背景和目的：一氧化氮在調控肺部換氣－灌流之平衡扮演著重要的角色。進行胸腔手術，病人採側臥姿或單肺換氣時會影響肺呼吸生理。而在胸腔手術時，姿勢之改變與單肺換氣時，從氣管中吐出之一氧化氮含量之改變並無相關之研究與觀查。方法：本研究共收案20人接受胸腔手術且採側臥姿或單肺換氣。病人在完成雙管支氣管內管放置後，以一氧化氮分析儀測量術中仰臥、雙肺側臥、單肺側臥與完成手術後之雙肺側臥及仰臥之吐氣一氧化氮濃度。結果：發現吐氣一氧化氮濃度在側臥姿或單肺換氣及術後側臥雙肺換氣時有顯著之下降。結論：本研究顯示，在胸腔手術時行側臥姿或單肺換氣時會造成吐氣一氧化氮之下降，而改變了肺部之血流和換氣之比例，此可能可以改善肺部之血流和換氣比例而改善血氧飽合度。

Background and purpose: Nitric oxide (NO) is known to play an important role in modulating ventilation-perfusion matching in the lungs. The lateral decubitus position (LDP) and 1-lung ventilation (OLV) alter the pulmonary physiology during thoracic surgery. However, changes in exhaled (e)NO in response to pulmonary physiology during position changes and OLV have not been investigated. This study examined the effect of the LDP and OLV on changes in eNO concentrations during thoracic surgery. Methods: Twenty patients who underwent elective thoracic surgery in the LDP with OLV were enrolled. After double-lumen endobronchial tube intubation, eNO concentrations were measured in real time and recorded in the supine position, in the LDP, during OLV, after re-establishment of 2-lung ventilation (TLV), and in the supine position postoperatively. Breath-to-breath eNO concentrations were measured with an NO analyzer. Results: eNO concentrations significantly decreased in the LDP, during OLV, and with TLV post-OLV. The present study demonstrates an association of changes in the eNO concentration with the LDP and OLV during thoracic surgery. Conclusions: The associated reduction in eNO during position changes and OLV, which altered pulmonary ventilation-perfusion matching, might have been a response to blood flow which improved blood oxygenation during thoracic surgery.