ALTERATIONS OF OCCLUSIVE CUFF IMPEDANCE PLETHYSMOGRAPHY RESULTS IN THE OBSTETRIC PATIENT

Abstract

Impedance plethysmography (IPG) is an attractive diagnostic method for evaluating deep vein thrombosis in the pregnant patient because it is noninvasive and it avoids X-ray or radionuclide exposure. The accurate diagnosis of deep venous thrombosis by IPG in pregnant patients might be altered by the normal physiologic and anatomic changes that occur during pregnancy. Healthy women [50] were evaluated by IPG throughout their pregnancies and during their nonpregnant state. Venous capacitance during pregnancy increases 50% over venous capacitance during the nonpregnant state. Most of this change occurs during early pregnancy because of a decrease in venous tone caused by rising levels of progesterone and estradiol. During the 3rd trimester of pregnancy venous outflow is diminished compared to outflow during early pregnancy. Venous obstruction by the gravid uterus and fetal head engaging in the pelvis are factors that contribute to this finding. The IPG results in 4 patients with ileofemoral thrombosis and in 3 with postpartum pulmonary emboli are reported. IPG may be utilized as an accurate diagnostic technique in the pregnant woman if the physiologic and anatomic alterations of pregnancy, which are reflected as significant changes in venous capacitance and outflow on IPG testing, are considered.