Dutta Abhijit, Chattopadhyay Himadri
Department of Mechanical Engineering, MCKV Institute of Engineering, Liluah, Howrah, 711204, West Bengal, India; Department of Mechanical Engineering, Jadavpur University, Kolkata, 700032, West Bengal, India.
Department of Mechanical Engineering, Jadavpur University, Kolkata, 700032, West Bengal, India.
J Therm Biol. 2021 Feb;96:102862. doi: 10.1016/j.jtherbio.2021.102862. Epub 2021 Jan 27.
The purpose of this study is to develop a comprehensive thermodynamic model of the human respiratory system and quantify the effects of inspiratory air temperature, relative humidity (RH), lung capacity and O fluctuation in metabolic reaction on the human respiratory system under three different physiological conditions, i.e. rest, moderate level of physical activity and extreme level of physical activity. Therefore, a second law-based analysis has carried out for the human respiratory system. It is observed that exergetic efficiency decreases by 21% and 16.5% during moderate and extreme level of activity respectively as compared to the physical condition of rest. The respiratory efficiency also increases with the increase in inspiratory air temperature and RH. For a given inspiratory air temperature, an increase in lung volume leads to a reduction in the efficiency. Increase in TV with a high airflow rate gives a higher magnitude of efficiency, such a situation appearing when a person's lung compliance harmed due to diseases. The respiratory efficiency decreases up to 2% with the increase in O percentage. The efficiency of the respiratory system is in maximum during rest followed by an extreme and moderate level of activity. However, with the controlled supply of O, the efficiency of the human respiratory performance increases with the decrease in O percentage. Due to partial oxidation of glucose at a reduced O level, exergy input from the metabolic reaction is less leading to increased exergetic efficiency.
本研究的目的是建立一个全面的人体呼吸系统热力学模型，并量化在三种不同生理条件下，即休息、适度体力活动和极度体力活动时，吸入空气温度、相对湿度（RH）、肺容量以及代谢反应中氧气波动对人体呼吸系统的影响。因此，对人体呼吸系统进行了基于第二定律的分析。结果发现，与休息时的身体状况相比，在适度和极度活动期间，有效能效率分别降低了21%和16.5%。呼吸效率也随着吸入空气温度和相对湿度的增加而提高。对于给定的吸入空气温度，肺容积的增加会导致效率降低。在气流速率较高时潮气量增加会使效率提高幅度更大，这种情况出现在人的肺顺应性因疾病而受损时。随着氧气百分比的增加，呼吸效率降低高达2%。呼吸系统的效率在休息时最高，其次是极度和适度活动时。然而，在氧气供应受控的情况下，人体呼吸性能的效率随着氧气百分比的降低而提高。由于在较低氧气水平下葡萄糖的部分氧化，代谢反应的有效能输入较少，从而导致有效能效率提高。
