(BQ) Part 2 book Egan''s fundamentals of respiratory care has contents: Pulmonary infections, interstitial lung disease, pleural diseases, pulmonary vascular disease, acute respiratory distress syndrome, lung cancer, mechanical ventilators,
SECTION IV REVIEW OF CARDIOPULMONARY DISEASE CHAPTER 24 Pulmonary Infections SARAH A LONGWORTH, STEVEN K SCHMITT, AND DAVID L LONGWORTH CHAPTER OBJECTIVES After reading this chapter you will be able to: ◆ State the incidence and economic impact of pneumonia in the United States ◆ Discuss the current classification scheme for pneumonia and be able to define hospital-acquired pneumonia, health care–associated pneumonia, and ventilator-associated pneumonia ◆ Recognize the pathophysiology and common causes of lower respiratory tract infections in specific clinical settings ◆ List the common microbiologic organisms responsible for community-acquired and nosocomial pneumonias ◆ Describe the clinical and radiographic findings seen in patients with pneumonia ◆ Describe risk factors associated with increased morbidity and mortality in patients with pneumonia ◆ State the criteria used to identify an adequate sputum sample for Gram stain and culture ◆ Describe the techniques used to identify the organism responsible for nosocomial pneumonia ◆ List the latest recommendations regarding empiric and pathogen-specific antibiotic regimens used to treat various types of pneumonia ◆ Discuss strategies to prevent pneumonia ◆ Describe how the respiratory therapist aids in diagnosis and management of patients with suspected pneumonia CHAPTER OUTLINE Classification Pathogenesis Microbiology Clinical Manifestations Chest Radiograph Risk Factors for Mortality and Assessing the Need for Hospitalization Diagnostic Studies Community-Acquired Pneumonia Health Care–Associated Pneumonia, HospitalAcquired Pneumonia, and Ventilator-Associated Pneumonia Antibiotic Therapy Community-Acquired Pneumonia Health Care–Associated Pneumonia, HospitalAcquired Pneumonia, and Ventilator-Associated Pneumonia Prevention Community-Acquired Pneumonia Health Care–Associated Pneumonia, HospitalAcquired Pneumonia, and Ventilator-Associated Pneumonia Tuberculosis Epidemiology Pathophysiology Diagnosis Precautions Treatment Role of the Respiratory Therapist in Pulmonary Infections KEY TERMS antibiotic therapy atypical pathogens community-acquired pneumonia fomites 494 health care–associated pneumonia hospital-acquired pneumonia lower respiratory tract infection nosocomial pneumonia pneumonia tuberculosis ventilator-associated pneumonia Pulmonary Infections • CHAPTER 24 I nfection involving the lungs is termed pneumonia or lower respiratory tract infection (LRTI) and is a common clinical problem in the practice of respiratory care Today, pneumonia remains a major cause of morbidity and mortality in the United States and worldwide Each year, million people die from pneumonia worldwide Five million cases of pneumonia occur annually in the United States, of which approximately 1.1 million require hospitalization at a projected yearly cost of more than $20 billion.1 Pneumonia is the ninth leading cause of death in the United States and the leading cause of infectionrelated mortality.2 CLASSIFICATION Pneumonia can be classified based on the clinical setting in which it occurs (Table 24-1) This classification is useful because it predicts the likely microbial causes and guides empiric antimicrobial therapy while a definitive microbiologic diagnosis is awaited (The term empiric therapy refers to treatment that is TABLE 24-1 Classifications and Possible Causes of Pneumonia Classification Likely Organisms Community-Acquired: Acute Typical Streptococcus pneumoniae Haemophilus influenzae Moraxella catarrhalis Staphylococcus aureus Atypical Legionella pneumophila Chlamydophila pneumoniae Mycoplasma pneumoniae Viruses Coxiella burnetii Community-acquired: Mycobacterium tuberculosis Chronic Histoplasma capsulatum Blastomycosis dermatitidis Coccidioides immitis Health care-associated Mixed aerobic and anaerobic mouth flora S aureus Enteric gram-negative bacilli Influenza Mycobacterium tuberculosis Immunocompromised Pneumocystis jiroveci host Cytomegalovirus Aspergillus species Cryptococcus neoformans Reactivation tuberculosis or histoplasmosis Nosocomial Aspiration Health care-associated Ventilator-associated Mixed aerobes and anaerobes, gram-negative bacilli S aureus Pseudomonas aeruginosa Acinetobacter species Enterobacter species Klebsiella species Stenotrophomonas maltophilia S aureus 495 initiated based on the most likely cause of infection when the specific causative organism is still unknown.) Community-acquired pneumonia (CAP) can be divided into two types—acute and chronic—based on its clinical presentation Acute pneumonia presents