Vital signs are essential measurements of a patient’s body function. Taken by a medical assistant or medical technician each time a patient sees their doctor, they give physicians important information to make the best clinical decisions. Readings help doctors diagnose disease, monitor the effects of therapy, and calculate dosages for high-risk medication. It’s a routine but critical task that requires both technical skill and accuracy.
What are Vital Signs?
Vital signs are a group of measurements that accurately reflect how well the body is functioning. They’re taken at every visit because trends and changes over time are as meaningful as single readings.
There are four primary vital signs: body temperature, heart rate, respirations and blood pressure. There are also three secondary measures that most doctors consider important: height, weight and peripheral oxygen saturation.
Vital Sign #1: Temperature
The average adult body temperature is 98.6 degrees Fahrenheit or 37 degrees Celsius, but research shows that it can range between 97 and 99-degrees Fahrenheit, or 36.5 to 37.2degrees Celsius, and still be healthy. A high or low body temperature may reflect conditions from infections to thyroid disease.
Temperature can be measured using one of five methods including oral, rectal, axillary, aural or tympanic, and skin.
Oral thermometers have digital probes that obtain the temperature under the tongue. Today’s models have disposable covers for cleanliness, and clinical versions are accurate to a tenth of a degree. Older mercury thermometers are an environmental hazard and are no longer used. Before taking an oral temperature, a medical assistant should ensure patients didn’t drink hot or cold liquids in the waiting area because it can affect readings. The patient’s mouth should remain closed around the probe during the process for the most accurate results.
Temperatures obtained rectally are among the most accurate, they range from 0.4–0.8 degrees higher than oral temperatures, but the method has fallen out of favor because it’s unpleasant and risky. Probes inserted in the rectum can damage delicate tissue and cause bleeding.
Axillary temperatures are taken in the armpit. Readings average half a degree lower than comparable methods, and the process takes up to two minutes. However, for patients unable to keep a thermometer in their mouth, it’s a reasonable alternative.
Aural or Tympanic Temperature
Aural thermometers measure the temperature of the tympanic membrane, or eardrum, using infrared rays. Early versions were not highly accurate, but new models are. Precise readings, however, depend on technique. The probe must be properly positioned to seal off the ear canal. Measurements can be affected by ear wax and scarring from past infections.
Skin, or forehead thermometers, measure temperature at the temporal artery. Readings are quick, and the procedure is non-invasive. However, the method isn’t as accurate as others and is used more for screening purposes or comfort for children.
At home, basic skin thermometers come in the form of tape that changes colors when applied to the forehead. Accuracy is low and only gives a ballpark idea of actual temperature, but it can help parents decide if a child is sick enough to see the doctor. Handheld clinical models look like a tympanic thermometer with a large probe on the end that is applied to the skin in one or more locations.
Vital Sign #2: Heart Rate
The heart rate, or pulse, measures how many times the heart beats per minute. As the ventricles pump blood, arteries expand and contract, causing a pulsation in vessels closest to the skin’s surface. These arteries are accessible in places from the neck and groin to the temple and feet, but the radial artery at the wrist, just above the thumb, is the easiest to use.
The quickest way for a medical assistant or medical technician to take a heart rate is to measure the number of pulsations in the radial artery for 15 seconds and multiply the result by four to get the number of beats in 60 seconds. If the heart rate seems irregular, however, it should be assessed over a full minute.
Skipped beats and changes in the character of a patient’s pulse can indicate heart dysrhythmias, such as a trial fibrillation or supraventricular tachycardia. For patients diagnosed with irregular heart rhythms, taking a so-called apical pulse by listening to the heartbeat for a full 60 seconds with a stethoscope is better at detecting subtle inconsistencies than a radial pulse.
The normal heart rate for a healthy adult ranges from 60–100 beats per minute, but that can fluctuate with activity or illness. Infants may have normal heart rates as high at 180 beats per minute, while performance athletes can have pulses as low as 50 and still be healthy.
An abnormal heart rate can indicate a broad range of conditions from cardiac and thyroid disease to infection. It can also mean patients are having side effects to some types of high-risk medications.
Vital Sign #3: Respirations
The respiratory rate is the number of breaths taken per minute. It’s measured at rest by watching the chest rise and fall. To avoid unintentional changes in breathing patterns due to anxiety, checking respirations is something a medical assistant or medical technician does without telling the patient.
