Using Korotkoff Sounds to Detect the Degree of Vascular Compliance in Different Age Groups

The principle behind the generation of the Korotkoff sounds is the turbulence of blood flowing through a partially occluded area in the artery. With increasing age, the vascular wall compliance is expected to decrease, which is due to the thickening of the vessel wall, due to which the amplitude of the transmitted Korotkoff sounds is decreased. There is also an accompanying rise in the systolic B.P. and pulse pressure.

To record and compare the amplitudes of the intermediate Korotkoff sounds and the blood pressures in individuals of the two age groups, and calculate the pulse pressure and determine whether they vary in relation to the amplitude of the intermediate Korotkoff sounds recorded.

The cross-sectional study was conducted on 50 young subjects (15-25 years) and 50 older subjects (50-70 years). The mid arm circumference was measured using a tape. A phonoarteriogram was placed over the left brachial artery and the sphygmomanometer cuff was tied 2cm above the cubital fossa of the left arm. The blood pressure was recorded using the Lab Tutor software. The Korotkoff sounds picked up and transmitted by the phonoarteriogram are represented as distinct lines on the graphical recording.

Independent samples t-test to look for significant mean amplitude differences and for correlating mean amplitude and pulse pressure. Null hypothesis rejected at p<0.05. Data analysed using the SPSS software version 20.0 (SPSS Inc.).

There was a significant difference in the mean amplitudes of Korotkoff sounds among the different age groups (p=0.001) and subject categories (p=0.043 among males, p=0.037 among females). A significant difference in pulse pressures was also seen among different age groups and subject categories. The decrease in the amplitudes of Korotkoff sounds in the older age group accompanies the increase in pulse pressures seen in this group and the same was seen among the different age groups within each sex (r=-0.574, p=0.001 among males) and (r=-0.449, p=0.002 among females).

Measuring the amplitude of Korotkoff sounds can give us an idea of the nature of the arterial wall as shown by a decrease in amplitude in older individuals when compared to the younger individuals and of the volume of blood flowing through the artery as shown by the higher amplitudes observed in males when compared to females.