Clerbaux T, Detry B, Reynaert M, Frans A
Department of Internal Medicine, Cliniques Universitaires Saint-Luc, Brussels, Belgium.
Pathol Biol (Paris). 1997 Apr;45(4):269-73.
Deep hypoxia is known to increase the intraerythrocytic 2,3 diphosphoglycerate (DPG) level and therefore to induce a right shift of the oxyhemoglobin dissociation curve (ODC), which is considered to be a protective mechanism against tissular hypoxia. Our purpose was to assess whether the ODC is shifted to the right in patients with acute respiratory distress syndrome (ARDS) and whether this shift had a beneficial effect on tissue oxygenation. We have determined the whole ODC and related indices in 29 control subjects and 29 patients suffering from ARDS for at least 5 days. The ODC of the patients were shifted to the right from 20 to 95% saturation. Their DPG level was increased (19.9 +/- 3.9 mumol/gHb, mean +/- SD) as compared to control subjects (12.5 +/- 2.1 mumol/gHb). There was a highly significant relation in patients between their P50 (pO2 necessary to achieve 50% saturation) and their DPG according to the equation: P50 (kPa) = 0.03 DPG (mumol/gHb) + 3.24 (r = 0,54) (p < 0,001). It is likely that in such patients hypoxia is severe enough to stimulate the DPG synthesis and induce a right shift of the ODC. It is not at all certain that this shift has a favourable effect on tissue oxygenation. Indeed, the extreme values for PaO2 were from 3.43 to 7.96 kPa that correspond to SO2 of 48 to 91% where the ODC has not yet his upper part. A right shift decreases therefore the captation of oxygen from the lung. On the other hand theoretical studies have shown that at low arterial PO2 values a right shift of the ODC has a detrimental effect on release of oxygen from hemoglobin if the mixed venous PO2 is decreased. In order to quantify the amount of oxygen actually transmitted to the tissues, others factors are to be investigate as the PCO2 or the temperature.
已知深度缺氧会增加红细胞内2,3 - 二磷酸甘油酸（DPG）水平，从而导致氧合血红蛋白解离曲线（ODC）右移，这被认为是一种针对组织缺氧的保护机制。我们的目的是评估急性呼吸窘迫综合征（ARDS）患者的ODC是否右移，以及这种右移是否对组织氧合有有益影响。我们测定了29名对照受试者和29名患有ARDS至少5天的患者的完整ODC及相关指标。患者的ODC在饱和度20%至95%之间右移。与对照受试者（12.5±2.1μmol/gHb）相比，他们的DPG水平升高（19.9±3.9μmol/gHb，平均值±标准差）。根据方程：P50（kPa）= 0.03 DPG（μmol/gHb）+ 3.24（r = 0.54）（p < 0.001），患者的P50（达到50%饱和度所需的pO2）与他们的DPG之间存在高度显著的关系。在这类患者中，缺氧可能严重到足以刺激DPG合成并导致ODC右移。但这种右移对组织氧合是否有有利影响还完全不确定。实际上，PaO2的极值为3.43至7.96 kPa，对应于SO2为48%至91%，此时ODC尚未达到其上部。因此，右移会减少肺对氧的摄取。另一方面，理论研究表明，在低动脉PO2值时，如果混合静脉PO2降低，ODC右移会对血红蛋白释放氧气产生不利影响。为了量化实际输送到组织的氧量，还需要研究其他因素，如PCO2或温度。
