SYMPTOMS OF RESPIRATORY DISORDERS THE PHYSICAL EXAMINATION AND THE RESPIRATORY SYSTEM. 134 The Body Systems: Clinical and Applied Topics

Transcription

1 34 The Body Systems: Clinical and Applied Topics The Respiratory System The anatomical components of the respiratory system can be divided into an upper respiratory system, which includes the nose, nasal cavity, paranasal sinuses, and pharynx, and a lower respiratory system, composed of the larynx, trachea, bronchi, and lungs. The respiratory tract consists of the airways that carry air to and from the exchange surfaces of the lungs. The respiratory tract can be divided into a conducting portion and a respiratory portion. The conducting portion begins at the entrance to the nasal cavity and extends through the pharynx and larynx, and along the trachea and bronchi to the terminal bronchioles. The respiratory portion of the tract includes the respiratory bronchioles and the alveoli that are part of the respiratory membrane, where gas exchange occurs. SYMPTOMS OF RESPIRATORY DISORDERS Individuals with lower respiratory disorders usually seek medical attention due to one or two major symptoms, specifically chest pain and dyspnea:. The chest pain associated with a respiratory disorder usually worsens when the person takes a deep breath or coughs. This pain with breathing distinguishes it from the chest pain experienced by individuals with angina (pain appears during exertion) or a myocardial infarction (pain is continuous, even at rest). Several disorders, such as those affecting the pleural membranes, cause chest pain that is localized to specific regions of the thoracic cage. A person with such a condition will usually press against the sensitive area and avoid coughing or deep breathing in an attempt to reduce the pain. 2. Dyspnea, or difficulty in breathing, may be a symptom of pulmonary disorders, cardiovascular disorders, metabolic disorders, or environmental factors such as hypoxia at high altitudes. It may be a chronic problem, or it may develop only on exertion or only when lying down. Dyspnea due to respiratory problems usually indicates one of the following classes of disorders: Obstructive disorders result from increased resistance to airflow along the respiratory passageways. The individual usually struggles to breathe, even at rest, and expiration is more difficult than inspiration. Examples of obstructive disorders include emphysema (p. 38) and asthma (p. 37). Restrictive disorders include () arthritis, (2) paralysis of respiratory muscles caused by trauma, muscular dystrophy, myasthenia gravis, multiple sclerosis, or polio, and (3) physical trauma or congenital structural disorders that limit lung expansion. Individuals with restrictive disorders usually experience dyspnea during exertion because pulmonary ventilation cannot increase enough to meet the respiratory demand. Cardiovascular disorders that produce dyspnea include coronary heart disease, congestive heart failure, and pulmonary embolism. In paroxysmal nocturnal dyspnea a person awakens at night, gasping for air. The underlying cause is usually a problem with cardiac output due to advanced heart disease or heart failure. Cheyne-Stokes respiration consists of cycles of rapid, deep breathing separated by periods of respiratory arrest. This breathing pattern is most often seen in persons with CNS disorders or congestive heart failure. Dyspnea may also be related to metabolic problems, such as the acute acidosis associated with diabetes mellitus (p. 92) or uremia (p. 8). The fall in blood ph can trigger Kussmaul breathing, which usually consists of rapid, deep respiratory cycles. THE PHYSICAL EXAMINATION AND THE RESPIRATORY SYSTEM Several components of the physical examination will detect indications of respiratory disorders:. Inspection can reveal abnormal dimensions, such as the barrel chest that develops in emphysema or other obstructive disorders (p. 38), or clubbing of the fingers (p. 38). Clubbing is most often a late sign of disorders such as emphysema or congestive heart failure. Cyanosis, a blue color of the skin and mucous membranes, usually indicates hypoxia. Laboratory testing of arterial blood gases will assist in determining the cause and extent of the hypoxia. 2. Palpation of the bones and muscles of the thoracic cage can detect structural problems or transmitted lung vibrations. For example, a one-sided pleural effusion blunts the vibration of speech passed through the bronchi to the chest wall on that side. 3. Percussion on the surface of the thoracic cage over the lungs will yield sharp, resonant sounds. Dull or flat sounds may indicate structural changes in the lungs, such as those accompanying pneumonia, or partial collapse of a lung (atelectasis). Increased resonance may result in obstructive disorders, such as emphysema, due to hyperinflation of the lungs as the individual attempts to improve alveolar ventilation.

