Vital Signs and

Oxygen Administration

Taking a patient's vital signs (also called cardinal signs) is an important part of a physical assessment and includes measurement of :• body temperature• pulse• respiration• 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 encountered

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 oxygen supply.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 oxygen increases.

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 congenitally absent)•Posterior tibial pulse: on the inner side of the anklesBrachial 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).

RespirationThe 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 vessel walls.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 pressure.

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.

Oxygen TherapyAn 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

Pulse OximetryA pulse oximeter is frequently used to monitor the oxygen saturation of hemoglobin (SaO2).

Normal SaO2

values are 95% to 100%. Values of less than 85% indicate that the tissues are not receiving adequate oxygen.

Hazards of Oxygen AdministrationOxygen 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 depress ventilation.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 SystemsOxygen 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 throat

Face MaskA 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 50%.

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 TentOxygen 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 generate sparks.