Advanced Issues in Advanced Issues in HumidificationHumidification

Presented by:Ruben Restrepo MD, RRT, FAARCProfessor , Department of Respiratory Care

The University of Texas Health Science Center, San Antonio

TELEFLEX MEDICAL

Medical Advisory Board

Speaker

COVIDIEN

Speaker, Consultant, and Investigator

SALTER LABS

Speaker and Consultant

FISHE & PAYKEL

Investigator

Disclosures

1. Discuss the impact of high and low ambient temperatures on heated humidification

2. Describe the role of inlet chamber gas temperatures on overall delivery of humidity

3. Discuss ventilator settings associated with significant changes in humidification

4. Discuss the relationship between aerosol therapy and heated humidification

Isothermic Saturation BoundaryIsothermic Saturation Boundary

Why Humidity Deficit?Why Humidity Deficit?•Effect of intubation

• Inspired gas AH is < BTPS• ISB is shifted down the

respiratory tract• Humidity comes from the

lower respiratory tract• Increased heat and

moisture loss from the airways

Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032

Typical Humidity ValuesTypical Humidity Values

Medical GasesMedical Gases Room Air Alveoli

Temperature 15ºC 20ºC 37ºC

RH 0-2% 50-60% 100%

AH 0-0.5 mg/L 8.7-10.4 mg/L 44 mg/L

RH 50% = not exactly 22 mg/LRH 50% = not exactly 22 mg/L

Supplemental heat and humidity

Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032

Adequate HumidificationAdequate Humidification• Heated humidification devices should at least mimic the physiologic

conditions

Relative Humidity

100%

Relative Humidity

100%

AbsoluteHumidity33.8-37.6Mg H2O/L

AbsoluteHumidity33.8-37.6Mg H2O/L

Temperature>340C

Temperature>340C

AdequateHumidification

AdequateHumidification

Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032

• Inadequate humidification → deleterious effects on airway mucosa.2

• Challenges:• Type of humidification device used• Issues external to humidifier’s function

1. AARC CPG. Respir Care 2012;12(57)5:782-7882. Williams R, et al. Crit Care Med. 1996;24:1920-1929.

• Humidification of inspired gases is standard of care for patients receiving mechanical ventilation (MV).1

•Recommended min water content (AH)

≥ 33 mg H2O/L of air (AH) = 75% RH

•Optimal AH

44 mg H2O/L at body Tº (37ºC) = 100% RH

•Heating unit should self-terminate at

Tº < 43ºC1 (tracheal thermal injury)

•Most HHs meet recommended Tº settings at normal conditions2,3

1. ISO 8185:2007 (3rd Ed)2. Williams RB. Respir Care Clin N Am. 1998;4(2):215-28.

3. AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788

37ºC for outlet chamber

43ºC at the Y piece

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AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788

10

KEY POINTS

Although modern active humidifiers can deliver gas at 41ºC at the Y-piece, a maximum delivered gas temperature of 37ºC and 100% RH (44 mg H2O/L) at the circuit Y-piece is recommended.

Insufficient heat and humidification can occur with HHs. Complications can occur when temperature selection is preset and nonadjustable, rather than based on clinical assessment.

NIV. Select gas temperatures during NIV based on patient comfort/tolerance/adherence and underlying pulmonary condition.

Change circuits as needed due to lack of functionality or when visibly soiled, unless otherwise specified by the manufacturer.

AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788

Every patient receiving invasive mechanical ventilation should get humidification. (1A)Active humidification is suggested for NIV, as it may improve adherence and comfort. (2B)When providing active humidification to patients who are invasively ventilated, the device should provide a humidity level between 33 mg H2O/L and 44 mg H2O/L, and a gas temperature between 34ºC and 41ºC at the circuit Y-piece, with an RH of 100%. (2B)When providing passive humidification to patients undergoing invasive mechanical ventilation, the HME should provide a minimum of 30 mg H2O/L. (2B)Passive humidification is not recommended for NIV. (2C)When providing humidification to patients with low tidal volumes, such as when lung-protective ventilation strategies are used, HMEs are not recommended because they contribute additional dead space, which can increase the ventilation requirement and PaCO2. (2B)HMEs should not be used as a prevention strategy for ventilator-associated pneumonia.(2B)

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AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788

• Factors that affect active humidification• Ambient temperature• Type of heater humidifier• Ventilator type and ventilator settings • Placement and removal of SVNs during MV• Humidification and heat effects on aerosol delivery

• Factors that affect passive humidification• Accumulation of condensate• Routine aerosol administered without

bypassing the HME• Increase airway resistance

Humidification delivery for these patients is still not considered standard of care in all clinical settings.

