Term
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Definition
| The force of contraction of the myocardium acting on the blood contained in the heart |
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Term
| Laplace's Law in BP measurement |
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Definition
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Term
| Laplace's Law in a distended failing heart |
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Definition
| a distended failing heart has a larger radius than normal so it produces less pressure, unless it can contract proportionately more forcefully |
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Term
| Starling's law of the heart |
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Definition
| In a normal heart, slight distension cause by an increased venous return and the consequent lengthening of cardiac muscle increases the force of contraction and the pressure is maintained. |
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Term
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Definition
Work = Pressure X stroke volume (increase in stroke volume or BP, increases work) |
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Term
| Elastic tissue of aorta and main vessels |
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Definition
| Stores the work of the heart in systole to maintain blood flow during diastole. |
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Term
| Standard reference point for BP measurement |
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Definition
| The level of the right atrium |
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Term
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Definition
- Varies with the site of measurement, caliber of vessel and its distance from the heart.
- BP is pulsatile and changes in the wave pattern in different vessels alter the systolic pressures. * BP is posture dependent.
- BP has a diurnal variation, lower at HS
- IPPV decreases BP
- Anxiety increases BP.
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Term
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Definition
| Mean (aortic) blood pressure/Cardiac output |
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Term
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Definition
| Peripheral resistance X Cardiac output |
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Term
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Definition
(2DBP + SBP)/3 An MAP of about 60 is necessary to perfuse coronary arteries, brain, kidneys. |
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Term
| Advantages of a cuff pressure |
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Definition
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Term
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Definition
| Identifies the pressure at which the pulse returns after occlusion. |
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Term
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Definition
Placed where center of its bladder is on medial side of arm over brachial artery and width should be 20% greater than diameter of arm. The mercury manometer must read zero before use and should be used vertically. Partial blockage of air vent in manometer or of connecting tubings may lead to inaccurate or sluggish readings. |
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Term
| Correct Use of BP dectector |
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Definition
| Inflate cuff above expected systolic pressure. Slowly release at a rate of 2-3mmHg/sec. (for sound) Systolic pressure is indicated by reappearance of peripheral pulse by manual palpation of radial pulse or auscultation over brachial artery. Listen throughout whole cycle for Korotkoff sound (5 phases). |
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Term
| Correct use of Oscillometry |
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Definition
| As bp cuff deflated from above systolic, needle on an aneroid gauge starts to oscillate when systolic pressure is reached. The oscillations increase in amplitude to a maximum at the mean BP, then decrease at a less precise point about the diastolic. |
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Term
| Automated Oscillometric Technique |
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Definition
| A single cuff collected to a pressure transducer measures both the pressure and oscillations. The processing unit analyzes the signal from the transducer to detect the ONSET of oscillations at the systolic pressure AND the point of MAXIMUM oscillation at mean pressure and to give an indication of the diastolic pressure. |
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Term
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Definition
If the interval between readings is too short, impeded blood flow may result. A minimum interval is preferred of 2 minutes per inflation. |
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Term
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Definition
| Readings are less accurate if the pt has a dysrhythmia. |
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Term
| Radial Artery Compression |
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Definition
| This technique is used to reduce the potential for injury resulting from repeated rapid inflation of a bp cuff. It uses a pressure sensor strapped to the wrist over the radial artery. The sensor is driven hydraulically by a control system and is used both to apply pressure to the wall of the radial artery and to measure pressure fluctuations at the wall of the artery due to pulsations during the cardiac cycle. Approx 12-15 heart beats are required to obtain a measurement. |
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Term
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Definition
| Used to give continuous measurement of finger blood pressure. Cuff is placed on finger and attached to a transducer to measure pressure and to an air pump. The apparatus detects the mean pressure from the point of maximum oscillation. The system also includes an infrared light-emitting diode and a photocell which act as a photoplethysmograph. |
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Term
| Other Automated Techniques for BP measurement |
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Definition
