Korotkoff's sounds in pregnancy.

Korotkoff described the sequence of vascular sounds heard with a stethoscope over the brachial artery during deflation of a pneumatic cuff. The initial sounds are produced by vibrations of the vessel wall, although the sequence of vascular sounds has frequently been ascribed to 'turbulence' of flow in the vessel. This study has been performed to determine the relationship between the vascular sounds (Korotkoff I-V) produced during blood pressure cuff deflation and specific changes in the brachial artery waveform. Ten nulliparous women admitted to hospital in the third trimester of pregnancy have been studied by means of concurrent Doppler ultrasound and phonocardiography. Changes in the brachial artery waveform during blood pressure cuff deflation were recorded using Doppler ultrasound (7.5 MHz) with concurrent objective demonstration of phases I-V of the vascular sounds using a phonocardiography microphone. Characteristic features of the brachial artery waveform were associated with phases I-IV of the vascular sounds in all patients (10/10). No consistent features of the brachial artery waveform were associated with phase V of the vascular sounds. Phases I-IV of the vascular sounds are associated with specific changes in the pattern and direction of flow within the brachial artery in normotensive primigravid women. The vascular sounds produced by vibration of the vessel wall are modulated by changes in blood flow to produce the characteristic sequence of vascular sounds detected with a stethoscope during blood pressure cuff deflation.