Chapter 5 Part Two Blood Pressure and flow by Ibrhim AlMohimeed BMTS /3/2013

BMTS 3532 Blood Pressure 12/3/2013 Originates from the left ventricle of the heart. One of the oldest physiological measurements. Observation of blood pressure allows dynamic tracking of pathology and physiology affecting to the cardiovascular system.

BMTS 3533 Blood Pressure Reading 12/3/2013 Systolic: the top number, which is also the higher of the two numbers, measures the pressure in the arteries when the heart beats (when the heart muscle contracts). Diastolic: the bottom number, which is also the lower of the two numbers, measures the pressure in the arteries between heartbeats (when the left ventricle muscle is resting between beats and refilling with blood). Read as "117 over 76 millimeters of mercury"

BMTS 3534 Blood Pressure Reading 12/3/2013 Blood Pressure Category Systolic mm Hg (upper #) Diastolic mm Hg (lower #) Normalless than 120andless than 80 Prehypertension120 – 139or80 – 89 High Blood Pressure (Hypertension) Stage – 159or90 – 99 High Blood Pressure (Hypertension) Stage or higheror100 or higher Hypertensive Crisis (Emergency care needed) Higher than 180orHigher than 110

BMTS 3535 Blood Pressure Reading 12/3/2013

BMTS 3536 Blood Pressure Risks 12/3/2013 High blood pressure (hypertension) increases the risk of:  Chest pain (angina).  Heart attack.  Heart failure.  Kidney failure.  Stroke.  Blocked arteries in the legs or arms (peripheral arterial disease.  Eye damage.  Aneurysms (permanent cardiac or arterial dilatation).

BMTS 3537 Cont. Blood Pressure Risks 12/3/2013

BMTS 3538 Cont. Blood Pressure Risks 12/3/2013 Low blood pressure (hypotension) increases the risk of:  Reduces the blood flow to the brain and other vital organs.  Dizziness or fainting.  Lack of concentration.  Blurred vision.  Fatigue.  Cold and clammy skin.  Rapid shallow breathing.

BMTS 3539 Blood Pressure Value 12/3/2013 Generally, the blood pressure value depends on two main factors: 1)Cardiac output (Blood Volume): The more blood present in the body, the higher the rate of blood return to the heart and the resulting cardiac output, potentially resulting in higher arterial pressure.

BMTS Cont. Blood Pressure Value 12/3/2013 2)Resestance of blood flow: The higher the resistance, the higher the arterial pressure. Resistance is related to vessel radius, blood viscosity, and the smoothness of the blood vessel walls.

BMTS Invasive & Non-invasive 12/3/2013 In general, there are two main categories which describe the invasiveness of a medical measurement:  Invasive: requiring the entry of a needle, catheter, or other instrument into a part of the body.  Non-invasive: not requiring entering or penetrating the body or disturbing body tissue.

BMTS Blood Pressure Measurement 12/3/2013 Invasive Non-Invasive Blood Pressure Palpatory Method (Riva-Rocci Method) Auscultatory Method Ultrasonic Method Oscillometric Method Extravascular Sensor Intravascular Sensor Automatic Method

BMTS Blood Pressure Measurement 12/3/2013 Blood Pressure

BMTS Measurement Site 12/3/2013 Blood Pressure Brachial artery is the most common measurement site:  Close to heart  Convenient for measuring Other sites are radial artery and wrist.

BMTS Palpatory Method 12/3/2013 Blood Pressure aka Riva-Rocci Method. 1)When the cuff pressure is higher than SBP, artery is closed, no pulse can be sensed. 2)When the cuff pressure drops below SBP, blood can pass through the artery and the pulse will be felt.

BMTS Cont. Palpatory Method 12/3/2013 Blood Pressure 3)The pulse will continue to be felt as the pressure in the cuff falls down to zero. 4)The pressure indicated on the gauge when the pulse reappears is noted. This is the systolic pressure.

BMTS Cont. Palpatory Method 12/3/2013 Blood Pressure The blood pressure can be measured in noisy environment. It is a simple technique. Only the systolic blood pressure (SBP) can be measured (not DBP). The technique does not give accurate results for infants and hypotensive patients.

BMTS Auscultatory Method 12/3/2013 Blood Pressure Auscultation: the act of listening, either directly or through a stethoscope or other instrument, to sounds within the body. This method is based on the fact that pulse waves when first propagate through the brachial artery, generate Korotkoff sounds. Video

BMTS Korotkoff sounds 12/3/2013 Blood Pressure If a stethoscope is placed over the brachial artery in a normal person (without arterial disease), no sound should be audible. As the heart beats, these pulses are transmitted smoothly via laminar (non-turbulent) blood flow throughout the arteries, and no sound is produced. Similarly, if the cuff of a sphygmomanometer is placed around a patient's upper arm and inflated to a pressure above the patient's systolic blood pressure, there will be no sound audible because the pressure in the cuff is high enough such that it completely blocks the blood flow.

BMTS Cont. Korotkoff sounds 12/3/2013 Blood Pressure If the pressure is dropped to a level equal to that of the patient's systolic blood pressure, the first Korotkoff sound will be heard. As the pressure in the artery rises above the pressure in the cuff and then drops back down (because of beating), resulting in turbulence that produces an audible sound. As the pressure in the cuff is allowed to fall further, thumping sounds continue to be heard as long as the pressure in the cuff is between the systolic and diastolic pressures, as the arterial pressure keeps on rising above and dropping back below the pressure in the cuff.

BMTS Cont. Korotkoff sounds 12/3/2013 Blood Pressure Eventually, as the pressure in the cuff drops further, the sounds change in quality, then become muted, and finally disappear altogether. This occurs because, as the pressure in the cuff drops below the diastolic blood pressure, the cuff no longer provides any restriction to blood flow allowing the blood flow to become smooth again with no turbulence and thus produce no further audible sound.