NIV reduces rate of intubations and adverse effects associated with invasive MV and bypassing the airway.1,2

1. Ambrosino, N Int J Chron Obstruct Pulmon Dis. 2007 December; 2(4): 471–476. 2. James CS, et al. Intensive Care Med 2011;37(12):1994-2001

HHs are considered the most efficient method of optimizing gas for patients with an artificial airway.1,2

HHs have been associated with higher rates of obstruction of artificial airway than HMEs.3 

1. Ricard JD, et al. Chest. 1999;115:1646-1652. 2. Diehl JL, et al. Am J Respir Crit Care Med. 1999;159:383–388.

3. Lacherade J-C, et al. Am J Respir Crit Care Med. 2005;172:1276-1282. .

• Good understanding of HH function and how different clinical conditions is critical.  

• HHs control Tº, not humidity levels.• Gas Tº at the HH inlet can be as high as 40ºC

(dry part of circuit).

Lellouche F, et al. Am J Respir Crit Care Med. 2004;170:1073-1079.

Heated Humidifier

• Gas passes over heated water Humidity of gas ↑ as Tº of gas ↑ Humidity is controlled by manipulating

water temperature in the reservoir

• Modified passover design Paper wick increases surface area

Ventilator

HumidifierChamber

Example: Example: Chamber T = 37°Chamber T = 37°

°°

Routine check of the HH and breathing circuit:

• Small amount of condensate or “rainout” = visible sign of humidity production

• Amount of condensate ≈ rate of water loss from the chamber

• May indicate suboptimal Tº setting in the HH

• Possible adjustments: Lowering humidifier T° Heated-wires can control Tº drop between the HH and

the patient → reduce condensate

• Ambient air temperatures• Humidifier inlet gas temperature (ventilator

outlet gas temperature)• Ventilator settings (including flows and minute

volumes)• Concomitant use of aerosol therapy while

administering active humidification

• Ambient air temperatures (high vs. low)• Humidifier inlet gas temperature (Ventilator

outlet gas temperature)• Ventilator settings (including flows and minute

volumes)• Concomitant use of aerosol therapy while

administering active humidification

• High ambient Tº = greatest influence on HH performance.1

• Ambient Tº in ICUs 22.0ºC‒30.0ºC.• Factors associated with increased ambient air

Tº: Inadequate air conditioning Burn units Neonatal units2

Warm conditions proximal to the humidifier 1. Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.

2. Todd DA, et al. J Paediatr Child Health. 2001;37(5):489-94.

Ambient air Tº > 28-30ºC

▼

Reduction in humidity levelsIncreased inlet Tº prevents heater plate

warming water inside the chamber

Dry Hot Air

Lower Heater Plate Tº

▼ Humidity Level

1. Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.

Large drops in ambient Tº ▼

Cooling of gas travels through the humidifier and circuit ▼

excess condensate

(avoid “lavaging” patient’s airway)

• Ambient air temperatures• Humidifier inlet gas temperature (ventilator

outlet gas temperature)• Ventilator settings (including flows and minute

volumes)• Concomitant use of aerosol therapy while

administering active humidification

• High inlet gas Tº = lower humidity production:1

From ≈ 36 mg H2O/L at chamber temp 18ºC

(82% relative humidity at 37ºC) To 26 mg H2O/L at 32ºC

(59% relative humidity at 37ºC)

• Critical impact on the amount of condensate in the breathing circuit

Carter BG, J Aerosol Med. 2002;15:7-13. International Organization for Standardization. ISO 8185:2007

Dry Hot Air

Lower Heater Plate Tº

▼ Humidity Level

• Most commonly used MVs in ICUs warm oxygen and air.

• Warming effect of different ventilators shown in several studies evaluating ventilator outlet gas Tº.1,2

• High speeds of turbine-powered vs. gas-powered ventilators generate the highest outlet Tº.2

LTV-1000 Vela

1. Carter BG, J Aerosol Med. 2002;15:7-13.2. Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.

USE THIS SLIDE OR FOLLOWING SLIDE

VentilatorVentilator Outlet Gas Tº

Min–Max T (ºC)

VIP 29.6 - 33.2

T Bird 36.0 – 45.1

Infant Star 27.9 - 30.0

EVITA 2 27.9 - 29.6

EVITA 4 30.2 – 35.8

3100A 24.4 - 27.3

1. Carter BG, J Aerosol Med. 2002;15:7-13.

Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.

• Extending length of inspiratory tubing prior to the heating chamber (“drop line”) may offset high Tº at the gas outlet. Drop line allows humidifier inlet Tº to decrease.

• Ambient air temperatures• Humidifier inlet gas temperature (Ventilator

outlet gas temperature)• Ventilator settings (pressure, flow and VE)• Concomitant use of aerosol therapy while

administering active humidification

• High VE reduces the time gas stays in the water reservoir, significantly decreasing HH performance.

• Changes in I:E ratio and inspiratory flow do not affect Tº or humidity.

Nishida T, et al. J Aerosol Med. 2001;14(1):43-51.

