UTMB RESPIRATORY CARE SERVICES
PROCEDURE - Heat and Humidity in Mechanical
Ventilation
Policy 7.3.53
Page 1 of 6
Mechanical Ventilation
Effective:
Revised:
Reviewed:
Formulated: 07/10
07/10/10
Heat and Humidity in Mechanical Ventilation
Purpose
To assure proper conditioning of mechanically ventilated patient’s inspired
gas.
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. This may be
accomplished using either a heated humidifier or a heat and moisture
exchanger (HME). (HMEs are a.k.a. hygroscopic condenser humidifiers or
artificial noses). The chosen device should provide a minimum of 30 mg
H2O/L of delivered gas at 30°C. Heated humidifiers operate actively to
increase the heat and water vapor content of inspired gas. HMEs operate
passively by storing heat and moisture from pt's exhaled gas and releasing it
to the inhaled gas.
Policy

Humidification is provided to all patients requiring mechanical
ventilation via an artificial airway. Conditioning of inspired gases
should be instituted using either an HME (if not contraindicated) or
a heated humidifier.

HMEs may be used for short-term use (< or = 96 hours) and during
transport.

Heated humidifiers will be used for patients requiring long term
mechanical ventilation (> 96 hours) or for patients who exhibit
contraindications for HME use.

HME's will be discarded and replaced with new daily.

HME's will be replaced with heated humidifiers after 96 hours of
use.
 HME's will be replaced with heated humidifiers if any of the
Hazards/Complications of HME's are observed.
Equipment
Humidification device:
Active: A Heated humidifier; that provides a minimum of 30 mg H2O/L of
delivered gas at 30°C. Such devices should incorporate a system to monitor
inspired gas temperature and to alarm when the temperature falls outside a
preset range.
Sterile water for heated humidifiers
Passive: HME; a.k.a. hygroscopic condenser humidifiers should operate at
Continued next page
UTMB RESPIRATORY CARE SERVICES
PROCEDURE - Heat and Humidity in Mechanical
Ventilation
Policy 7.3.53
Page 2 of 6
Mechanical Ventilation
Effective:
Revised:
Reviewed:
Formulated: 07/10
07/10/10
70% efficiency or better ( Providing at least 30 mg/L Water vapor).
Indications
Humidification of inspired gas during mechanical ventilation is mandatory
when an endotracheal or tracheostomy tube is present.
Contraindic
ations:
There are no contraindications to providing physiologic conditioning of
inspired gas during mechanical ventilation.
An HME is contraindicated under some circumstances:

Use of an HME is contraindicated for patients with thick, copious,
or bloody secretions.

Use of an HME is contraindicated for patients with an expired tidal
volume less than 70% of the delivered tidal volume (e.g. those with
large bronchopleurocutaneous fistulas or incompetent or absent
endotracheal tube cuffs).

Use of an HME is contraindicated for patients with body
temperatures less than 32°C.

Use of an HME may be contraindicated for patients with high
spontaneous minute volumes (> 10L/min).
An HME must be removed from the patient circuit during aerosol
treatments when the nebulizer is placed in the patient circuit.
Procedure
Step
1
Action
Select a humidification device in accordance with
policy.
If an HME is chosen
Place the HME in the circuit between the inspiratory and
expiratory limb (so both inspired and expired gas passes
through it).
2
Attach the circuit to the patient's endotracheal or
tracheostomy tube.
3
Inspect HME with patient/ventilator system checks and
prn. Replace the HME anytime secretions contaminate
the insert or filter.
Continued next page
UTMB RESPIRATORY CARE SERVICES
PROCEDURE - Heat and Humidity in Mechanical
Ventilation
Policy 7.3.53
Page 3 of 6
Mechanical Ventilation
Effective:
Revised:
Reviewed:
Formulated: 07/10
07/10/10
Procedure
Continued
Step
4
Action
If a heated humidifier is chosen
Set up unit in accordance with manufacturer's
instructions and place in inspiratory limb of circuit.
Hazards/Co
mplications:
5
Connect water supply as instructed by manufacturer.
6
Place temperature probe to monitor temperature as near
the patient's airway opening as possible
7
Turn heater unit on and set temperature to maintain
inspired gas at 33 ± 2°C .
8
Set high temperature alarm no higher than 37°C, and the
low temperature alarm no lower than 30°C.
9
Check the humidification device as well as inspired gas
temperature, water level and function of automatic feed
system (if applicable) during the patient-ventilator
system checks and prn.
10
If using heated wire circuit adjust wire heat to maintain
some condensate in the inspiratory limb of the circuit.
Remove excess condensate from the patient circuit as
necessary.

