13. The Respiratory System



The Respiratory System


Objectives


Theory



Clinical Practice



Key Terms


adventitious (ăd-vĕnt-TĬ-shŭs, p. 264)


antitussive (ăn-tĭ-TŬS-ĭv, p. 272)


aphonia (ă-FŌ-nē-ă, p. 262)


apnea (ĂP-nē-ă, p. 259)


bradypnea (brād-ĕp-NĒ-ă, p. 262)


compliance (kŏm-PLĪ-ăns, p. 259)


crackles (KRĂK-ŭlz, p. 263)


cyanosis (sī-ă-NŌ-sĭs, p. 262)


dyspnea (DĬSP-nē-ă, p. 259)


expectorate (ĕk-SPĔK-tō-rāt p. 257)


hypercapnia (hī-pĕr-KĂP-nē-ă, p. 273)


hypocapnia (hī-pō-KĂP-nē-ă, p. 273)


hypoxia (hī-PŎK-sē-ă, p. 274)


kyphosis (kĭ-FŌ-sĭs, p. 259)


orthopnea (ŏr-thŏp-NĒ-ă, p. 263, 272)


perfusion (pĕr-FŪ-zhŭn, p. 260)


sputum (SPŪ-tŭm, p. 262)


stridor (STRĪ-dŏr, p. 264)


tachypnea (tăk-ĭp-NĒ-ă, p. 262)


wheezes (wēz-ĕz, p. 263)


imagehttp://evolve.elsevier.com/deWit/medsurg


Overview of Anatomy and Physiology of the Respiratory System


What are the Functions of Each of the Structures of the Upper Respiratory System?



• Air passes through the nose, mouth, pharynx, larynx, and trachea and then into the lungs (Figure 13-1).


• The nasal cavity is lined with mucous membrane that warms and moistens the air as it passes through; moisture protects the cilia.


• The mucous membrane secretes mucus, which traps dust particles and bacteria.


• The cilia (small, hairlike projections) propel the mucus toward the larynx, so the person can swallow or expectorate it (cough up and spit out).


• The paranasal sinuses (maxillary, frontal, sphenoid, and ethmoid) are air-filled cavities lined with mucous membrane and situated among the facial bones around the nasal cavity (Figure 13-2).


• The sinuses reduce the weight of the skull, produce mucus, and influence voice quality.


• The pharynx is about 5 inches long and extends from the back of the mouth to the esophagus.


• The pharynx is a passageway for moving air to the lungs and food to the esophagus.


• The tonsils, which are part of the lymphatic system, are located in the pharynx; if they become inflamed and enlarged, they may interfere with breathing.


• The epiglottis forms a hinged “door” at the entrance to the larynx.


• The larynx sits between the pharynx and the trachea. The vocal cords are located in the larynx.


• The trachea is made up of cartilage, smooth muscle, and connective tissue and is lined with mucous membrane and extends from the larynx to the bronchi; it is the “windpipe” and carries air to the lungs.




How Does the Epiglottis Protect the Airway?



How is Speech Produced in the Larynx?



What are the Functions of the Structures of the Lower Respiratory System?



How is Oxygen Delivered to the Alveolar Membrane, Where it Can Diffuse Into the Blood?




How is the Lung Protected?



• The pleural sac, which encloses each lung and protects it, is an airtight compartment. If the pleural sac is punctured, air will rush into the pleural cavity and collapse the lung.


• The pleura is a serous membrane of two layers. One layer, the parietal pleura, covers each lung, and the visceral pleura lines the inner wall of the chest cavity.


• A small amount of fluid between the two layers of pleura lubricates the pleural cavity and prevents friction between the pleural layers when the lungs expand and deflate.


• The pleural cavity is a potential space between the pleural layers where there is normally only a small amount of fluid.


• The mucous membrane lining the many small branches of the bronchial tree contains tiny hairlike projections (cilia) that trap and propel small foreign particles that are inhaled towards the entrance of the respiratory tract; the cough reflex works to expel the secretions.


• The alveoli contain macrophages that quickly destroy inhaled bacteria and other foreign particles.


How is Respiration Controlled?



• The central nervous system controls both involuntary and voluntary respiration via the pons and the medulla. The vagus nerve supplies the pharynx, larynx, respiratory airways, and lungs.


• The brainstem chemoreceptors are sensitive to changes in carbon dioxide (CO2) and hydrogen ions in the cerebrospinal fluid; the chemoreceptors in the aorta and the carotid arteries are sensitive to low oxygen (O2) levels in the blood.