BMTS Auscultatory Method Procedure 12/3/2013 Blood Pressure

BMTS Auscultatory Method Procedure 12/3/2013 Blood Pressure 1)The cuff pressure is inflated quickly to a pressure higher than the systolic pressure. Then the air is let out of the cuff at a small rate. 2)When the cuff pressure equal to that of the patient's systolic blood, a korotkoff sound will be heard with each heartbeat. This point marks the systolic pressure.

BMTS Auscultatory Method Procedure 12/3/2013 Blood Pressure 1)As the pressure is lowered further, the character of the Korotkoff sounds change. At some point, the sounds will disappear. The pressure reading at this point gives the diastolic pressure.

BMTS Using Auscultatory Method 12/3/2013 Blood Pressure Auscultatory technique is considerd simple. It may be difficult to be done in a noisy environment. The effect of human error is large. It could be difficult to be used with infant.

BMTS Oscillometric Method 12/3/2013 Blood Pressure the observation of oscillations of blood flow during the pulsation. It uses a sphygmomanometer cuff, like the auscultatory method, but with pressure sensor (transducer) to observe cuff pressure oscillations The pressure sensor (within the inflated cuff) detects the pulsation of the artery wall as a pressure vibration. The interpretation of these small vibrations amplitude provide the blood pressure value.

BMTS Cont. Oscillometric Method 12/3/2013 Blood Pressure

BMTS Cont. Oscillometric Method 12/3/2013 Blood Pressure In the recent years, oscillometric methods have become popular for their simplicity of use and reliability. It can be used with case of hypotension and infant. It use algorithms that may leads to large variance in blood pressures measurement. Motion artifact is considered a major drawback of this method.

BMTS Automatic Method 12/3/2013 Blood Pressure Many limitations of manual intermittent blood pressure measurement have been overcome by automated non- invasive blood pressure (NIBP) devices. There are now used widely in medical care. NIBP devices provide consistent, reliable values for systolic, diastolic, and mean arterial pressure (MAP). Automated NIBP devices provide alarm systems to draw attention to extreme blood pressure value.

BMTS Cont. Automatic Method 12/3/2013 Blood Pressure The greatest advantage of automated NIBP devices compared with manual methods of blood pressure measurement is that they don’t require an operator to perform the measurement. It can easily provide a repetitive blood pressure measurements. Most automated NIBP devices are based on the oscillometry method.

BMTS The Device Diagram 12/3/2013 Blood Pressure Pressure sensor Air pump Bleed valve Micro- processor Micro- processor Display

BMTS Automatic Method Errors 12/3/2013 Blood Pressure Sources of error for the automatic method: I.Cuff size: Oscillations are direct result of BP cuff application - Cuff too small = overestimation of BP - Cuff too large = underestimation of BP II.Cuff position: Bladder needs to be placed over brachial artery.

BMTS Cont. Automatic Method Errors 12/3/2013 Blood Pressure III.Movement:

BMTS Cont. Automatic Method Errors 12/3/2013 Blood Pressure III.Beat to beat variation: Oscillometric method requires reasonably stable BP during cuff deflation. If BP varies due to arrhythmia, difficult to estimate BP accurately.

BMTS Ultrasonic Method 12/3/2013 Blood Pressure The ultrasonic Doppler technique is applied by this method. The motion of blood-vessel walls of occlusion (opining and closing) is measured by Doppler technique. The vessel opens and closes with each heartbeat when DP < P cuff < SP

BMTS Doppler Effect 12/3/2013 Blood Pressure It is the change in frequency of the returned sound wave (echo) from a moving object.

BMTS Cont. Doppler Effect 12/3/2013 Blood Pressure Video

BMTS Principle of Ultrasonic Method 12/3/2013 Blood Pressure

BMTS Cont. Ultrasonic Method 12/3/2013 Blood Pressure Can be also used in noisy environment. The device is considiered contatin compicated part. Highly affect by motion.

BMTS Blood Pressure Measurement 12/3/2013 Blood Pressure

BMTS The first invasive blood pressure measurement 12/3/2013 Blood Pressure The first invasive attempt to measure blood pressure was made by Stephen Hales in He inserted tubes directly into the arteries of animals.

BMTS Invasive Method 12/3/2013 Blood Pressure This technique involves direct measurement of arterial pressure by inserting a catheter (thin, hollow, and flexible tube). Invasive (intra-arterial) blood pressure (IBP) monitoring is a commonly used technique in the Intensive Care Unit (ICU) and in the operating theatre.

BMTS Con.t Invasive Method 12/3/2013 Blood Pressure IBP technique also allows accurate blood pressure readings specially the very low pressures, for example in shocked patients. it allows continuous ‘beat-to-beat’ blood pressure monitoring. It complex procedure involving many risks.

BMTS Invasive Method Types 12/3/2013 Blood Pressure Generally, the Invasive technique can be divided into two division:  Extravascular Sensor System  Intravascular Sensor System

BMTS Extravascular Sensor System 12/3/2013 Blood Pressure The sensor is located behind the catheter and the vascular pressure is transmitted by hydraulic connection.

BMTS Cont. Extravascular Sensor System 12/3/2013 Blood Pressure The actual pressure sensor can be:  strain gage  variable inductance  variable capacitance  optoelectronic  piezoelectric  etc…

BMTS Intravascular Sensor System 12/3/2013 Blood Pressure The sensor is located in the tip of the catheter (inside the body). The sensor connected by an electrical or optical connection. The frequency response is not limited by the hydraulic properties of the system. No time delay. Breaks easily. More expensive.

End of the Chapter 12/3/2013BMTS 35348