with sudden onset over a few hours to several days The clinical presentation may be typical or atypical, depending on the pathogen The onset of chronic pneumonia is more insidious, often with gradually escalating symptoms over days, weeks, or months Pneumonia acquired in health care settings is often caused by microorganisms different from those that cause CAP Previously termed nosocomial pneumonia, this clinical entity has been further classified as health care–associated pneumonia (HCAP), hospital-acquired pneumonia (HAP), and ventilatorassociated pneumonia (VAP).3 HCAP is defined as pneumonia occurring in any patient hospitalized for or more days in the past 90 days in an acute-care setting or who in the past 30 days has resided in a long-term care or nursing facility; attended a hospital or hemodialysis clinic; or received intravenous antibiotics, chemotherapy, or wound care HAP is defined as an LRTI that develops in hospitalized patients more than 48 hours after admission and excludes community-acquired infections that are incubating at the time of admission VAP is defined as an LRTI that develops more than 48 to 72 hours after endotracheal intubation HAP is a common clinical problem and represents the second most common nosocomial infection in the United States, accounting for 15% to 22% of all such infections.4-6 Current estimates suggest that more than 150,000 individuals develop HAP each year HAP increases hospital length of stay to days at an average incremental per-patient cost of $40,000 In selected populations, such as patients in the intensive care unit (ICU) and bone marrow transplant recipients, the crude mortality rate from HAP may approach 30% to 70%, with attributable mortality of 33% to 50% Certain microorganisms, such as Pseudomonas aeruginosa and Acinetobacter species, are associated with higher rates of mortality.7 PATHOGENESIS Six pathogenetic mechanisms may contribute to the development of pneumonia (Table 24-2) Knowledge of these mechanisms is important to both the understanding of the various disease processes and the formulation of effective strategies within the hospital to minimize nosocomial spread Inhalation of infectious particles is a common route of inoculation; this method of acquiring an infection occurs with pulmonary tuberculosis and justifies the policy of respiratory isolation for patients with suspected or proved tuberculosis who are coughing Aspiration of oropharyngeal secretions is the second mechanism that may contribute to the development of LRTI Healthy individuals may aspirate periodically, especially during sleep Aspiration of even a small volume of oropharyngeal secretions, which can be colonized with potential pathogens such as Streptococcus pneumoniae and Haemophilus influenzae, 496 SECTION IV • Review of Cardiopulmonary Disease TABLE 24-2 Pathogenetic Mechanisms Responsible for the Development of Pneumonia Mechanism of Disease Examples of Specific Infections Inhalation of aerosolized infectious particles Tuberculosis Histoplasmosis Cryptococcosis Blastomycosis Coccidioidomycosis Q fever Legionellosis Community-acquired bacterial pneumonia Aspiration pneumonia Hospital-acquired pneumonia Ventilator-associated pneumonia Hospital-acquired pneumonia Ventilator-associated pneumonia Mixed anaerobic and aerobic pneumonia from subdiaphragmatic abscess Amebic pneumonia from rupture of amebic liver abscess into the lung Staphylococcus aureus pneumonia arising from right-sided bacterial endocarditis Parasitic pneumonia: Strongyloidiasis, ascariasis, hookworm Pneumocystis jiroveci pneumonia Reactivation tuberculosis Cytomegalovirus Aspiration of organisms colonizing the oropharynx Direct inoculation of organisms into the lower airway Spread of infection to the lungs from adjacent structures Spread of infection to the lung through the blood Reactivation of latent infection, usually resulting from immunosuppression may contribute to development of CAP Certain patient populations are at risk for large-volume aspiration, such as patients with impaired gag reflexes from narcotic use, alcohol intoxication, or prior stroke Aspiration also may occur after a seizure, cardiac arrest, or syncope Aspiration seems to be the major mechanism responsible for the development of some types of mixed aerobic and anaerobic, gram-negative, and staphylococcal HAPs In intubated patients, chronic aspiration of colonized secretions through a tracheal cuff has been linked to the subsequent occurrence of pneumonia,4 which led to the development of strategies to prevent HAP, such as continuous suctioning of subglottic secretions in mechanically ventilated patients and elevation of the head of the bed.8,9 Direct inoculation of microorganisms into the lower airway is a less common cause of pneumonia