• The signals of changing levels of hydrogen ions (measured by pH), CO2, and O2 trigger the respiratory center to send signals through the spinal cord. The signals travel along the peripheral nervous system to the phrenic and intercostal nerves that control the diaphragm and respiratory muscle contractions.


• When CO2 and hydrogen ion levels in the cerebrospinal fluid become higher than normal, the central receptors in the brainstem signal the nerves to initiate faster respiration to “blow off” the excess CO2. Carbon dioxide levels give the primary signals for respiration.


• When arterial blood O2 levels fall below normal, the respiratory centers in the aorta and carotid arteries signal the nerves to cause the lungs to inflate more fully, making the person breathe more deeply and at a faster rate.


• When CO2 levels are constantly high (as occurs with chronic lung disease such as emphysema) the respiratory drive comes from the receptors for low arterial O2 instead of high levels of CO2. If these patients are given too much oxygen, their respiratory drive is suppressed and they will stop breathing. (Normal blood gas levels are listed in Table 13-3 on pp. 265-267.)



Table 13-1


Characteristics of Sputum and Possible Causes*































Characteristic Possible Cause
Thick, tenacious, and “ropey”; difficult to cough up Chronic bronchitis, emphysema
Scant, sticky, rust colored Pneumococcal pneumonia
Frothy, pinkish or blood tinged Pulmonary edema
Yellow, yellow-green, or grayish yellow, with foul odor or taste Pulmonary infection
Blood tinged, bloody, or blood streaked Tuberculosis, or ulcerated pulmonary vessel, or bronchogenic carcinoma
Large amounts Pneumonia or bronchitis
Scanty Asthma
Very thick and viscous Inadequate hydration

*Normal sputum is white and slightly viscous and has no odor or taste.


How do the Bones of the Thorax and the Respiratory Muscles Affect the Respiratory Process?



• Inspiration (inhalation) and expiration (exhalation) occur by movement of the diaphragm and the intercostal muscles in the chest wall. During normal breathing, about 500 mL of air moves in and out of the lungs with each breath.


• When the diaphragm contracts, it moves downward; the other chest muscles contract, pulling the rib cage up and out, expanding the lungs and creating a greater area of negative pressure. Air from the atmosphere, which has a positive higher pressure, flows into the lungs.


• When the muscles relax, the lungs are allowed to return to a resting position that has a smaller internal volume and air is pushed out in exhalation.


• If damage to the spinal cord occurs above the level where the respiratory nerves are located (T1), voluntary respiration ceases.


• If the muscles of the diaphragm and chest are paralyzed, apnea (absence of breathing) occurs.


• The thoracic cage—composed of the thoracic vertebrae, the sternum, and the ribs—forms a stable unit that allows the respiratory muscles to function correctly. If any bones of the thorax or chest wall are injured or fractured, breathing becomes harder and dyspnea (difficult breathing) occurs.


• Compliance describes the elasticity of the lungs or how easily the lungs inflate; when compliance is decreased, the lungs are more difficult to inflate. Chronic obstructive pulmonary disease (COPD) and aging alter compliance due to damage in the alveoli.


• Weakness of the respiratory muscles, such as occurs with neuromuscular diseases, also causes decreased lung capacity.


• Kyphosis (inward curvature and collapse) of the spine constricts the thoracic cavity and restricts the capacity of the lungs to expand fully.


What Factors can Affect the Exchange of Oxygen and Carbon Dioxide?



• Alveoli are tiny air sacs covered with a permeable membrane that come into contact with the pulmonary arterioles and venules; oxygen passes into the blood and carbon dioxide passes from the blood into the alveoli.


• Surfactant is secreted by cells in the alveoli; it decreases surface tension on the alveolar wall so that diffusion of O2 and CO2 can take place. Surfactant facilitates expansion with inspiration and prevents alveolar collapse on expiration. When surfactant levels are low, alveoli cannot properly expand and O2 and CO2 cannot cross the membrane adequately.


• When interstitial edema occurs in the lung tissue, the alveolar membrane is thickened and gases cannot diffuse across the membrane as easily. During inflammation if fluid fills the alveoli, gases cannot diffuse across the membrane. Tumors may create blockage.


• Edema in the lungs occurs with infectious processes such as pneumonia and in disorders such as congestive heart failure.


