Kuo et al. compared bland aerosol and heated humidity in spontaneously breathing patients with nasal endotracheal tubes and normal lungs and found a detrimental effect on patient's oxygenation status when using a heated jet nebulizer for short-term use. It is interesting to note that these effects were improved by exchanging therapy to heated humidity. However, contradictory results were observed by Rozsasi et, al. in which tracheal humidity remained at higher levels after use of particulate aerosol spray (300µL H2O/L air at 26°C, 90% relative humidity) in comparison to molecular water vapor (32µL H2O/L air at 32°C, 100% relative humidity). Studies have in addition compared the use of heat and moisture exchangers (HMEs), a type of passive humidification, in comparison to HH in mechanically ventilated patients and have shown mixed results regarding the superior efficacy of one over the other. However, a recent systematic review found no difference in adverse clinical events such as artificial airway occlusion, mortality, pneumonia, or respiratory complications between HH and HME.