Evaluation of Exhaled Nitric Oxide in Thoracic Surgery Patients under One Lung Ventilation Using a Newly Designed Online Exhaled Nitric Oxide Measuring System

Measurement of exhaled nitric oxide (NO) has been gaining much interest lately. However, an ideal measuring system is not yet available in the clinical setting. The aims of the present study were to construct an exhaled NO measuring system and to investigate the effects of one lung ventilation (OLV) on exhaled NO output in patients who underwent thoracic surgery. At first, the NO measuring system was constructed with an NO analyzer, a respiratory flowmeter and a data processing computer system in which the algorithm was indwelled for correcting the distorted NO output wave form. Then, accuracy of this system was tested by using a simulator. This simulator was reworked in order to simulate NO production from the lung under both spontaneous respiration and mechanical ventilation. The data of peak NO concentration (pNO) and NO output (VNO) obtained with the NO monitoring system were significantly correlated with "alveolar" NO concentration (aNO) and exhaled NO volume from the simulator. Then, exhaled NO was measured in 12 thoracic surgery patients who underwent OLV using this system. pNO and VNO were significantly decreased by about half during OLV, and returned to baseline 25 min after releasing OLV. These data suggest that the newly designed online exhaled NO measuring system accurately detected aNO and exhaled NO volume in a breath-by-breath manner, and OLV for about 3 h did not influence the NO output from the lung after releasing OLV in thoracic surgery patients.