To interpret heart sounds accurately, the examiner must be able to time the events of the cardiac cycle. The most reliable way of identifying S1 and S2 is to time the sounds by palpating the carotid artery. While the examiner's right hand is positioning the stethoscope, the left hand is placed on the patient's carotid artery. This technique is demonstrated in Figure 14-32. The sound that precedes the carotid pulse is the S1. The S2 follows the pulse. The carotid, not
Figure 14-32 Technique for timing the heart sounds.
the radial pulse, must be used. The time delay from S2 to the radial pulse is significant, and errors in timing will result.
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