2 4. Auscultation of the lungs with a stethoscope yields the distinctive sounds of inspiration and expiration. These sounds vary in intensity, pitch, and duration. Abnormal breath sounds accompany several pulmonary disorders: Rales (rahls) are hissing, whistling, scraping, or rattling sounds associated with increased airway resistance. The sounds are created by turbulent airflow past accumulated pus or mucus, or through airways narrowed by inflammation or bronchospasms. Moist rales are gurgling sounds produced as air flows over fluids within the respiratory tract. They are heard in conditions such as bronchitis, tuberculosis, or pneumonia. Dry rales are produced as air flows over thick masses of mucus, through inflamed airways, or into fluid-filled alveoli. Dry rales are characteristic of asthma and pulmonary edema. Rhonchi are loud, dry rales produced by mucus buildup in the air passages. Stridor is a very loud, high-pitched sound that can be heard without a stethoscope. Stridor usually indicates acute airway obstruction, such as the partial blockage of the glottis by a foreign object. Wheezing is a whistling sound that can occur with inspiration or expiration. It usually indicates airway obstruction, due to mucus buildup or bronchospasms. Coughing is a familiar sign of several respiratory disorders. Although primarily a reflex mechanism that clears the airway, coughing may also indicate irritation of the lining of the respiratory passageways. The duration, pitch, causative factors, and productivity (a productive cough ejects sputum; a nonproductive cough does not) may be important clues in the diagnosis of a respiratory disorder. If the cough is productive, the sputum ejected can be analyzed. This analysis will provide information about the presence of epithelial cells, macrophages, blood cells, and/or pathogens. The sputum can be cultured to permit identification of the specific microorganism involved. A friction rub is a distinctive crackling sound produced by abrasion between abnormal serous membranes. A pleural rub accompanies respiratory movements and indicates problems with the pleural membranes, such as pleurisy. A pericardial rub accompanies the heartbeat and indicates inflammation of the pericardium, as in pericarditis.. During assessment of vital signs, the respiratory rate (number of breaths per minute) is recorded, along with notations concerning the The Respiratory System 3 general rhythm and depth of respiration. Tachypnea is defined as a respiratory rate faster than 20/min. in an adult; bradypnea is an adult respiratory rate below 2/min. DISORDERS OF THE RESPIRATORY SYSTEM The respiratory system provides a route for air movement in and out of the lungs and supplies a large, protected surface area for the exchange of oxygen and carbon dioxide between the air and circulating blood. Disorders affecting the respiratory system (Figure A-49) may therefore involve:. Interfering with the movement of air along the respiratory passageways. Internal or external factors may be involved. Within the respiratory tract, constriction of small airways, as in asthma (p. 37), can reduce airflow to the lungs. Blockage of major airways, as in choking on a piece of food or strangulation, may completely shut off the air supply. External factors that interfere with air movement include () the introduction of air (pneumothorax) or blood (hemothorax) into the the pleural cavity, with subsequent lung collapse; (2) the buildup of fluid within the pleural cavities (a pleural effusion), which compresses and collapses the lungs; and (3) arthritis, muscular paralysis, or other conditions that prevent the normal skeletal or muscular activities responsible for moving air in and out of the respiratory tract. 2. Damaging or otherwise impeding the diffusion of gases at the respiratory membrane. The walls of the alveoli are part of the respiratory membrane, where gas exchange occurs. Any disease process that affects the alveolar walls will reduce the efficiency of gas exchange. In emphysema (p. 38) or lung cancer, alveoli are destroyed. Respiratory exchange can also be disrupted by the buildup of fluid or mucus within the alveoli. This disruption may occur as the result of inflammation or infection of the lungs, as in the various types of pneumonia. 3. Blocking or reducing the normal circulation of blood through the alveolar capillaries. Blood flow to portions of the lungs may be prevented by a pulmonary embolism, a circulatory blockage discussed in the text (p. 466). A pulmonary embolism not only prevents normal gas exchange in the affected regions of a lung, but also results in tissue damage and, if the blockage persists for several hours, permanent alveolar collapse. Pulmonary blood pressure may rise, a condition called pulmonary hypertension, leading to pulmonary edema and a reduction in alveolar function in other portions of the lungs.

