Dynamic characteristics of heat capacity of the human nasal cavity during a respiratory cycle

The dynamic characteristics of air-conditioning in the human nasal cavity during a respiratory cycle were investigated using unsteady numerical simulations to assess whether inhaled air is sufficiently conditioned by the nasal cavity. Variations in the epithelial surface temperature, surface heat, and water vapor fluxes were found to vary significantly during inspiration while providing substantial air conditioning to the inhaled air, but variations and magnitudes were significantly reduced during the expiration period. Air temperature (31.3-35.3 degrees C) and relative humidity (85.1-100 %) in the nasopharynx exhibited significant variations during inspiration. Flow rate-weighted average values of the air temperature and relative humidity during inspiration were estimated to be 32.0 degrees C and 89.1 %, respectively. Inhaled air did not attain alveolar conditions before reaching the nasopharynx, and was therefore thought to be insufficiently conditioned by the nasal cavity alone. A steady flow of approximately 250 mL/s appears to be useful for evaluating the accumulated thermal state of air in the nasopharynx during inspiration.

Automated summary

The study found that the nasal cavity provides substantial air conditioning to inhaled air during inspiration, but this effect is reduced during expiration. Significant variations in air temperature and relative humidity were observed in the nasopharynx during inspiration, with inhaled air not reaching alveolar conditions before reaching the nasopharynx. A steady air flow of approximately 250 mL/s was suggested to evaluate the accumulated thermal state of air in the nasopharynx during inspiration.