Blood Pressure, Oximetry and Body Measurements

This is Unit Thirteen of Medical Assistant Prep. Unit Twelve read every number against the right reference. This unit applies that idea to the remaining measurements: blood pressure, oxygen saturation, height, weight and body mass index. Carry one idea through this lecture. A measurement is only as accurate as its preparation, and one reading is never a diagnosis. A constructed case at the end shows a reading that needed a second look. By the end you will be able to prepare a patient and choose the right cuff. To take a manual reading and recognize the categories to report. To use a pulse oximeter and know its limits. And to measure height, length and weight, and calculate body mass index.

Five entries on preparation: what the reading measures, the arm check, rest, cuff size and position.

Systolic over diastolic.

MAS 301 What Blood Pressure Measures

Blood pressure is the force of blood against the artery walls as the heart pumps, reported in millimeters of mercury. It is measured with a cuff, called a sphygmomanometer, and a stethoscope, or with an automated device; the reading is written systolic over diastolic. A single reading is a snapshot; pressure changes through the day.

Reasons not to use an arm.

MAS 302 Ask Before You Wrap the Cuff

Before placing a cuff, check for any reason not to use that arm. Ask about and look for a dialysis fistula, a past mastectomy on that side, clots, lymphedema, wounds or an IV line, and ask which arm the patient prefers. Record any arm restriction so the next person does not use it.

Five minutes, and caffeine.

MAS 303 Rest First, and Ask About Caffeine

Blood pressure should be measured after the patient has rested quietly for at least five minutes. If the patient had caffeine or nicotine within the past thirty minutes, record that with the reading, since both can affect it. A patient who rushed in from the parking lot needs those five minutes.

Sized to the arm.

MAS 304 Choose the Right Cuff Size

A cuff must fit the arm, measured around its circumference. The cuff's width should be about forty percent of the arm's circumference, and its inflatable bladder should wrap about eighty to one hundred percent of the way around. A cuff that is too small gives an inaccurate reading, so measure, do not guess.

Bare skin, feet flat.

MAS 305 Position for an Accurate Reading

Position the patient and the cuff correctly before you inflate it. The patient sits upright with legs uncrossed and feet flat; the cuff goes on bare skin, snug and even, with the bladder centered over the brachial artery and its lower edge about an inch above the inner elbow. Never place the cuff over a sleeve; it belongs on bare skin.

Nine entries on the reading itself: the manual method, its sounds, automated cuffs, categories, and documentation.

Feel, then listen.

MAS 306 The Two-Step Manual Method

A manual pressure is often taken in two steps: estimate by feel, then measure by sound. Feel the radial or brachial pulse and inflate until it disappears, note that level, and deflate fully. Place the stethoscope lightly over the brachial artery and inflate to about thirty points above that level. Release the valve slowly and steadily, about two to three points a second. The first tapping sound is the systolic pressure, and the point where sounds disappear completely is the diastolic. Deflate, remove the cuff and record. The first step tells you how high to inflate, so follow the full method rather than guessing.

First and last.

MAS 307 Korotkoff Sounds

The sounds heard through the stethoscope during a manual reading are called Korotkoff sounds. The first clear sound marks the systolic pressure; the point where the sounds disappear completely marks the diastolic pressure. If you cannot hear the sounds well, do not guess; tell the provider or use another method the practice allows.

Upper arm at home.

MAS 308 Automated and Home Cuffs

Automated devices inflate, deflate and read the cuff pressure on their own. For home monitoring, a cuff around the upper arm is more accurate than wrist or finger devices, and it must fit snugly without being too small. An automated reading still needs correct cuff size, rest and posture to be accurate.

Normal to crisis.

MAS 309 Blood Pressure Categories

Adult readings fall into categories using both numbers. Normal is below one hundred twenty over below eighty. Elevated is one hundred twenty to one hundred twenty-nine systolic with diastolic below eighty. Stage one is one hundred thirty to one hundred thirty-nine systolic, or eighty to eighty-nine diastolic. Stage two is one hundred forty or higher systolic, or ninety or higher diastolic. Above one hundred eighty systolic, or above one hundred twenty diastolic, is a hypertensive crisis. In the higher categories the word is or, so either number alone can place a reading there. The category is the provider's call, but recognizing a reading to report is yours.

Ninety over sixty or below.

MAS 310 Low Blood Pressure

A reading of ninety over sixty or lower is considered low, a condition called hypotension. Causes include dehydration, bleeding, heart conditions and medication side effects; confusion, a weak, rapid pulse or cold skin with a low reading needs immediate attention. Report low readings promptly, especially with symptoms or after standing up.

An emergency with symptoms.

MAS 311 A Crisis-Level Reading

A reading above one hundred eighty over one hundred twenty is in the hypertensive crisis range. Symptoms such as a sudden severe headache, chest or back pain, numbness or weakness, trouble breathing or a sudden vision change with such a reading are an emergency. Report a crisis-level reading to the provider at once, and follow the practice's protocol.

