Richard Jean-Christophe, Janier Marc, Lavenne Franck, Tourvieille Christian, Le Bars Didier, Costes Nicolas, Gimenez Gerard, Guerin Claude
Service de Réanimation Médicale et d'Assistance Respiratoire, Lyon, France.
J Nucl Med. 2005 Aug;46(8):1375-83.
Measurement of alveolar volume (Va) and regional ventilation (a) is crucial to understanding the pathophysiology of acute lung injury and ventilator-induced lung injury. PET has previously been used as a noninvasive, quantitative method to assess a, but formal validation of this technique in experimental lung injury is lacking. This study aims to validate Va and a regional assessment with PET, using inhaled (13)N-N(2) in pigs.
Two normal and 2 oleic acid-injured pigs were tracheotomized, mechanically ventilated, and studied in 5 different levels of ventilation by changing respiratory rate. In each experimental condition, lungs were washed-in and then washed-out with (13)N-N(2) through an open circuit in the ventilator. Using this method, multiframe images were acquired with a dedicated PET camera. Regions of interest (ROIs) were drawn on each lung. Regional time-activity curves during washout were generated for each ROI and fitted to a mono- and a bicompartmental model. Validation of this method was performed in 2 ways. First, regional values of predicted Va (Va(emission)) were compared with regional volume obtained independently from density analysis on a transmission scan (Va(trans)). Second, regional values of predicted a were summed in each animal during each experimental condition and compared with minute-ventilation values set on the ventilator.
The bicompartmental model best fitted the experimental values in normal (94.7% [62.2%-100.0%] (median [interquartile range]) of the ROIs) as well as in injured animals (90.7% [81.6%-97.4%] of the ROIs) (P = 0.49). Va(emission) significantly correlated with Va(trans) (R(2) = 0.89, P < 0.001) but exceeded Va(trans) by 10%. Finally, a strongly and positively correlated with minute-ventilation in both normal (R(2) = 0.96, P < 0.001) and injured (R(2) = 0.96, P < 0.001) animals.
Measurement of (13)N-N(2) washout using PET is accurate to assess regional alveolar volume and ventilation during experimental acute lung injury.
测量肺泡容积（Va）和局部通气（a）对于理解急性肺损伤和呼吸机诱导性肺损伤的病理生理学至关重要。正电子发射断层扫描（PET）此前已被用作评估a的一种非侵入性定量方法，但该技术在实验性肺损伤中的正式验证尚缺乏。本研究旨在使用猪吸入的（13）N-N₂，通过PET验证Va和局部评估。
对2只正常猪和2只油酸损伤猪进行气管切开，机械通气，并通过改变呼吸频率在5种不同通气水平下进行研究。在每种实验条件下，通过呼吸机的开放回路用（13）N-N₂对肺进行冲洗和随后的洗脱。使用该方法，用专用PET相机采集多帧图像。在每侧肺上绘制感兴趣区域（ROI）。为每个ROI生成洗脱期间的局部时间-活性曲线，并拟合到单室和双室模型。通过两种方式对该方法进行验证。首先，将预测的Va（Va（发射））的局部值与通过透射扫描上的密度分析独立获得的局部容积（Va（透射））进行比较。其次，在每种实验条件下，将每只动物预测的a的局部值相加，并与呼吸机上设置的分钟通气值进行比较。
双室模型最能拟合正常动物（ROI的94.7%[62.2%-100.0%]（中位数[四分位间距]））以及损伤动物（ROI的90.7%[81. .6%-97.4%]）的实验值（P = 0.49）。Va（发射）与Va（透射）显著相关（R² = 0.89，P < 0.001），但比Va（透射）超出10%。最后，在正常动物（R² = 0.96，P < 0.001）和损伤动物（R² = 0.96，P < 0.001）中，a均与分钟通气呈强烈正相关。
使用PET测量（13）N-N₂洗脱对于评估实验性急性肺损伤期间的局部肺泡容积和通气是准确的。
