Chapter 62 Pneumonia
PATHOPHYSIOLOGY
Pneumonia is an inflammation or infection of the pulmonary parenchyma. Pneumonia is attributable to one or more agents: viruses, bacteria (e.g., Mycoplasma pneumoniae, Streptococcus pneumoniae, Staphylococcus aureus), fungi, parasites, or aspirated foreign substances. The pattern of the illness depends on the following: (1) causative agent, (2) age of the child, (3) child’s reaction, (4) extent of lesions, and (5) degree of bronchial obstruction. The clinical features of viral, mycoplasmal, and other bacterial pneumonias are listed in Box 62-1.
Box 62-1 Clinical Features of Bacterial, Viral, and Mycoplasmal Pneumonia
Bacterial Pneumonia
Chlamydia trachomatis, Chlamydia pneumoniae, staphylococcal, streptococcal (90% of bacterial cases), and pneumococcal pneumonia occur most frequently.
Progresses to Abrupt Onset
Productive cough, diminished breath sounds, rales on auscultation
Rapid and shallow respirations (50 to 80 breaths/min), dyspnea
Nasal flaring, retractions, expiratory grunt
Increased white blood cell count, predominantly PMNs
Younger than 2 years of age—vomiting and mild diarrhea
Older than 5 years of age—headache and chills, often complaint of chest and abdominal pain
Viral Pneumonia
Causative viruses include RSV (usually in infants 2 to 5 months old), influenza virus, parainfluenza virus, adenovirus, and enterovirus.
Progresses to Insidious or Abrupt Onset
Range of symptoms—mild fever, slight cough, and malaise to high fever, severe cough, cyanosis and respiratory fatigue
Tachypnea, although infants with RSV infection may have apnea; retractions, nasal flaring
Scattered rales, rhonchi, wheezing
Normal or slight elevation in white blood cell count, with lymphs predominant
Chest radiographic finding of diffuse or focal lobar infiltrates; hyperinflation due to air trapping is common
PMNs, polymorphonuclear cells; RSV, respiratory syncytial virus.
