Korotkoff sounds

Nicolai Sergei Korotkoff described the auscultatory method for measuring blood pressure in the early

Table 18.2. Korotkoff sounds in pregnancy

Phase I:

''A loud clear-cut snapping tone.''

Phase II:

''A succession of murmurs.''

Phase III:

''The disappearance of the murmurs

and the appearance of a tone

resembling to a degree the first

phase but less well marked.''

Phase IV:

(The tone) ''becomes less clear in

quality or dull.''

Phase V:

''The disappearance of all sounds.''

1900s (Segall, 1987). It relies on the auscultation of Korotkoff sounds heard over the brachial artery, distal to a deflating cuff. In 1907 Ettinger described the ''muffling'' in the sequence of vascular sounds and in 1911 Goodman and Howell described five distinct phases, still being used today, as shown in Table 18.2.

The origin of the Korotkoff sounds are not fully understood but it is generally accepted that they are related to either pressure-induced movements of the arterial wall or turbulent flow through a compressed arterial lumen or both (Dock, 1980; London and London, 1967). A study using Doppler ultrasound during a cuff deflation in pregnancy demonstrated that phase I was consistently identified at the onset of flow distal to the cuff, while phase IV was associated with the onset of continuous flow. Phase V occurred when there was an increase in the diastolic component of the arterial waveform (Quinn, 1995).

An auscultatory gap (where no sounds may be heard) can sometimes occur between phases II and III (Cook and Taussig, 1917) and subsequent work has shown this phenomenon to be related to venous congestion. Variation in blood pressure measuring techniques are not uncommon (Perry et al., 1990) and are known to differ widely from the recommended guidelines (Petrie et al., 1986).

Accurate determination of diastolic pressure is still largely dependent on the auscultation of Korotkoff sounds. Various controversies exist around which Korotkoff phase should be used

Table 18.3. Suggested recommendations for blood pressure measurement in pregnancy

Recommendation

Instrument

Setting

Position

Korotkoff sounds

Mercury, aneroid or electronic sphygmomanometer for auscultation or validated oscillometric automated device

Relaxed, quiet environment, preferably after rest Lying or sitting (cuff at heart level) Either arm - right is preferred (higher value if difference >10 mmHg). Dependent upon arm if in a lateral position First (systolic) and fifth (diastolic); if diastolic persistently <40 mmHg use muffling/fourth sound and make a note to identify diastolic pressure: the muffling sound known as Korotkoff phase 4 (K4) or the ''disappearance of sound'' (K5). In non-pregnant individuals, phase 5 is universally recognized to be the diastolic identification point (Kirkendall et al., 1981; Petrie et al., 1986). In pregnancy, hemody-namic changes may cause a number of women to have sounds approaching (or at) zero cuff pressure (MacGillivray etal., 1969). This could be as a result of the diaphragm of the stethoscope being applied with too great pressure (Brown and Whitworth, 1991; Perry etal., 1990; Rubin, 1996).

As K5 is invariably heard and therefore more reproducible than the muffling sounds of K4 (Rubin, 1996; Shennan et al., 1996a), it is our view that K5 should be used in pregnancy. In randomized controlled trials the abandonment of K4 appears to be safe and even beneficial (Brown etal., 1998).

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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Responses

  • maire
    Are korotkoff sounds still used today?
    6 years ago
  • Valente
    When would phase 4 Korotkoff sounds be used?
    6 years ago
  • Makda Nebay
    What causes loud Korotkoff sounds?
    4 years ago

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