A microphone may be positioned over the brachial artery to detect either audible sound or infrasound. An ultrasonic transmitter and receiver used to detect Doppler changes of frequency from arterial wall movement. |
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Term
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Definition
| Have problems with pts with an irregular pulse and it does not measure BP continuously. |
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Term
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Definition
| A peripheral artery is preferred for arterial cannulation so the whole limb is not threatened if a clot or hematoma forms. Radial artery is most preferred site, after Allen’s test performed. |
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Term
| Possible complications of invasive BP techniques |
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Definition
| Intra-arterial cannulations may rarely cause thrombosis to occur. |
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Term
| Steps to minimize complications with IBP techniques |
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Definition
To prevent thrombosis, the cannula should be constructed of Teflon, be short with parallel sides. To prevent dislodgement, it should be sutured in place |
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Term
| Care of IBP devices after insertion |
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Definition
The cannula and its connections must be fixed securely to avoid leakage resulting in blood loss. To avoid clotting, intermittent flushing is recommended. Care should be taken when flushing, and syringes smaller than 5ml should not be used because they generate high pressures that can damage arterial walls or the diaphragm of the pressure transducer. |
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Term
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Definition
1) The hand is elevated and the patient/person is asked to make a fist for about 30 seconds. 2) Pressure is applied over the ulnar and the radial arteries so as to occlude both of them. 3) Still elevated, the hand is then opened. It should appear blanched (pallor can be observed at the finger nails). 4) Ulnar pressure is released and the color should return in 7 seconds. If color does not return or returns after 7-10 seconds, then the ulnar artery supply to the hand is not sufficient and the radial artery therefore cannot be safely pricked/cannulated. |
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Term
| Fiberoptic Catheter Tip Transducer |
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Definition
| Employs a mirror-coated moving diaphragm which reflects light carried to the tip by an optical fiber |
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Term
| Arterial Pressure Recordings |
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Definition
| The form of the pressure wave alters as blood flows to the periphery. Systolic pressure is found to be an average of 5 mmHg higher and diastolic 8mmHg lower with direct measurement at the radial artery than with indirect techniques. The frequency range of the arterial pressure wave is 0 Hz to 40 Hz. |
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Term
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Definition
| Main advantages of invasive = bp accuracy and bp can be monitored continuously. |
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Term
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Definition
Arterial damage,
costly,
technical skill |
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Term
| Conversion of BP into an electrical signal |
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Definition
Movement of the diaphragm of the pressure transducer converts the BP change into an electrical signal. This movement of the diaphragm is associated with a very small movement of saline to and fro along the catheter with changes of pressure.
The system possesses a resonant frequency at which oscillations can occur and produce a blood pressure waveform |
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Term
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Definition
| Occurs if the resonant frequency is outside the range of frequencies in the BP waveform. |
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Term
| Ways to avoid Resonance in arterial pressure tracings |
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Definition
| Use a shorter, wider, or stiffer cathter. |
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Term
| Dampened arterial tracings |
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Definition
Caused by restriction to the transmission of the BP from the artery to the transducer diaphragm.
Produced by air bubbles in the catheter or in the transducer chamber OR by blood clot in the cannula. |
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Term
| Placement of CVP catheter |
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Definition
| To measure CVP, a catheter is inserted via an arm or neck vein and advanced so that it reaches the superior vena cava. |
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Term
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Definition
| Faulty techniques can increase the risk of pneumothorax, hemothorax, or hydrothorax and of infection. |
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Term
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Definition
| Before CVP reading is taken, pt is placed in horizontal position. The transducer is zeroed to the pt midaxillary line, which represents the level of the right atrium. |
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Term
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Definition
| The filling of the heart depends on adequate venous pressure. If venous pressure rises, the normal heart fills to a greater extent and automatically increases its output. If there is appreciable blood loss, venous pressure falls. |
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Term
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Definition
| Measurement of pulmonary wedge pressure gives an indication of the left arterial pressure. It is obtained by advancing a special venous catheter through the right heart and pulmonary artery until it wedges into a small branch of the pulmonary artery, where it would be used to measure the pressure of the pulmonary capillaries. |
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