School of Mechanical Engineering, Shiraz University, Shiraz, Iran.
Department of Internal Medicine, Shiraz University of Medical Science, Shiraz, Iran.
Comput Biol Med. 2022 Aug;147:105702. doi: 10.1016/j.compbiomed.2022.105702. Epub 2022 Jun 17.
The primary function of the human respiratory system is gas and moisture exchange, and conditioning inhaled air to prevent damage to the lungs and alveoli. In a fire incident, exposed soft tissues contract and the respiratory system may be severely damaged, possibly leading to respiratory failure and even respiratory arrest. The purpose of this study is to numerically simulate hot airflow in the human upper airway and trachea to investigate heat and moisture transfer and induced thermal injuries.
For analysis, the airflow is assumed to be laminar and steady, and simulations have been carried out at volume flow rates of 5 and 10 L/min, inlet temperatures of 70-240 °C, and relative humidity up to 40%. The mucous layer and surrounding tissues are incorporated into the conducting zone of the model. The blood perfusion is considered at different rates up to 5(Kg/m.s) to regulate the temperature, and the vapor concentration is coupled with the energy equation.
The temperature and humidity distribution on the airway wall were calculated for all the studied conditions in order to find the mild and severe burn for different inhaled air temperatures. At the inlet temperatures of 70 and 100 °C, there are mild burns in several nasal cavity regions. At the higher temperatures of 160 and 200 °C, these areas suffer from severe burns and mild burns occur at the superior parts and nasopharynx. Rapid evaporation and tissue destruction will be observed if anyone breathes the 240 °C air.
The results show that the hot inlet temperatures drop below 44 °C when passing through the upper airway, and the lower airway was not affected. Increasing the inlet temperature from 70 to 240 °C extends the burns from mild to severe and the affected areas from the beginning of the nasal cavity to the pharynx.
人体呼吸系统的主要功能是进行气体和水分交换，并调节吸入的空气，以防止肺部和肺泡受损。在火灾事件中，暴露的软组织会收缩，呼吸系统可能会受到严重损害，可能导致呼吸衰竭甚至呼吸停止。本研究的目的是数值模拟人体上呼吸道和气管中的热气流，研究热量和水分传递以及由此引起的热损伤。
为了进行分析，假设气流为层流和稳定流，并在体积流量为 5 和 10 L/min、入口温度为 70-240°C 以及相对湿度高达 40%的条件下进行了模拟。黏液层和周围组织被纳入模型的传导区。血液灌注以不同的速率（最高可达 5(Kg/m.s)）被考虑在内，以调节温度，蒸汽浓度与能量方程耦合。
为了找到不同吸入空气温度下的轻度和重度烧伤，计算了所有研究条件下气道壁上的温度和湿度分布。在入口温度为 70 和 100°C 的情况下，几个鼻腔区域存在轻度烧伤。在较高的 160 和 200°C 温度下，这些区域遭受重度烧伤，而上部和鼻咽部则出现轻度烧伤。如果有人吸入 240°C 的空气，将观察到快速蒸发和组织破坏。
结果表明，热入口温度在通过上呼吸道时降至 44°C 以下，而下呼吸道不受影响。将入口温度从 70°C 升高到 240°C 会使烧伤从轻度扩展到重度，受影响的区域从鼻腔的起始部位扩展到咽部。
