Metafratzi Zafiria M, Vassiliou Miltos P, Maglaras George C, Katzioti Froso G, Constantopoulos Stauros H, Katsaraki Afroditi, Efremidis Stauros C
Department of Radiology, University Hospital of Ioannina, Panepistimiou Avenue, Ioannina 45500, Greece.
AJR Am J Roentgenol. 2006 Jan;186(1):213-9. doi: 10.2214/AJR.04.1320.
The purpose of our study was to investigate the relation between the pulmonary artery obstruction index assessed with helical CT and impairment in blood gases in patients with acute pulmonary embolism.
Helical CT pulmonary angiography was performed in 78 patients who were suspected of having acute pulmonary embolism and selected as being free of underlying cardiopulmonary disease. Findings consistent with acute pulmonary embolism were observed in 34 patients. The severity was assessed by the pulmonary artery obstruction index, defined as Sigma (n x d), where n is the number of segmental arteries occluded and d is the degree of obstruction. Spearman's rank correlation coefficients were used to assess the correlation between the index of arterial obstruction and arterial partial pressure of oxygen (Pao(2)); alveolar-arterial difference in partial pressure of oxygen (Pao(2)-Pao(2)); arterial partial pressure of carbon dioxide (Paco(2)); and arterial oxygen saturation (Sao(2)). The statistical difference of the arterial blood gas values between the two groups of patients (those with and those without pulmonary embolism) was evaluated using the Mann-Whitney U test. Blood gases were comparatively evaluated below and above different index values (from 40% to 70%) and different Paco(2) values (25, 30, and 35 mm Hg) as possible indexes of embolism severity using the same test. The level of significance was set at 95% (p = 0.05).
The values of Pao(2), Sao(2), and Paco(2) were significantly lower (p = 0.024, p = 0.0062, and p = 0.000075, respectively) and the values of Pao(2)-Pao(2) were significantly higher (p = 0.0169) in the pulmonary embolism group than in the no-pulmonary-embolism group. A significant correlation was observed between the obstruction index and Pao(2) (r = -0.33, p = 0.05), Paco(2) (r = -0.34, p = 0.05), Pao(2)-Pao(2) (r = 0.39, p = 0.02), and Sao(2) (r = -0.35, p = 0.04). Using cutoff values for the pulmonary artery obstruction index of 40%, 50%, 60%, and 70%, we observed that Paco(2) and Pao(2)-Pao(2) differed significantly between above and below the 40% (p = 0.018 and p = 0.03), 50% (p = 0.0087 and p = 0.029), and 60% (p = 0.005 and p = 0.003) cutoffs. Pao(2) differed significantly for the cutoff values of 60% (p = 0.03) and 70% (p = 0.004). The same was observed for Sao(2) at 60% (p = 0.05) and 70% (p = 0.03). Comparisons for Paco(2) showed that a value of 30 mm Hg significantly separates levels of the pulmonary artery obstruction index (p = 0.002), with 78% sensitivity and 82% specificity indicating a pulmonary artery obstruction index greater than 50%.
In patients with acute pulmonary embolism but no other underlying cardiopulmonary disease, the severity of the pulmonary arterial tree obstruction assessed using the CT obstruction index is significantly correlated to the blood gas values. The strongest correlation was observed between the index and the Pao(2)-Pao(2). Furthermore, a Paco(2) value of 30 mm Hg or less is highly suggestive of an obstruction index of more than 50% of the arterial bed.
本研究旨在探讨螺旋CT评估的肺动脉阻塞指数与急性肺栓塞患者血气损害之间的关系。
对78例疑似急性肺栓塞且无基础心肺疾病的患者进行螺旋CT肺动脉造影。34例患者观察到与急性肺栓塞相符的表现。严重程度通过肺动脉阻塞指数评估，定义为∑(n×d)，其中n为闭塞的节段动脉数量，d为阻塞程度。采用Spearman等级相关系数评估动脉阻塞指数与动脉血氧分压（Pao₂）、肺泡 - 动脉氧分压差值（Pao₂ - Pao₂）、动脉血二氧化碳分压（Paco₂）及动脉血氧饱和度（Sao₂）之间的相关性。采用Mann - Whitney U检验评估两组患者（有肺栓塞和无肺栓塞患者）动脉血气值的统计学差异。使用相同检验对不同指数值（40%至70%）和不同Paco₂值（25、30和35 mmHg）上下的血气进行比较评估，作为栓塞严重程度的可能指标。显著性水平设定为95%（p = 0.05）。
肺栓塞组的Pao₂、Sao₂和Paco₂值显著低于无肺栓塞组（分别为p = 0.024、p = 0.0062和p = 0.000075），而Pao₂ - Pao₂值显著高于无肺栓塞组（p = 0.0169）。阻塞指数与Pao₂（r = -0.33，p = 0.05）、Paco₂（r = -0.34，p = 0.05）、Pao₂ - Pao₂（r = 0.39，p = 0.02）及Sao₂（r = -0.35，p = 0.04）之间存在显著相关性。使用肺动脉阻塞指数的截断值40%、50%、60%和70%，我们观察到Paco₂和Pao₂ - Pao₂在40%（p = 0.018和p = 0.03）、50%（p = 0.0087和p = 0.029）及60%（p = 0.005和p = 0.003）截断值上下存在显著差异。Pao₂在60%（p = 0.03）和70%（p = 0.004）截断值时存在显著差异。Sao₂在60%（p = 0.05）和70%（p = 0.03）时也观察到相同情况。Paco₂的比较显示，30 mmHg的值显著区分肺动脉阻塞指数水平（p = 0.002），78%的敏感性和82%的特异性表明肺动脉阻塞指数大于50%。
在无其他基础心肺疾病的急性肺栓塞患者中，使用CT阻塞指数评估的肺动脉树阻塞严重程度与血气值显著相关。指数与Pao₂ - Pao₂之间观察到最强的相关性。此外，Paco₂值≤30 mmHg高度提示动脉床阻塞指数超过50%。