More than two numbers.

MAS 312 Documenting a Blood Pressure

A blood pressure record includes more than the two numbers. Record the reading with the arm used, the patient's position, and whether it was manual or automated; note any recent caffeine or nicotine and any repeat reading. Without the arm and position, two readings cannot be compared.

Two or more days.

MAS 313 One High Reading Is Not a Diagnosis

Providers usually diagnose high blood pressure only after two or more high readings on different days. That is why a high reading is retaken as the practice directs and reported, rather than labeled; the provider weighs the pattern. Never tell a patient they have high blood pressure based on your reading.

Compared with peers.

MAS 314 Blood Pressure in Children

Blood pressure is not routinely measured in children under three unless there are heart concerns. For children under thirteen, readings are compared with what is typical for children of the same age, sex and height, not with adult categories. Use a cuff sized for the child's arm.

Three entries on pulse oximetry: what it estimates, the ranges references give, and what makes it wrong.

Saturation and pulse.

MAS 315 Pulse Oximetry

Pulse oximetry estimates how saturated the blood's hemoglobin is with oxygen, shown as a percentage. A small probe, usually clipped on a fingertip, shines light through the skin and reports the oxygen saturation along with the pulse rate. It is an estimate. A reading that does not match how the patient looks is reported, not trusted blindly.

References differ.

MAS 316 Oxygen Saturation Ranges

References differ slightly on expected oxygen saturation. One nursing text gives a target of ninety-four to ninety-eight percent for adults, and eighty-eight to ninety-two for some patients with COPD; a federal health site calls ninety-five to one hundred percent normal. Use the practice's parameters, and report any reading below them.

Blocked light.

MAS 317 Nail Polish and Oximeter Accuracy

Nail polish, especially dark polish, and artificial nails can make a fingertip oximeter inaccurate. They block the light the device needs, so use a sensor placed elsewhere, or remove the polish from that nail, as the practice allows. If a reading seems wrong for how the patient looks, check the probe and its placement, and report it.

Six entries on body measurements: height and weight, a stadiometer, infant length, wheelchair weighing, BMI, and a constructed case.

Same way each visit.

MAS 318 Height and Weight

Height and weight reflect general health, and weight is checked at routine visits. Infants and children are measured to track growth and development; changes in an adult's weight can signal illness or fluid changes. Record weight the same way at each visit, as the practice directs, so readings can be compared.

Four touch points.

MAS 319 Measuring Standing Height

Standing height is measured on a stadiometer, with a fixed backboard and a sliding head piece. Ask the patient to remove shoes and anything on top of the head, stand straight with heels together, and touch the board with head, shoulder blades, buttocks and heels. Many older adults cannot touch all four points; measure what you can.

Two people.

MAS 320 Measuring an Infant's Length

Infants and young children who cannot stand are measured lying down, a measurement called recumbent length. The child lies on a measuring board, head against the fixed end; one person holds the head while another straightens the legs and slides the footpiece up. Lying down can frighten a child, so let a parent stay close.

Chair and patient.

MAS 321 Weighing a Patient in a Wheelchair

A patient who cannot stand can be weighed in their wheelchair on a wheelchair scale. Weigh the empty chair, or use its recorded weight; then weigh the patient seated in it with the brakes on; subtract the chair's weight from the total. Use the same chair each time, because chairs differ in weight.

Weight over height squared.

MAS 322 Body Mass Index

Body mass index, or BMI, relates weight to height as weight in kilograms divided by height in meters squared. Below eighteen point five is underweight; eighteen point five to twenty-four point nine is healthy; twenty-five to twenty-nine point nine is overweight; thirty or more is obesity. BMI can mislead for athletes, people with swelling, and older adults who have lost muscle.

A rushed reading, retaken.

MAS 323 A Reading That Needed a Second Look

A constructed case pays off the opening idea. A large-framed man hurries in with coffee and sits with legs crossed; the first automated reading is one hundred fifty-eight over ninety-six. The assistant checks her process. No reason excludes his right arm, but the cuff barely closes, so she measures the arm and switches to the larger cuff. She seats him upright, feet flat, legs uncrossed, cuff on bare skin, rests him five minutes, and notes the coffee ten minutes earlier. The repeat is one hundred forty-four over ninety. She records both with arm, position, cuff size and caffeine, tells the provider, and offers no label when he asks. Both readings are high. Better technique gave an accurate number, not a clean one, and diagnosis rests on a pattern and the provider's judgment.

Look at what you can now do. You can prepare a patient for a blood pressure with an arm check, five minutes of rest, a cuff sized to the arm and the right position. You can take a manual reading in two steps, recognize the categories to report, and record the arm, position and method. You can use a pulse oximeter against the practice's parameters, and you know polish and placement can make it wrong. And you can measure height, length and weight, calculate body mass index, and report a reading without labeling the patient. Unit Fourteen turns to positioning, examinations, screening and irrigations.