In mechanically ventilated patients who undergo frequent suctioning of lower airway secretions, passage of a suction catheter through the oropharynx may result in inoculation of colonizing organisms into the trachea and subsequent development of VAP Contiguous spread of microorganisms to the lungs or pleural space from adjacent areas of infection, such as subdiaphragmatic or liver abscesses, is an infrequent cause of pneumonia This may occur in patients with pyogenic or amebic liver abscesses involving the dome of the liver in whom rupture of the abscess through the diaphragm leads to the development of pulmonary infection or empyema Hematogenous dissemination is the spread of infection through the bloodstream from a remote site; it is an uncommon cause of pneumonia It may occur in the setting of right-sided bacterial endocarditis, in which fragments of an infected heart valve break off and embolize through the pulmonary arteries to the lungs, producing either pneumonia or septic pulmonary infarcts Certain parasitic pneumonias, including strongyloidiasis, ascariasis, and hookworm, arise through hematogenous dissemination In such cases, migrating parasite larvae travel to the lungs through the bloodstream from remote sites of infection, such as the skin or the gastrointestinal (GI) tract Pneumonia may develop when a latent infection, acquired earlier in life, is reactivated This may occur for no apparent reason, as in the case of reactivation pulmonary tuberculosis However, reactivation is usually attributable to the development of cellular immunodeficiency, as is the case with Pneumocystis jiroveci (previously called Pneumocystis carinii) pneumonia In developed countries, most healthy individuals have acquired P jiroveci by age years and show serologic evidence of prior infection The organism remains dormant in the lung but may reactivate later in life and produce pneumonia in individuals with compromised cell-mediated immunity, such as patients with human immunodeficiency virus (HIV) infection or recipients of long-term immunosuppressive therapy Cytomegalovirus pneumonia is another example of a latent infection that can reactivate during chronic immunosuppression, especially in solid organ and bone marrow transplant recipients Immunosuppressive drugs used to modify inflammatory diseases, such as tumor necrosis factor (TNF) inhibitors, have been associated with the development of pulmonary and extrapulmonary tuberculosis.10 MICROBIOLOGY The microbiology of CAP and nosocomial pneumonia has been studied extensively Knowledge of which organisms are most commonly associated with pneumonia in different settings is essential because the microbial differential diagnosis guides the diagnostic evaluation and the selection of empiric antimicrobial therapy In most studies, S pneumoniae, also called pneumococcus, is the most commonly identified cause of CAP, accounting for 20% to 75% of cases (Table 24-3) Various other organisms have been implicated with varying frequencies H influenzae, Staphylococcus aureus, and gram-negative bacilli each account for 3% to 10% of isolates in many reports.11 Notably, the incidence of H influenzae pneumonia has decreased dramatically since the introduction of the type B H influenzae (also known as Hib) vaccine in the 1980s Legionella species, Chlamydophila pneumoniae, and Mycoplasma pneumoniae together account for 10% to 20% of cases These latter organisms, called atypical pathogens, vary in frequency in more recent reports, depending on the age of the patient population, the season of the year, and Pulmonary Infections • CHAPTER 24 TABLE 24-3 Frequency of Pathogens in Community-Acquired Pneumonia Cause Cases (%) Streptococcus pneumoniae Aspiration Chlamydophila pneumoniae Haemophilus influenzae Gram-negative bacilli Staphylococcus aureus Legionella species Viruses Moraxella catarrhalis Mycoplasma pneumoniae Pneumocystis jiroveci Mycobacterium tuberculosis No diagnosis 20-75 6-10 4-11 3-10 3-10 3-5 2-8 2-16 1-3 1-24 0-13 0-5 25-50 geographic locale Legionellosis and C pneumoniae, in particular, exhibit significant geographic variation in incidence RULE OF THUMB S pneumoniae remains the most common cause of CAP Many studies examining the epidemiology and microbiology of CAP are potentially biased because they focus on patients requiring hospitalization In patients with less severe illnesses not requiring hospitalization, more recent studies suggest that M pneumoniae and C pneumoniae account for 38% of cases and may be more common than typical bacterial pathogens such as pneumococcus and H influenzae.12 In patients who are ill enough to require admission to the ICU, Legionella species, gram-negative bacilli, and pneumococcus are disproportionately more common.13 A virulent strain of