3 36 The Body Systems: Clinical and Applied Topics Inflammation and infection Rhinitis Common cold Sinusitis Pharyngitis Laryngitis Epiglottitis Bronchitis Diphtheria Pertussis Pneumonia Tuberculosis Influenza Adult respiratory distress syndrome (ARDS) Congenital disorders Tumors Cystic fibrosis Neonatal respiratory distress syndrome (NRDS) Lung cancer Degenerative disorders Emphysema Chronic obstructive pulmonary disease (COPD) DISORDERS OF THE RESPIRATORY SYSTEM Asthma Immune disorders Cardiovascular disorders Pulmonary embolism Nosebleeds Pneumothorax Trauma Figure A-49 Disorders of the Respiratory System Cystic Fibrosis EAP p. 460 Cystic fibrosis (CF) is the most common lethal inherited disease affecting Caucasians of northern European descent, occurring at a frequency of birth in 200. It occurs, with less frequency, in those with southern European ancestry, in the Ashkenazic Jewish population, and in African Americans. The condition results from a defective gene located on chromosome 7. Within the Unites States Caucasian population, person in 2 carries one copy of the gene for this disorder, and an infant receiving a copy from each parent will develop CF. Each year, 2000 babies are born with CF, and there are roughly 30,000 persons with this condition in the United States Individuals with classic CF seldom survive past age 30; death is usually the result of a massive bacterial infection of the lungs and associated heart failure. The gene involved carries instructions for a transmembrane protein responsible for the active transport of chloride ions. This membrane protein is abundant in exocrine cells that produce watery secretions. In persons with CF, the protein does not function normally. The secretory cells cannot transport salts and water effectively, and the secretions produced are thick and gooey. Mucous glands of the respiratory tract and secretory cells of the pancreas, salivary glands, and digestive tract are affected. The most serious symptoms appear because the respiratory defense system cannot transport such dense mucus. The mucus escalator stops working, and mucus plugs block the smaller respiratory passageways. This blockage reduces the diameter of the airways, and the inactivation of the normal respiratory defenses leads to frequent bacterial infections. Treatment has primarily been limited to supportive care and antibiotic therapy to control infections. In a few instances, lung transplants have provided relief, but the technical and logistical problems involved with this approach are formidable. The normal and abnormal gene structure has now been determined, and the current goal is to correct the defect by inserting normal genes within the cells in critical areas of the body. In the meantime, it has been discovered that one of the factors

4 contributing to the thick nature of the mucus is the presence of DNA released from degenerating cells within areas of inflammation. Inhaling an aerosol spray containing an enzyme that breaks down DNA has proven to be remarkably effective in improving respiratory performance. Asthma EAP p. 463 Asthma (AZ-muh) affects an estimated 3 6 percent of the United States population. There are several different forms of asthma, but all are characterized by unusually sensitive and irritable conducting passageways. In many cases the trigger appears to be an immediate hypersensitivity reaction to an allergen in the inspired air. Drug reactions, air pollution, chronic respiratory infections, exercise, and/or emotional stress can also cause an asthmatic attack in sensitive individuals. The most obvious and potentially dangerous symptoms include () the constriction of smooth muscles all along the bronchial tree, (2) edema and swelling of the mucosa of the respiratory passageways, and (3) accelerated production of mucus. The combination makes breathing very difficult. Exhalation is affected more than inhalation; the narrowed passageways often collapse before exhalation is completed. Although mucus production increases, mucus transport slows, and fluids accumulate along the passageways. Coughing and wheezing then develop. Severe asthmatic attacks reduce the functional capabilities of the respiratory system, and the peripheral tissues become oxygen-starved. This condition can prove fatal, and asthma fatalities have been increasing in recent years. The annual death rate from asthma in the United States is approximately 4 deaths per million population (for ages 34). Mortality among asthmatic African Americans is twice that of asthmatic Caucasian Americans. Treatment of asthma involves dilation of the respiratory passageways by administering bronchodilators (brong-k -dª-l -torz) and reducing inflammation and swelling of the respiratory mucosa. Important bronchodilators include theophylline, epinephrine, albuterol, and other beta-adrenergic drugs. Although the strongest beta-adrenergic drugs are very useful in a crisis, they are effective only for relatively brief periods, and the individual must be closely monitored because of the potential effects on cardiovascular function. Anti-inflammatory medication with less acute effects, such as inhaled or ingested steroids, is becoming increasingly important. Respiratory Distress Syndrome (RDS) EAP p. 466 Surfactant cells begin producing surfactants at the end of the sixth fetal month. By the eighth month surfactant production has risen to the level The Respiratory System 37 required for normal respiratory function. Neonatal respiratory distress syndrome (NRDS), also known as hyaline membrane disease (HMD), develops when surfactant production fails to reach normal levels. Although there are inherited forms of HMD, the condition most often accompanies premature delivery. In the absence of surfactants, the alveoli tend to collapse during exhalation, and although the conducting passageways remain open, the newborn infant must then inhale with extra force to reopen the alveoli on the next breath. In effect, every breath must approach the power of the first, and the infant rapidly becomes exhausted. Respiratory movements become progressively weaker, eventually the alveoli fail to expand, and gas exchange ceases. One method of treatment involves assisting the infant by administering air under pressure, so that the alveoli are held open. This procedure, known as positive end expiratory pressure (PEEP), can keep the newborn alive until surfactant production increases to normal levels. Surfactant from other sources can also be provided; suitable surfactants can be extracted from cow lungs (Survanta), obtained from the liquid (amniotic fluid) that surrounds full-term infants, or synthesized using gene-splicing techniques (Exosurf). These preparations are usually administered in the form of a fine mist of surfactant droplets. Surfactant abnormalities may also develop in adults as the result of severe respiratory infections or other sources of pulmonary injury. Alveolar collapse follows, producing a condition known as adult respiratory distress syndrome (ARDS). PEEP is often used in an attempt to maintain life until the underlying problem can be corrected, but at least 0 60 percent of ARDS cases result in fatalities. Tuberculosis EAP p. 468 Tuberculosis spreads rapidly because it can be transmitted through the air, without direct personto-person contact. Coughing, sneezing, or speaking by an infected individual will spread the pathogen through the air, in the form of tiny droplets that can be inhaled by others. Once infection has occurred, the disease progresses in stages. At the site of the infection, macrophages and fibroblasts proceed to wall off the area, forming an abscess. If the scartissue barricade fails, the bacteria move into the surrounding tissues and the process repeats itself. The resulting masses of fibrous tissue distort the conducting passageways, increasing resistance and decreasing airflow. In the alveoli, the attacked surfaces are destroyed. The combination severely reduces the area available for gas exchange. Treatment for TB is complex, because () the bacteria can spread to many different tissues, and (2) they can develop a resistance to standard antibiotics relatively quickly. As a result, several drugs are

5 38 The Body Systems: Clinical and Applied Topics used in combination over a period of 6 9 months. The most effective drugs now available include isoniazid, which interferes with bacterial replication, and rifampicin, which blocks bacterial protein synthesis. The TB problem is much less severe in developed nations, such as the United States, than in developing nations. However, tuberculosis was extremely common in the United States earlier in the twentieth century. An estimated 80 percent of Americans born around 900 became infected with tuberculosis. Although many were able to meet the bacterial challenge, it was the number one cause of death in 906. These statistics have been drastically changed with the advent of antibiotics and techniques for early detection of infection. Between 906 and 984, the death rate fell from 200 deaths per 00,000 population to. deaths per 00,000 population. From 984 to 992, TB incidence was rising; there were roughly 2,000 new TB cases in 994. Although the number of cases in 99 were slightly lower (22,000), as of 997 an estimated 0 million people in the United States are infected with