Therapeutic Agents for the Respiratory System

Transcription

1 Therapeutic Agents for the Respiratory System Chapter 19 1 Structure and Function of the Respiratory System Respiratory system resembles large inverted tree Large trunk: Trachea Two main branches: Bronchi Smaller branches: Bronchioles Leaves: Alveolar sacs (gas exchange) Function: To oxygenate the blood and remove carbon dioxide Upper respiratory infections occur above the lungs. The main type of dosage forms for respiratory infections is inhalers. The lungs facilitate the absorption of oxygen from breathed air during inhalation and also the removal of carbon dioxide from the body during exhalation. The exchange of oxygen and carbon dioxide also helps keep the ph of the blood balanced. 2 Diagram of the Respiratory System Unwanted particles are removed by the fine hairs in the nose before the particles can enter the body. The mucosal lining of the bronchi also removes unwanted particles. The air is heated in the nose so that it is more compatible with our body temperature. 3

2 Upper Respiratory System Composed of nose, pharynx, larynx, and nasal cavities Mucosal lining The nasal septum separates the interior of the nose into two distinct cavities that are lined by a mucous membrane with microscopic, hairlike structures called cilia. The fine hairs of the nose (cilia) and the mucosal lining of the bronchi act as filters to trap dust, microorganisms, and foreign particles. The nose helps heat and humidify cold, dry air, functions as the sensory organ for the sense of smell, and acts as a drainage system for tears from the eye. Produces 125 ml of mucus each day Protects respiratory tree Mucus purifies air by trapping irritants Nasal septum separates nose into two cavities 4 Upper Respiratory System (Cont.) Cavities lined with mucosal lining and cilia Mucous membrane warms and moistens air Cilia catch dust particles Nose provides sense of smell, drainage for tears A thin, leaf-shaped cartilaginous structure, the epiglottis, is located at the entrance of the larynx. The epiglottis closes off the trachea automatically when swallowing takes place to keep food, liquid, and saliva from going down the airway and causing choking. Tonsils help the body fight off disease. The epiglottis, a thin leaf-shaped structure made of cartilage, is located at the entrance of the larynx. Its function is to obstruct the trachea automatically. Similar to a trap door, the epiglottis keeps food, liquid, and saliva from entering the airway when swallowing takes place. 5 Bronchial Tree Even though the composition of the air taken in during respiration is 79% nitrogen, the body does not use the nitrogen. What happens to the nitrogen? (It is expelled into the air along with the carbon dioxide and leftover oxygen molecules.) 6

3 Lower Respiratory System Composition: Trachea, bronchial tree, lungs Trachea lined with mucosal lining (traps airborne particles) and cilia Trachea branches to left and right bronchi à smaller bronchi à smaller bronchioles à alveoli There are millions of clusters of microscopic alveolar sacs deep in the lungs. The average respiratory rate for adults is 12 to 18 breaths per minute, whereas the rate is higher in a 6- to 12-year-old child at 18 to 30 breaths per minute. The respiratory rate can range from 30 to 60 breaths per minute in an infant from birth to 1 year of age. 7 Lower Respiratory System (Cont.) The trachea is reinforced with incomplete rings of cartilage to keep it from collapsing when the neck is bent. Pleural cavity lines chest cavity and covers lungs Trachea: Windpipe; branches into lungs Right bronchus is bigger than left (heart displacement) Diaphragm separates chest cavity from abdominal cavity 8 Lower Respiratory System (Cont.) Lungs divided into lobes: Three on right and two on left Right lung has greater capacity Left lung is longer, has less capacity Mediastinum: Location of heart; separates right and left lung Main function of lungs is breathing, pulmonary ventilation Bronchi lead to smaller airways called bronchioles and finally to alveoli sacs where oxygen and carbon dioxide are exchanged When you step outside on a cold winter day, the asthma-like tightening you might feel in your chest is reflex bronchoconstriction. Researchers now believe that one trigger for this protective reflex is cold air hitting the face, before the actual inhalation of cold air. The outer surface of the lungs is covered by moist, smooth, slippery membranes that reduce friction between the lungs and chest wall during breathing. The lungs fill the chest cavity, except for the space occupied by the heart and large vessels, and their primary function is breathing and the facilitation of gas exchange. As breathing occurs, the lungs exchange inspired oxygen for carbon dioxide (waste), which is, in turn, expired. 9

