Prediction of upper airway dryness and optimal continuous positive airway pressure conditions.

Continuous positive airway pressure is the most effective long-term treatment for obstructive sleep apnoea, which is a sleeping disorder characterized by pauses in breathing during sleep. It introduces pressurized atmospheric air into the respiratory system in order to maintain open airways without blockage. Some continuous positive airway pressure devices incorporate a convective heat transfer humidifier to overcome dryness. However, many side effects, including the unacceptable excess of water droplets in the air supply line, have been reported and improvements are essential for better patient's comfort and acceptance of the therapy. The excess of water droplets is attributed to the qualitative rather than the quantitative approach of determining the rise in temperature and humidity of the inspired air. Therefore, a human upper airway mathematical model is developed to predict the heat and water transfer variation between normal breathing and continuous positive airway pressure conditions and determine the optimal input temperature and relative humidity in the continuous positive airway pressure humidifier.