The airflow and cooling characteristics in the airway of NHBD lung with hypothermic ventilation

Abstract

Hypothermic ventilation through trachea can cool Non-heart beating donor (NHBD) lungs noninvasively in vivo, thus avoiding warm ischemic damage. However, previous experimental studies with large lungs have shown poor cooling effect in bronchial terminal of NHBD lungs. To investigate the airflow and cooling characteristics of this process, a physiologically realistic upper airway model was established. In addition, droplet spraying was considered to enhance the heat transfer during the cooling process. The results show that the irregular geometry of realistic airway will lead to non-uniformity distribution of internal flow and temperature, and the local cooling effect in different regions is related to the velocity distribution. The secondary flow at the bifurcation can forcibly strengthen the heat exchange between the cold air and the hot air in the nearby low-speed area. Increasing the ventilation flow will strengthen the turbulence and heat exchange in the airway, so as to improve the overall cooling effect. The synergistic effect of cold air and droplet spraying can enhance the cooling effect in the airway. And large droplets (i.e. 10 μm) are conducive to the cooling enhancement of the central airway, while small droplets (i.e. 2 μm) are conducive to the cooling of the distal bronchus.