4 Respiration When a person actively inhales, the increase in the size of the thoracic cavity reduces the pressure inside so that air can enter the lungs. During expiration, the chest relaxes, and the thoracic cavity becomes smaller. This causes the pressure within the thoracic cavity to increase and air to leave the lungs. Act of respiration has two distinct phases: Inspiration: Movement of air into lungs Expiration: Movement of air out of lungs Inspiration: Diaphragm flattens, intercostal muscles expand, thoracic cavity increases in size Expiration is passive response 10 Gas Exchange Composition of air: 21% oxygen, 79% nitrogen, 0.5% carbon dioxide Average adult consumes about 250 ml of oxygen; produces about 200 ml of carbon dioxide Travel of air: Bronchioles à alveolar sacs oxygen moves across membrane à blood cell à blood cell drops off carbon dioxide before picking up oxygen à moves to large veins à left atrium à left ventricle à arteries à tissues and organs The waste carbon dioxide is exchanged for oxygen in the lungs. People with chronic respiratory conditions, such as emphysema or COPD, might have such reduced lung function that they need more oxygen than their body can derive from normal air. How can supplemental oxygen be provided? (Portable oxygen tanks or larger systems can increase the concentration of oxygen in an entire room or house.) The carbon dioxide molecules move into the alveolar sacs and out of the body via expired air. Respiration occurs in the alveoli, and oxygen and carbon dioxide pass between the tiny capillaries surrounding the alveoli and the air within them. 11 Gas Exchange The medulla is influenced by various receptors located in other body areas. This allows it to regulate respiration to adjust to varying demands for oxygen supply and carbon dioxide removal. Medulla: Contains respiratory center Located in brainstem ph balance: Exchange of O 2 and CO 2 keeps it balanced in the blood CO 2 makes bicarbonate to keep ph balance; becomes alkaline CO 2 can also increase hydrogen in blood; becomes acidic Blood ph: 7.4 to sustain life 12

5 Breathing As the lungs fill with air, nerve impulses from the stretch receptors of the lungs are transferred to the respiratory center in the medulla. The respiratory center in the medulla then sends neuronal impulses to the respiratory muscles telling them to relax, resulting in expiration. Involuntary mechanism Breathing rates vary according to size of person Smaller size means faster breathing Children can breathe twice as fast as adults Exhalation: 500 ml of air Lung capacity is 5 L Elasticity of lungs allows for a variety of capacities depending on need for oxygen 13 Exchange of Oxygen and Carbon Dioxide What gives red blood cells their color? (Hemoglobin is an iron and protein molecule that gives red blood cells their color.) Each hemoglobin molecule transports four oxygen molecules. The total lung capacity for an average adult is more than 5 L of air. This means that if an average adult exhales the typical volume (500 ml), that adult could exhale 10 times without inhaling before running out of air. 14 Disorders/Conditions of the Upper Respiratory System Causes include: Genetics, contagious infections, habits (smoking), environmental factors Symptoms include: Abnormal breathing and coughing Treatment includes: Antitussives, analgesics, and antipyretics Antibiotics; corticosteroids for severe conditions There are many conditions that affect the respiratory system. Fluoroquinolone antibiotics, such as Levaquin, have a boxed warning associating them with an increased risk of tendinitis and tendon rupture. Some medications can alter respiratory rates. Opioids (such as morphine), for example, can suppress the respiratory rate. Phenergan with codeine is classified as a schedule C-V controlled substance. At the strength of 6.25 mg codeine per 5 ml of syrup, it contains less than 200 mg of codeine per 100 ml. 15

