of what type of system is being used,
the clinician should question its effectiveness.
Since no system reports the actual amount of
humidity being delivered, other signs must be
relied on.
83

84.  Hygrometer will give baseline readings.
 Observation of the circuit elbow itself between
breaths for signs of small droplets of
moisture.
 Extra moisture condensation within the housing
of the passive humidifier would be an
indicator.
84

85.  Sputum evaluation.
 How many HME change outs per day.
 Viewing the circuit itself for signs of small
droplets of moisture.
 When heated humidifiers have been used, the
presence of these small droplets in the
chamber has been used as an indicator that
the gas is fully saturated but...
85

86. This is probably not an accurate method, since the
temperature of the gas that leaves the ventilator
can be quite high and will artificially raise the
point at which condensation appears.
High or low ambient room temperature would
influence the presence of moisture in the circuit.
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