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226 PA R T III / Assessment of Heart Disease

160
Artery
occluded, Silence
no flow

Systolic
120
pressure
Artery
compressed,
mm Hg blood flow Sounds of
turbulent flow
audible
Diastolic
80 ■ Figure 10-12 Auscultation of the blood pres-
pressure
sure.
Artery not
compressed,
Silence
flow free
40
and audible

Arterial Effect of cuff Auscultatory
pulse on arterial findings
tracing blood flow

Korotkoff sounds are the sounds created by turbulence of blood of Korotkoff sounds, increase brachial flow by having the patient
flow within the vessel caused by constriction of the blood pressure open and clench a fist; quickly inflate cuff to a value 30 mm above
cuff (Fig. 10-12). The five Korotkoff sounds are summarized in the palpable systolic blood pressure.
Table 10-4. Auscultatory gap is a temporary disappearance of sound that
Systolic blood pressure is the highest point at which initial tap- occurs during the latter part of phase I and phase II (Fig. 10-13).
ping (phase I) is heard in two consecutive beats (to ascertain that
the sound is not extraneous) during expiration. Systolic blood
pressure is higher in the expiratory phase compared to the inspi- Table 10-4 ■ PHASES OF THE KOROTKOFF SOUNDS *
ratory phase of the respiratory cycle (see “Measurement of Para-
doxical Blood Pressure” section). Systolic blood pressure should be Phase I
read to the nearest 2 mm Hg mark on the manometer. The pressure level at which the first faint, consistent tapping sounds are
heard. The sounds gradually increase in intensity as the cuff is deflated.
Diastolic blood pressure is equated with disappearance of Ko- The first of at least two of these sounds is defined as the systolic pressure.
rotkoff sounds (phase V) in adults. Phase V most closely approx- Phase II
imates intra-arterial diastolic pressure. Muffling of sounds (phase The time during cuff deflation when a murmur of swishing sounds is heard.
IV) usually occurs at pressures 5 to 10 mm Hg higher than intra- Phase III
arterial diastolic pressures and, therefore, is not a good indicator The period during which sounds are crisper and increase in intensity.
of diastolic blood pressure in adults. However, muffling, rather Phase IV
than disappearance of sounds, is a better index of intra-arterial di- The time when a distinct, abrupt, muffling of sound (usually of a soft blow-
astolic pressure in children and in adults with hyperkinetic states. ing quality) is heard. This is defined as the diastolic pressure in anyone in
Hyperkinetic conditions, including hyperthyroidism, aortic insuf- whom sounds continue to zero.
ficiency, and exercise, increase the rate of blood flow, resulting in Phase V
disappearance of sounds (absence of turbulence) far below intra- The pressure level when the last regular blood pressure sound is heard and
after which all sound disappears. This is defined as the diastolic pressure
arterial diastolic pressure. In children and adults with hyperki- unless sounds are heard to zero.
netic states, sounds can be detected below muffling for much
longer than normal. 22 As with systolic blood pressure, read dias- *To avoid error, the observer must be prepared to recognize two normal Korotkoff sound
tolic pressure to the nearest 2 mm Hg mark on the manometer. variations associated with blood pressure (BP) readings. The auscultatory gap is a period
If there is a difference of 10 mm Hg or more between disappear- of silence occurring during Korotkoff phases I and II. This disappearance of sound is
temporary and is usually short, but the gap can occur over a period of 40 mm Hg. It
ance and muffling of sounds, record both diastolic pressures (e.g., seems to be associated with higher BP readings. An absent Korotkoff phase V occurs
140/56/20 mm Hg). 22 when sounds are heard to zero. When this is the case, phase IV should be recorded
along with phase V. In this case, phase IV is the best reference for diastolic pressure.
In some patients, Korotkoff sounds may be soft and could re-
Grim, C. M., & Grim, C. E. (2003). Blood pressure measurement. In J. L. Izzo & H. R.
sult in falsely low blood pressure values. To augment the loudness Black (Eds.), Hypertension primer (3rd ed.). Dallas, TX: American Heart Association.