Taking a patient's vital signs (also called cardinal
signs) is an important part of a physical assessment
and includes measurement of :
• body temperature
• blood pressure
The radiographer must know how to measure each
vital sign to be prepared in case an emergency
situation in which these skills are needed is ever
Changes in vital signs can be an indication of a problem
or a potential problem. A patient's baseline vital signs
cannot be established with one reading of pulse,
respiration, or blood pressure because of the many
variables that can make one reading unreliable. Vital
signs must be measured if the patient comes to the
diagnostic imaging department for an extensive
procedure or examination without a chart and no
registered nurse is available.
Oxygen is an essential physiologic need for survival. It comes
from the environment to the lungs and then is transported to
the bloodstream and body tissues. The human brain cannot
function for longer than 4 to 5 minutes without an adequate
It is occasionally necessary to administer oxygen in the
diagnostic imaging department. The radiographer is expected
to assist in its administration. Also, a patient receiving oxygen
therapy in the hospital room may be unable to leave the room
to go to the diagnostic imaging department for necessary
procedures. In this instance, the mobile units will be required to
make the radiographic exposure at the bedside. Because
oxygen is a potentially toxic and volatile substance, the
radiographer needs to understand the precautions that are to
be taken when assisting with oxygen administration or when
using radiographic equipment while oxygen is in use.
Body temperature is the physiologic balance between heat
produced in body tissues and heat lost to the environment.
A patient whose body temperature is elevated above
normal limits is said to have a fever, or pyrexia. Fever
indicates a disturbance in the heat-regulating centers of
the body, usually as a result of a disease process. As
body temperature increases, the body's demand for
There are four areas of the body in which temperature is
usually measured: the oral site, the tympanic site, the rectal
site, and the axillary site.
Temperature readings are reported in most health care
facilities as follows:
•A rectal temperature of 99.6°F is written 99.6 R.
•An oral temperature of 98.6°F is written 98.6 O.
•An axillary temperature of 97.6°F is written 97.6 Ax.
•A tympanic temperature of 97.6°F is written 97.6 T.
As the heart beats, blood is pumped in a pulsating fashion into the
arteries. This results in a throb, or pulsation, of the artery. At areas of the
body in which arteries are superficial, the pulse can be felt by holding the
artery beneath the skin against a solid surface such as bone. The pulse
can be detected most easily in the following areas of the body:
•Apical pulse: over the apex of the heart (heard with a stethoscope)
•Radial pulse: over the radial artery at the wrists at the base of the thumb
•Carotid pulse: over the carotid artery at the front of the neck
•Femoral pulse: over the femoral artery in the groin
•Popliteal pulse: at the posterior surface of the knee
•Temporal pulse: over the temporal artery in front of the ear
•Dorsalis pedis pulse (pedal): at the top of the feet in line with the groove
between the extensor tendons of the great and second toe (may be
•Posterior tibial pulse: on the inner side of the ankles
Brachial pulse: in the groove between the biceps and triceps muscles
above the elbow at the antecubital fossa
The pulse rate is a rapid and relatively efficient
means of assessing cardiovascular function.
Tachycardia is an abnormally rapid heart rate (over
100 beats/min), and bradycardia is an abnormally
slow heart rate (below 60 beats/min).
The function of the respiratory system is to exchange
oxygen and carbon dioxide between the external
environment and the blood circulating in the body.
Oxygen is taken into the lungs during inspiration. It
passes through the bronchi, into the bronchioles, and
then into the alveoli, which are the gas-exchange units
of the lungs
The average rate of respiration (one inspiration and one
expiration) for an adult man or woman is 15 to 20
breaths/min, and for an infant it is 30 to 60 breaths/min.
Respiration of fewer than 10 breaths/min for an adult may
result in cyanosis, apprehension, restlessness, and a
change in level of consciousness because the supply of
oxygen is inadequate to meet the needs of the body.
Normal respirations are quiet, effortless, and uniform.
