Pneumonia risk factors

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hamid Qazi, MD, BSc [2], Priyamvada Singh, M.D. [3]Philip Marcus, M.D., M.P.H.[4]

Overview

The risk factors for pneumonia include: smoking, age>65, immuno-suppression, exposure to chemicals, and underlying lung disease.

Risk Factors

Airway Obstruction

• When part of the airway (bronchi) leading to the alveoli is obstructed, the lung is not able to clear fluid when it accumulates. This can lead to infection of the fluid resulting in community-acquired pneumonia (CAP).
• One cause of obstruction, especially in young children, is inhalation of a foreign object such as a marble or toy. The object is lodged in the small airways and pneumonia can form in the trapped areas of lung.
• Another cause of obstruction is lung cancer, which can grow into the airways blocking the flow of air.

Lung Disease

• Smoking, and diseases such as emphysema, result in more frequent and severe bouts of CAP.
• In children, recurrent episodes of CAP may be the first clue to diseases such as cystic fibrosis or pulmonary sequestration.

Immune Compromise

• People who have immune system problems are more likely to get CAP.
• Risk factors for increased mortality from community acquired pneumonia are: active malignancy, immuno-suppression, neurological disease, congestive heart failure, coronary artery disease, and diabetes mellitus
• People who have AIDS are much more likely to develop CAP. Pneumonia could be the first manifestation of an underlying undiagnosed HIV. It is thus recommended by the Center for Disease Control (CDC) that all patients aged 13 to 64 in a medical setting regardless of known risk factors be screened for HIV. The American College of Physicians and HIV Medicine Association recommends expanding screening for HIV from age 13 to 75 , .
• Other immune problems range from severe immune deficiencies of childhood such as Wiskott-Aldrich syndrome to less severe deficiencies such as common variable immunodeficiency.
• Elderly people are affected with increased incidence and severity of community acquired pneumonia. It is the fifth most common cause of death among individuals who are > 65 years of age, and fourth in individuals who are 85 years or older. The clinical picture in elderly could be subtle and could present only as delirium without any fever, cough or sputum. Therefore, a high index of suspicion should be kept in these groups of people.

Community Acquired Pneumonia

The following are risk factors related to specific causative pathogens in community-acquired pneumonia:

Condition	Most Common Pathogens
Alcoholism	Streptococcus pneumoniae, oral anaerobes, Klebsiella pneumoniae, Acinetobacter spp, Mycobacterium tuberculosis
COPD	Haemophilus influenzae, Pseudomonas aeruginosa, Legionella spp, S. pneumoniae, Moraxella catarrhalis, Chlamydophila pneumoniae
Smoking	Haemophilus influenzae, Pseudomonas aeruginosa, Legionella spp, S. pneumoniae, Moraxella catarrhalis, Chlamydophila pneumoniae
Aspiration	Oral anaerobes, Gram-negative enteric bacteria
Lung Abscess	Community-acquired MRSA, M. tuberculosis, oral anaerobes, atypical mycobacteria, endemic fungal infection
Early HIV infection	S. pneumoniae, H. influenzae, M. tuberculosis
Late HIV infection	S. pneumoniae, H. influenzae, M. tuberculosis, Pneumocystis jirovecii, Cryptococcus, Histoplasma, Aspergillus, atypical mycobacteria (especially Mycobacterium kansasii), P.aeruginosa
> 2 weeks of cough with whoop or vomiting	Bordetella pertussis
Structural lung disease	P. aeruginosa, Burkholderia cepacia, S. aureus
IV drug use	S. aureus, anaerobes, M. tuberculosis, S. pneumoniae
Bioterrorism	Bacillus anthracis (anthrax), Yersinia pestis (plague), Francisella tularensis (tularemia)
Endobronchial obstruction	S. pneumoniae, anaerobes, H influenzae, S. aureus
Table adapted from IDSA/ATS Guidelines for CAP in Adults

Exposure to Animals

Animals	Most Common Pathogens
Bat or bird droppings	Histoplasma capsulatum
Birds	Chlamydophila psittaci
Rabbits	Francisella tularensis
Farm animals or parturient cats	Coxiella burnetti (Q fever)
Table adapted from IDSA/ATS Guidelines for CAP in Adults

Travel

Condition	Most Common Pathogens
Hotel or cruise ship stay	Legionella spp
Travel to southwestern US	Coccidioides spp, Hantavirus
Travel to southeast or east Asia	Burkholderia pseudomallei, avian influenza, SARS
Table adapted from IDSA/ATS Guidelines for CAP in Adults

Obstruction

• Airway obstruction may cause fluid accumulation in the lungs and result in CAP if the fluids become infected.

