Post on 05-Mar-2018
Advanced Issues in Humidification
Presented by:
Ruben Restrepo MD, RRT, FAARC Professor , Department of Respiratory Care
The University of Texas Health Science Center, San Antonio
• Advisory Board and Speaker for TELEFLEX • Speaker and Investigator for ORIDION CAPNOGRAPHY
(COVIDIEN)
No off-label use of products are discussed in this webinar.
Continuing Education Credit (CRCE)
• The AARC has approved this program for 1.0 contact hour of CRCE.
• At the end of this webinar, you can obtain those continuing education credits by logging on to www.saxetesting.com/cf
• Complete the post-test and evaluation form. • Upon successful submission, you will be able to print
your certificate of completion.
Accreditation • American Association for Respiratory Care, 9425 N.
MacArthur Blvd., Suite 100, Irving, TX 75063.
At the conclusion of this webinar, participants will be able to: • Discuss the impact of high and low ambient
temperatures on heated humidification • Describe the role of inlet chamber gas temperatures on
overall delivery of humidity • Discuss ventilator settings associated with significant
changes in humidification • Discuss the relationship between aerosol therapy and
heated humidification
Isothermic Saturation Boundary
Why Humidity Deficit? • Effect of intuba.on
• Inspired gas AH is < BTPS • ISB is shi=ed down the respiratory tract
• Humidity comes from the lower respiratory tract
• Increased heat and moisture loss from the airways
Typical Humidity Values Medical 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/L
Supplemental heat and humidity
Adequate Humidification • Heated humidifica.on devices should at least mimic the
physiologic condi.ons
Relative Humidity
100%
Absolute Humidity 33.8-37.6 Mg H2O/L
Temperature >340C
Adequate Humidification
Modified from: Sottiaux TM. Respir Care Clinics North Am. 2006;12(2):233-252.
• 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-‐788 2. 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 2007:8185 (3rd Ed) 2. Williams RB. Respir Care Clin N Am. 1998;4(2):215-‐28.
3. AARC Clinical Prac.ce Guideline. Respir Care. 2012:12(57)5:782-‐788
37ºC for outlet chamber
43ºC at the Y piece
10
AARC Clinical Practice Guideline
Humidification During Invasive and NoninvasiveMechanical Ventilation: 2012
Ruben D Restrepo MD RRT FAARC and Brian K Walsh RRT-NPS FAARC
We searched the MEDLINE, CINAHL, and Cochrane Library databases for articles publishedbetween January 1990 and December 2011. The update of this clinical practice guideline is basedon 184 clinical trials and systematic reviews, and 10 articles investigating humidification duringinvasive and noninvasive mechanical ventilation. The following recommendations are made follow-ing the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) scoringsystem: 1. Humidification is recommended on every patient receiving invasive mechanical ventila-tion. 2. Active humidification is suggested for noninvasive mechanical ventilation, as it may improveadherence and comfort. 3. When providing active humidification to patients who are invasivelyventilated, it is suggested that the device provide a humidity level between 33 mg H2O/L and44 mg H2O/L and gas temperature between 34°C and 41°C at the circuit Y-piece, with a relativehumidity of 100%. 4. When providing passive humidification to patients undergoing invasivemechanical ventilation, it is suggested that the HME provide a minimum of 30 mg H2O/L. 5. Passivehumidification is not recommended for noninvasive mechanical ventilation. 6. When providinghumidification to patients with low tidal volumes, such as when lung-protective ventilation strate-gies are used, HMEs are not recommended because they contribute additional dead space, whichcan increase the ventilation requirement and PaCO2
. 7. It is suggested that HMEs are not used as aprevention strategy for ventilator-associated pneumonia. Key words: active humidification, heat andmoisture exchanger, heated humidifier, hydrophobic, hygroscopic condenser humidification, passivehumidification. [Respir Care 2012;57(5):782–788. © 2012 Daedalus Enterprises]
HMV 1.0 DESCRIPTION
When the upper airway is bypassed during invasive me-chanical ventilation, humidification is necessary to preventhypothermia, disruption of the airway epithelium, bron-chospasm, atelectasis, and airway obstruction. In severe
cases, inspissation of airway secretions may cause occlu-sion of the endotracheal tube.1 While there is not clearconsensus on whether or not additional heat and humidityare always necessary when the upper airway is not by-passed, such as in noninvasive mechanical ventilation(NIV), active humidification is highly suggested to im-prove comfort.2-7
Two systems, active humidification through a heatedhumidifier (HH) and passive humidification through a heatand moisture exchanger (HME), are available for warmingand humidifying gases delivered to mechanically venti-lated patients. There are 3 types of HME or artificial nose:hydrophobic, hygroscopic, and a filtered HME.
