Blood Pressure
Exerpt: Blood Pressure, from the Gold Cross Magazine CEU Article "Vital Signs As Directional Signals" By, Charles Livesey, edited by Julie Aberger. (Read the entire article.)
Blood Pressure
Blood must be kept constantly circulating in order to keep the body’s cells perfused.
The circulatory system does this job with its three components: the heart, the blood vessels and the blood, often referred to as the pump, the container and the volume.
Blood pressure is the pressure exerted against the inside walls of the arteries as the heart pumps and then relaxes. We measure two pressures: systolic and diastolic.
The difference between the systolic and diastolic pressure is referred to as the pulse pressure.
How To Take A Blood Pressure
To determine a patient’s blood pressure, the EMT needs a properly sized blood pressure (BP) cuff. Adult cuffs should have a width of one-third to one-half the circumference of the limb. Pediatric cuffs should have a width of about two-thirds of the upper arm. Using a BP cuff that is too big gives a false low reading. Cuffs that are too small yield a false high reading.
Auscultation: The blood pressure cuff should be placed on the patient’s arm an inch or so above the elbow. Air is pumped into the bladder that inflates and temporarily halts arterial blood flow. The stethoscope is then placed over the patient’s brachial artery. When the pressure in the cuff is released and falls below the internal systolic pressure, blood flow resumes and produces sounds. When the pressure in the cuff falls below the internal diastolic pressure, blood flow remains continuous and the sounds disappear completely. Pressure is measured in millimeters of mercury (mmHg).
Palpation: An alternative method of determining blood pressure is by palpation. No stethoscope is needed. This method can be used if there is too much ambient noise to auscultate the pulse sounds, like in the back of an ambulance enroute to the hospital. To “palp” a BP, the EMT locates a radial pulse with two fingers prior to pumping up the cuff. The cuff is then inflated until the pulse is no longer felt. The EMT should note the point on the gauge where this occurs and continue to inflate the cuff 30 mmHg beyond this point. The cuff should then be slowly deflated, and the EMT should note the reading at which the radial pulse returns, i.e., where it can be felt again. This results in a reading of about 10 mmHg lower than the systolic pressure determined by auscultation. Palpating a blood pressure has a disadvantage in that the diastolic pressure cannot be determined. Palpation should be used only when auscultation is not possible. High blood pressure is called hypertension. For an adult, this is usually defined as a systolic pressure that persists above 140 mmHg or a diastolic pressure that persists above 90 mmHg. Hypertension may be a sign of a possible illness (such as renal disease), injury (such as traumatic brain injury), exertion, anxiety, or even fright.
Low blood pressure is called hypotension and causes poor perfusion to the cells. There must be an adequate pressure for oxygen and carbon dioxide exchange to occur between the capillaries and cells. A decreased blood pressure is a late sign of shock that occurs when the body can no longer compensate.
Blood pressure varies among individuals. The accepted rule for “normal” systolic blood pressure for adults up to 40 years of age is the patient’s age plus 100 for a male, and the patient’s age plus 90 for a female. Thus a “normal” systolic BP for a 25-year old female would be approximately 115 mmHg. Children’s “normal” systolic blood pressures are estimated with the formula: 80 + 2 times the child’s age. It is now advised that EMTs not take blood pressures on children under the age of three, (although some providers still believe it is important to practice).
Although there has been controversy lately about ideal blood pressure numbers, the American Heart Association declared in October, 2015:
“A report published late in 2013 recommends healthcare providers take a new approach to treating high blood pressure for people older than 6 0. But based on the current research available, the American Heart Association recommends that healthcare providers continue to follow existing guidelines for treating high blood pressure. “‘We believe there’s just not enough evidence at this point to justify such a major change in how we treat people with high blood pressure,’ American Heart Association Past President Mariell Jessup, M.D., said of the new opinion published in the Journal of the American Medical Association (JAMA).
“One in three American adults has high blood pressure, which is a reading of 140/90 millimeters of mercury or higher. The opinion published in JAMA advises treatment at 140/90 for adults from ages 30 to 59, but starting only at 150/90 for people 60 and older. The American Heart Association maintains its recommendation of initiating treatment — starting with lifestyle changes and then medication if necessary.
Blood must be kept constantly circulating in order to keep the body’s cells perfused.
The circulatory system does this job with its three components: the heart, the blood vessels and the blood, often referred to as the pump, the container and the volume.
- The heart is a pump that pushes blood through the blood vessels to the cells for perfusion.