6 Common Cold Common cold is characterized by an infection of the nasal passages and upper respiratory system Normally caused by a rhinovirus There are 140 cold viruses, all untreatable Treatments Antitussives, antihistamines, expectorants, and decongestants Using good hand washing techniques and covering your mouth during sneezing can help to prevent the spread of germs. Expectorants, such as guaifenesin, are agents that break up thick mucous secretions of the lungs or bronchi so that they can be easily expelled from the respiratory tract by coughing. 16 Common Cold (Cont.) Symptoms: Coughing, congestion, and sometimes wheezing Common treatments: Decongestants and antihistamines Other symptoms: Rhinitis, coryza, pharyngitis, and rhinorrhea Drug treatments: Decongestants, antihistamines, antitussives, expectorants, and decongestants Liquids, lozenges, nasal sprays, oral tablets, and capsules What are rhinitis, coryza, pharyngitis, and rhinorrhea? (Rhinitis is an inflammation of the lining of the nose; coryza is a common cold; pharyngitis is a sore throat; and rhinorrhea is a runny nose.) Treating the symptoms and letting it run its course is the best way to treat the common cold. Many of these drugs are available as OTC products singly or in combination form. Expectorants, such as guaifenesin, are agents that break up thick mucous secretions of the lungs or bronchi to enable the lungs or bronchi to expel the mucus easily from the respiratory tract by coughing. After administering expectorants, the patient should be counseled to increase his or her fluid (water) intake to assist with thinning the mucosal secretions. 17 Allergies Allergens include pollens, animal dander, foods, medications, chemicals, and environmental pollutants Symptoms and reactions include rash, hives, itching, and nasal congestion Severe reactions include stomach pain, vomiting, wheezing, shortness of breath, low blood pressure, swelling of the throat, and anaphylactic shock Abnormal response of the immune system; can be life threatening Removal of the allergen is best treatment What is the drug action of antihistamines? (Antihistamines inhibit the central nervous system and block H-1 allergic responses, thus stopping inflammation and vasoconstriction.) Some of these drugs come in oral dose form and some are inhalers. Severe anaphylactic reactions can cause stomach pain, vomiting, wheezing, shortness of breath, hypotension (low blood pressure), swelling of the throat, and shock if left untreated. 18

7 Rhinitis Irritation/inflammation of mucous membrane of nasal passages Causes: Cold, influenza, allergens, air pollution, and strong odors Can be acute (colds/flu) or chronic (seasonal exposure to allergens) Drink fluids to decrease postnasal drip Treatment: OTC saline irrigation, air purifiers, and humidifiers Drug treatment: Steroid nasal spray, antihistamines/ decongestants, and allergy shots Common symptoms include runny and itchy nose, sneezing, congestion, and postnasal drip. When used as an irrigating solution, saline can help relieve postnasal drip symptoms. Many decongestants can actually contribute to a worsening of nasal congestion attributable to a phenomenon known as rebound congestion. This is particularly common with some over-the-counter (OTC) nasal inhaler medications, such as oxymetazoline (Afrin) and phenylephrine (Neo- Synephrine). Because of the rebound congestion, decongestants should not be overused, and patients should follow the instructions for their duration of use. Antihistamines used for allergies exert their effect by blocking H 1 receptors. 19 Influenza Viral respiratory illness Types A, B, and C Annual flu vaccine lessens risk Treatment: Rest, fluids, and antivirals The flu strikes millions of people annually. In the United States, between 5% and 20% of people get the disease each year. About 36,000 Americans die every year from complications of the flu. With proper treatment, most people recover from influenza; however, the very old and young and those with a weakened immune system can experience a slow recovery or even death. For severe influenza, antiviral medications may be prescribed at the early onset of symptoms (usually within 48 hours) to help shorten the course or lessen the severity of the illness or upon exposure to somebody with the virus as prophylaxis. Vaccines are commonly given during the peak influenza season. 20 Asthma Dyspnea: Difficult breathing Cracking and wheezing sounds Can be triggered by allergens Produces mucus, which can cause bronchiole constriction Drug treatment in two categories: Those used for maintenance and those used when an attack occurs Corticosteroids: Lessen constriction of bronchiole tubes; available as inhalants or orals It is one of several obstructive lung diseases that share some clinical characteristics of chronic obstructive pulmonary disease (COPD). Management of asthma begins with patient education aimed at avoiding allergens and irritants that trigger asthmatic attacks. Inhaled corticosteroids are a mainstay of the management of chronic asthma. Asthma is a chronic inflammatory condition that affects the airways. It is one of several obstructive lung diseases and shares some clinical characteristics of chronic obstructive pulmonary disease (COPD). The classic signs of asthma include intermittent dyspnea (shortness of breath), cough, and wheezing. In people with asthma, the muscles around the bronchioles contract, narrowing the air passages to the extent that air cannot be properly inhaled. Two general categories of medications are used in the management of asthma: (1) those used for prophylaxis (prevention therapies) or maintenance, and (2) those used when an attack occurs (abortive therapies). The airways contain beta-2 receptors; when these receptors are activated, the smooth muscle surrounding the airways relaxes, thus opening the airways. 21

