Measuring Blood Pressure

Blood Pressure Measuring blood pressure Blood pressure is the force that blood exerts against the vessel wall. During a normal cardiac cycle, blood pressure reaches a high point and a low point. The high point is referred to as systole and occurs when the ventricles of the heart contract, forcing blood into the aorta. The low point is referred to as diastole and occurs when the ventricles relax and minimal pressure is exerted against the vessel wall A normal blood pressure for a healthy adult ranges from 90 to 119 mm Hg systolic and from 60 to 79 mm Hg diastolic. Under normal circumstances, blood volume remains constant at 5,000 mL. Changes in this volume can affect blood pressure, as can age, ethnicity, gender, position changes, exercise, weight, anxiety, medications, time of day, and smoking. For hemodynamically unstable patients, blood pressure is often measured invasively by inserting a small catheter into the brachial, radial, or femoral artery. For healthy patients, use either a sphygmomanometer and stethoscope or an electronic device. The sphygmomanometer consists of a pressure manometer, a cloth or vinyl cuff that covers an inflatable rubber bladder, and a pressure bulb. The manometer has metal parts that can expand and contract at certain temperatures and should be calibrated at least every 6 to 12 months to ensure accurate blood-pressure readings. Be sure to use the appropriate-size cuff to help ensure an accurate reading. The width of the cuff should be 40% of the circumference of the midpoint of the limb on which you position the cuff, and the length of the bladder should be twice its width. The bladder should encircle at least 80% of the arm. To measure blood pressure, listen for the five Korotkoff sounds. As you deflate the blood-pressure cuff, you’ll hear a clear, rhythmic tapping sound that coincides with the patient’s systolic blood pressure. The second sound is a whooshing sound, the third is a knocking sound, and the fourth is a softer blowing sound that fades. For most adult patients, you’ll document the fifth sound, which is actually the disappearance of sound, as the diastolic blood pressure. However, with some patients, there is no distinct fifth sound. You’ll hear sounds all the way to 0 mm Hg. For these patients, you’ll record the fourth Korotkoff sound as the diastolic blood pressure. Blood pressure two-step Provide privacy, explain the procedure, and perform hand hygiene. Clean stethoscope earpieces and diaphragm with alcohol swab. With the arm at heart level and the palm turned up, palpate for the brachial pulse. Center the bloodpressure cuff about an inch (about 2.5 centimeters) above where you palpated the brachial pulse. Wrap the cuff evenly and snugly around the patient’s upper arm. If sitting, instruct the patient to keep feet flat on the floor without crossing legs. If the patient crosses his or her legs, it can falsely increase the systolic blood pressure. Inflate the blood-pressure cuff with your dominant hand while you use the fingertips of your nondominant hand to palpate the brachial pulse. The point at which you no longer feel the pulse is the estimated systolic pressure. Continue to inflate the blood-pressure cuff 30 mm Hg more. Slowly deflate the blood-pressure cuff by turning the valve on the bulb counterclockwise. Note the number at which the pulse reappears. Wait 30 seconds. Listening to the brachial pulse with your stethoscope, inflate the blood-pressure cuff to 30 mm Hg above the patient’s estimated systolic pressure. Slowly deflate the blood-pressure cuff and note the number on the manometer when you hear the first clear sound. This is the patient’s systolic blood pressure. Continue to deflate the blood-pressure cuff slowly, noting the number at which the sound disappears. This number is the patient’s diastolic blood pressure. Remove the blood-pressure cuff, perform hand hygiene, and document your findings. Be sure to indicate the site and whether you measured the blood pressure on the right or the left side of the patient’s body. Palpate a patient's pulse to determine circulation distal to the pulse site and for rhythm, quality, and strength. Is it normal, weak or thready, full or bounding, or absent? Perform hand hygiene before and after patient care and document your findings on the appropriate flow sheet or record. Blood pressure one-step Provide privacy, explain the procedure, and perform hand hygiene. With the arm at heart level and the palm turned up, palpate for the brachial pulse. Center the bloodpressure cuff about an inch (about 2.5 centimeters) above where you palpated the brachial pulse. Wrap the cuff evenly and snugly around the patient’s upper arm. If sitting, instruct the patient to keep feet flat on the floor without crossing legs. If the patient crosses his or her legs, it can falsely increase the systolic blood pressure. Place the bell or the diaphragm of your stethoscope over the pulse. Quickly inflate the blood-pressure cuff to 30 mm Hg above the patient’s usual systolic blood pressure. Slowly release the valve on the bulb and allow the manometer needle to drop at a rate of 2 to 3 mm Hg per second. Note the number on the manometer when you hear the first clear sound. This is the patient’s systolic blood pressure. Continue to deflate the blood-pressure cuff slowly, noting the number at which the sound disappears. This is the patient’s diastolic blood pressure. Remove the blood-pressure cuff, perform hand hygiene, and document your findings. Be sure to indicate the site and whether you measured the blood pressure on the right or the left side of the patient’s body. Palpate a patient's pulse to determine circulation distal to the pulse site and for rhythm, quality, and strength. Is it normal, weak or thready, full or bounding, or absent? Perform hand hygiene before and after patient care and document your findings on the appropriate flow sheet or record. When documenting blood pressure, record the systolic number first, followed by a slash and the diastolic number, as in 120/80. The difference between the systolic and diastolic values is called the pulse pressure. This number is usually between 30 and 50 mm Hg and provides information about a patient’s cardiac function and blood volume. How often you measure blood pressure varies from patient to patient. For critically ill patients, it might be every 5 to 15 minutes around the clock. For stable patients, you might only measure blood pressure every 4 or 8 hours or even less often. When a patient's blood pressure is outside the normal range, further evaluation is often necessary. A blood pressure with a systolic of 140 mm Hg or higher or a diastolic pressure of 90 mm Hg or higher is considered high, although for patients with certain chronic conditions, like coronary artery disease, the guidelines vary. In any case, a single high reading does not automatically mean that a patient has hypertension. Hypertension is commonly diagnosed after a patient has had two or more high readings at two or more visits after the initial blood-pressure measurement. Some patients can control hypertension with diet and exercise alone, but many must take antihypertensive medication. A blood pressure with a systolic reading below 90 mm Hg or a diastolic reading below 60 mm Hg is usually considered hypotension. Some patients with low blood pressure experience no problems. Others report feeling dizzy or lightheaded with position changes. Orthostatic hypotension is a term used when systolic pressure drops more than 20 mm Hg or the pulse increases by 20 beats per minute or more when the patient moves from a recumbent to a standing position. Orthostatic hypotension is often related to a decrease in blood volume, prolonged bed rest, older age, and medications. Measuring blood pressure in lower extremities If you cannot measure a patient’s blood pressure on the upper extremities, use the lower extremities. You might also measure blood pressure on a lower extremity if an arm pressure in an adolescent or young adult seems unusually high. If the patient has coarctation of the aorta, a congenital heart defect, the arm blood pressure will be higher than the leg pressure. Two areas on the leg where you can measure blood pressure are the thigh just above the knee, using the popliteal pulse, and the calf just above the ankle, using the posterior tibial pulse. The systolic reading in the thigh is usually 10 to 40 mm Hg higher than in the arm, and the diastolic number usually remains the same. Remove the patient’s clothing to expose the leg, and be sure to use the appropriate-size blood-pressure cuff to ensure an accurate reading. Wrap the cuff evenly and snugly around the leg about 1 inch, or 2.5 centimeters, above the popliteal artery, with the bladder over the posterior aspect of the mid-thigh. Place the bell or diaphragm of your stethoscope over the pulse and inflate the cuff quickly to 30 mm Hg above the patient’s usual systolic blood pressure. Then slowly deflate the cuff at a rate of 2 to 3 mm Hg per second. The first sound you hear is the systolic pressure and silence denotes the diastolic pressure.