The typical patient has had problems with oral secretions or coughing with meals, suggesting gastroesophageal reflux. 8 Patients who require tube feedings are at risk for aspiration.8 In the elderly, localizing symptoms may be minimal, and the complaint may be a change in baseline mental status. There may be a specific witnessed episode of aspiration.
Physical findings include those common to pneumonia: fever; cough; localized rales, wheezes, or rhonchi; tachycardia; and tachypnea. Cyanosis can develop quickly in patients with underlying lung disease or in patients with overwhelming pulmonary bacterial contamination. Aspiration of large volumes of fluid can also precipitate the rapid development of cyanosis.
Chest radiographs may show an interstitial or alveolar pattern. The right lower lobe is the most common area for the development of aspiration pneumonia when aspiration occurs in an upright sitting posture because the right main stem bronchus has a more direct course from the trachea than does the left main stem bronchus (Fig. .6.0.-1). Aspiration in a supine position may produce infection in any lobe, although the posterior pulmonary segments are more susceptible.
Laboratory tests may demonstrate an elevated white blood cell count. In elderly patients the typical leukocytosis may be blunted. In these situations it is helpful to assess the differential and look for a left shift with an increased percentage of immature forms. An elevated C-reactive protein level is a nonspecific indicator of an inflammatory process and may be the only indication of an aerobic infectious pulmonary process resulting from an aspiration. 9 Arterial blood gas measurements may reveal hypoxia if the aspiration or inflammatory process is large enough to significantly interfere with alveolar gas exchange. oxygen content may be normal early in the course of the illness, but evidence of pulmonary injury can be found by detecting hyperventilation (decreased Pa co2) and ventilation-perfusion mismatching (elevated A-a gradient).
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