Chapter 28 Respiratory Tract Infections, Neoplasms, and Childhood Disorders
Areas Involved in Respiratory Tract Infections • Upper respiratory tract • Nose, oropharynx, and larynx • Lower respiratory tract • Lower airways and lungs
General symptoms of respiratory disease • Hypoxia : Decreased levels of oxygen in the tissues • Hypoxemia : Decreased levels of oxygen in arterial blood • Hypercapnia : Increased levels of CO2 in the blood • Hypocapnia : Decreased levels of CO2 in the blood • Dyspnea : Difficulty breathing • Tachypnea : Rapid rate of breathing • Cyanosis : Bluish discoloration of skin and mucous membranes due to poor oxygenation of the blood • Hemoptysis : Blood in the sputum
Common Respiratory Infections • Common cold • Influenza • Pneumonia • Tuberculosis • Fungal infections of the lung
Upper respiratory tract Infections The common cold The most common viral pathogens for the “common cold” are rhinovirus, parainfluenza virus, respiratory syncytial virus, adenovirus and coronavirus. • These viruses tend to have seasonal variations in their peak incidence. • They gain entry to the body through the nasal mucosa and the surfaces of the eye. They are readily spread from person to person via respiratory secretions. • Manifestations of the common cold include: • Rhinitis: Inflammation of the nasal mucosa • Sinusitis :Inflammation of the sinus mucosa • Pharyngitis : Inflammation of the pharynx and throat • Headache • Nasal discharge and congestion
Upper respiratory tract Infections Influenza • Influenza is a viral infection that can affect the upper or lower respiratory tract. • Three distinct forms of influenza virus have been identified: A, B and C, of these three variants, type A is the most common and causes the most serious illness. • The influenza virus is a highly transmissible respiratory pathogen. • Because the organism has a high tendency for genetic mutation, new variants of the virus are constantly arising in different places around the world. Serious pandemics (spread of infection across a large region) of influenza are seen every 8 to 10 years as a result of this genetic mutation .
Upper respiratory tract Infections Influenza • Symptoms of influenza infection: • Headache • Fever, chills • Muscle aches • Nasal discharge • Unproductive cough • Sore throat • Influenza infection can cause marked inflammation of the respiratory epithelium leading to acute tissue damage and a loss of ciliated cells that protect the respiratory passages from other organisms. • As a result, influenza infection may lead to co-infection of the respiratory passages with bacteria. • It is also possible for the influenza virus to infect the tissues of the lung itself to cause a viral pneumonia.
Upper respiratory tract Infections Treatment of influenza: Bed rest, fluids, warmth Antiviral drugs Influenza vaccine : Provides protection against certain A and B influenza strains that are expected to be prevalent in a certain year. The vaccine must be updated and administered yearly to be effective but will not be effective against influenza strains not included in the vaccine. The influenza vaccine is particularly indicated in elderly people, in individuals weakened by other disease and in health-care workers Influenza
Upper respiratory tract Infections Influenza Drugs for Treating Influenza: • Amantidine • Used orally or by aerosol administration • Effective only against type A influenza • Inhibits viral fusion, assembly and release from the infected host cell • Neuraminidase inhibitors (Zanamavir, Oseltamivir) • New drugs that can be used by inhalation (Zanamavir) or orally (Oseltamivir) • Effective against both type A and B influenza • Inhibits the activity of viral neuraminidase enzyme that is necessary for spread of the influenza virus
Types of Influenza Vaccinations • Trivalent inactivated influenza vaccine (TIIV) • Developed in the 1940s • Administered by injection • Live, attenuated influenza vaccine (LAIV) • Approved for use in 2003 • Administered intranasally
Lower respiratory tract Infections Pneumonia • Pneumonia is a condition that involves inflammation of lower lung structures such as the alveoli or interstitial spaces. • It may be caused by bacteria or viruses such as pneumocystiscarinii. • The prevalence and severity of pneumonia have been heightened in recent years due to the emergence of HIV as well as antibiotic resistance. • Pneumonia may be classified according to the pathogen that is responsible for the infection. • There tend to be distinct organisms that cause pneumonia in the hospital setting vs. the community setting.
Lower respiratory tract Infections Pneumonia • • Community acquired pneumonia (CAP) • • Aspiration pneumonia • • Hospital • –Hospital acquired pneumonia (HAP) • –Ventilator associated pneumonia (VAP) • –Healthcare associated pneumonia (HCAP)
Lower respiratory tract Infections Pneumonia Individuals Most at Risk for Pneumonia • Elderly • Those with viral infection • Chronically ill • AIDS or immunosuppressed patients • Smokers • Patients with chronic respiratory disease e.g. bronchial asthma.
Potential Pathogens • Typical • Streptococcus pneumoniae • Hemophilusinfluenzae • Mycobacterium catarrhalis • Klebsiellapneumoniae • Atypical • Chlamydiapneumoniae • Legionellapneumophila • Mycoplasmapneumoniae.
