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Chapter 24 Coordinating Care for Patients With Infectious Respiratory Disorders
of these protective mechanisms to function that a respira- tory infection occurs. Establishment of a Respiratory Tract Infection In order for a respiratory infection to be fully established in the lower respiratory tract, the following barriers must be avoided and conditions met: 1. Avoidance of trapping in the mucociliary layer of the upper respiratory tract. 2. Avoidance of the phagocytic action of the alveolar macrophages in the lower respiratory tract. 3. Infectious organisms must be airborne (particles less than 5 μm that remain suspended in the air for a pro- longed period of time) and have the ability to remain virulent (toxic) while in the air. 4. There must be sufficient numbers of infectious organisms inhaled and deposited on susceptible tissues within both the upper and lower respiratory tracts, preventing innate protective mechanisms from func- tioning effectively. The Inflammatory Response of the Respiratory Tract Once pathogens have been established in the respiratory tract, an inflammatory response is initiated. Direct stim- ulation by infecting organisms leads to the secretion of pro-inflammatory cytokines (interleukin [IL] and tumor necrosis factor [TNF]) by airway epithelial cells. Neu- trophils (a type of white blood cell [WBC]) are recruited to the infected alveoli along with other immune cells and serum components (see Chapter 18). Capillary permea- bility increases, and the alveoli fill with fluid and plasma proteins. This accumulation of exudate (a mass of cells and fluid) provides the perfect medium for the proliferation of the infecting organism(s) and assists with movement
to other nearby alveoli. The fluid- and exudate-filled alveoli are prevented from effective gas exchange at the alveolar-capillary level. This produces varying degrees of hypoxia depending on the severity of the infection.
INFLUENZA Epidemiology
Influenza is a highly contagious infection that is rapidly spread from one individual to another. Outbreaks of influ- enza are tracked, recorded annually, and reported by the Centers for Disease Control and Prevention (CDC). The extent and severity vary widely among geographical areas throughout the United States. Localized outbreaks that affect more than the expected population (e.g., when the disease is expected to affect 15% of the population, but 40% become infected) are called epidemics . They occur at varying intervals, usually every 1 to 3 years. Epidemics typically begin abruptly, peak at 2 to 3 weeks, last approxi- mately 2 to 3 months, and then rapidly subside. Global out- breaks (outbreaks that spread across a large geographical area) or outbreaks that are limited to a smaller geographi- cal area but affect more people than expected (again using the example of an expected outbreak of 15%, but 70% of the population is affected) are referred to as pandemics. They also occur at variable intervals but less frequently than local outbreaks. The last influenza pandemic was the H1N1 pandemic in 2009, where estimates of the number of deaths ranged from 151,700 to 575,400. Morbidity and mortality rates were high, predominantly among those with underlying comorbid medical conditions or those of very young or advanced age. Other predominant risk factors for influenza are outlined in Table 24.1. The CDC reported the highest influenza burden in the 2017–2018 season since the 2009 pandemic. Estimates for
Table 24.1 Risk Factors for Influenza Infection
Risk Factor
Description
Age
Young children and older adults (younger than 2 years and older than 65 years) due to immature or less active immune systems Healthcare workers, family caregivers, daycare providers, and early childhood educators are more likely to be in frequent contact with those who are infected with the influenza virus. People living in dormitories, military quarters, and long-term care facilities who remain in close proximity for lengthy periods of time Those with malignancies treated with chemotherapy, transplant recipients receiving antirejection medica- tions, individuals with HIV/AIDS with CD4+ counts less than 200 cells/mm 3 People with diabetes, renal failure, asthma, and cardiac and respiratory diseases are at higher risk for develop- ing serious complications. Patients who are considering pregnancy, are pregnant, or have recently given birth are at greater risk for devel- oping severe viral pneumonia and have a fourfold overall mortality rate, even if they are otherwise healthy.
Occupation
Environmental
Immune system compromise
Chronic illness
Pregnancy
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