Measuring Blood Pressure


Related Posts:

This figure includes two photographs. The first photo shows a young adult male placing a blood pressure cuff on the upper arm of a young adult female. The second image shows a typical sphygmomanometer, which includes a black blood pressure cuff, tubing, pump, and pressure gauge.
Figure 1. (a) A medical technician prepares to measure a patient’s blood pressure with a sphygmomanometer. (b) A typical sphygmomanometer uses a valved rubber bulb to inflate the cuff and a diaphragm gauge to measure pressure. (credit a: modification of work by Master Sgt. Jeffrey Allen)

Measuring Blood Pressure (OpenStax Chemistry 2e)

Blood pressure is measured using a device called a sphygmomanometer (Greek sphygmos = “pulse”). It consists of an inflatable cuff to restrict blood flow, a manometer to measure the pressure, and a method of determining when blood flow begins and when it becomes impeded. Since its invention in 1881, it has been an essential medical device. There are many types of sphygmomanometers: manual ones that require a stethoscope and are used by medical professionals; mercury ones, used when the most accuracy is required; less accurate mechanical ones; and digital ones that can be used with little training but that have limitations. When using a sphygmomanometer, the cuff is placed around the upper arm and inflated until blood flow is completely blocked, then slowly released. As the heart beats, blood forced through the arteries causes a rise in pressure. This rise in pressure at which blood flow begins is the systolic pressure—the peak pressure in the cardiac cycle. When the cuff’s pressure equals the arterial systolic pressure, blood flows past the cuff, creating audible sounds that can be heard using a stethoscope. This is followed by a decrease in pressure as the heart’s ventricles prepare for another beat. As cuff pressure continues to decrease, eventually sound is no longer heard; this is the diastolic pressure—the lowest pressure (resting phase) in the cardiac cycle. Blood pressure units from a sphygmomanometer are in terms of millimeters of mercury (mm Hg).


Flowers, P., Theopold, K., Langley, R., & Robinson, W. R. (2019, February 14). Chemistry 2e. Houston, Texas: OpenStax. Access for free at:


Related Research

Research Article: A Man with Labile Blood Pressure

Date Published: April 24, 2007 Publisher: Public Library of Science Author(s): Ronald C. W Ma, Kwok Hing Yiu, Edward H. C Wong, Kin Hung Liu, Joseph Y. S Chan, Chun Chung Chow, Clive S Cockram Abstract: Ronald Ma and colleagues discuss the differential diagnosis and management of a patient who presented with recurrent episodes of … Continue reading

Research Article: Blood Pressure Modifies Retinal Susceptibility to Intraocular Pressure Elevation

Date Published: February 16, 2012 Publisher: Public Library of Science Author(s): Zheng He, Christine T. O. Nguyen, James A. Armitage, Algis J. Vingrys, Bang V. Bui, Demetrios Vavvas. Abstract: Primary open angle glaucoma affects more than 67 million people. Elevated intraocular pressure (IOP) is a risk factor for glaucoma and may reduce nutrient availability by … Continue reading

Research Article: Blood pressure and expression of microRNAs in whole blood

Date Published: March 9, 2017 Publisher: Public Library of Science Author(s): Zhou Zhang, Brian Thomas Joyce, Jacob K. Kresovich, Yinan Zheng, Jia Zhong, Ruchi Patel, Wei Zhang, Lei Liu, Chang Dou, John P. McCracken, Anaité Díaz, Valeria Motta, Marco Sanchez-Guerra, Shurui Bian, Pier Alberto Bertazzi, Joel Schwartz, Andrea A. Baccarelli, Sheng Wang, Lifang Hou, Zhanjun … Continue reading

Research Article: Valuation of Normal Range of Ankle Systolic Blood Pressure in Subjects with Normal Arm Systolic Blood Pressure

Date Published: June 8, 2015 Publisher: Public Library of Science Author(s): Yi Gong, Kai-wu Cao, Jin-song Xu, Ju-xiang Li, Kui Hong, Xiao-shu Cheng, Hai Su, Tatsuo Shimosawa. Abstract: This study aimed to establish a normal range for ankle systolic blood pressure (SBP). A total of 948 subjects who had normal brachial SBP (90-139 mmHg) … Continue reading

Research Article: Gene Silencing and Haploinsufficiency of Csk Increase Blood Pressure

Date Published: January 11, 2016 Publisher: Public Library of Science Author(s): Hyeon-Ju Lee, Ji-One Kang, Sung-Moon Kim, Su-Min Ji, So-Yon Park, Marina E. Kim, Baigalmaa Jigden, Ji Eun Lim, Sue-Yun Hwang, Young-Ho Lee, Bermseok Oh, Zhanjun Jia. Abstract: Recent genome-wide association studies have identified 33 human genetic loci that influence blood pressure. The 15q24 … Continue reading