Heated humidifiers operate actively to increase the heatand water vapor content of inspired gas.8 HMEs operatepassively by storing heat and moisture from the patient’sexhaled gas and releasing it to the inhaled gas.9
The upper airway provides 75% of the heat and mois-ture supplied to the alveoli. When bypassed, the humidi-fier needs to supply this missing heat and moisture. Since
Ruben D Restrepo MD RRT FAARC is affiliated with the Department ofRespiratory Care, The University of Texas Health Sciences Center at SanAntonio, San Antonio, Texas. Brian K Walsh RRT-NPS FAARC isaffiliated with the Respiratory Care Department, Children’s Medical Cen-ter, Dallas, Texas.
The authors have disclosed a relationship with Teleflex Medical, whichmanufactures humidification devices.
Correspondence: Ruben D Restrepo MD RRT FAARC, Department ofRespiratory Care, The University of Texas Health Sciences Center at SanAntonio, 7703 Floyd Curl Drive, MSC 6248, San Antonio TX 78229.E-mail: restrepor@uthscsa.edu.
DOI: 10.4187/respcare.01766
782 RESPIRATORY CARE • MAY 2012 VOL 57 NO 5
AARC Clinical Prac.ce Guideline. Respir Care. 2012:12(57)5:782-‐788
11
KEY POINTS Although modern ac.ve 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 humidificaNon can occur with HHs. Complica.ons can occur when temperature selec.on is preset and nonadjustable, rather than based on clinical assessment.
NIV. Select gas temperatures during NIV based on pa.ent comfort/tolerance/adherence and underlying pulmonary condi.on.
Change circuits as needed due to lack of func.onality or when visibly soiled, unless otherwise specified by the manufacturer.
AARC Clinical Prac.ce Guideline. Respir Care. 2012:12(57)5:782-‐788
Every pa.ent receiving invasive mechanical ven.la.on should get humidifica.on. (1A) Ac.ve humidifica.on is suggested for NIV, as it may improve adherence and comfort. (2B) When providing ac.ve humidifica.on to pa.ents who are invasively ven.lated, 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 humidifica.on to pa.ents undergoing invasive mechanical ven.la.on, the HME should provide a minimum of 30 mg H2O/L. (2B) Passive humidifica.on is not recommended for NIV. (2C) When providing humidifica.on to pa.ents with low .dal volumes, such as when lung-‐protec.ve ven.la.on strategies are used, HMEs are not recommended because they contribute addi.onal dead space, which can increase the ven.la.on requirement and PaCO2. (2B) HMEs should not be used as a preven.on strategy for ven.lator-‐associated pneumonia.(2B)
1 2 3 4 5 6 7 AARC Clinical Prac.ce 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
James CS, et al. Intensive Care Med 2011;37(12):1994-‐2001
þ HHs are considered the most efficient method of optimizing gas for patients with an artificial airway.1,2
ý 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.
þý
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
Humidifier Chamber
37º
Preset T°
Tº decreases as gas travels through inspiratory limb between ventilator HH outlet and the wye adapter.
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 levels Increased 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
Interna.onal Organiza.on for Standardiza.on. ISO 2007;8185
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
VenNlator VenNlator 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. Lellouche L, et al. Am J Respir Crit Care Med. 2004;1073-‐1079.
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
• Aerosol delivery is INVERSELY proportional to water vapor content in the ventilator circuit.
1. Garner SS Pharmacotherapy. 1994;14:210-‐214. 2. Dhand R, et al. Eur Respir J. 1996; 9(3):585-‐595.
SVN • High RH and Tº in circuit = large reductions of lung dose. • 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. § This practice should be abandoned.
pMDI No significant differences on mass median aerodynamic diameter (MMAD) with dry vs. high RH.1
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-‐218
Fink 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 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.
Dhand R. J Aerosol Med Pulm Drug Deliv. 2012;25(2):63-‐78.
• The level of humidifica.on in NIV is influenced by several factors.
• Op.mal humidifica.on may affect dosing.
Aerosol 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 § Up to 35% greater airway resistance
Hart MT, et al. Respir Care. 2009;54(11):1524.
• 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.
• 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.
• 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.
Continuing Education Credit (CRCE)
• At the end of this webinar, you can obtain 1.0 contact hour by going to www.saxetesting.com/cf
• Complete the post-test and evaluation form. • Upon successful submission, you can print your
certificate of completion.
Questions?
Additional Information
• This webinar will archived on www.clinicalfoundations.org
in 7‒10 days.
• A .pdf of Dr. Restrepo’s slides will also be available to download at that time.
• Answers to some questions not addressed during the webinar will also be posted on the website.