What is the auscultatory gap and how can it lead to misreading SBP?

• A. A normal phenomenon with no effect
• B. A period of loud sounds during deflation causing overestimation
• C. A period of absent or muffled sounds during deflation often in older hypertensive patients; can cause underestimation of SBP if not recognized
• D. A recommended technique to improve accuracy

Answer: (C)

The auscultatory gap is a period during cuff deflation when the Korotkoff sounds disappear or become muffled, even though the cuff pressure is still higher than the true systolic blood pressure. This phenomenon is more common in older individuals with longstanding hypertension because arteries become stiffer and transmit pressure differently.

Why this matters for systolic readings: the true SBP is the pressure at which sounds first appear as you deflate the cuff. If a gap occurs and sounds disappear, you might stop listening or read the pressure at the point where sounds reappear, which is typically lower than the actual SBP. This leads to underestimating the systolic pressure and can mask how high the patient’s SBP truly is.

To reduce errors, be aware that a gap can exist and use strategies such as palpating the pulse during deflation to estimate SBP, or taking multiple measurements and averaging, and deflating slowly so you don’t misread the pressure during the gap.