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.