• Increases in Paw, VE, and flow increase ventilator load = increased operating Tº of most ventilator driving systems.

• Ambient air temperatures• Humidifier inlet gas temperature (Ventilator

outlet gas temperature)• Ventilator settings (including flows and minute

volumes)• Concomitant use of aerosol therapy while

administering active humidification

• Humidification is essential for patients on MV receiving aerosolized medications.

• Effects of humidification on aerosol delivery and lung deposition may differ according to the type of system used.

Dhand R. J Aerosol Med Pulm Drug Deliv. 2012;25(2):63-78.

• Ventilator• Circuit

• Type of circuit• Inhaled gas humidity• Inhaled gas density

• Type of Interface• Device nebulizer / pMDI• Drug• Patient

• Aerosol delivery is proportional to gas Tº change in the ventilator circuit. • 25ºC to 37ºC = increase inhaled drug mass up to 25%.

(faster evaporation = accelerates delivery rate of small particles).1

• Positive effect of higher gas Tº on aerosol efficiency is negated by drastic effects of increased water vapor in the delivered gas.2,3

• Aerosol delivery is INVERSELY proportional to water vapor content in the ventilator circuit.

1. Lange Am J Respir Crit Care Med Vol 161. pp 1614–1618, 20002.. Garner SS Pharmacotherapy. 1994;14:210-214.3. Dhand R, et al. Eur Respir J. 1996; 9(3):585-595.

SVN •High RH and Tº in circuit = large reductions of lung dose.

pMDI

No significant differences on mass median aerodynamic diameter (MMAD) with dry vs. high RH.1

•Clinicians often turn off HH before administering aerosols. Failure to turn on after tx = inadequate humidification. Turning heater off prior to tx does not result in greater

aerosol drug delivery. 1. Lin HL, et al. Respir Care. 2009;54(10):1336-41. 2. Lange C, et al. Am J Respir Crit Care Med. 2000;161(5):1614-1618.

3. Zhou Y, et al. J Aerosol Med. 2005;18(5):283-293.4. Kim CS, et al. Am Rev Respir Dis. 1985;132(1):137-142.

O’Riordan TG, et al. Am Rev Respir Dis. 1992;145:1117–1122. Fuller HD, et al. Chest 1994;105:214-218Fink JB, et al. Am J respir Crit Care Med 1996;154:382-387 Diot P, et al. Am J Respir Crit Care Med 1995;152:1391-1394

1. Fink, et al. Am J Respir Crit Care Med. 1996;154:382-387.2. Ari A, et al. Respir Care. 2010;55:837-44.

Aerosol Placement and HH FunctionAerosol Placement and HH Function

• Placement of the aerosol generator device affects aerosol delivery efficiency and may also affect HH.

• Heated wires prevent placement of aerosol devices halfway between the humidifier and the Y piece.

• If a SVN is placed at the humidifier outlet chamber, cold gas may cause humidifier overheating.

• Placement of nebulizer at the inlet of the HH chamber will prevent overheating, as the aerosol and gas from the ventilator are heated before exiting the humidifier, potentially improving drug deposition.

Ari A, et al. Respir Care. 2010;55:837-44.

Dhand R. J Aerosol Med Pulm Drug Deliv. 2012;25(2):63-78.

• The level of humidification in NIV is influenced by several factors.

• Optimal humidification may affect dosing.

Aerosol Generator Placement and HMEAerosol Generator Placement and HME

• Use of HMEs is a routine practice in many ICUs.• It is common to place the aerosol generator between the

HME and the Y piece to administer aerosolized treatments to patients receiving MV.

• Contraindication for HME use = need for aerosol therapy

• Performance of HHs can be greatly affected by conditions external to humidifier function.

• High ambient air Tº is associated with high inlet chamber temperatures and poor HH performance.

• Very high ambient Tº, the Tº of the chamber water may be too low to evaporate—causing an extremely low level of AH.

• To optimize HH performance, closely monitor inlet chamber gas Tº.

• The presence of heated wires may help only to maintain the set outlet chamber Tº.

• Varying Tº gradients vs. using fixed Tº gradient (i.e., between the outlet chamber and Y piece Tº) may improve humidification in a variety of clinical scenarios.

• Alternatively, use compensation features incorporated into some HHs.

Lin, H RESPIRATORY CARE • OCTOBER 2009 VOL 54 NO 10Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-1079.

• There is a dramatic reduction of aerosol delivery in humidified conditions.

• Conditions that facilitate the accumulation of condensate on the ventilator circuit and the spacer may adversely affect aerosol lung delivery and clinical response.

Lin, H RESPIRATORY CARE • OCTOBER 2009 VOL 54 NO 10

• Humidification devices that control the humidifier outlet Tº independently of ambient air Tº, ventilator gas output, or ventilator settings appear to be the logical approach to optimizing humidifier function.

Additional Information

• This webinar is archived on www.clinicalfoundations.org