The normal adult respiratory rate is 12–16 breaths per minute. An increased rate could indicate a fever while a low rate in a patient with lung disease suggests carbon dioxide retention.
Vital Sign #4: Blood Pressure
Blood pressure is the force of blood pushing against artery walls. It’s reported with two numbers, the “systolic” blood pressure, measured when the heart contracts over the “diastolic” blood pressure, measured when the heart relaxes.
Both readings are recorded as millimeters of mercury, or “mm Hg,” referring to the movement of a column of mercury in older blood pressure devices called sphygmomanometers. While these units are still in use today, most doctor’s offices have transitioned to electronic blood pressure devices.
Blood pressure is among the most important vital signs because it reflects how well the circulatory system is working. High blood pressure, or hypertension, is among the most significant risk factors for serious medical conditions, including heart disease, kidney failure and stroke. Low blood pressure could mean dehydration or a change in the heart’s pumping ability. Normal blood pressure is currently categorized at 120/80 or less while high blood pressure is divided into these four stages:
Patients with Stage 1, or prehypertension, consistently have blood pressure between 120/80–138/89. Single readings in this range are not usually concerning, however, when it becomes a trend, doctors know there’s an increased risk of disease, and they can take action. Changes in lifestyle, such as increased exercise and eating a healthy diet, are the most common recommendations. A medical assistant or medical technician is a doctor’s partner in patient education.
Stage 2, or mild hypertension, is defined as blood pressure of 140/90–149/99. It can reflect a number of physiological issues, but because it increases the risk of heart attack or stroke, doctors may prescribe small doses of anti-hypertensive medications.
For a medical assistant or medical technician, this makes taking accurate blood pressures at subsequent visits even more critical because readings show how well therapy is, or isn’t, working.
Patients with blood pressures from 150/100–159/109 have moderate hypertension, meaning they have an even higher risk of cardiovascular or renal complications, and require more aggressive treatment. Medical assistants or medical technicians can help patients with home monitoring programs by teaching them how to take accurate blood pressure readings at home.
Stage 4, or severe hypertension, is marked by a blood pressure of 160/110 or higher. A single reading this high is cause for concern, and consistent measurements in this range could signal a medical emergency.
Vital Sign #5: Height
Height is an important clinical indicator for two reasons. First, it’s used to calculate Body Mass Index or BMI. BMI is a screening tool used in place of less accurate weight tables to determine if a patient has a healthy body size. It’s also the basis on which doctors calculate the dosages for many high-risk medications.
A decrease in height can also indicate bone disease such as osteoporosis. Because it causes curvatures in the spine to deepen, it can cause some to lose as many as four inches in height. A bone density test is recommended for women aged 65 and older who lose more than an inch in a year.
Vital Sign #6: Weight
Weight is the second measurement in the BMI calculation, and it’s also used to determine drug dosages. More than height, however, even minor changes can have serious clinical significance. For example, a gain of just two pounds can cause respiratory symptoms in a patient with heart failure.
Height and weight are simple to take, but for a medical assistant or medical technician, using a consistent method is essential. Measuring patients with their shoes on at one visit but not at the next can suggest a change where none exists.
Vital Sign #7: Peripheral Oxygen Saturation
Peripheral oxygen saturation is the percentage of oxygen in tissues located away from the heart. It can tell doctors how well the lungs, heart and blood vessels are working.
It’s checked with a fingertip oximeter in a process known as pulse oximetry. The device uses light to detect how much of the body’s hemoglobin, the oxygen-carrying component of blood, is saturated with oxygen. Readings of over 90-percent are ideal in most cases.
Pulse oximetry is not recognized as a vital sign in all practices. It’s easy to take, but not as simple to interpret as other vital signs. Some physicians believe it’s too complex to do regularly. Others, however, think it’s a good screening test that adds detail to the clinical picture. A medical assistant or medical technician may be asked to take it on every patient or just those with respiratory or cardiovascular disease. It’s non-invasive and virtually risk-free, but inaccurate readings are common without diligence. Cold fingers, for example, give a false low measurement.
Medical assistants or medical technicians are jacks-of-all-trades with many responsibilities, but few have the clinical significance of taking accurate vital signs. It’s a highly skilled and meaningful role.
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