Cabon Yann, Bommart Sebastien, Marin Gregory, Ahmed Engi, Suehs Carey, Vachier Isabelle, Gamez Anne Sophie, Molinari Nicolas, Bourdin Arnaud
Department of Medical Information, Hospital La Colombiere, University of Montpellier, Montpellier, France.
Department of Thoracic Imaging, Hospital Arnaud de Villeneuve, University of Montpellier, Montpellier, France.
Eur Radiol. 2025 Jun 28. doi: 10.1007/s00330-025-11751-6.
Severe airway hyper-responsiveness is associated with poor outcomes in asthma. Spatial heterogeneities in airway closures and subsequent air trapping (AT) during bronchoconstriction have been poorly assessed in asthma.
We assessed the spatial distribution of AT by acquiring expiratory lung CT at each dose of a methacholine challenge in 31 women with asthma. A statistical method based on k-nearest-neighbors (knn) informed about between AT-area distance toward uniformity at the peak of bronchoconstriction (PC20). Fractal dimensions of binarized low attenuation areas were also computed at each methacholine dose.
Whereas AT progressed with methacholine concentration and peaked at PC20, the clustering of knn curves identified two patterns of AT-spatial distribution. The first cluster (23 patients) presented heterogeneous patterns of AT assessed at the PC20, eventually fitting with segmental or lobar distribution. Conversely, the second cluster (8 patients) had spatial distribution close to uniformity, suggestive of an even progression of airway closure throughout the whole airway tree. This last cluster had lower PC20 concentrations (153 µg [83-392] vs 693 µg [370-980], p = 0.01), lower baseline FEV1 values (0.72 [0.65-0.77] vs 0.82 [0.74-0.88]% predicted, p < 0.05) and lower recovery of airflow after albuterol, a short-acting beta2-agonist (SABA) (0.66 [0.63-0.69] vs 0.76 [0.67-0.86]% predicted, p = 0.04). Expiratory-to-inspiratory ratio of the fractal dimension progressed with the methacholine concentration, peaked at the PC20, and remained significantly higher throughout the challenge in the uniform cluster.
Unevenly distributed spatial progression of AT with methacholine might represent a protective mechanism against excessive bronchoconstriction. Patients at risk of uniform AT might be identified by either low PC20 concentrations and limited SABA recovery.
Question How does regional heterogeneity of air trapping affect asthmatic patients? Findings Acquisition of expiratory CT at each dose of a methacholine challenge allowed for assessing k-nearest-neighbors and fractal dimensions informing about spatial uniformity of air trapping. Clinical relevance Low methacholine concentrations, low baseline FEV1 and limited FEV1 recovery post bronchodilator are indicative of uniformly distributed air trapping, deserving clinical attention.
严重气道高反应性与哮喘患者的不良预后相关。哮喘患者在支气管收缩过程中气道闭合及随后的气体陷闭（AT）的空间异质性评估不足。
我们对31例哮喘女性患者在每次乙酰甲胆碱激发剂量下进行呼气肺CT扫描，以评估AT的空间分布。基于k近邻（knn）的统计方法用于了解在支气管收缩峰值（PC20）时AT区域距离向均匀性的变化。还计算了每个乙酰甲胆碱剂量下二值化低衰减区域的分形维数。
虽然AT随乙酰甲胆碱浓度增加而进展并在PC20时达到峰值，但knn曲线聚类确定了两种AT空间分布模式。第一组（23例患者）在PC20时呈现出异质性的AT模式，最终符合节段性或叶性分布。相反，第二组（8例患者）的空间分布接近均匀，提示气道闭合在整个气道树中均匀进展。最后一组的PC20浓度较低（153μg[83 - 392] vs 693μg[370 - 980]，p = 0.01），基线FEV1值较低（0.72[0.65 - 0.77] vs 0.82[0.74 - 0.88]%预测值，p < 0.05），且使用短效β2激动剂（SABA）沙丁胺醇后气流恢复较低（0.66[0.63 - 0.69] vs 0.76[0.67 - 0.86]%预测值，p = 0.04）。分形维数的呼气与吸气比值随乙酰甲胆碱浓度增加而进展，在PC20时达到峰值，并且在均匀组的整个激发过程中显著更高。
乙酰甲胆碱引起的AT空间进展分布不均可能是一种防止过度支气管收缩的保护机制。可通过低PC20浓度和有限的SABA恢复来识别有均匀AT风险的患者。
问题气体陷闭的区域异质性如何影响哮喘患者？研究结果在每次乙酰甲胆碱激发剂量下进行呼气CT扫描，可评估k近邻和分形维数，以了解气体陷闭的空间均匀性。临床意义低乙酰甲胆碱浓度、低基线FEV1和支气管扩张剂后有限的FEV1恢复表明气体陷闭分布均匀，值得临床关注。
