The stethoscope
The original stethoscope, a rigid wooden cylinder with a funnel, has evolved into the modern instrument which has two chest pieces, a shallow bell and a stiff diaphragm, connected to the ear pieces by 25-30 cm of tubing. You should perform auscultation after the traditional examination sequence of inspection, palpation, and percussion. The patient should be lying comfortably in a quiet environment-clinical signs may occasionally be missed in a noisy casualty department. It is helpful to be aware of the findings expected in health and disease before approaching the patient with a stethoscope. This avoids spending many hours listening without hearing.

High frequency sounds or murmurs (for example, splitting of sounds, opening snaps, aortic diastolic murmurs) are easier to hear with the diaphragm. The bell, which should be applied lightly to the chest, transmits low frequency sounds more effectively-for example, diastolic murmur of mitral stenosis and third and fourth heart sounds. For routine examination of the heart you should use both the bell and diaphragm. The diaphragm is usually adequate for examination of the chest and abdomen.

The patient should be sitting or lying comfortably. Wrap an occlusion cuff connected to a sphygmomanometer around the upper arm and inflate it to a pressure about 30 mm Hg above the level at which the radial pulsation can no longer be felt. Place the stethoscope lightly over the brachial artery-it helps to feel for this artery before inflating the cuff. Next lower the pressure until you hear the first sounds (phase I Korotkoff). This is the systolic blood pressure. You should then lower the cuff pressure continuously until the sounds become faint or muffled (phase IV) and subsequently disappear completely (phase V). The phase V reading is usually taken as the diastolic pressure, but the true pressure probably lies between phases IV and V. Blood pressure should be recorded as rapidly as accuracy allows because compression of the arm can itself cause a rise in blood pressure.
In patients with severe aortic regurgitation, when the disappearance point may be extremely low or even 0 mm Hg, the Korotkoff IV reading is closer to the true diastolic pressure. If you find a large difference between phase IV and V pressures both readings should be recorded. Occasionally a gap may occur between the first appearance of the Korotkoff sounds and their reappearance at a lower pressure. This auscultatory gap, if not appreciated, may cause you to overestimate the diastolic pressure or underestimate systolic pressure.
The average adult cuff measures 12 cm, but if the patient has very fat arms a wider cuff such as a thigh cuff should be used to avoid false readings. It is important that the patient should be as relaxed as possible when the blood pressure is taken. Readings can be significantly altered by anxiety, exertion, postural changes, or the "white coat" effect. The first reading is often high due to anxiety, which may be indicated by a high pulse rate. The second reading is usually more representative. Patients should not be regarded as having hypertension on the basis of a single measurement unless the blood pressure is very high. You should normally have evidence of raised blood pressure on at least three occasions several weeks apart to confirm hypertension.