Blood pressure Lecture 5 Dr. Mervat Abdelrahman M

Blood vessels Blood vessels – tubular structures, with particular named layers from innermost to outermost: INNERMOST to OUTERMOST Tunica Intima Tunica Media Tunica Adventitia 2

Blood Pressure What drives blood along the blood vessels after it has left the heart? Blood pressure is the pressure exerted by the blood on the walls of the blood vessels. Blood pressure values are universally stated in millimeters of mercury (mmHg). The systolic pressure is defined as the peak pressure in the arteries during the cardiac cycle; the diastolic pressure is the lowest pressure (at the resting phase of the cardiac cycle). 3

Blood Pressure Typical values for a resting, healthy adult are approximately 120 mmHg systolic and 80mm Hg diastolic (written as 120/80 mmHg), with individual variations. These measures of blood pressure are not static, but undergo natural variations from one heartbeat to another, and throughout the day they also change in response to stress, nutritional factors, drugs, or disease. 4

Arterial Blood Pressure (continued)  Diastolic pressure is more important, because diastolic period is longer than the systolic period in the cardiac cycle.  Diastolic time is important Because it is the time for filling of the coronary arteries with blood  So in case of increased diastolic pressure there is angina pain In normal adult  120/80 mmHg. 5

The peripheral resistance Blood pressure= Cardiac output× peripheral resistance  As the blood flows from the arterial to the venous side of the circulation, it meets resistance because of the smaller caliber of the vessels and the viscous nature of the blood. This is called the peripheral resistance.  It is an important factor in generating and maintaining the arterial blood pressure.  Vasoconstriction of the small vessels increases the peripheral resistance, which in turn elevates the arterial blood pressure. Whilst vasodilatation decreases the resistance and lowers the pressure. 6

Blood pressure Blood pressure Preparation for measurement  Patient should abstain from eating, drinking, smoking and taking drugs that affect the blood pressure one hour before measurement.  Instruct your patients to avoid coffee, smoking or any other un prescribed drug on the day of the measurement  Because a full bladder affects the blood pressure it should have been emptied 7

Preparation for measurement Painful procedures and exercise should not have occurred within one hour. Patient should have been sitting quietly for about 5 minutes. BP take in quiet room and comfortable temperature, must record room temperature and time of day. Position of the Patient Sitting position Arm and back are supported. Feet should be resting firmly on the floor Feet not dangling. 8

Position of the arm The measurements should be made on the right arm whenever possible. Patient arm should be resting on the desk and raised (by using a pillow) Raise patient arm so that the brachial artery is roughly at the same height as the heart. If the arm is held too high, the reading will be artifactually lowered, and vice versa. Palm is facing up. The arm should remain somewhat bent and completely relaxed 9

In order to measure the Blood Pressure (equipment) Pediatric Cuff size Adult Cuff size –Cuff Width –Cuff Length –If it is too small, the readings will be artificially elevated. The opposite occurs if the cuff is too large. Clinics should have at least 2 cuff sizes available, normal and large. –The manometer scale should be at eye level, and the column vertical. The patient should not be able to see the column of the manometer 10

Arterial Blood Pressure Measurement o With the subject seated, apply the cuff of the sphygmomanometer around the upper arm of the subject so that the hosing for the cuff is positioned over the cubital fossa. o Apply the bell of the stethoscope to the skin over the brachial artery in the cubital fossa. o Close the screw valve on the hand pump and pump the cuff to a pressure of ~160 mmHg. Do not exceed 180 mmHg. o Open the screw valve on the pump to slowly release the pressure, listening to the brachial artery through the stethoscope and noting at what pressure the sounds of Korotkoff (the sounds generated by blood turbulence in a partially occluded artery) begin (systolic pressure) and end (diastolic pressure). Record these values. 11

Measuring blood pressure –Blood Pressure: Measured with two numbers 1.First number – systolic pressure 2.Second number – diastolic pressure 12

Remember the following for accuracy of your readings If the BP is surprisingly high or low, repeat the measurement towards the end of your exam (Repeated blood pressure measurement can be uncomfortable). Physician will want to see multiple blood pressure measurements over several days or weeks before making a diagnosis of hypertension and initiating treatment. 13

Blood pressure Hypotension: abnormal low blood pressure. Sustained systolic blood pressure of below 100 mmHg. Hypertension : High blood pressure arterial blood pressure of 140/90 mm Hg or above. 14

Factors affecting ABP ■ Sex … M > F …due to hormones/ equal at menopause. ■ Age … Elderly > children …due to atherosclerosis. ■ Emotions …  due to secretion of adrenaline & noradrenaline. ■ Exercise …  due to  venous return. ■ Hormones …  (e.g. Adrenaline, noradrenaline, thyroid H). ■ Gravity …  Lower limbs > upper limbs. ■ Sleep …  due to  venous return. ■ Pregnancy …  due to  metabolism. "White coat hypertension" may occur if the medical visit itself produces extreme anxiety 15