• One cause of obstruction, especially in young children, is inhalation of a foreign object such as a marble or toy. The object is lodged in the small airways and pneumonia can form in the trapped areas of lung.

• Another cause of obstruction is lung cancer, which can grow into the airways blocking the flow of air.

Lung Disease

• Smoking, and diseases such as emphysema, result in more frequent and severe bouts of CAP.

• In children, recurrent episodes of CAP may be the first clue to diseases such as cystic fibrosis or pulmonary sequestration.

• Hypoxemia

• Pulmonary edema

• Chronic obstructive pulmonary disease (COPD)

• Previous episode of pneumonia or chronic bronchitis

Immune Problems

• People who have immune disorders are more likely to acquire CAP.

• Risk factors for increased mortality from community-acquired pneumonia are: active malignancy, immunosuppression, neurological disease, congestive heart failure, coronary artery disease, and diabetes mellitus.

• People who have AIDS are much more likely to develop CAP. Pneumonia could be the first manifestation of an underlying undiagnosed HIV. It is, thus, recommended by the Center for Disease Control (CDC) that all patients aged 13 to 64 in a medical setting, regardless of known risk factors, be screened for HIV. The American College of Physicians and HIV Medicine Association recommends expanding screening for HIV from age 13 to 75 , .

• Other immune problems range from severe immune deficiencies from childhood, such as Wiskott-Aldrich syndrome, to less severe deficiencies, such as common variable immunodeficiency.

• Elderly people are affected with increased incidence and severity of community-acquired pneumonia. It is the fifth most common cause of death amongst individuals who are greater than 65 years of age, and it is the fourth most common cause of death in individuals who are 85 years or older. The clinical picture in elderly could be subtle and it could be present only as delirium without any fever, cough or sputum. Therefore, a high index of suspicion should be kept in these groups of people.

• Immotile cilia syndrome
• Kartagener's syndrome (ciliary dysfunction, situs inversus, sinusitis, bronchiectasis)
• Young's syndrome (azoospermia, sinusitis, pneumonia)

Other Risk Factors

A few other conditions may lead to pneumonia due to altered pulmonary defense mechanisms.

• Dysphagia due to esophageal lesions and motility problems

• HIV infection (especially for pneumococcal pneumonia)

Drugs

Acid-Suppressing Drugs

• Usage of H2 blockers, proton pump inhibitors, and antacids may increase the pH and, as a result, may increase the risk of pneumonia.

• A similiar study showed increase risk of pneumonia after starting PPI, especially within the first 48 hours. However, the association between PPI and CAP may be cofounded.

Antipsychotic Drugs

• A case control study has shown a significant correlation between the use of antipsychotic drugs and community-acquired pneumonia. A 60 percent increase in the rate of pneumonia can be seen in elderly patients who utilize antipsychotic medications.

• The use of atypical antipsychotics was associated with an increases risk of community-acquired pneumonia.

ACE Inhibitors

• A randomized trial has shown that ACE inhibitors reduce the risk of pneumonia.

Hospital Acquired Pneumonia

Major risk factors for hospital-acquired pneumonia
Primary admitting diagnosis of burns, trauma, or disease of the CNS
Thoraco-abdominal surgery
Depressed level of consciousness
Prior episode of a large-volume aspiration
Underlying chronic lung disease
>70 years of age
Fall-winter season
24-hour ventilator-circuit changes
Stress-bleeding prophylaxis with cimetidine with or without antacid
Administration of antimicrobial agents
Presence of a nasogastric tube
Severe trauma
Recent bronchoscopy
Table adapted from CDC

The following are major points for risk factors of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia:

