Of Funnel Arms, Popeye, and Other‐Sized Challenges

One problem that occasionally challenges the ability of a health care provider to measure blood pressure is the physical shape of the upper arm. As an example, in my last clinic session, I evaluated a woman short in stature (approximately 5 feet tall) whose arm circumference near the shoulder was much greater than the arm circumference near the elbow. Moreover, her short stature also translated into a relatively short humerus length. When I applied the standard adult thigh‐sized cuff (the Velcro on the large adult cuff was unable to meet at the two surfaces), the shoulder end of the thigh cuff was snug, but the elbow end of the cuff was loose and extended past the elbow by 2 inches. When the bladder is inflated, it will expand in multiple irregular directions, rendering that odd sound that indicates that the standard approach to blood pressure measurement is inadvisable. What do you do when faced with rogue anatomy like this “funnel arm”? The American Heart Association devotes two lines to it on page 705 of the citation below, ¹ which supports what I recommend.

The tactic I use to measure blood pressure in this instance is to apply the cuff to the forearm. Most of the time a funnel upper arm has a “Popeye” forearm that is quite amenable to a regular or large adult cuff. I turn the cuff 180 degrees to keep the rubber tubes from being a nuisance since there is limited working space at the wrist with this technique. By inflating the cuff while palpating the radial artery you will have a good sense of the systolic pressure. When possible, I confirm the systolic pressure by using the thigh cuff on the upper arm and palpating the radial artery even though the brachial artery is buried and inaccessible to the stethoscope. Once you are 20‐30 mm Hg above the palpated systolic at the radial, deflate the forearm cuff and listen over the radial artery. Sometimes, however, the sounds are very soft and it is difficult to be certain what the blood pressure is. In this instance, I have the patient reach upward using the arm with the cuff and count slowly to 10. This drains the arm's venous system and results in an improvement in the sounds that the blood makes as the cuff is deflated; this often makes it possible to get a good (and accurate) blood pressure reading. At least one clinical study confirms that a forearm blood pressure in obese patients is comparable to the standard upper arm one. ² The only caveat is that the systolic pressure will generally be a little higher (2‐3 mm Hg on average) in the wrist.

Lastly, if you can feel the radial pulse but cannot hear any beating sounds over the radial artery with a forearm cuff, consider using an oscillometric wrist blood pressure kit. The Omron RX (Omron Healthcare UK, West Sussex, United Kingdom), the Nissei WS‐310 (Nissei Seinutsu Sokki, Ca, Ltd, Gunma, Japan), and the Braun PrecisionSensor (Braun GmbH, Kronberg, Germany) have been used for this purpose. ³ , ⁴ The former two tend to have more variability in the systolic pressure readings than the latter.