- Blood vessels of the body form a closed delivery system, or sort of container, that begins and ends at the heart. The diameter of the blood vessels constricts or dilates (gets bigger or smaller) depending upon the pressure needed in the system. For example, if a patient is hemorrhaging and losing a lot of blood or volume, the blood vessels will constrict in order to shunt the blood to the vital organs. The heart will also speed up to keep whatever volume is still in the system moving fast enough to keep the cells in the vital organs perfused.
- Adequate blood pressure also depends on adequate blood volume. The average adult blood volume is about six liters; an eight-year old has about two liters, and an infant’s blood volume almost fills a soda can (0.35 liters).
Blood pressure is the pressure exerted against the inside walls of the arteries as the heart pumps and then relaxes. We measure two pressures: systolic and diastolic.
- Systolic pressure measures the maximum pressure within the arteries when the heart pumps.
- Diastolic pressure measures the minimum pressure within the arteries when the heart relaxes.
The difference between the systolic and diastolic pressure is referred to as the pulse pressure.
How To Take A Blood Pressure
To determine a patient’s blood pressure, the EMT needs a properly sized blood pressure (BP) cuff. Adult cuffs should have a width of one-third to one-half the circumference of the limb. Pediatric cuffs should have a width of about two-thirds of the upper arm. Using a BP cuff that is too big gives a false low reading. Cuffs that are too small yield a false high reading.
Auscultation: The blood pressure cuff should be placed on the patient’s arm an inch or so above the elbow. Air is pumped into the bladder that inflates and temporarily halts arterial blood flow. The stethoscope is then placed over the patient’s brachial artery. When the pressure in the cuff is released and falls below the internal systolic pressure, blood flow resumes and produces sounds. When the pressure in the cuff falls below the internal diastolic pressure, blood flow remains continuous and the sounds disappear completely. Pressure is measured in millimeters of mercury (mmHg).
Palpation: An alternative method of determining blood pressure is by palpation. No stethoscope is needed. This method can be used if there is too much ambient noise to auscultate the pulse sounds, like in the back of an ambulance enroute to the hospital. To “palp” a BP, the EMT locates a radial pulse with two fingers prior to pumping up the cuff. The cuff is then inflated until the pulse is no longer felt. The EMT should note the point on the gauge where this occurs and continue to inflate the cuff 30 mmHg beyond this point. The cuff should then be slowly deflated, and the EMT should note the reading at which the radial pulse returns, i.e., where it can be felt again. This results in a reading of about 10 mmHg lower than the systolic pressure determined by auscultation. Palpating a blood pressure has a disadvantage in that the diastolic pressure cannot be determined. Palpation should be used only when auscultation is not possible. High blood pressure is called hypertension. For an adult, this is usually defined as a systolic pressure that persists above 140 mmHg or a diastolic pressure that persists above 90 mmHg. Hypertension may be a sign of a possible illness (such as renal disease), injury (such as traumatic brain injury), exertion, anxiety, or even fright.
Low blood pressure is called hypotension and causes poor perfusion to the cells. There must be an adequate pressure for oxygen and carbon dioxide exchange to occur between the capillaries and cells. A decreased blood pressure is a late sign of shock that occurs when the body can no longer compensate.
Blood pressure varies among individuals. The accepted rule for “normal” systolic blood pressure for adults up to 40 years of age is the patient’s age plus 100 for a male, and the patient’s age plus 90 for a female. Thus a “normal” systolic BP for a 25-year old female would be approximately 115 mmHg. Children’s “normal” systolic blood pressures are estimated with the formula: 80 + 2 times the child’s age. It is now advised that EMTs not take blood pressures on children under the age of three, (although some providers still believe it is important to practice).
Although there has been controversy lately about ideal blood pressure numbers, the American Heart Association declared in October, 2015:
“A report published late in 2013 recommends healthcare providers take a new approach to treating high blood pressure for people older than 6 0. But based on the current research available, the American Heart Association recommends that healthcare providers continue to follow existing guidelines for treating high blood pressure. “‘We believe there’s just not enough evidence at this point to justify such a major change in how we treat people with high blood pressure,’ American Heart Association Past President Mariell Jessup, M.D., said of the new opinion published in the Journal of the American Medical Association (JAMA).
“One in three American adults has high blood pressure, which is a reading of 140/90 millimeters of mercury or higher. The opinion published in JAMA advises treatment at 140/90 for adults from ages 30 to 59, but starting only at 150/90 for people 60 and older. The American Heart Association maintains its recommendation of initiating treatment — starting with lifestyle changes and then medication if necessary.
