A Q&A column for those new to the cath lab

I don’t work in the cath lab, but I do read the articles in CLD. I work in an EKG department at a small hospital. When performing stress tests, the cardiologist often tells me to listen closely for the “thumps” when I am taking a blood pressure. Is he talking about what I am listening to? – Via www.facebook.com/RCISREVIEW, from a hospital staff member in rural Montana What he is probably talking about are the “Korotkoff” sounds you hear when you are taking the blood pressure of your patient. One important note about taking blood pressures: make sure the brachial artery is at the level of the heart. The same principles apply to this procedure as for the use of a transducer during invasive pressure monitoring in the cath lab. The equipment being used to measure the pressure must be placed at the level where the heart is (phlebostatic axis…a topic for another article). These are the thumping/swooshing sounds you hear when taking a blood pressure with a manual blood pressure cuff. Simply put, when the cuff pressure is higher than the systolic pressure, the vessel is occluded and no sounds are heard. As the cuff pressure drops, you can hear the thumping noise as the systolic pressure rises above the cuff pressure. As the cuff is being deflated and eventually exerts pressure less than the diastolic pressure, the sounds go away (Figure 1).This usually happens in 5 discrete stages. Dr. Korotkoff, a vascular surgeon, spent much of his life studying these principles and wrote a paper on them in 1905.¹ While performing his research, he found that these 5 stages could be distinguished by careful listening (Figure 2). Korotkoff actually described five types of sounds: 1. The 1st sound is the ‘snapping’ sound first heard at the systolic pressure. Clear tapping, repetitive sounds for at least two consecutive beats is considered the systolic pressure. This tapping occurs because there is enough pressure during systole to force the vessel open and squeeze some blood through it, snapping shut as systole wanes and closing the vessel again. 2. The 2nd sounds are the murmurs heard for most of the area between the systolic and diastolic pressures. These are “swooshing” sounds as more blood flow occurs through the vessel during systole* 3. The 3rd sound is a loud, crisp tapping sound.* 4. The 4th sound, at pressures within 10 mmHg above the diastolic blood pressure, were described as “thumping” and “muting” because the blood flow is become less turbulent as the cuff pressure is decreasing. 5. The 5th sound is silence, as the cuff pressure drops below the diastolic blood pressure. The disappearance of sound is considered diastolic blood pressure — two points below the last sound heard. *These sounds have not been shown to have any clinical relevance.² If you would like to hear these sounds, or other sounds through a stethoscope, a great online resource is available via through “Think Labs Stethoscope Community,” online at: https://www.thinklabsmedical.com/stethoscope_community/Sound_Library Email your question to tginapp@rcisreview.com.

References

1. Shevchenko YL, Tsitlik JE. 90th anniversary of the development by Nikolai S. Korotkoff of the auscultatory method of measuring blood pressure. Circulation 1996; 94: 116-118. Available online at https://circ.ahajournals.org/cgi/content/full/94/2/116. Accessed April 13, 2010. 2. Pickering TG, Hall JE, Appel LJ, et al. Recommendations for blood pressure measurement in humans and experimental animals. Part 1. Hypertension 2005; 45(5): 142-161. Available online at https:// hyper.ahajournals.org/cgi/content/full/45/1/142. Accessed April 13, 2010.

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