NEW YORK NURSE: October/November 2007
by Gina Myers, PhD, RN, CCRN, Assistant Professor, SUNYIT School of Nursing and Health Systems; Member, Foundation Center for Nursing Research Planning Committee
In practice there are times when a blood pressure (BP) measurement cannot be taken in the upper arm and the forearm is used. You may wonder if the two measures are equivalent. Research has produced conflicting evidence suggesting that upper and forearm measurements are both similar and different. Singer, et al. (1999) concluded that the forearm could be used when the upper arm was not available. Conversely, Schell, et al. (2005) determined there were large differences in systolic pressure depending on the location.
Recently, a follow-up study to assess noninvasive automatic BP measurement was published in the American Journal of Critical Care (2006). The study (a) compared BP measurements in the upper and forearm and (b) looked at the impact of positioning on BP taken in the upper and forearm. A convenience sample of 221 stable patients was recruited from medical-surgical units in an acute care hospital. Each patient’s BP was taken in the upper arm and forearm, in both the supine and 45-degree positions. The arm was placed at the patient’s side for each measurement. Men (46.6%) and women (52.9%) in the study were mainly Caucasian (82.5%) with a mean age of 61.5 years. Most patients were considered overweight or obese and were admitted for cardiovascular, respiratory, or gastrointestinal disorders. The researchers used the same automatic BP equipment for all patients and trained data collectors to apply cuffs and take measurements in the same way to ensure consistency.
The data was analyzed to assess the correlation between the upper and forearm pressure measurements. Researchers also used a special statistical procedure, called the Bland-Altman analysis, to determine if pressures in the upper and forearm can be considered compatible.
Overall, the pressure measurements in the forearm were significantly higher than the upper arm, regardless of position (supine or 45-degree elevation). Correlation analysis determined there was a relationship between the pressures – if one was high, the other was high. There was a large difference, however, in the average systolic and diastolic blood pressure depending on where it was taken and regardless of patient position. Further, the Bland-Altman analysis did not find systolic or diastolic pressure readings in the upper and forearms to be interchangeable, regardless of position.
Should we continue to use the forearm for measurement when necessary? Before answering this question, there are a few points that must be considered. In previous studies the patient’s arm was positioned at the level of the heart. In this study the arm was placed by the patient’s side. The researchers note that this difference in arm position might have caused some of the difference in the BP readings. Also, this study did not include many non-white patients, patients who smoke, or those needing an extra large cuff. Thus, the results may not be able to be directly applied to those populations.
Here’s how we can apply this to practice: (a) BP does vary depending on the location of the cuff and on how the patient and the patient’s arm is positioned; (b) when taking a BP in the forearm, the nurse needs to be aware that those readings may be higher than those in the upper arm; and (c) those sitting at a 45-degree elevation will have higher BP readings. Therefore, if the BP is not taken in the traditional location, this needs to be documented and reported. The elevation of the head of the bed also makes a difference in pressure readings and must be documented. It is important to follow your organization’s procedure for taking a BP with regard to location of the cuff and positioning of the arm to provide consistency in measurements. If your organization’s procedure does not specify where the cuff or the arm should be positioned, you can take this study to the procedure committee to ask for a clarification or change in policy. The appropriate use of the forearm for BP measurements should also be specified in policy.
Schell, K., Lyons, D., Bradley, E., Bucher, L., Seckel, M., Wakai, S., et al. (2006). Clinical comparison of automatic, noninvasive measurements of blood pressure in the forearm and upper arm with the patient supine or with the head of the bed raised 45°: A follow-up study. American Journal of Critical Care, 15(2), 196-205.
Schell, K., Bradley, E., Bucher, L., Seckel, M., Lyons, D., Wakai, S., et al. (2005). Clinical comparison of automatic, noninvasive measurements of blood pressure in the forearm and upper arm. American Journal of Critical Care, 14(3), 232-241.
Singer, A.J., Kahn, S. R., Thode, H.C., & Hollander, J.E. (1999). Comparison of forearm and upper arm blood pressure. Prehospital Emergency Care, 3(2), 123-126.