tuberculosis. Today, tuberculosis is unevenly distributed through the United States population, with several groups at relatively high risk of infection. For example, Hispanics, African Americans, prison inmates, individuals with immune disorders (such as AIDS patients), and hospital employees who work around infected patients are more likely to be infected than are other members of the population. At present 2 percent of young American adults have been infected. A growing percentage of these cases are caused by antibiotic-resistant strains. An estimated 4 percent of TB patients diagnosed in the United States each year are resistant to both isoniazid and rifampin. The statistics for some parts of the country are worse; in New York City, 33 percent of new cases in the early 990s were drug-resistant. The most frightening part about this surge in resistant TB is that the fatality rate for infections resistant to two or more antibiotics is 0 percent. Strong, traditional public health measures of TB surveillance, lab identification, drug susceptibility testing, Directly Observed Treatment (DOT), including isolation of infectious patients, and investigation and treatment of close contacts reduced TB cases from 992 to 2000.Despite this progress, strong efforts to combat the spread of TB in the United States must continue in order to avoid a public health crisis as deadly as HIV infection and even more difficult to control. Decompression Sickness EAP p. 472 Decompression sickness can develop when an individual experiences a sudden change in pressure. Nitrogen is the gas responsible for this condition. Nitrogen, which accounts for 78.6 percent of the atmospheric gas mixture, has a relatively low solubility in body fluids. Under normal atmospheric pressures there are few nitrogen molecules in the blood, but at higher than normal pressures additional nitrogen molecules diffuse across the alveolar surfaces and into the bloodstream. As more nitrogen enters the blood it is distributed throughout the body. Over time nitrogen diffuses into peripheral tissues and into body fluids such as the cerebrospinal fluid (CSF), aqueous humor, and synovial fluids. If the pressure decreases, the change must occur slowly enough that the excess nitrogen can diffuse out of the tissues, into the blood, and across the alveolar surfaces. If the pressure falls suddenly, this gradual movement of nitrogen from the periphery to the lungs cannot occur. Instead, the nitrogen leaves solution and forms bubbles of nitrogen gas in the blood, tissues, and body fluids. A few bubbles in peripheral connective tissues may not be particularly dangerous, at least initially. However, these bubbles can fuse together, forming larger bubbles that distort tissues, causing pain. Bubbles often develop in joint capsules first. These bubbles cause severe pain, and the afflicted individual tends to bend over or curl up. This symptom accounts for the popular name of this condition, the bends. Bubbles in the systemic or pulmonary circulation can cause infarcts, and those in the cerebrospinal circulation can cause strokes, leading to sensory losses, paralysis, or respiratory arrest. Treatment consists of recompression, exposing the individual to pressures that force the nitrogen back into solution and alleviate the symptoms. Pressures are then reduced gradually over a period of or more days. Breathing air with a higher percentage of oxygen and a lower percentage of nitrogen than atmospheric air accelerates the removal of excess nitrogen from the blood. Today most bends cases involve scuba divers who have gone too deep or stayed at depth for too great a time. The condition is not restricted to divers, however, and the first reported cases involved construction crews working in pressurized surroundings. Although such accidents are exceedingly rare, the sudden loss of cabin pressure in a commercial airliner can also produce symptoms of decompression sickness. Emphysema EAP p. 472 Bronchitis (brong-kī-tis) is an inflammation of the bronchial lining. The most characteristic symptom is the overproduction of mucus, which leads to frequent coughing. An estimated 20 percent of adult males have chronic bronchitis. This condition is most often related to cigarette smoking, but it can also result from other environmental irritants, such as chemical vapors. Over time, the increased mucus production can block smaller airways and reduce respiratory efficiency. This condition is called chronic airways obstruction. Emphysema (em-fi-s -muh) is a chronic, progressive condition characterized by shortness of

