Guazzi M, Marenzi G, Assanelli E, Perego G B, Cattadori G, Doria E, Agostoni P G
Istituto di Cardiologia dell' Università degli Studi, Centro di Studio per le Ricerche Cardiovascolari del CNR, Fondazione Monzino, IRCSS, Milan, Italy.
J Card Fail. 1995 Dec;1(5):401-8. doi: 10.1016/s1071-9164(05)80009-0.
Dead space/tidal volume ratio (VD/VT) evaluation is currently performed in patients with respiratory and cardiac disorders, and includes measurement of arterial CO2 partial pressure (PaCO2). PaCO2 is generally derived from either PETCO2 (end-expiratory CO2 pressure) or PJCO2 (calculated as PJCO2 = 5.5 + 0.9 PETCO2 - 2.1 VT). The applicability of these methods may be questionable in chronic heart failure due to its frequent association with lung dysfunction. In 63 patients with congestive heart failure, the authors compared PaCO2 versus PETCO2 and PJCO2 and VD/VT measured with PaCO2 versus VD/VT estimated with PETCO2 (estimation 1) or PJCO2 (estimation 2). Comparisons were made at rest, at submaximal exercise, and at peak exercise. Considering all 326 measurements, there was a strong correlation, but not an identity, between PaCO2 and PETCO2 (PaCO2 = 7.25 + 0.80 PETCO2, r = .84, P < .0001) and between PaCO2 and PJCO2 (PaCO2 = 6.18 + 0.84 PJCO2, r = .85, P < .0001). Results were comparable concerning PaCO2 versus PJCO2. Measured VD/VTs also strongly correlated with estimated VD/VTs (VD/VT measured = -0.03 + 1.11 VD/VT [estimation 1], r = .90, P < .0001, and VD/VT measured = 0.03 + 0.92 VD/VT [estimation 2], r = .90, P < .0001). However, only at rest and, solely for estimation 1, at submaximal exercise were the slopes and y intercepts of measured versus estimated VD/VT not different from 1 and 0, respectively; in this regard, lung dysfunction was more influential than the severity of cardiac failure. Although PaCO2 strongly correlates with PETCO2 and PJCO2, these measurements may not be reliable for a noninvasive calculation of VD/VT in chronic congestive heart failure.
目前，死腔/潮气量比值（VD/VT）评估用于患有呼吸和心脏疾病的患者，包括测量动脉血二氧化碳分压（PaCO2）。PaCO2通常来自呼气末二氧化碳分压（PETCO2）或计算得出的PJCO2（计算公式为PJCO2 = 5.5 + 0.9PETCO2 - 2.1VT）。由于慢性心力衰竭常伴有肺功能障碍，这些方法的适用性可能存在疑问。在63例充血性心力衰竭患者中，作者比较了PaCO2与PETCO2和PJCO2的差异，以及用PaCO2测量的VD/VT与用PETCO2（估计1）或PJCO2（估计2）估计的VD/VT的差异。在静息状态、次极量运动和峰值运动时进行了比较。综合所有326次测量结果，PaCO2与PETCO2之间（PaCO2 = 7.25 + 0.80PETCO2，r = 0.84，P < 0.0001）以及PaCO2与PJCO2之间（PaCO2 = 6.18 + 0.84PJCO2，r = 0.85，P < 0.0001）存在很强的相关性，但并非完全相同。关于PaCO2与PJCO2的结果具有可比性。测量得到的VD/VT与估计的VD/VT也高度相关（测量的VD/VT = -0.03 + 1.11VD/VT[估计1]，r = 0.90，P < 0.0001，以及测量的VD/VT = 0.03 + 0.92VD/VT[估计2]，r = 0.90，P < 0.0001）。然而，仅在静息状态下，且仅对于估计1，在次极量运动时，测量的VD/VT与估计的VD/VT的斜率和y轴截距才分别与1和0无差异；在这方面，肺功能障碍比心力衰竭的严重程度影响更大。尽管PaCO2与PETCO2和PJCO2高度相关，但这些测量结果可能无法可靠地用于慢性充血性心力衰竭患者VD/VT的无创计算。
