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Blood pressure (BP) measurement

BP recording is essential to assess the patient's blood pressure, to know whether the patient is
having normal blood pressure, hypertension o hypotension.
BP apparatus 
Sphygmomanometer was discovered by Riva Rocci. 
Mercury type of manometer is the most reliable standard instrument.
Cuff dimensions
Rubber cuff has a width of 12.5 cm and length of 25 cm, Length: breadth—2:1
In obese people cuff width is 15 cm.
For measuring lower limb, BP cuff width is 18 cm, in children 7.5 cm.
Standard - 15 x 30 cm
Ideal - 12 x 24 cm
Ideal - 18 x 36 cm
Ideal cuff length should be 80% of arm circumference and width should be 40% of arm circumference.

Method of examining blood pressure
  • BP should be first recorded by palpation and then by auscultatory method
  • Patient should be seated in a chair or in supine position
  • Recording should be done after 5 minutes of rest.
  • No smoking or coffee for 30 minutes prior to BP recording
  • Rubber cuff should cover 80% of arm.
  • Cuff 2-5 cm above cubital fossa, Lower border of cuff is not < 2 cm from the cubital fossa.
  • BP apparatus is kept at the level of heart
  • Arm horizontally supported
  • Cuff at the level of the heart
  •  Inflate the cuff while palpating the radial pulse to 30 mm Hg above the level at which the radial pulse is not felt.
  •  Keep the stethoscope over the brachial artery and deflate at a rate of 5 mm/1 sec until the first sound of the Korotkoff heard (Phase I). This is taken as the systolic BP, continue to lower the pressure in the cuff until the sounds disappear (phase V), this indicates the diastolic BP. NIKOLAI KOROTKOFF described the korotkoff sounds in 1905.. 

Three BP measurements done. 2 minutes apart if the value difference is > 5 mm Hg then the first two measurements, then the average  is taken. BP difference between the right and Lt. arm is 10 mm Hg. Arm and leg difference  is 20 mm Hg.

Lower Limb Blood Pressure
Check for calf blood pressure and auscultate over the posterior tibial vessels with the bell.Lowerlimb BP is recorded if coarctation of aortoarteritis and A.R. (Hill's sign) is present

On standing systolic and diastolic BP rises. Fall of systolic 10 mm Hg while standing for 3 minutes is indicative of postural hypotension,
Before labeling a person as hypertensive, 2 or more BP recording at each visit for 3 or occasions at an interval of 2 -3 weeks is a must
Normal          -    130-139/85-89 mm Hg, 
Hypertension > 140/90 mm Hg
Isolated systolic hypertension – SBP mm Hg DBP < 90 mm Hg
Accelerated hypertension-recent increase in BP the previous BP value with evidence of vascular changes in the optic fundi without papilledema
Malignant hypertension-is a triad of high BP of 130-140, papilledema and renal dysfunction

Korotkoff's sounds
Phase 1 : Tapping sound
Phase 2 : Soft murmurs
Phase 3 : Loud murmurs
Phase 4 : Muffled sounds
Phase 5 : Disappearence of sounds
Phase 4 taken as the diastolic pressure in aortic regurgitation and pregnancy.
Auscultatory gap
At times the Korotkoff's sounds disappear between auscultations, it is called the 'auscultatory gap' or the 'silent gap'.This will underestimates sytolic and overestimates diastolic  pressures
Mean blood pressure
Diastolic blood pressure + l/3rd of pulse pressure
Bp measurement in Atrial fibrillation
Average of three readings in the same limb is taken