“

Major Points and Recommendations for Modifiable Risk Factors General Prophylaxis Effective infection control measures: staff education, compliance with alcohol-based hand disinfection, and isolation to reduce cross-infection with MDR pathogens should be used routinely (Level I). Surveillance of ICU infections, to identify and quantify endemic and new MDR pathogens, and preparation of timely data for infection control and to guide appropriate, antimicrobial therapy in patients with suspected HAP or other nosocomial infections, are recommended (Level II). Intubation and Mechanical Ventilation Intubation and reintubation should be avoided, if possible, as it increases the risk of VAP (Level I). Noninvasive ventilation should be used whenever possible in selected patients with respiratory failure (Level I). Orotracheal intubation and orogastric tubes are preferred over nasotracheal intubation and nasogastric tubes to prevent nosocomial sinusitis and to reduce the risk of VAP, although direct causality has not been proved (Level II). Continuous aspiration of subglottic secretions can reduce the risk of early-onset VAP, and should be used, if available (Level I) The endotracheal tube cuff pressure should be maintained at greater than 20 cm H2O to prevent leakage of bacterial pathogens around the cuff into the lower respiratory tract. Contaminated condensate should be carefully emptied from ventilator circuits and condensate should be prevented from entering either the endotracheal tube or in-line medication nebulizers (Level II). Passive humidifiers or heat–moisture exchangers decrease ventilator circuit colonization, but have not consistently reduced the incidence of VAP, and thus they cannot be regarded as a pneumonia prevention tool (Level I). Reduced duration of intubation and mechanical ventilation may prevent VAP and can be achieved by protocols to improve the use of sedation and to accelerate weaning (Level II). Maintaining adequate staffing levels in the ICU can reduce length of stay, improve infection control practices, and reduce duration of mechanical ventilation (Level II). Aspiration, Body Position, and Enteral Feeding Patients should be kept in the semirecumbent position (30–45°) rather than supine to prevent aspiration, especially when receiving enteral feeding (Level I). Enteral nutrition is preferred over parenteral nutrition to reduce the risk of complications related to central intravenous catheters and to prevent reflux villous atrophy of the intestinal mucosa that may increase the risk of bacterial translocation (Level I). Modulation of Colonization: Oral Antiseptics and Antibiotics Routine prophylaxis of HAP with oral antibiotics (selective decontamination of the digestive tract or SDD), with or without systemic antibiotics, reduces the incidence of ICU-acquired VAP, has helped contain outbreaks of MDR bacteria (Level I), but is not recommended for routine use, especially in patients who may be colonized with MDR pathogens (Level II). Prior administration of systemic antibiotics has reduced the risk of nosocomial pneumonia in some patient groups, but if a history of prior administration is present at the time of onset of infection, there should be increased suspicion of infection with MDR pathogens (Level II). Prophylactic administration of systemic antibiotics for 24 hours at the time of emergent intubation has been demonstrated to prevent ICU-acquired HAP in patients with closed head injury in one study, but its routine use is not recommended until more data become available (Level I). Modulation of oropharyngeal colonization by the use of oral chlorhexidine has prevented ICU-acquired HAP in selected patient populations such as those undergoing coronary bypass grafting, but its routine use is not recommended until more data become available (Level I). Use daily interruption or lightening of sedation to avoid constant heavy sedation and try to avoid paralytic agents, both of which can depress cough and thereby increase the risk of HAP (Level II). Stress bleeding prophylaxis, transfusion, and hyperglycemia. Comparative data from randomized trials suggest a trend toward reduced VAP with sucralfate, but there is a slightly higher rate of clinically significant gastric bleeding, compared with H2 antagonists. If needed, stress bleeding prophylaxis with either H2 antagonists or sucralfate is acceptable (Level I). Transfusion of red blood cell and other allogeneic blood products should follow a restricted transfusion trigger policy; leukocyte-depleted red blood cell transfusions can help to reduce HAP in selected patient populations (Level I). Intensive insulin therapy is recommended to maintain serum glucose levels between 80 and 110 mg/dl in ICU patients to reduce nosocomial blood stream infections, duration of mechanical ventilation, ICU stay, morbidity, and mortality (Level I).

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For Level of evidence and classes click here.