Laboratory Studies
Arterial blood gas analysis is useful for judging the adequacy of ventilation and identifying the evolution of acute ventilatory failure. Administer the test in conjunction with an assessment of appearance, voice, speech, vital signs, physical examination, and pulse oximetry.
Imaging Studies
Perform standard posteroanterior inspiratory chest radiography to look for unilateral hyperinflation, lobar or segmental atelectasis, mediastinal shift, or pneumomediastinum. Most foreign bodies are radiolucent. Less than 20% of aspirated foreign bodies are radiopaque. The sensitivity for detecting signs of foreign body aspiration improves over time. On chest radiographs, children have air trapping more often, while adults have atelectasis more often. The proportion of patients with foreign body aspiration who have normal findings on chest radiographs varies widely in the literature, and atelectasis or consolidation is often not appreciated for at least 24 hours. If foreign body aspiration is suspected, a normal finding on chest radiographs does not exclude the diagnosis. [13]
Expiratory chest radiographs are more sensitive for air trapping than inspiratory chest radiographs. Signs are enhanced lucency and relatively low diaphragm position. If the patient cannot cooperate, lateral decubitus views may demonstrate air trapping in the dependent lung. [14]
CT scanning of the chest may show the object or may identify localized air trapping. [15] The presence of a foreign body and its condition, anatomic location (ie, larynx, trachea, main, lobar or segmental bronchus), shape, composition, position, size (ie, number of fragments), and extent of entrapment by edema or granulation tissue must be identified prior to attempts at extraction. The foreign body may be missed if it is of a color that would camouflage it from the surrounding mucosa (eg, carrot, rubber pencil eraser) or if it is completely engulfed by granulation tissue. The object also may not be visualized if it is too distal. Straight pins can migrate into deep segmental bronchi beyond the visual range of even a flexible bronchoscope. [2]
CT scanning supplemented with virtual bronchoscopic imaging may further provide such useful information prior to an attempt at bronchoscopy, especially when attempting to pass a flexible bronchoscope beyond the first object encountered is not an advisable course of action. [16, 17, 18] Whether virtual bronchoscopy can adequately replace early bronchoscopic inspection when other evidence to support a suspicion of foreign body aspiration is not yet manifest remains undetermined. Virtual bronchoscopy is not yet widely available.
Fluoroscopy of the chest can be performed to observe diaphragmatic and mediastinal shifting of air trapping while the patient is breathing if the diagnosis is in doubt or if the patient cannot cooperate.
Radioisotope lung perfusion scanning may demonstrate perfusion defects due to hypoxic vasoconstriction in poorly ventilated regions, even when physical examination and radiography findings are minimal.
Procedures
Bronchoscopy (both rigid and flexible) can be both diagnostic and therapeutic. (See Medical Care.)
Most aspirated foreign bodies are radiolucent. Radiologic procedures do not have extreme diagnostic accuracy, and aspiration events are not always detected. Other medical conditions are possible. The presentation may be delayed, and the patient may have been unsuccessfully treated for other conditions.
The presence of a foreign body and its condition, anatomic location (eg, larynx; trachea; main, lobar, or segmental bronchus), shape, composition, position, and extent of entrapment by edema or granulation tissue must be identified prior to extraction attempts. If the foreign body is of a color that might camouflage it within the surrounding mucosa (eg, carrot, rubber pencil eraser) or if the object is completely engulfed by granulation tissue, it may be missed. If it is too distal, the object may not be visualized.
Straight pins (typically aspirated by tailors and seamstresses) can migrate into deep segmental bronchi beyond the visual range of even a flexible bronchoscope.
Histologic Findings
Organic foreign bodies such as oily nuts (commonly peanuts) induce inflammation and edema. Local inflammation, edema, cellular infiltration, ulceration, and granulation tissue formation may contribute to airway obstruction while making bronchoscopic identification and removal of the object more difficult. Mediastinitis or tracheoesophageal fistulas might result. Distal to the obstruction, air trapping might lead to local emphysema, atelectasis, hypoxic vasoconstriction, suppurative pneumonia, or bronchiectasis. Bronchoscopically, the object may appear as a tumor, and scar carcinoma may develop over time. Even if the object is removed, the inflammatory changes may not be completely reversible.
