Chart — Clinical Skills
Humidity & Aerosol Devices Compared
Bubble humidifier, HME, large-volume nebulizer, or heated high-flow? This grid sorts the humidity and bland-aerosol devices by output and use so you can match the device to the airway and the gas flow.
Written by Apex Respiratory Editorial Team
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Humidity & Aerosol Devices
| Device | Type | Output | Typical Use | Limitation |
|---|---|---|---|---|
| Bubble humidifier | Active humidifier (vapor) | Low (molecular water) | Low-flow nasal cannula above ~4 L/min | Minimal humidity at high flow; not for a bypassed airway |
| Passover / wick / membrane humidifier | Active humidifier, heated | High | Invasive and noninvasive ventilation; bypassed airway | Requires a heater and water reservoir |
| Heat-and-moisture exchanger (HME) | Passive ("artificial nose") | Moderate | Short-term ventilation and transport | Adds deadspace and resistance; avoid with thick secretions, hypothermia, or a large leak |
| Large-volume nebulizer (LVN) | Bland aerosol generator | Particulate water/saline, heated or cool | Bypassed airway, post-extubation cool mist, oxygen at a set FiO₂ | Can aerosolize bacteria (infection risk); condensate |
| Ultrasonic nebulizer (USN) | Bland aerosol generator | High-density particulate | Sputum induction, dense aerosol | Overhydration risk (especially infants); cost |
| Heated high-flow nasal cannula (HFNC) | Active heated humidified high flow | Very high (about 37°C, 100% RH) | High-flow oxygen with comfort and some PEEP effect | Equipment and cost |
How to Use This Chart
Match the device to the patient’s airway and the prescribed gas flow. The three bullets below capture the key decision points.
- Bypassed airway (ETT or trach).Active heated humidification is required for continuous use. An HME is acceptable for short-term ventilation or transport but adds deadspace and resistance — avoid it with thick secretions, hypothermia, or a large leak.
- Infection control.Large-volume and ultrasonic nebulizers generate particulate water that can aerosolize pathogens — an infection-control concern especially in immunocompromised patients.
- High-flow situations. Bubble humidifiers lose effectiveness above ~4 L/min. Heated passover humidification and HFNC are designed for high gas flows and provide near-physiologic heat and humidity.
Related Resources
Sources
- Restrepo RD, Walsh BK. AARC Clinical Practice Guideline: Humidification during invasive and noninvasive mechanical ventilation: 2012. Respir Care. 2012;57(5):782-788.
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021. Humidity and bland aerosol therapy.