methicillinresistant S aureus (MRSA) has emerged as a cause of severe necrotizing CAP.14 In urban settings that have a high incidence of endemic HIV infection, P jiroveci may be an occasional cause of CAP.15 Viruses such as influenza, respiratory syncytial virus, parainfluenza, and adenovirus can cause CAP, especially in patients with milder illnesses not requiring hospitalization, and are encountered in the late fall and winter months A worldwide pandemic of H1N1 influenza during 2009 to 2010 and ongoing sporadic cases of transmission of H5N1 influenza from birds to humans have led to heightened international awareness of influenza epidemiology, pathogenesis, and prevention.16 Mixed aerobic and anaerobic aspiration pneumonia may account for 10% of cases This cause of pneumonia is an important consideration for nursing home residents and for individuals with impaired gag reflexes or recent loss of consciousness The outbreak in 2000 to 2001 of inhalation anthrax in the United States adds another microbial differential diagnostic 497 consideration in patients with fulminant community-acquired LRTI.17 To date, inhalation anthrax remains a rare disease Several new coronaviruses have emerged as important pathogens within the past decade Severe acute respiratory syndrome (SARS) emerged out of Asia and spread globally in 2002 to 2003 Fortunately, no cases have been identified since 2004.18 More recently, Middle East respiratory syndrome (MERS) has arisen as a global health concern First described in Saudia Arabia in 2012, the virus is found within the Arabian peninsula and causes a severe respiratory illness with a 30% mortality rate The first cases imported to the United States were confirmed in 2014, both in travelers from Saudia Arabia.19 Albeit rare in the United States, both viruses also should be considered in the appropriate clinical and epidemiologic setting In addition, enterovirus D68 is an emerging cause of pneumonia in children.20 In most published series, no microbiologic diagnosis is established in 50% of patients This is attributable to many factors, including: • Inability of many patients to produce sputum • Acquisition of sputum specimen after antibiotics have been started • Failure to perform numerous serologic studies routinely in all patients • The fact that many organisms (e.g., viruses and anaerobic bacteria) were not routinely sought • Failure, until more recently, to recognize pneumonia pathogens, such as C pneumoniae and some viral agents The common microbial agents producing HCAP, HAP, and VAP are summarized in Table 24-1 and include gram-negative bacilli, S aureus, Legionella species, and rarely viruses such as influenza or respiratory syncytial virus The last-mentioned viruses are considerations only during the winter months, when they are endemic in the community and may enter the hospital via health care workers, visitors, or patients with incubating or active infections The relative frequencies and antimicrobial susceptibilities of these respective bacteria may vary considerably from one institution to another Knowledge of which nosocomial isolates are most common within one’s own institution and community, along with their drug-sensitivity profiles, has important implications with regard to selecting antibiotic therapy, formulating infection control policies, investigating potential outbreaks, and selecting antimicrobial agents for the hospital formulary For example, patients developing severe VAP in ICUs with a high prevalence of carbapenem resistance among gram-negative organisms such as Klebsiella pneumoniae and Acinetobacter baumannii may warrant empiric antimicrobial therapy for these organisms pending culture information Similarly, nosocomial legionellosis occurs with variable frequency at different institutions, such that empiric therapy in critically ill patients with nosocomial LRTI may or may not require coverage of this pathogen Nosocomial pathogens capable of producing HAP can be transmitted directly from one patient to another, as in the case for tuberculosis However, transmission from health care 498 SECTION IV • Review of Cardiopulmonary Disease workers (including respiratory therapists [RTs]), contaminated equipment, or fomites (objects capable of transmitting infection through physical contact with them) is more common, especially for gram-negative bacilli, S aureus, and viruses The RT has an important role to play in preventing the transmission and development of nosocomial pneumonia M I N I CLINI Distinguishing Between Different Types of Nosocomial Pneumonia PROBLEM: A 52-year-old man with a history of severe low back pain is admitted to the hospital with a GI bleed in the setting of excessive NSAID use He has not seen a doctor in years His presenting symptoms include