Medication, illness, exercise, or age may increase or
decrease respirations, depending on the body's metabolic
need for oxygen. When a patient is using more than the
normal effort to breathe, he or she is described as dyspneic
or as having dyspnea
Blood Pressure In general terms, pressure is
defined as the product of flow times resistance. Blood
pressure is the amount of blood flow ejected from the
left ventricle of the heart during systole and the amount
of resistance the blood meets due to systemic vascular
resistance. Maintenance of blood pressure depends
on peripheral resistance, pumping action of the heart,
blood volume, blood viscosity, and the elasticity of the
If the volume of blood decreases because of
hemorrhage or dehydration, the blood pressure falls
because of a diminished amount of fluid in the arteries.
Fluid or blood replacement reverses the problem.
The number of red blood cells in the blood plasma
determines the viscosity of the blood. With an
increased number, the blood thickens or becomes
more viscous and subsequently increases the blood
The instrument used to measure blood pressure is called a
sphygmomanometer. Two numbers, read in millimeters
of mercury (mm Hg), are recorded when reporting blood
pressure: systolic pressure and diastolic pressure. The
systolic reading is the highest point reached during
contraction of the left ventricle of the heart as it pumps
blood into the aorta. The diastolic pressure is the lowest
point to which the pressure drops during relaxation of the
ventricles and indicates the minimal pressure exerted
against the arterial walls continuously.
In men and women, the normal ranges are 90 to 120 mm
Hg for systolic pressure and 50 to 70 mm Hg for diastolic
pressure. Adolescent patients' blood pressure ranges from
85 to 130 mm Hg systolic and 45 to 85 mm Hg diastolic.
An adequate oxygen supply is essential to life. Because
oxygen cannot be stored in the body, the supply from the
external environment must be constant. When a human
being's oxygen supply is suddenly interrupted or interfered
with in any manner, it is an emergency that must be dealt with
immediately to prevent a life-threatening situation. This type of
emergency may occur in the diagnostic imaging department;
therefore, the radiographer performing the procedure may be
the first person to observe such a problem. It is that person's
responsibility to ensure that the equipment needed to
administer oxygen is available at all times and in functioning
condition in the work area. It is also that person's
responsibility to assist with oxygen administration in
emergency situations. Therefore, understanding the methods
of oxygen administration that may be encountered in the care
of the patient is critical.
When pulmonary function is disturbed, the level of oxygen
in the arterial blood becomes inadequate to meet the
patient's physiologic needs. This condition is referred to as
hypoxemia. Carbon dioxide may be retained in the arterial
blood, which results in a condition called hypercapnia.
When the PaO2 is below 60 mm Hg or the hemoglobin
saturation is less than 90%, it can be assumed that
adequate oxygenation of the blood is not taking place
A pulse oximeter is frequently used to monitor
the oxygen saturation of hemoglobin (SaO2).
values are 95% to 100%. Values of less than
85% indicate that the tissues are not
receiving adequate oxygen.
Hazards of Oxygen Administration
Oxygen is considered to be a medication and,
like all other forms of medical therapy, must be
prescribed by a physician. Excessive amounts
of oxygen may produce toxic effects on the
lungs and central nervous system or may
Varying degrees of oxygen toxicity may result
from inhalation of high concentrations of
oxygen for more than a brief period of time.
Mild oxygen toxicity may produce reversible
tracheobronchitis. Severe oxygen toxicity may
cause irreversible parenchymal lung injury.
Because of the potential for adverse effects
from excessive amounts of oxygen, oxygen
should be administere
Oxygen Delivery Systems
Oxygen is administered by artificial means when the
patient is unable to obtain adequate amounts from the
atmosphere to supply the needs of the body. If the patient
requires supplementary oxygen, it is delivered to the
respiratory tract under pressure. When the flow rate is
high, the oxygen is humidified to prevent excessive drying
of the mucous membranes. Passing the oxygen through
distilled water can do this, because oxygen is only slightly
soluble in water. The procedure for moisturizing oxygen
varies somewhat from one institution to another, but often,
the receptacle for distilled water is attached at the wall
outlet, and the oxygen passes through the water and then
into the delivery system.
