Vital signs

Almost every patient encounter begins with vital signs, which are often performed by a medical assistant or a nurse. You should know how to measure pulse, blood pressure and respiratory rate yourself so you can identify and confirm abnormal findings. You may also check vitals yourself in service learning or on international rotations. Temperature, weight, and oxygen saturation are also checked in some settings.

Key landmarks & structures

Each physical exam chapter identifies key landmarks and structures to locate on yourself or your physical exam partner. For measurement of vital signs, the key structures are the brachial and radial arteries.

Radial artery:	Brachial artery:
Runs just lateral to the tendons of the ventral wrist.	Runs just medial to the biceps tendon. Make a fist and flex the arm slightly to locate the tendon.

Step 1. Measure the radial pulse

With your first two fingers placed on the radial artery, just lateral to the tendons of the ventral wrist, count the beats for 15 seconds and multiply by four. If the pulse is irregular, it is more accurate to count for 30 seconds and multiply by two.

The normal adult pulse is 60-100 bpm.

Step 2. Measure the respiratory rate

Continue to palpate the radial pulse and count respirations for 30 seconds, discreetly observing the rise and fall of the chest or movement of the abdomen. If the patient realizes you are counting breaths, their awareness of breathing may cause them to speed up or slow down. The normal adult respiratory rate is 8-20 breaths per minute.

Step 3. Measure the blood pressure by auscultation

Errors in blood pressure measurement are common and can lead to both over- and undertreatment of hypertension, both of which can harm patients.  To maximize the accuracy of blood pressure measurement:

• Allow your patient to rest for 5 minutes before blood pressure is measured.
• The back should be supported
• Both feet should be on the floor
• The upper arm should be supported at heart level, either held by you or resting on a table
• The patient should be quiet – even chatting can falsely elevate the BP

Position the cuff

The brachial artery is located

Wrap the blood pressure cuff snugly around the bare arm just proximal to the antecubital fossa with the marker aligned with the brachial artery.

The bladder of the cuff should encircle at least 80% of the upper arm.  An indicator will show if they are appropriately sized for your patient. A cuff that is too large will underestimate the blood pressure, while one that is too small will overestimate it.

Auscultate for Korotkoff sounds

These low-pitched sounds are made by blood flowing through a partially compressed brachial artery. When the pressure in the blood pressure cuff is high enough to completely occlude the artery, blood flow stops and no sound is heard at all. As the cuff is deflated and the artery partially re-opens, Korotkoff sounds become audible. As the pressure in the cuff falls to the point that blood flows freely, Korotkoff sounds go away.

1. With your patient’s arm supported on a surface or your hand, position the stethoscope over the brachial artery between the edge of the cuff and the antecubital fossa.
2. Inflate the cuff to 200 millimeters of mercury (mm Hg) or until the radial pulse goes away
3. Slowly deflate the cuff at a rate of ~ 2 mmHg/sec. Note the pressure when sounds are first heard and when they go away.

Systolic blood pressure is defined as the point at which Korotkoff sounds first become audible and diastolic blood pressure as the point at which they go away. Classic physical exam texts describe five different phases of Korotkoff sounds; this is more complicated than necessary for Immersion. In the example below, the systolic blood pressure is 120 mm Hg, and diastolic BP is 80 mm Hg.

•  < 120/80 mmHg is defined as normal blood pressure
• 120-139 / 80-89 mmHg is defined as pre-hypertension
• ≥ 140 / 90 mmHg is defined as hypertension

Adaptations for children

Know that normal vital signs in children vary substantially with age. A respiratory rate of 60 breaths per minute and a pulse of 170 can be perfectly normal in an infant 0-3 months. For reference, you can find normal ranges for each age group on UptoDate (NetID login required):

• Pediatric respiratory and heart rate by age LINK
• Blood pressure levels for male children by age and height percentile LINK
• Blood pressure levels for female children by age and height percentile LINK