Blood Pressure Measurement and methods of Blood Pressure Measurement

 What is normal blood pressure?

Blood pressure is a measurement of the force applied to the walls of the arteries as the heart pumps blood through the body. The pressure is determined by the force and amount of blood pumped, and the size and flexibility of the arteries. Blood pressure is continually changing depending on activity, temperature, diet, emotional state, posture, physical state, and medication use. The ventricles of heart have two states: systole (contraction) and diastole (relaxation). During diastole 

blood fills the ventricles and during systole the blood is pushed out of the heart into the arteries. The auricles contract anti-phase to the ventricles and chiefly serve to optimally fill the ventricles 

with blood. The corresponding pressure related to these states are referred to as systolic pressure and diastolic pressure The range of systolic pressure can be from 90 mm of Hg to 145mm of Hg with the average being 120 mm of Hg. The diastolic pressure typically varies from 60mm of Hg to 90 mm of Hg and the average being 80 mm of Hg.

'Normal' or 'acceptable' blood pressure varies with age, state of health and clinical situation. At birth, a typical blood pressure is 80/50 mmHg. It rises steadily throughout childhood, so that in a young adult it might be 120/80 mmHg. As we get older, blood pressure continues to rise and a rule of thumb is that normal systolic pressure is age in years + 100. Blood pressure is lower in late pregnancy and during sleep.

From this, you can see that a systolic pressure of 160mmHg for an elderly man or 90 mmHg for a pregnant woman may be quite normal. To judge whether any particular reading is too high or too low, we must compare the reading with the 'normal' for that patient.

This technique involves direct measurement of arterial pressure by placing a cannula needle in an artery (usually radial, femoral, dorsalispedis or brachial). The cannula must be connected to a sterile, fluid-filled system, which is connected to an electronic patient monitor.

The advantage of this system is that pressure is constantly monitored beat-by-beat, and a waveform (a graph of pressure against time) can be displayed.

Patients with invasive arterial monitoring require very close supervision, as there is a danger of severe bleeding if the line becomes disconnected. It is generally reserved for critically ill patients where rapid variations in blood pressure are anticipated.

There are a variety of monitors with invasive blood pressure monitoring for Trauma, critical care and operating room applications. These include single pressure, dual pressure, and multi-parameter (i.e. Pressure / temperature)

Invasive Blood Pressure monitors are pressure monitoring systems designed to acquire pressure information for display and processing. This can be used to monitor arterial, central venous, pulmonary arterial, left atrial, right atrial, femoral arterial, umbilical venous, umbilical arterial and intracranial pressures.

Usually, systolic, diastolic and mean pressures are displayed simultaneously for pulsatile waveforms (i.e. arterial and pulmonary arterial).

Some monitors also calculate and display CPP (cerebral perfusion pressure). Normally, a zero key on the front of the monitor makes pressure zeroing extremely fast and easy. Alarm limits may be set to assist the medical professional responsible for observing the patient.

Blood Pressure Measurement

Before the blood pressure measurement begins the following conditions should be met

Subjects should abstain from eating, drinking (anything else than water), smoking and taking drugs that affect the blood pressure one hour before measurement. Because a full bladder affects the blood pressure it should have been emptied. Painful procedures and exercise should not have occurred within one hour. Subject should have been sitting quietly for about 5 minutes. Subject should have removed outer garments and all other tight clothes. The sleeve of shirts, blouses, etc. should have been rolled up so that the upper right arm is bare. The remaining garments should not be constrictive and the blood pressure cuff should not be placed over the garment. Blood pressure should be measured in a quiet room with comfortable temperature. The room temperature should have been recorded. The time of day should have been recorded. The blood pressure measurer should be identified on the blood pressure data recording form. 

Position of the subject

Measurements should be taken in sitting position so that the arm and back are supported. Subject's feet should be resting firmly on the floor, not dangling. If the subject's feet do not reach the floor, a platform should be used to support them.  Select the correct cuff for the arm circumference and record the size of the selected cuff in the blood pressure recording data form. The instructions for deriving rules to select the proper cuff size for each arm circumference are given in The cuff should be placed on the right arm so that its bottom edge is 2-3 cm above the antecubital fossa, allowing sufficient room for the bell of the stethoscope. The top edge of the cuff should not be restricted by clothing.

Methods of B.P.Measurement

• Indirect Method
• Sphygmomanometer
• Pulpatory
• Flush
• Direct Method
• H2O measurement
• Electronic measurement

Sphygmomanometer: - It is an instrument measuring the arterial blood pressure.