Humidificación Activa Vs. Humidificación Pasiva - Dr. Santiago Esquivel - Dr. Matías Herrera

Main ideas, concepts, and lessons

• Core purpose of humidification in ventilated patients

  • The upper airway normally helps generate adequate ventilation, warmth, and filtration of inspired gases.
  • If upper-airway conditioning is poor (e.g., insufficient humidification), the respiratory epithelium can be damaged, especially in the pharynx (rich vascular network), leading to impaired function.

• Why humidity matters physiologically

  • As air travels from the pharynx toward lower airways, it progressively warms and humidifies.
  • Recommended targets (as stated):
    • Absolute humidity: ~44 mg/L
    • Relative humidity: ~100%
  • Poor humidification contributes to:
    • Mucus transport dysfunction
    • Airway dehydration
    • Higher risk of endotracheal tube obstruction from thick secretions
    • Increased infection risk (for both active and passive systems)

• General guideline targets and standards

  • The American Respiratory Care Association (as cited) recommends basic conditions:
    • > 30 mg/L absolute humidity
    • 100% / near-target humidity (subtitles were inconsistent; intent was described as ~100%)
    • Temperature between 31 and 35°C
  • Evidence cited as limited (“not well documented”), but clinical experience suggests risk from prolonged inadequate humidification, including if humidification is not used from the beginning.

• Ventilator viral protection and filtering principles

  • Humidification devices and filters are discussed together because they both:
    • Condition inspired gases (heat + moisture)
    • Filter viral/bacterial particles to reduce environmental contamination
  • Airborne particle size mentioned: 0.1 to 1.2 microns (within filterable range).

• Key trade-offs: dead space and resistance (especially in children)

  • Filters create additional dead space and can increase resistance, which is especially important in pediatric ventilation.
  • Dead space/resistance may impact outcomes by:
    • Worsening CO₂ clearance (risk of hypercapnia)
    • Increasing work of breathing and ventilatory load
    • Possibly affecting mortality indirectly (via ventilation mechanics and low tidal volumes)
  • Pediatric examples were given showing how filter-induced dead space can become a large fraction of tidal volume in small children.

• Active vs. passive humidification (why a choice is recommended)

  • Active humidification (heater + humidifier control)
    • Intended to reach higher and more controlled absolute humidity (closer to ~40–44 mg/L).
    • Maintains a more “closed” water vapor system; vapor was described as smaller than 5 microns and not carrier-like for pathogens (as argued).
    • May allow fewer interruptions/openings of circuits than passive systems in practice.
  • Passive humidification (heat-and-moisture exchanger style)
    • Often believed to be cheaper/less complex, but may be less able to maintain high humidity targets—sometimes “lucky to reach” ~30 mg/L (as claimed).
    • Can still be effective in many cases if filtration/humidity are properly managed.

• Practical device selection principles

  • Emphasis on:
    • Preventing leaks around masks/interfaces (leaks reduce humidification effectiveness)
    • Using the right filter with appropriate placement (in inspiratory vs expiratory limb depending on system type and whether the humidifier is active/passive)
    • Choosing based on patient factors: tidal volume, secretions, circuit type, pathology, and pediatric considerations
  • Warned to avoid or use extreme caution with filters when:
    • Copious/bloody secretions
    • Pleural fistula scenarios (as stated)
    • Protective ventilation with low tidal volumes (dead space/resistance concerns)
    • Hypothermia (<32°C) in some circumstances (as stated)
    • Obstructive pathology where increased dead space may worsen CO₂ retention

• Filter types mentioned and what each accomplishes

  • HEPA filters: high-efficiency filtration of airborne particulate matter (viral/bacterial).
  • Heat and Moisture Exchanger (HME/HM): humidifies (not necessarily a strong filter by itself).
  • HM + filter (HM-EFE / HM+ filter; terminology varies):
    • Combines heat/humidity exchange with filtration.
  • Mechanical filters:
    • Filter paper + absorbent surface; used commonly in Latin America.
  • Electrostatic filters:
    • Filament network with salts to increase efficiency.
  • Some devices are “modifier-only” (don’t filter); placement can enable aerosol therapy (as described).

• How to choose filters (detailed selection criteria)

  • Because characteristics may not be printed clearly on the filter back, the speaker recommends evaluating:
    • Dead space (especially important for children)
    • Recommended volume/tidal volume range the filter can handle
    • Humidity output (generated humidity)
    • Filtration efficiency (%)
      • Target stated: 90% to 99.9%
      • HEPA designations mentioned: H12, H3 (examples)
    • Resistance the filter introduces
    • Compressible volume
    • Weight (important in pediatric circuits because it can affect traction)

• Filter placement concepts (where suggested)

  • Several circuit schematic ideas were discussed depending on:
    • System type (dual circuit vs single-limb)
    • Whether humidification is active or passive
    • Whether exhaled air must be specifically filtered
    • Patient pathology
  • Themes described:
    • Active ventilation with an active modifier: emphasized need to filter exhaled air; inspiratory filtration may be unnecessary if gases are already certified and equipment is functioning correctly.
    • Passive systems: placement is more complex; using multiple filters can be controversial due to dead space.
    • Non-invasive ventilation (NIV):
      • Different circuit ports/interfaces exist by brand.
      • Some circuits suggest filtering around expiratory ports and ensuring humidifier/filter function occurs before air exits.
      • Caution: adding multiple filters may create unacceptable dead space.

