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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. TELEFLEX MEDICAL Medical Advisory Board Speaker COVIDIEN Speaker, Consultant, and Investigator SALTER LABS

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  1. Advanced Issues in HumidificationPresented by:Ruben Restrepo MD, RRT, FAARCProfessor , Department of Respiratory CareThe University of Texas Health Science Center, San Antonio

  2. TELEFLEX MEDICAL Medical Advisory Board Speaker COVIDIEN Speaker, Consultant, and Investigator SALTER LABS Speaker and Consultant FISHE & PAYKEL Investigator Disclosures

  3. Learning Objectives • 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

  4. Why Humidity Deficit? Effect of intubation Inspired gas AH is < BTPS ISB is shifted down the respiratorytract Humiditycomes from the lowerrespiratorytract Increased heat and moisture loss from the airways Isothermic Saturation Boundary Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032

  5. Typical Humidity Values RH 50% = not exactly 22 mg/L Supplemental heat and humidity Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032

  6. Heated humidification devices should at least mimic the physiologic conditions Adequate Humidification Temperature >340C Adequate Humidification Relative Humidity 100% Absolute Humidity 33.8-37.6 Mg H2O/L Teleflex Advances in Respiratory Therapy. Humidification Basics: Module 1 2010-0032 ISO = 33 mg/L

  7. Standard of Care • Inadequate humidification → deleterious effects on airway mucosa.2 • Challenges: • Type of humidification device used • Issues external to humidifier’s function • Humidification of inspired gases is standard of care for patients receiving mechanical ventilation (MV).1 1. AARC CPG. Respir Care 2012;12(57)5:782-788 2. Williams R, et al. Crit Care Med. 1996;24:1920-1929.

  8. Humidification Standards • 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 • 37ºCfor outlet chamber • 43ºCat the Y piece 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

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

  10. AARC Clinical Practice GuidelineRESPIRATORY CARE • MAY 2012 Vol 57 No 5 • 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

  11. Evidence-Based Recommendations, AARC Clinical Practice Guideline (2012) AARC Clinical Practice Guideline. Respir Care. 2012:12(57)5:782-788 1 2 3 4 5 67 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)

  12. Humidification During CMV • 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

  13. Humidification During NIV 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

  14. Heated Humidifiers  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. .

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

  16. Heated Humidifiers 101 • HHs control Tº, not humidity levels. • Gas Tº at the HH inlet can be as high as 40ºC (dry part of circuit). TEMPERATURE  HUMIDITY  Lellouche F, et al. Am J Respir Crit Care Med. 2004;170:1073-1079.

  17. 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

  18. HH – Temperature Gradients Ventilator ° Example: Chamber T = 37° Humidifier Chamber

  19. HH – Temperature Gradients

  20. “Rainout” in the Ventilator Circuit 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

  21. Controlling Excessive Condensate • 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

  22. Troubleshooting Condensation

  23. Factors Affecting Humidification • 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

  24. Factors Affecting Humidification (cont’d) • 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

  25. Conditions that Ambient Air T° • 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 RespirCrit Care Med. 2004;1073-1079. 2. Todd DA, et al. J Paediatr Child Health. 2001;37(5):489-94.

  26. High Ambient Air Temperature (Tº) Ambient air Tº > 28-30ºC ▼ Reduction in humidity levels Increased inlet Tº prevents heater plate warming water inside the chamber ▼ Humidity Level Dry Hot Air Lower Heater Plate Tº 1. Lellouche L, et al. Am J RespirCrit Care Med. 2004;1073-1079.

  27. Low Ambient Air Temperature (Tº) Large drops in ambient Tº ▼ Cooling of gas travels through the humidifier and circuit ▼ excess condensate (avoid “lavaging” patient’s airway)

  28. Factors Affecting Humidification (cont’d) • 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

  29. High Humidifier Inlet Gas Temperatures ▼ Humidity Level Dry Hot Air Lower Heater Plate Tº Carter BG, J Aerosol Med. 2002;15:7-13. International Organization for Standardization. ISO 8185:2007 • 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

  30. Variation in Ventilator Outlet Gas T° • 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 RespirCrit Care Med. 2004;1073-1079.

  31. Variation in Ventilator Outlet Gas Tº1 USE THIS SLIDE OR FOLLOWING SLIDE 1. Carter BG, J Aerosol Med. 2002;15:7-13.

  32. Effect of Ambient Air Temp, Ventilator Type, and VE on Ventilator Output and Inlet Chamber Temperature Lellouche L, et al. Am J RespirCrit Care Med. 2004;1073-1079.

  33. Changing Gas Outlet Tº– Drop Lines • 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.

  34. Factors Affecting Humidification (cont’d) • 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

  35. Ventilator Settings • High VE reduces the time gas stays in the water reservoir, significantly decreasing HH performance. • Changes in I:E ratio and inspiratory flow do notaffect Tº or humidity. • Increases in Paw, VE, and flow increase ventilator load = increased operating Tº of most ventilator driving systems. Nishida T, et al. J Aerosol Med. 2001;14(1):43-51.

  36. Factors Affecting Humidification (cont’d) • 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

  37. Mechanical Ventilation and Aerosol Administration • 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.

  38. Factors Affecting Aerosol Delivery • Ventilator • Circuit • Type of circuit • Inhaled gas humidity • Inhaled gas density • Type of Interface • Device nebulizer / pMDI • Drug • Patient Dhand R. J Aerosol Med Pulm Drug Deliv. 2012;25(2):63-78.

  39. Aerosol Administration and Heater Tº • 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, 2000 2.. Garner SS Pharmacotherapy. 1994;14:210-214. 3. Dhand R, et al. Eur Respir J. 1996; 9(3):585-595.

  40. SVN vs. pMDI Administration and Heater Tº 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.

  41. Effect of Humidity on Aerosol Delivery in Patients Receiving Invasive MV DhandR. J Aerosol Med 2012;25(2)63-79 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

  42. 2 1 3 • Fink, et al. Am J Respir Crit Care Med. 1996;154:382-387. • Ari A, et al. Respir Care. 2010;55:837-44.

  43. 2 3

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

  45. Effect of Humidity on Aerosol Delivery in Patients Receiving NIV • The level of humidification in NIV is influenced by several factors. • Optimal humidification may affect dosing. Dhand R. J Aerosol Med Pulm Drug Deliv. 2012;25(2):63-78.

  46. 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

  47. Summary • 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.

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