Computational Fluid Dynamics Study on the Effects of Ambient Air Temperature on Obstructive Sleep Apnea

The upper airway comprising the pharynx and nasal cavity has several functions, including heat transfer during the respiratory cycle to the surface. The ambient temperature is generally consistent in the air flow of the upper airway. Computational fluid dynamics (CFD) was therefore used to analyze the effects of ambient temperatures (16 degrees C, 20 degrees C, and 24 degrees C) and flow patterns of obstructive sleep apnea (OSA) patients. Heat transfer was observed to be stable in the anterior zone, and the Reynolds (Re) and Nusselt (Nu) numbers tended to decrease when the ambient temperature increased. The pressure drops in the pre-orthognathic operation condition were 4.71 Pa at 16 degrees C and 4.50 Pa at 24 degrees C, whereas those in the post-operation condition were 11.78 Pa at 16 degrees C and 11.64 Pa at 24 degrees C. The airway resistance also exhibited the same tendency as the pressure drop. Thus, a higher ambient temperature is likely to be beneficial for reducing OSA.