Both HME's and heated humidifiers.

Hypothermia--HME or heated humidifiers.

Underhydration and impaction of mucus secretions--HME or heated
humidifiers.

Hypoventilation and/or alveolar gas trapping due to mucus plugging
of airways--HME or heated humidifier.

Possible increased resistive work of breathing due to mucus
plugging of airways--HME or heated humidifiers.

Possible increased resistive work of breathing through the
humidifier--HME or heated humidifiers.
Continued next page
UTMB RESPIRATORY CARE SERVICES
PROCEDURE - Heat and Humidity in Mechanical
Ventilation
Policy 7.3.53
Page 4 of 6
Mechanical Ventilation
Effective:
Revised:
Reviewed:
Formulated: 07/10
07/10/10
HME's only:

Possible hypoventilation due to increased dead space--HME.

Ineffective low-pressure alarm during disconnection due to
resistance through HME.
Heated humidifiers only:

Inadvertent overfilling resulting in unintentional tracheal lavage-heated reservoir humidifiers.

Some ventilators generate a high flow through the patient circuit that
may aerosolize contaminated condensate, putting both the patient
and clinician at risk for nosocomial infection--heated humidifiers.

Elevated airway pressures or inadvertent tracheal lavage from
pooled condensate in patient circuit--heated humidifiers.

Patient-ventilator dysynchrony and improper ventilator performance
due to pooled condensation in the circuit--heated humidifiers.

Hyperthermia or thermal injury to the airway from heated
humidifiers; burns to the patient and tubing meltdown if heated-wire
circuits are covered or circuits and humidifiers are incompatible.

Potential for electrical shock or burns --heated humidifiers.
Frequency:
All patients with an artificial airway requiring mechanical ventilation
should receive continuous humidification of inspired gases.
Infection
Control
Follow procedures outlined in Healthcare Epidemiology Policies and
Procedures #2.24; Respiratory Care Services.
http://www.utmb.edu/policy/hcepidem/search/02-24.pdf
Infection
Control
Follow procedures outlined in Healthcare Epidemiology Policies and
Procedures #2.24; Respiratory Care Services.
Heated humidifier
Sterile water should be used.
When using a closed, automatic feed system, the unused portion of water in
the water feed reservoir remains sterile and need not be discarded when the
Continued next page
UTMB RESPIRATORY CARE SERVICES
PROCEDURE - Heat and Humidity in Mechanical
Ventilation
Policy 7.3.53
Page 5 of 6
Mechanical Ventilation
Effective:
Revised:
Reviewed:
Formulated: 07/10
07/10/10
patient circuit is changed. However, the water feed system should be
designated for single patient use only.
Because condensate is potentially infectious waste, it should never be
drained back into the humidifier reservoir. (somewhat controversial - gas
flow through certain reservoirs can produce aerosol, others may not)
http://www.utmb.edu/policy/hcepidem/search/02-24.pdf
Source/Refe
rences:
AARC Clinical Practice Guideline - Humidification during Mechanical
Ventilation. Respir Care 1992;37:887-890 .
* HME are preferred in short term ventilation (see Policy 7.4.24; Addendum)
Continued next page
UTMB RESPIRATORY CARE SERVICES
PROCEDURE - Heat and Humidity in Mechanical
Ventilation
Policy 7.3.53
Page 6 of 6
Mechanical Ventilation
Effective:
Revised:
Reviewed:
Formulated: 07/10
Safety


07/10/10
All alarms on ventilators will be activated at all times.
Anesthesia gases will not be administered through ventilator.
Correspond- Respiratory Care Services Policy # 7.4.11; Operating Instructions For Adult
Microprocessor Controlled Ventilators
ing Policies
References
AARC Clinical Practice Guidelines; Patient-Ventilator System Checks,
Respiratory Care; 1992; 37: 882-886
AARC Clinical Practice Guidelines; Humidification During Mechanical
Ventilation, Respiratory Care; 1992; 37: 887-890
Donald F. Egan, Craig L. Scanlan, Robert L. Wilkins, James K. Stoller,
Egan's Fundamentals of Respiratory Care, Eighth Edition, Mosby; June 2,
2003
Dean Hess, Robert Kacmarek, Essentials of Mechanical Ventilation,
McGraw-Hill Professional; 1st edition (March 1, 1996)
Ventilator Operating Manuals