Factors Facilitating Development of Pneumonia • Virulence of organism • Inoculum size • Impaired host defenses
Seen here are two lung abscesses, • one in the upper lobe and one in the lower lobe of this left lung. • An abscess is a complication of severe pneumonia, most typically from virulent organisms such as S. aureus. • Abscesses are complications of aspiration, where they appear more frequently in the right posterior lung.
The area of abscess is yellow tan, and it was very firm. • The infectious agent responsible here was Nocardia, which is known to produce chronic abscessing inflammation.
Lower respiratory tract Infections Pneumonia A second classification scheme for pneumonia is based on the specific structures of the lung that the organisms infect and includes typical and atypical pneumonia. Typical pneumonia • Usually bacterial in origin. • Organisms replicate in the spaces of the alveoli. Manifestations: • Inflammation and fluid accumulation are seen in the alveoli. • White cell infiltration and exudation can been seen on chest radiographs. • High fever, chest pain, chills, and malaise are present. • Purulent sputum is present. • Some degree of hypoxemia is present.
Lower respiratory tract Infections Pneumonia Atypical pneumonia • Usually viral in origin. • Organisms replicate in the spaces around the alveoli. Manifestations: • Milder symptoms than typical pneumonia. • Lack of white cell infiltration in alveoli. • Lack of fluid accumulation in the alveoli. • Not usually evident on radiographs. • May make the patient susceptible to bacterial pneumonia.
Lower respiratory tract Infections Pneumonia Treatment of pneumonia: • Antibiotics if bacterial in origin. The health-care provider should consider the possibility that antibiotic-resistant organisms are present. • Oxygen therapy for hypoxemia. • A vaccine for pneumococcal pneumonia is currently available and highly effective. This vaccine should be considered in high-risk individuals.
Tuberculosis • Caused by a mycobacterium, M. tuberculosis • Outer waxy capsule makes the organism more resistant to destruction • Infects practically any organ of the body; the lungs are most frequently involved • Macrophage-directed attack, resulting parenchymal destruction • Cell-mediated immune response • Confers resistance to the organism • Development of tissue hypersensitivity
Forms of Tuberculosis • M. tuberculosis hominis (human tuberculosis) • Airborne infection spread by minute droplet nuclei harbored in the respiratory secretions of persons with active tuberculosis • Living under crowded and confined conditions increases the risk for spread of the disease. • Bovine tuberculosis • Acquired by drinking milk from infected cows; initially affects the gastrointestinal tract • Has been virtually eradicated in North America and other developed countries
Positive Tuberculin Skin Test • Results from a cell-mediated immune response • Implies that a person has been infected with M. tuberculosis and has mounted a cell-mediated immune response • Does not mean the person has active tuberculosis
Question • Which of the following involves infection of the entire respiratory tract? • Common cold • Pneumonia • Tuberculosis • Cancer
Answer • Common cold • Pneumonia: Pneumonia can involve all respiratory tissues and, due to its virulence, is a major health risk. • Tuberculosis • Cancer
Classification and Spread of Fungi • Yeasts • Are round and grow by budding • Molds • Form tubular structures called hyphae • Grow by branching and forming spores • Dimorphic fungi • Grow as yeasts at body temperatures and as molds at room temperatures • Mechanisms of fungal spread • Inhalation of spores
Laboratory Tests to Diagnose Histoplasmosis • Cultures • Fungal stain • Antigen detection • Serologic tests for antibodies
The dense white encircling tumor mass is arising from the visceral pleura and is a mesothelioma.
Respiratory Disorders in the Neonate • Respiratory distress syndrome • Bronchopulmonary dysplasia
Respiratory Disorders in Children • Upper airway infections • Viral croup • Spasmodic croup • Epiglottis • Lower airway infections • Acute bronchiolitis
Impending Respiratory Failure in Infants and Children • Rapid breathing • Exaggerated use of the accessory muscles • Retractions • Nasal flaring • Grunting during expiration
Question • The lungs are a common site of secondary tumor development. Why? • Due to the highly vascular nature and small capillaries • Due to the fragility of the cells • Due to the rapid replication of type I alveolar cells • Due to dumb luck
Answer • Due to the highly vascular nature and small capillaries • Due to the fragility of the cells • Due to the rapid replication of type I alveolar cells • Due to dumb luck
Gases of Respiration • Primary function of respiratory system • Remove CO2 • Add of O2 • Insufficient exchange of gases • Hypoxemia • Hypercapnia
Hypoxemia • Hypoxemia results from • Inadequate O2 in the air • Diseases of the respiratory system • Dysfunction of the neurological system • Alterations in circulatory function • Mechanisms • Hypoventilation • Impaired diffusion of gases • Inadequate circulation of blood through the pulmonary capillaries • Mismatching of ventilation and perfusion