Cuff size, arm position and patient preparation change a blood pressure more than most pathology does — and a corrupted number changes medication decisions. Size the cuff, watch technique errors corrupt a reading in front of you, classify what you get with its MAP and pulse pressure, run a set of orthostatics, and then build the call.
Step 1 — size the cuff
The inflatable bladder width should be about 40 percent of the arm circumference at the midpoint of the upper arm, and the bladder length should encircle about 80 percent of the arm. Measure the arm or use the range printed on the cuff — do not eyeball it.
Step 2 — corrupt the reading
This patient’s true pressure is 124/78. Tick the errors you made and watch what gets recorded instead.
Classify the pressure
Enter a blood pressure and tick anything the patient is telling you. Category, mean arterial pressure and pulse pressure all come out of the same two numbers.
Target-organ symptoms
Orthostatic vital signs
Supine for at least five minutes, then measure. Sitting, wait one minute, repeat. Standing, measure at one minute and again at three minutes. Gait belt on, chair behind the patient, and stop immediately if symptoms appear.
SystolicDiastolicHR
What did the patient report?
Build the call
Mr Delgado, room 412, 68 years old, admitted yesterday with pyelonephritis. At 1000 he was 37.2 °C, HR 88, RR 18, BP 124/72, SpO2 97 percent on room air. It is now 1405: T 38.4 °C oral, HR 118 regular, RR 26, BP 96/54, SpO2 92 percent on room air, and he is more confused than this morning. Choose the strongest line for each letter.
What you would actually record
124/78true value 124/78 — no error
Enter an arm circumference and choose a cuff. A cuff that is too small requires more pressure to compress the artery and therefore reads falsely high — the single most common cause of a spurious hypertension diagnosis, and it happens constantly on patients with large arms.
The rest of the technique, in order. Five minutes of quiet rest, seated, back supported, feet flat, legs uncrossed, bladder empty, no caffeine, nicotine or exercise in the preceding 30 minutes, and no talking — by the patient or by you. Bare the arm. Support it at heart level, roughly the mid-sternum or fourth intercostal space. Palpate the radial pulse and inflate until it disappears, note that number, deflate fully and wait 30 to 60 seconds. Place the diaphragm lightly over the brachial artery in the antecubital fossa, not under the cuff edge. Inflate to 20 to 30 mm Hg above the palpated estimate. Deflate at 2 to 3 mm Hg per second.
The palpation step is not optional. It protects you from the auscultatory gap — a silent interval between the first and second Korotkoff phases seen in some patients with hypertension, which can make you record a systolic pressure 20 to 40 mm Hg too low if you inflated only until the sounds vanished.
Korotkoff phases
I first clear tapping = systolic · II swishing murmur, where the auscultatory gap may appear · III crisper, more intense tapping · IV abrupt muffling, recorded as diastolic only when sounds continue to zero — document all three numbers, for example 130/72/0 · V disappearance of sound = diastolic in adults, in pregnancy and, per current paediatric guidance, in children.
Arms to avoid, and the two-arm rule
Avoid an arm with an arteriovenous fistula or graft, an intravenous infusion or PICC line, lymphoedema or axillary node dissection, a cast, injury or paralysis. On first assessment measure both arms and use the higher; a persistent difference greater than 10 to 15 mm Hg between arms is abnormal, and a large acute difference raises the question of aortic dissection. If no cuff fits the upper arm, use a correctly sized cuff on the forearm with the radial artery auscultated, and document that you did.
The reading, decoded
—enter a pressure
Enter a systolic and diastolic, then press Classify. The default is Mr Delgado’s 1400 pressure — watch what the mean arterial pressure does.
ACC/AHA adult categories
Normal under 120 and under 80 · Elevated 120–129 and under 80 · Stage 1 130–139 or 80–89 · Stage 2 140 or higher or 90 or higher · Crisis higher than 180 and/or higher than 120.
Automated devices lie in exactly the patients who worry you. Oscillometric machines calculate systolic and diastolic from a measured mean arterial pressure. They are accurate on stable patients with regular rhythms and unreliable in atrial fibrillation, tremor, shivering, severe hypotension and extremes of arm size. Any automated reading that would change management — especially a very low one — should be confirmed manually before you act on it.
Pearl. If a machine reports a systolic of 74 on a patient who is awake, talking and warm, take a manual pressure before you call anyone. If it reports 74 on a patient who is confused and tachycardic with cool, mottled skin — mottling that on darker skin shows as a dull greyish patterning best seen at the knees, palms and soles rather than as purple lace — call first and confirm while you wait.
Positive or negative?
—enter the four sets
The test is positive when, within three minutes of standing, the systolic falls by 20 mm Hg or more or the diastolic falls by 10 mm Hg or more.
When to do them. Dizziness on standing, a fall, antihypertensives or diuretics, suspected bleeding or dehydration, or first mobilisation after prolonged bed rest. This assessment stays with the RN — interpretation and fall risk are nursing judgment, and the patient may go grey mid-test.
Symptoms are part of the result. Lightheadedness, greying vision and near-syncope belong in the note alongside the numbers. And a patient who drops pressure without raising the heart rate may have autonomic failure or be beta-blocked — the missing tachycardia is itself a finding.
Your call, scored
Choose one line for each of S, B, A and R, then press Make the call.
Then close the loop.Read the orders back. Document the time of the call and the response. If the patient continues to deteriorate or the provider does not respond, move up the chain of command — charge nurse, rapid response team, nursing supervisor. A rapid response team may be activated by any nurse without a provider’s permission, and in most facilities by the patient or family as well.
The CUS words. “I am concerned, I am uncomfortable, this is a safety issue” is a scripted escalation phrase that most facilities recognise. Use it when a call is not producing action; it signals that you are invoking the chain of command, not making conversation.
Have this in front of you before you dial
The chart, the last two sets of vital signs, the medication list and the times of the last relevant doses, the admission diagnosis, and the number you are asking for. Escalation done badly wastes the minutes it was meant to buy.