The nasal cannula is a disposable plastic device with
two hollow prongs that deliver oxygen into the nostrils). The other
end of the cannula is attached to the oxygen supply, which may or
may not pass through a humidifier, and it has a flow meter attached.
The cannula is held in place by an elastic strap that fits over the
patient's ears and behind the head. This device is the most
commonly seen delivery system in the diagnostic imaging
department. Patients on long-term oxygen delivery have a nasal
cannula because of the comfort and convenience of the cannula.
The concentration of oxygen delivered by nasal cannula varies from
21% to 60%, according to the amount of room air inspired by the
patient. Oxygen delivery by nasal cannula is indicated for patients
whose breathing range and depth are normal and even. With this
method, 1 to 4 LPM of oxygen is usually prescribed for adults. For
children, the rate is much lower (1/4 to 1/2 LPM). Rates at higher
levels dry the nasal mucosa because of the position of the tubes
against the skin of the nostrils.
A nasal catheter is another means of low-flow delivery
of oxygen. While this method of oxygen delivery is not
routinely used, it warrants description in the event that the
radiographer may come in contact with it. In this system, a
French-tipped catheter is inserted into one nostril until it
reaches the oral pharynx. This type of catheter is used to
deliver a moderate to high concentration of oxygen. As with
the nasal cannula, the other end of the French-tipped
catheter is attached to the oxygen supply with a flow meter
attached. The prescribed flow rate for this method of delivery
is usually 1 to 5 LPM. Oxygen delivered by this method does
have associated hazards. For example, oxygen may be
misdirected into the stomach, causing gastric distention; or
the mucous membranes may become dry, causing a sore
A simple face mask is used to deliver oxygen for short
periods of time It, too, is attached to an oxygen supply
and a flow meter. The mask is placed over the nose
and mouth and attached over the ears and behind the
head with an elastic band). A mask is uncomfortable
for long periods because the patient is unable to eat,
drink, or talk with it in place. Moreover, the percentage
of oxygen is so variable with the face mask that it is
not the method of choice for long periods. Because the
mask does not fit tightly against the face, the
concentration of oxygen delivered varies from 30% to
When the face mask is used, it should be run at no less than 5 LPM. This
rate is needed to flush the CO2 from the mask. Other face masks are
usually used to administer more precise concentrations of oxygen. Several
types of face mask delivery systems are available at present, and the
physician will prescribe the one best suited to the patient's needs.
The different types of mask include a nonrebreathing mask, which, if
correctly used, may supply 100% oxygen. This high-flow system has a
reservoir bag attached. The bag fills with oxygen to provide a constant
supply of oxygen. A valve prevents the exhaled gases from entering the
reservoir bag and prevents rebreathing of exhaled gases. A partial
rebreathing mask, which delivers 60% to 90% oxygen, operates similarly to
the nonrebreather mask. The rebreather mask does not have a valve
between the mask and the bag; therefore, exhaled air flows into the
reservoir bag and allows the patient to breathe a mixture of oxygen and
carbon dioxide. Two other types of face mask delivery systems include a
Venturi mask, which limits oxygen to 24% to 50% by mixing room air and
the oxygen in specific percentages; and an aerosol mask, which provides
60% to 80% oxygen mixed with particles of water.
Oxygen tents are used when there is a need for
humidity and a higher concentration of oxygen than
is present in the natural environment of the patient.
This method of delivery is rarely used for adults, but
one may be encountered in a pediatric unit. If this is
the case, the oxygen may be turned off for a brief
period while the required exposures are made with
the mobile equipment. The hazard of fire is
especially great with an oxygen tent. Smoking is not
permitted, nor is the use of any equipment that might