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Jesús Moisés Suárez Gómez edited this page May 4, 2016 · 3 revisions

The measurement of arterial blood pressure plays an important role in both investigational and clinical spheres of Medicine. Several non-invasive methods of measurement of the systolic and the diastolic arterial blood pressure have been described and developed: sphygmomanometry, oscillometry, Doppler ultrasound, pulse transit time (PTT) and photoplethysmography (PPG). (1.2.3.4.5)

Sphygmomanometry consists in a device composed by an inflatable cuff which collapses and then releases an artery under the cuff, most frequently an artery of the arm, and a manometer to measure the pressure; combined with the audible detection of Korotkoff sounds with a phonendoscope. Manual sphygmomanometry with a phonendoscope has several examiner-dependant sources of error, but still remains as the standard method of blood pressure measurement in the clinical practice. (1.6)

Oscillometry is the most extended method for automatic non-invasive blood pressure (NIBP) measurement. It is based on the analysis of the pressure waves in the cuff during cuff deflation after inflating it above the systolic blood pressure (SBP). The process is similar to that of the manual sphygmomanometry, so it is known as automatic sphygmomanometry. The estimation of the pressure by empirical criteria is the main source of error in oscillometry since it is dependant on cuff and arterial factors. (7)

Trans-esophageal and thoracic echocardiography or Doppler is a feasible technique for non-invasive, real-time measurement of arterial blood flow and blood pressure. Information is obtained from the size, shape, and changes in shape of the velocity waveforms of arterial blood flow. Minute distance, the product of waveform area (stroke distance) and heart rate, provides a measure of cardiac output. This technique provides a useful alternative to invasive hemodynamic monitoring, both in the ICU and perioperatively. (3.8)

PTT has been suggested for NIBP monitoring however its implementation into clinical practice was hampered by lack of non-expensive practical solutions. In this case, there might be a need for an improved measurement accuracy of the sensors and data processing techniques in use. The applicability of the Moens-Korteweg equation used in the estimation is also questionable for young people having flexible arteries. In this later case, significant radius changes do occur in the large arteries during exercise, which might counteract a PTT decrease with the blood pressure elevation. These radius effects are excluded from the Moens-Korteweg model. (4.9.10)

When PPG is combined with pressure cuffs, the PPG pulses disappear for cuff-pressures above the SBP and reappear when decreases below the SBP. The high signal-to-noise ratio of measured PPG pulses indicates that automatic measurement of the SBP by means of automatic detection of the PPG signals is feasible. However, PPG-based SBP and diastolic blood pressure (DBP) could underestimate cuff-measured pressure by 8 mmHg and overestimate by 10 mmHg respectively, which is a clinically significant error. However, due to the scarce publications about the potential use of PPG in the NIBP measurement and the many factors implicated in the fiability of the technique, we hypothesized that the assumed limitations should be reevaluated. (5.11)

References.
  1. Kaplan NM. Kaplan's Clinical Hypertension. 8. Ch. 2. Philadelphia: Lippincott Williams & Wilkins; 2002.
  2. Reshetnik A., Gohlisch C., Zidek W., Tölle M., van der Giet M. Central blood pressure assessment using oscillometry is feasible for everyday clinical practice. J Hum Hypertens. 2016 Apr 28. doi: 10.1038/jhh.2016.21.
  3. de Bisschop C., Montaudon M., Glénet S., Guénard H. Feasibility of intercostal blood flow measurement by echo-Doppler technique in healthy subjects. Clin Physiol Funct Imaging. 2015 Oct 2. doi: 10.1111/cpf.12298.
  4. Patzak A., Mendoza Y., Gesche H., Konermann M. Continuous blood pressure measurement using the pulse transit time: Comparison to intra-arterial measurement. Blood Press. 2015;24(4):217-21. doi: 10.3109/08037051.2015.1030901. Epub 2015 Apr 10.
  5. Li Y., Wang Z., Zhang L., Yang X., Song J. Characters available in photoplethysmogram for blood pressure estimation: beyond the pulse transit time. Australas Phys Eng Sci Med. 2014 Jun;37(2):367-76. doi: 10.1007/s13246-014-0269-6. Epub 2014 Apr 11.
  6. Pickering TG, Blank SG. Blood pressure measurement and ambulatory blood pressure monitoring. In: Laragh JH, Brenner BM, editor. Hypertension: Pathophysiology, Diagnosis and Management. Ch. 89. New York: Raven Press; 1990.
  7. van Monfrans GA. Oscillometric blood pressure measurement: progress and problems. Blood Pressure Monitoring. 2001;6:287–290. doi: 10.1097/00126097-200112000-00004.
  8. Singer M, Clarke J, Bennett ED. Continuous hemodynamic monitoring by esophageal Doppler. Crit Care Med. 1989 May;17(5):447-52.
  9. Jeong Ic, Finkelstein J. Optimizing non-invasive blood pressure estimation using pulse transit time. Stud Health Technol Inform. 2013;192:1198.
  10. Proença J, Muehlsteff J, Aubert X, Carvalho P. Is pulse transit time a good indicator of blood pressure changes during short physical exercise in a young population? Conf Proc IEEE Eng Med Biol Soc. 2010;2010:598-601. doi: 10.1109/IEMBS.2010.5626627.
  11. Nitzan M, Adar Y, Hoffman E, Shalom E, Engelberg S, Ben-Dov IZ, Bursztyn M. Comparison of systolic blood pressure values obtained by photoplethysmography and by Korotkoff sounds. Sensors (Basel). 2013 Oct 31;13(11):14797-812. doi: 10.3390/s131114797.
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