• Non-invasive ventilation (NIV) recommendations as presented

  • NIV circuit design was emphasized, including expiratory port filter variations by brand.
  • For NIV “single-limb” systems with a filter/humidifier combination:
    • Described as fulfilling humidifier + filter functions.
  • COVID-19-era statement (as spoken):
    • NIV humidification controversy existed early, but current recommendations suggest it could be used if gases are properly filtered.

• Tracheostomy patients

  • Limited literature acknowledged.
  • Suggested approach:
    • Use a heat and moisture exchanger with built-in high-efficiency filter
    • Ensure expiratory flows are filtered (HEPA/high-efficiency bacterial medical filters suggested)
    • When using active modification, place an appropriate high-efficiency filter in the inspiratory branch
    • Always use appropriate personal protective equipment

• Filter lifecycle / maintenance steps

  • Filters have a replacement cycle, often 24 to 72 hours (per manufacturer; humidifiers explicitly mentioned).
  • Replace only if needed and ensure filters are not:
    • Damaged
    • Soaked with water
    • Impacted (performance compromised)

---

Methodology / instruction-style content (stepwise & checklist-style)

A) Objectives for the humidification/ventilator setup talk (as explicitly stated)

• Suggest procedures for assembling ventilators with viral protection
• Emphasize proper gas filtration
• Understand advantages and disadvantages of each physiological ventilation method (active vs passive humidification)

B) Filter and humidification selection checklist (practical “evaluate before choosing” list)

Evaluate filter specifications:

• Dead space (especially for pediatrics)
• Recommended volume/tidal volume range
• Humidification generated (if a combined device)
• Filtration efficiency (%)
  • Aim 90%–99.9%
  • Look for HEPA-style designations (e.g., H12 / H3)
• Resistance introduced
• Compressible volume
• Weight (critical for pediatrics due to traction effects)

Use extreme caution / avoid in stated clinical situations:

• Copious or bloody secretions
• Pleural fistula
• Protective strategies with low tidal volumes
• Hypothermia (notably < 32°C)
• Obstructive pathology (dead space risk → possible CO₂ retention)
• Situations where circuit leakage can impair adequacy (example mentioned: BPH—leak control emphasized)

C) Leaks/interface handling (especially NIV or mask interfaces)

• Ensure proper sealing around:
  • Mask surfaces
  • Interface ports
• Rationale:
  • Leaks can cause inadequate humidification
  • Leaks may be contaminated, so correct adjustment matters for infection control

D) Circuit/filter placement logic (conceptual algorithm)

Determine setup variables:

• Active humidification system vs passive humidification system
• Dual-limb vs single-limb circuit
• Invasive ventilation vs non-invasive ventilation

Decide whether inspiratory and/or expiratory filtration is necessary:

• If gases are already properly certified and equipment is functioning:
  • inspiratory filtration may be less necessary (as argued)
• In active ventilation:
  • filter exhaled air is highlighted as very important

Account for the trade-off:

• Adding filters increases:
  • Dead space
  • Resistance
• Pediatric rule-of-thumb:
  • Minimize additional dead space when it threatens ventilatory adequacy

E) Filter lifecycle / replacement procedure (operational steps)

• Track filter time in service:
  • Manufacturer suggests 24–72 hours (humidifiers called out)
• Inspect before replacing:
  • Confirm the filter is not damaged
  • Confirm the filter is not soaked with water
• Operational handling (as described):
  • Put ventilator on standby
  • Use a technique/tool to clamp/pick up the filter (two operators mentioned)
  • Perform correct trapping/removal steps
• Timing tie-in:
  • Replacement may align with other care needs such as endotracheal tube management (referenced within passive humidification handling)

---

Speakers / sources featured

Speakers

• Dr. Santiago Esquivel
  • Pediatric intensivist; Posadas Hospital
  • Director, pediatric critical care pulmonology committee at Lasarte
• Dr. Matías Herrera
  • Pediatric intensivist; Garrahan Hospital
  • Secretary, pediatric critical care pulmonology committee at Lasarte
• (At the beginning, an unnamed “committee”/moderator voice appears but is not identified beyond that role.)

Organizations / referenced sources (as mentioned)

• American Respiratory Care Association
• European recommendations for mechanical ventilation
• SAT (mentioned as including adult recommendations published by the Ministry)
• Pediatric Critical Immunology Committee and CIP committee (as named)
• INAMEH (selection discussed as potentially impacting outcomes)
• Sharp Code 2 (reported median duration referenced; exact document unclear)
• Toronto experience (circuit/filter evidence mentioned; exact study not specified)
• HEPA/H12/H3 (filter classification examples)
• Ministry / adult recommendations (as referenced; country/document not fully specified)

Other items

• COVID-19 is discussed as the context driving viral protection and NIV circuit considerations.