Korotkoff sounds

西元1905年，一位俄國心血管外科醫生Nikolai Korotkov發現讓醫生以非侵性的方式，經由聲音來辨別血壓的方法。

以前我們在幫別人量血壓都只知道，選擇合適的cuff，接著加壓應高於收縮壓20-30mmHg以上，每秒下降2-3mmHg的速度放氣。一開始血管完全被壓扁，所以是聽不見聲音的，隨著cuff慢慢降壓，此時血壓大於cuff壓力，開始有一些血液流過，因為是亂流(turbulent blood flow)的關係會有聲音產生，這時候的壓力就是收縮壓(systolic pressure)，接著再繼續放氣，直到聲音完全消失的時候，此時血管完全放鬆，就是所謂的舒張壓(diastolic pressure)。
一直以來量血壓的步驟就被視為理所當然，綁cuff→打氣→放氣→有聲音(收縮壓)→再放氣→沒聲音(舒張壓)，一直到後來才知道，原來一開始有的第一聲是Korotkoff sounds(phase I)，而最後聲音完全消失是Korotkoff sounds(phase V)。

克羅克夫聲(Korotkoff sounds) 總共可以分成5 phase，一開始的聲音較大聲也較為響亮，隨著壓力的減弱，聲音的質地也有所改變，變得比較減弱且不清楚(muted and muffled)

1. The first Korotkoff sound is the snapping sound first heard at the systolic pressure. Clear tapping, repetitive sounds for at least two consecutive beats is considered the systolic pressure.
2. The second sounds are the murmurs heard for most of the area between the systolic and diastolic pressures.
3. The third = A loud, crisp tapping sound.
4. The fourth sound, at pressures within 10 mmHg above the diastolic blood pressure, were described as "thumping" and "muting".
5. The fifth Korotkoff sound is silence as the cuff pressure drops below the diastolic blood pressure. The disappearance of sound is considered diastolic blood pressure -- two mm Hg above the last sound heard.

The second and third Korotkoff sounds have no known clinical significance.