• The major portion of the O2 (about 97%) attaches to the heme portion of the hemoglobin molecule carried by the erythrocytes (red blood cells) and forms oxyhemoglobin. The plasma also transports a portion of each gas; about 3% of O2 is dissolved in the plasma.


• CO2, a cellular waste product, combines with water in the red blood cell, forming carbonic acid; dissociation (uncombining) occurs, forming hydrogen ions and bicarbonate ions. About 77% of CO2 is transported in the blood plasma in the form of bicarbonate ions. The remaining 23% of CO2 combines with hemoglobin and is carried to the lungs. In the lung, the process reverses and the bicarbonate ions reenter the red blood cells and combine with hydrogen ions to form carbonic acid, which then dissociates into water and CO2. The CO2 diffuses across the alveolar membrane and is exhaled.


What Age-Related Changes Affect the Respiratory System?



• The decrease in the immune system’s efficiency makes the elderly more susceptible to upper respiratory infections.


• Aging results in a decreased cough reflex and an increased potential for aspiration.


• Osteoporosis may cause kyphosis, which impinges on lung expansion.


• Adults age 70 and older have some degree of change in connective tissue that causes decreased elasticity and affects lung function and ventilation.


• Total body water decreases to 50% after age 70, thus mucous and respiratory membranes are not as moist and mucous becomes much thicker.


• There is some impairment of the ciliary action, which makes it more difficult for the elderly to remove mucus, and retained mucus provides a breeding ground for bacterial infection.


• There is a loss of normal elastic recoil of the lung during expiration, and the patient must use muscle action to complete expiration. This increases the work of breathing.


• Muscle atrophy may affect the respiratory muscles, diminishing their strength.


• Connective tissue changes and loss of elastic tissue in the alveoli cause the alveolar membranes to become thickened. Oxygen saturation decreases for the elderly, with partial pressure of oxygen (PO2) dropping to 75 to 80 mm Hg from the usual 80 to 100 mm Hg.


• There is a decreased response to hypoxia (oxygen deficit in tissues) and hypercapnia (excessive amounts of carbon dioxide)


Causes of Respiratory Disorders


Trauma or disease can affect structures of the respiratory system, nerves controlling respiration, or diffusion of oxygen or carbon dioxide across the alveolar membranes into the capillaries. Perfusion (blood flow into cellular tissue) is essential because the bloodstream carries the oxygen to the cells of the body. Blood must be pumped past the alveolar membrane for oxygen and carbon dioxide diffusion to take place (Box 13-1). Cardiac disease, emboli, and other disorders of the heart and pulmonary blood vessels eventually cause problems in the respiratory system.



Box 13-1


Terms Commonly Used in Respiratory Care



• Diffusion: The movement of oxygen and carbon dioxide across the alveolar-capillary membrane. It takes place between the gas in the alveolar spaces and the blood in the pulmonary capillaries.


• Elastance: The extent to which the lungs are able to return to their original position after being stretched or distended.


• Hypoxemia: Deficient oxygenation of the blood.


• Hypoxia: A broad term meaning diminished availability of oxygen to the body tissues.


• Lung compliance: The ability of the lungs to distend in response to changes in volume and pressure of inhaled air. Lung compliance first increases and then decreases with age as the lungs become stiffer and the chest wall more rigid.


• Perfusion: The passage of a fluid through the vessels of a specific organ.


• Pulmonary hygiene: Methods used to clear secretions from the airways


• Resistance: The force working against the passage of air. The major determinant is the radius of the airway.


• Respiratory failure: An abnormality of gas exchange with either an excess of carbon dioxide or a deficit of oxygen, or both.


• Shunting: Intrapulmonary shunting is the diverting of blood so that it does not take part in the gas exchange at the alveolar sites. When intrapulmonary shunting occurs, blood enters the left side of the heart without being oxygenated. It is, therefore, a possible cause of hypoxemia.


• Surfactant: A complex lipoprotein produced by cells lining the alveoli, which lowers surface tension within the alveoli. It prevents collapse of the lung by stabilizing the alveoli and decreasing capillary pressures.


• Ventilation: The movement of air from the external environment to the gas exchange units of the lung. It can be spontaneous or done by a mechanical ventilator.


The respiratory system is particularly susceptible to harmful substances in the environment. Inhalation of bacteria and other organisms can quickly produce an infection in either the upper or lower respiratory tract. Tobacco smoke, allergens, poisonous gases, and other toxic substances cause irritation and inflammation of the air passages and can eventually lead to chronic inflammation, obstructive diseases, and tumors. There may be a familial tendency toward allergies, asthma, or other lung problems.


