Ueki J, Hughes J M, Peters A M, Bellingan G J, Mohammed M A, Dutton J, Ussov W, Knight D, Glass D
Department of Medicine (Respiratory Division), Royal Postgraduate Medical School, Hammersmith Hospital, London.
Thorax. 1994 Apr;49(4):327-31. doi: 10.1136/thx.49.4.327.
Patients with arteriovenous malformations are routinely monitored with arterial oxygen saturation (SaO2) estimations (breathing air) from which an oxygen shunt fraction can be calculated. This simple estimation has been compared with an anatomically defined estimate of the right to left shunt using a radioisotopic method. The fall in SaO2 which occurs in patients with pulmonary arteriovenous malformations in the erect posture and at high lung volumes was used to test the ability of SaO2 alone to follow changes in right to left shunt.
Radiolabelled albumin macroaggregates (99mTc-MAA) or microspheres (MS) were injected intravenously and kidneys and lungs were imaged. The shunt fraction (QS/QTTc) in the supine position at functional residual capacity (baseline) was obtained by quantifying right kidney radioactivity. On standing or while breath holding at total lung capacity, shunt fraction was calculated from baseline QS/QTTc and from lung counts and the injected dose. Arterial oxygen saturation (SaO2) was recorded by a pulse oximeter for calculation of the oxygen shunt (QS/QTO2) (breathing air).
In the postural study (n = 8) SaO2 decreased from a mean (SD) value of 89 (5)% supine to 80 (6)% erect, corresponding to QS/QTO2 28 (8)% and 44 (8)% respectively. QS/QTTc increased from 28.7 (10.3)% to 39 (14.3)%. In the lung volume study (n = 8) QS/QTTc increased from 16.6 (11.5)% at functional residual capacity to 23.3 (11.9)% at total lung capacity while QS/QTO2 increased from 19.5 (7.5)% to 25.9 (10.6)% respectively. When all measurements were compared for QS/QTTc% and QS/QTO2% (n = 32) the difference in the mean values was 2.5% (absolute) and the limits of agreement between the two methods were +38% to -18% (relative). In neither the postural nor the volume study did delta (QS/QTO2) reliably predict delta (QS/QTTc)%.
In pulmonary arteriovenous malformations the simple physiological shunt calculated from SaO2 breathing air agreed well with the anatomical right to left shunt measured with 99mTc-MAA, but predicted poorly the changes in anatomical shunt induced by postural or lung volume changes.
动静脉畸形患者通常通过测定动脉血氧饱和度（SaO₂）（呼吸空气时）进行监测，由此可计算氧分流分数。已将这种简单的测定方法与使用放射性同位素法对右向左分流进行的解剖学定义估算进行了比较。肺动静脉畸形患者在直立姿势和高肺容量时出现的SaO₂下降被用于测试仅靠SaO₂追踪右向左分流变化的能力。
静脉注射放射性标记的白蛋白大聚合体（⁹⁹ᵐTc-MAA）或微球（MS），对肾脏和肺部进行成像。通过对右肾放射性进行定量，获得功能残气量（基线）仰卧位时的分流分数（QS/QTTc）。站立时或在肺总量屏气时，根据基线QS/QTTc以及肺部计数和注射剂量计算分流分数。用脉搏血氧仪记录动脉血氧饱和度（SaO₂），以计算氧分流（QS/QTO₂）（呼吸空气时）。
在体位研究中（n = 8），SaO₂从仰卧位时的平均（标准差）值89（5）%降至直立位时的80（6）%，分别对应QS/QTO₂为28（8）%和44（8）%。QS/QTTc从28.7（10.3）%增至39（14.3）%。在肺容量研究中（n = 8），QS/QTTc从功能残气量时的16.6（11.5）%增至肺总量时的23.3（11.9）%，而QS/QTO₂分别从19.5（7.5）%增至25.9（10.6）%。当对所有测量的QS/QTTc%和QS/QTO₂%（n = 32）进行比较时，平均值差异为2.5%（绝对值），两种方法的一致性界限为+38%至 -18%（相对值）。在体位研究和容量研究中，Δ（QS/QTO₂）均未可靠地预测Δ（QS/QTTc）%。
在肺动静脉畸形中，根据呼吸空气时的SaO₂计算出的简单生理性分流与用⁹⁹ᵐTc-MAA测量的解剖学右向左分流吻合良好，但对体位或肺容量变化引起的解剖学分流变化预测不佳。