epigastric abdominal pain, black stools, and dizziness with standing Admission hemoglobin is 5.2 g/dl and white blood count (WBC) count is 6.2 × 109 He is transfused red blood cells (RBCs) and undergoes upper GI endoscopy, which reveals a large bleeding duodenal ulcer Three days into his admission, the patient develops a fever to 40.2° C, shortness of breath, and cough Laboratory testing reveals a WBC count of 16.8 × 109 Chest radiography reveals a patchy infiltrate in the right lower lobe What type of pneumonia does this patient have? How might this infection have developed? DISCUSSION: The patient has HAP, because he did not have any evidence of pneumonia at the time of admission and developed his infection more than 48 hours into his hospital stay He may have developed pneumonia secondary to inhalation of infectious particles via exposure to patients or health care providers working with a respiratory illness More likely, he aspirated oropharyngeal or gastric secretions during his upper endoscopy procedure or during a vomiting episode Empiric antimicrobial coverage should target mixed aerobic and anaerobic mouth flora, S.aureus, enteric gram-negative bacilli, and potentially influenza, depending on the season CLINICAL MANIFESTATIONS Patients with CAP typically have fever and respiratory symptoms, such as cough, sputum production, pleuritic chest pain, and dyspnea Not all of these symptoms are present all the time, especially in elderly patients in whom the presentation may be subtle Other problems, such as hoarseness, sore throat, headache, and diarrhea, may accompany certain pathogens Fever, cough, and sputum production may occur in other illnesses such as acute bronchitis or exacerbations of chronic bronchitis In the past, clinicians often distinguished between typical and atypical clinical syndromes as a means of predicting the most likely microbial causes A typical presentation consisted of the sudden onset of high fever, shaking, chills, and cough with purulent sputum Such a presentation was considered more common with bacterial pathogens such as pneumococcus and H influenzae An atypical presentation was an illness characterized by the gradual onset of fever, headache, constitutional symptoms, diarrhea, and cough, often with minimal sputum production Cough was often a relatively minor symptom at the outset, and the illness was initially dominated by nonrespiratory symptoms Such a presentation was thought to be more common with pathogens such as M pneumoniae, C pneumoniae, Legionella species, and viruses More recent studies have shown that considerable overlap exists in the clinical presentations of pneumonia with typical and atypical pathogens.21 The occurrence of concomitant diarrhea, previously considered indicative of legionellosis, is now known to be common in pneumococcal and mycoplasmal pneumonia Despite the limitations in predicting the microbial diagnosis based on the clinical presentation, clinicians use certain historical clues and physical findings at the bedside to determine the likely cause of pneumonia in patients presenting from the community In patients presenting with high fever, teeth-chattering chills, pleuritic pain, and a cough producing rust-colored sputum, pneumococcal pneumonia is the most likely diagnosis Patients with pneumonia accompanied by foul-smelling breath, an absent gag reflex, or recent loss of consciousness are most likely to have a mixed aerobic and anaerobic infection as a consequence of aspiration CAP accompanied by hoarseness suggests C pneumoniae Pneumonia in a patient with a history of splenectomy suggests infection with an encapsulated pathogen such as pneumococcus or H influenzae Pneumonia occurring after resolution of a flulike illness raises concern for S aureus Epidemics of pneumonia occurring within households or closed communities, such as dormitories or military barracks, suggest pathogens such as M pneumoniae or C pneumoniae Pneumonia accompanied by splenomegaly suggests psittacosis (caused by Chlamydophila psittaci and associated with bird exposure) or Q fever (caused by Coxiella burnetii and associated with exposure to farm animals) Bullous myringitis and erythema multiforme are associated with Mycoplasma infection Relative bradycardia (defined as a heart rate 50 years B Male sex C Comorbid illnesses Cerebrovascular disease Cancer Congestive heart failure Renal disease Liver disease Immunosuppression Alcoholism Diabetes mellitus Chronic lung disease II Clinical parameters at presentation A Altered mentation B Systolic hypotension 30 breaths/min D Hypothermia (temperature 40° C) F Pulse rate >125 beats/min G Extrapulmonary site of infection III Laboratory and radiographic findings at presentation A Arterial pH 30 mg/dl C Serum sodium 250 mg/dl E Hematocrit