8 More Asthma Treatments Long-acting beta agonists: Activate receptors, muscles relax Leukotriene receptor antagonists: Reduce the inflammatory actions of leukotrienes that induce bronchial smooth muscle contraction, airway edema, and mucus formation Short-acting beta agonists: Used as rescue inhalers, used in nebulizers Anticholinergics: Block effects of acetylcholine Nonselective beta-agonists and the high doses of beta-2 selective agonists used for asthma treatment have the side effect of tachycardia due to beta-1 receptor stimulation. These agents, most notably albuterol, can be used on a scheduled basis or as needed to help with worsening of asthma symptoms. Metered-dose inhalers (MDIs) are delivery devices that propel medication into the lungs via the use of a propellant. Ipratropium (Atrovent) blocks the effects of acetylcholine, which leads to bronchial smooth muscle relaxation. Short-acting beta-agonists, most notably albuterol (Proventil, Ventolin), can be used on a scheduled basis or as needed to help alleviate worsening asthma symptoms. 22 Chronic Obstructive Pulmonary Disease Three types: Chronic bronchitis, emphysema, and asthma Emphysema causes destruction of alveolar walls Loss of elasticity caused by smoking, exposure to environmental hazards Treatments: Quitting smoking, lung transplant Drug treatments: Similar to those used for asthma Any long-term lung condition or exposure to lung irritants that damages the lungs can contribute to the development of COPD. Because normal exhalation requires elastic recoil of the lungs, the affected lungs allow air to be inhaled, but the individual cannot exhale all the air. Theophylline is a methylxanthine that relaxes the smooth muscle of the bronchial airways and pulmonary blood vessels and is used for prophylaxis of asthma and treatment of asthma and COPD. 23 Pneumonia Acute inflammation of lung airways; blocked by thick mucus Sources: Bacterial, viral, fungal, protozoal, and parasitic Streptococcus pneumoniae causes rapid onset Treatment: Rest, proper hydration, and avoidance of irritants Drug treatment: Antibiotics, antifungals (if fungal infection occurs), and respiratory medications A form of pneumonia known as aspiration pneumonia can be caused by aspirating food, fluids, or other foreign substances into the lungs. Bacterial pneumonia may be orally treated by: 1) Azithromycin, 500 mg on day 1, followed by 250 mg once daily on days 2 through 5 2) Levofloxacin, 750 mg daily for 5 days 3) Levofloxacin, 500 mg daily for 7 through 14 days 24

9 Management difficult Tuberculosis Treatment consists of several medications in a regimen Affects organs, such as kidneys, brain, and spine Highly contagious Diagnosed with a chest x-ray and PPD skin test Sputum test to determine if cured Tuberculosis (TB) is a leading cause of morbidity and mortality worldwide and at one time was the leading cause of death in the United States. Isoniazid (INH) is the most common drug given. Most of the primary antituberculin agents are bactericidal, which means that they kill M. tuberculosis. These agents are often used in combination for a course of treatment lasting many months. 25 Lung Cancer Malignancies of airways Classifications: Small cell or non-small cell Important in diagnosis Treatment: Quitting smoking, radiation, and surgical resection Drug treatment: Chemotherapy Lung cancer is the most common cancer worldwide. Lung cancer became the most common cause of cancer deaths in men in the 1950s and the leading cause of cancer death in women in the mid-1980s. Chemotherapy additionally plays a role as adjuvant therapy after surgical resection. 26