There are two major types of ventilatory diseases: restrictive and obstructive. Restrictive diseases are characterized by decreased lung capacity. They are not necessarily primarily lung disorders, but eventually the expansion of the lung and chest wall will be limited. Examples include scoliosis and kyphosis, both of which decrease the size of the chest cavity. Arthritis increases stiffness of the chest wall and results in a decreased ability of the chest cavity to expand and contract. Pneumothorax (collapsed lung) diminishes lung surface; neuromuscular disorders weaken the strength of the muscles of respiration (e.g., myasthenia gravis); and disorders of the lung (e.g., pneumonia, atelectasis, and fibrosis) increase stiffness and decrease lung volume.


Obstructive pulmonary diseases are characterized by problems moving air into and out of the lungs. Narrowing of the openings in the tracheobronchial tree increases resistance to the flow of air, making it difficult for oxygen to enter and contributing to air trapping; therefore exhalation is also difficult. Asthma, emphysema, and chronic bronchitis are examples of obstructive lung diseases. Tumor in the lung can also obstruct airflow to the alveoli.


Respiratory Disorders


Prevention


The best ways to prevent infection and inflammation of the respiratory system are to practice hand hygiene frequently; stay out of crowds, especially during cold and flu season; refrain from smoking; avoid known allergens as much as possible; maintain adequate nutrition; and obtain sufficient rest to help keep the immune system healthy. Nurses should identify persons that have a high risk for infection (Box 13-2).



Allergy to airborne substances causes the mucous membranes of the nose and sinuses to become irritated and inflamed. When these membranes are inflamed, bacteria and viruses can more easily invade the cells and cause infection. By controlling inhaled allergens we can decrease the incidence of upper respiratory infection (URI).



Elimination of such widespread respiratory diseases as the common cold and influenza is not possible; therefore nurses must practice good hand hygiene and use Standard Precautions and airborne or droplet precautions when working with patients with respiratory infections. For certain groups such as the elderly and the chronically ill, immunization against influenza is an effective means of reducing the incidence of respiratory disease. Physicians, nurses, and others involved in providing health care should also be immunized. Among the more serious reactions to influenza vaccine are allergic reactions, fever, malaise, or muscle soreness. Guillain-Barre syndrome occurs in about 1 in 100,00 individuals. The vaccine is prepared from chicken embryos; therefore vaccination is contraindicated for anyone with an allergy to eggs, chicken, or feathers.


The U.S. Public Health Service Advisory Committee on Immunization also recommends immunization against pneumococcal infection for high-risk persons.


Perhaps one of the most important preventive measures is to avoid prolonged and repeated inhalation of irritating substances. Such substances include tobacco smoke, industrial gases, coal dust, soot and other carbons, and air polluted by automobile exhaust. Proposed Healthy People 2020 objectives include reducing tobacco use by adults, adolescents, and pregnant women. Smoking cessation efforts are supported by increasing insurance coverage for evidenced-based interventions, increasing smoke-free environments, and strengthening tobacco laws. Beginning in early 2010, the Joint Commission began to develop and define Core Measures for the assessment and treatment of tobacco use. Nurses should participate by identifying patients at risk for tobacco-related disease and encourage cessation programs.




Nursing Management


Assessment (Data Collection)


History Taking


Observe respiratory function while you are talking with the patient and ask about frequency of URIs, known inhalant allergies, and sinus problems. Chest pain can occur with frequent coughing, pleurisy, or trauma to the lungs; however whenever there is a complaint of chest pain be vigilant for cardiac problems. Patients with sinus problems may complain of headache, malaise, a bad taste in the mouth, nasal congestion or obstruction, purulent drainage from the nose, and painful upper teeth. Those with pharyngitis often report a sore or “scratchy” throat, malaise, headache, and sometimes a cough. Dysphagia also might be a problem for patients with pharyngitis, because swallowing involves pushing the food back against the inflamed oropharynx. Hoarseness and loss of the voice (aphonia) are common symptoms of laryngitis. Hoarseness or a sore throat that lasts longer than 2 weeks, should be noted as this will assist in the early detection of throat malignancy. If the patient is in obvious respiratory distress, ask only a few



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Focused Assessment


Data Collection for the Respiratory System


History Taking



Physical Assessment


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Nov 17, 2016 | Posted by in NURSING | Comments Off on 13. The Respiratory System

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