What equipment does a paramedic need to measure a blood pressure?
A sphygmomanometer (known as a sphyg) is used to measure a blood pressure, there are three main types of sphygmomanometers used to measure blood pressure: mercury, aneroid, and digital.
Reading blood pressure by auscultation is considered the gold standard, this method requires the use of a manual mercury or aneroid sphygmomanometer and a stethoscope.
Prepare the patient for blood pressure measurement
- Position: supine (lying down) or seated, sometimes you may need to check a standing blood pressure.
- In seated position, the subject's arm should be flexed.
- The flexed elbow should be at the level of the heart.
- If the subject is anxious, wait a few minutes before taking the pressure, a raise in blood pressure at this time is called white coat hypertension.
Taking the manual blood pressure reading
- To begin taking blood pressure measurement, use a properly sized blood pressure cuff. The length of the cuff's bladder should be at least equal to 80% of the circumference of the upper arm.
- Wrap the cuff around the upper arm with the cuff's lower edge one inch above the antecubital fossa (the triangular area on the anterior view of the elbow).
- Lightly press the stethoscope's bell over the brachial artery just below the cuff's edge. Some health care workers have difficulty using the bell in the antecubital fossa, so we suggest using the bell or the diaphragm to measure the blood pressure.
- There are a couple methods that can be used to prepare and take the blood pressure. The first method requires the clinician to palpate the radial or brachial artery, inflate cuff until pulsation disappears - take a note of the pressure, deflate the cuff, place the stethoscope over the brachial artery and inflate the cuff to 20mmHg over the initial reading you had taken (take blood pressure using the next step), The second method involves rapidly inflating the cuff to 180mmHg.
- With both methods of taking the blood pressre you must listen with the stethoscope and simultaneously observe the sphygmomanometer. Release the air from the cuff at a moderate rate (3mm/sec). The first knocking sound (Korotkoff) you hear is the subject's systolic pressure. When the knocking sound disappears, that is the diastolic pressure (such as 120/80).
- Record the pressure in both arms and note the difference; also record the subject's position (supine, sitting, standing etc), which arm was used, and the cuff size (small, standard or large adult cuff).
- Aneroid and digital manometers may require periodic calibration.
- Use a larger cuff on obese or heavily muscled subjects.
- Use a smaller cuff for paediatric patients.
- For paediatric patients a lower blood pressure may indicate the presence of hypertension.
- Don't place the cuff over clothing.
- Flex and support the subject's arm.
- In some patients the Korotkoff sounds disappear as the systolic pressure is bled down. After an interval, the Korotkoff sounds reappear. This interval is referred to as the "auscultatory gap." This pathophysiologic occurrence can lead to a marked under-estimation of systolic pressure if the cuff pressure is not elevated enough. It is for this reason that the rapid inflation of the blood pressure cuff to 180mmHg was recommended above. The "auscultatory gap" is felt to be associated with carotid atherosclerosis and a decrease in arterial compliance in patients with increased blood pressure.