6 The Respiratory System 39 breath and an inability to tolerate physical exertion. The underlying problem is destruction of respiratory exchange surfaces. In essence, respiratory bronchioles and alveoli are functionally eliminated. The alveoli gradually expand, capillaries deteriorate, and gas exchange in the affected region is severely decreased or completely eliminated. Emphysema has been linked to the inhalation of air containing fine particulate matter or toxic vapors, such as those found in cigarette smoke. Early in the disease, local regulation shunts blood away from the damaged areas, and the individual may not notice problems, even with strenuous activity. As the condition progresses, the reduction in exchange surface limits the ability to provide adequate oxygen. However, obvious clinical symptoms typically fail to appear until the damage is extensive. An enzyme, alpha -antitrypsin, that is normally present in the lungs helps prevent degenerative changes in lung tissue. Most people requiring treatment for emphysema are adult smokers; this group includes individuals with alpha -antitrypsin deficiency and those with normal tissue enzymes. In the United States, person in 000 carries two copies of a gene that codes for an abnormal and inactive form of this enzyme. A single change in the amino acid sequence appears responsible for this inactivation. At least 80 percent of nonsmokers with abnormal alpha -antitrypsin will develop emphysema, usually at age 4 0. All smokers will develop at least some emphysema, typically by age Unfortunately, the loss of alveoli and bronchioles in emphysema is permanent and irreversible. Further progression can be limited by cessation of smoking; the only effective treatment for severe cases is administration of oxygen. Lung transplants have helped some patients. For persons with alpha-antitrypsin deficiency who are diagnosed early, attempts are under way to provide enzyme supplements by daily infusion or periodic injection. Two patterns of symptoms may appear in individuals with advanced obstructive lung disease. In one group of patients other aspects of pulmonary structure and function are relatively normal. The respiratory rate in these patients increases dramatically. The lungs are fully inflated at each breath, and expirations are forced. These individuals maintain near-normal arterial PO 2. Their respiratory muscles are working hard, and they use a lot of energy just breathing. As a result, these patients are usually relatively thin. Because blood oxygenation is near normal, skin color in Caucasian patients will be pink. In the second group, emphysema has been complicated by chronic bronchitis and chronic airways obstruction. This combination, known as chronic obstructive pulmonary disease (COPD), is particularly dangerous. Individuals with COPD often expand their chests permanently, in an effort to enlarge their lung capacities and make the best use of the remaining functional alveoli. This adaptation gives them a distinctive barrel-chested appearance. COPD sufferers also have symptoms of heart failure, including widespread edema. Blood oxygenation is low, and the skin has a bluish coloration. CRITICAL-THINKING QUESTIONS 8-. During an intramural football game, Joe is tackled and breaks a rib. On the way to the hospital, Joe is having a difficult time breathing. Joe may be suffering from a. a collapsed trachea b. an obstruction in the bronchi c. a pneumothorax d. decreased surfactant production e. a bruised diaphragm 8-2. A patient recovering from bacterial pneumonia goes to Dr. Smith complaining of recurrent shortness of breath and pain when breathing. The patient reluctantly admits not finishing his antibiotics as prescribed. Dr. Smith auscultates the thorax with a stethoscope and detects a scratching sound during inspiration and decreased breath sounds at the base of one lung. A chest X-ray reveals fluid surrounding the base of that lung. Thoracentesis yields a cloudy fluid a large number of WBCs and the presence of bacteria in the cultured pleural fluid specimen. What condition is the patient most likely suffering from? 8-3. Ann, a respiratory care technician, complains of low-grade fever, persistent cough, night sweats, and unexplained weight loss over the last two months. Ann does not have a history of cigarette smoking. She has coughed up blood several times in the last two days. The physician orders routine lab tests that are within normal limits. Ann s chest X- ray shows lesions related to prior infection. The doctor is awaiting the results of the sputum culture, and has placed a skin test on Ann s forearm. What is a reasonable preliminary diagnosis? a. emphysema b. lung cancer c. tuberculosis d. pleurisy e. pneumonia What is the significance of the skin test?