645 Effects of position on blood pressure measurement in pregnancy

Abstract

Hypertension in pregnancy is a leading cause of maternal morbidity and mortality. Studies demonstrate that body positions affect the blood pressure (BP) measurements and have led to guidelines for proper positioning by the ACC and AHA. However, studies excluded pregnant women and did not include all common patient positions, such as semi-Fowlers. These studies cannot be applied to pregnant women due to dynamic cardiovascular changes in pregnancy. Our objective was to determine if common patient positions affect BP measurements in pregnant women. This was a prospective study (N=61). We measured BP in pregnant women in inpatient and outpatient settings in several positions including semi-Fowler’s, seated without back and arm support (as on an exam table), and left lateral recumbent. The order of the measurements was randomized, and participants were kept sitting still for 5 minutes between positions. The measurements were compared to BP measurements observed in the published ACC/AHA guideline position: seated with arms and feet supported. Trained team members used an aneroid sphygmomanometer and stethoscope and/or a validated electronic BP machine. There is no significant difference between BP measurements using a sphygmomanometer/stethoscope vs. an electronic BP machine in the ACC/AHA guideline position (systolic p=0.60 diastolic p=0.91). There was not a significant difference in either systolic or diastolic means in the semi-Fowlers position (at 45 degrees measured by goniometer) (systolic P=0.60 diastolic P=0.95). Positioning did affect the diastolic BP measurement in the seated without support position (p=0.01) and both the systolic (p< 0.0001) and diastolic (p<0.0001) measurements in the left lateral recumbent position. Our data demonstrate that an accurate BP measurement in pregnancy is dependent upon patient position. Blood pressure measurements in left lateral recumbency result in clinically significant variation in pregnant women. Semi-Fowler's is a clinically reasonable alternative for measuring blood pressure when pregnant patients need to be lying down.