Hypotension is generally considered when the blood pressure falls to 90/60 mmHg or below. Hypotension can be also caused by bleeding, shock, severe burn, prolonged diarrhea and vomiting. Orthostatic hypotension refers to the low blood pressure when the client sits or stands. It is usually the result of peripheral vasodilatation in which the blood flow increases and the blood flowing to main body organs decreases, especially the brain, often causing the person to feel fainted.
Nursing Process and Blood Pressure Determination
The assessment of blood pressure along with pulse assessment is used to evaluate the general state of cardiovascular health and its response to other system imbalances. The assessment includes the client’s usual condition, such as age, sex, the state of illness and treatment, and whether the clients have hemiplegia and dysfunctions or other complications.
Hypotension, hypertension, and narrow or wide pulse pressures are defining characteristics of many nursing diagnoses and are considered along with other assessment data. For example, the defining characteristics of hypotension, dizziness, pulse deficit and dysrhythmia lead to a diagnosis of decreased cardiac output. Related nursing diagnoses include activity intolerance, anxiety, cardiac output decreasing, and fluid volume deficit.
The nursing care plan includes appropriate interventions based on the nursing diagnosis identified and the related factors, the client’s understanding on the purpose of taking blood pressure and cooperating with nursing and treatment．
·Keep surroundings quiet and the temperature appropriate.
·Have light and digestible, low fat and low cholesterol, high vitamins and high fiber diet. Limit salt intake according to the client’s blood pressure level.
·Form the habit of regular life. Have enough sleep, stop smoking and drinking alcohol, maintain stool smoothly.
·Keep stable mood and decrease factors affecting emotion.
·Monitor the clients’ blood pressure and condition closely. Instruct clients to take medicine on time and observe reactions of medicine.
·Health instruction: Teach the clients and family members to take blood pressure and observe the complications of hypertension and basic first-aid skills.
The nurse evaluates the clients’ outcomes by assessing the blood pressure following each intervention; evaluates clients’ mental state and cooperation with treatment and nursing; and evaluates clients’ knowledge about health.
Section Ⅳ Respiration
Human survival depends on the ability of oxygen (O2) to reach body cells and for carbon dioxide (CO2) to be removed from the cells. Respiration is the mechanism the body uses to exchange gases between the atmosphere and the blood and the cells. Respiration involves external respiration and internal respiration. External respiration refers to the exchange of oxygen and carbon dioxide between the alveoli of lung and the pulmonary blood. Internal respiration refers to the exchange of oxygen and carbon dioxide between the circulating blood and the cells of the body tissues.
Inspiration refers to the intake of air into the lungs. Expiration refers to breathing out or the movement of gases from the lungs to the atmosphere. Ventilation is also used to refer to the movement of air in and out of the lungs.
There are two basic types of breathing: thoracic breathing and diaphragmatic breathing. Thoracic breathing involves the external intercostals muscles and other accessory muscles, such as the sternocleidomastoid muscles. It can be observed by the upward and outward movement of the chest. Diaphragmatic breathing involves the contraction and relaxation of the diaphragm, and it is observed by the movement of the abdomen.
Regulation of Respiration
The respiratory center is composed of several clusters of neurons which stimulate and regulate respiration in central nervous system. They are distributed over the cerebral cortex of the brain, diencephalons, pons, medulla, and spinal cord. Pons and medulla oblongata control normal respiratory rhythm. Higher centers above midbrain lie in cerebral ganglion and the cerebral cortex of the brain. The cerebral cortex of the brain voluntarily controls ventilation and regulates activity of brain stem center. So respiration is controlled by consciousness.
Respiratory center receives various impulses from respiratory organs and other systems, and controls respiratory movement by reflex mechanisms.
Hering-Breuer reflex As the lungs inflate, pulmonary stretch receptors activate the inspiratory center to inhibit further lung expansion, while as lungs deflate, expiration is inhibited and inspiration is stimulated. This is called Hering-Breuer reflex. When the lungs become overdistended, the stretch receptors activate an appropriate feedback response that “switches off” the inspiration ramp and thus stop further inspiration and transform inspiration to expiration in time for maintaining normal respiration rhythm.
Proprioceptor reflex Proprioceptors are present in the chest wall and diaphragm and provide information about thoracic inflation. Proprioceptors provide feedback and introduce impulse to maintain normal respiration, which enables the strength of the contraction to be varied if the airway resistance increases.
Defense reflex Respiratory defense mechanisms are very efficient in protecting the lungs from inhaled particles, microorganisms, and toxic gases. The defense mechanisms include filtration of air, mucociliary clearance system, the cough reflex, sneeze reflex, reflex bronchoconstriction, and alveolar macrophages.
Respiration is controlled by the level of carbon dioxide (CO2), oxygen (O2), and the concentration of hydrogen ion ([H+]) in the arterial blood. Central chemoreceptors are located in the medulla and respond to changes in [H+]. An increase in [H+] (acidosis) causes the medulla to increase the respiratory rate and depth. A decrease in [H+] (alkalosis) has the opposite effect. The most important factor in the control of ventilation is the level of CO2 in the arterial blood．Changes in PaCO2 regulate ventilation primarily by their effect on the pH of the cerebrospinal fluid. When the PaCO2 level is increased, more CO2 is available to combine with H2O and form carbonic acid (H2CO3). This lowers the cerebrospinal fluid pH and stimulates an increase in respiratory rate. The opposite process occurs with a decrease in PaCO2 level.
Peripheral chemoreceptors are located in the carotid bodies at the bifurcation of the common carotid arteries and in the aortic bodies above and below the aortic arch. The peripheral chemoreceptors respond to decrease in PaO2 and pH and to increase in PaCO2. These changes also cause stimulation of the respiratory center.
In a healthy person an increase in PaCO2 or decrease in pH causes an immediate increase in the respiratory rate. The PaCO2 does not vary more than about 3mmHg if lung function is normal. Conditions such as chronic obstructive pulmonary disease (COPD) alter lung function and may result in chronically elevated PaCO2 levels. The chemoreceptors in the carotid artery and aorta of these clients are sensitive to hypoxemia, or low levels of arterial O2. If PaO2 levels fall, these receptors signal the brain to increase the rate and depth of ventilation．Hypoxemia helps to control ventilation in clients with chronic lung disease．Hypercarbia is constant in clients with chronic lung disease. Once an elevated CO2 level fails to increase the rate and depth of breathing, hypoxemia, also present in these clients, becomes the stimulus to increase ventilation. Because low levels of arterial O2 provide the stimulus that allows the client to breathe, administration of high oxygen 1evels can be fatal for clients with chronic lung disease．