The cuff pressure at the onset of phase I sounds (often referred to as K1) is thought to represent systolic BP. Each of the four sounds heralds a phase of similar sounds and thereby produces four corresponding Korotkoff phases (phases I, II, III, and IV). There are four different types of Korotkoff sounds described when one listens at the antecubital fossa during arm cuff deflation. Blood pressure was first measured with a mercury sphygmomanometer, using K5 (if present) for diastolic pressure. A Doppler ultrasound probe (Dopplex, Huntleigh Healthcare Luton, Bedfordshire, UK) was used to locate the clearest pulsatile signal at the antecubital fossa and the skin marked with a waterproof pencil. A pressure cuff (bladder width at least 40% of arm circumference) was placed around the left arm and supported near heart level using a cushion. Participants sat quietly for at least 10 min before the measurements. The studies were carried out in a quiet room, in the school for children and in the University campus for adults. In adults the cuff deflated from 190 mm Hg and rapidly deflated after 35 mm Hg. 4 The cuff deflation was programmed to start at 160 mm Hg in children and rapidly deflate below 30 mm Hg. The average deflation rate was −2.9 mm Hg/beat, which is within the recommendations of the British Hypertension Society for Blood Pressure measurement. To obtain a controlled release of air from the arm cuff, the deflation device from an automatic BP monitor (A&D Blood Pressure Monitor, TM2421 ) was used to provide consistent cuff deflation. The operator listened through studio quality audio headphones during recording and playback. The signal was then passed to a MiniDisc digital recorder (Sony, Japan), which provided high quality sound reproduction with low noise. An amplifier was connected to the microphone with the bandwidth of the amplifier extending to 3 kHz, which was chosen to provide realistic and faithful audio quality reproduction on listening. The bell of a pediatric or adult stethoscope was used, depending on the age group being studied. 3 Briefly, the bell of a Littmann cardiology grade stethoscope was attached to a miniature, high sensitivity ceramic microphone. The Korotkoff sound measurement system has been described in detail in another study. Anyone with a history of hypertension was excluded. Adult volunteers were recruited from the domestic and clerical staff of the nearby hall of residence. The study was carried out on a normal school day that did not include a physical educa-tion class. After a visit to the school, children interested in participating in the study took a consent form home, which was approved by the local ethics committee, for their parent or guardian to sign. The study was confined to children aged 7 to 8 years. Two local primary schools agreed to participate in the study. The aims of this study were to describe the pattern of Korotkoff phase distribution in a population of normal adults and children to measure the duration of each of the phases and to describe the differences in the Korotkoff phases between adults and children. Even though it is well recognized that normal children may have no phase V, 2 it is not known whether the other phases may be absent. The onset of phases I, IV, and V are currently of clinical interest, but the intervening phases have received almost no clinical attention. 1 The five phases that we now recognize as the “Korotkoff phases” are heard by placing a stethoscope over the brachial artery and listening for the changing character of the sounds during deflation of the blood pressure (BP) cuff. Nikolai Korotkoff described the sounds that bear his name in 1905. Blood pressure determination, auscultationĭr.
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