TABLE 46-1 Aspiration Syndromes | |
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TABLE 46-2 Diagnostic Evaluation for Aspiration Syndromes | ||||||||||||||||||||||||||||||||||
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Aspiration and Drowning
Aspiration and Drowning
Nicholas A. Smyrnios
Richard S. Irwin
I. ASPIRATION
A. General principles.
1. Definition. Aspiration: inhaling fluid or a foreign body into the bronchi and lungs. The material may be particulate matter (food particles), fluids, or oropharyngeal secretions containing infectious agents.
2. Aspiration syndromes. Syndromes caused by aspiration are determined by (a) the material aspirated, (b) the amount aspirated, and (c) the state of the patient’s defenses at the time of the event. The various syndromes caused by aspiration are listed in Table 46-1.
B. Pathogenesis.
1. Normal gastrointestinal and respiratory defenses against aspiration. An aspiration event requires bypassing or overwhelming one or more of these mechanisms.
a. Swallowing mechanism: Hypopharyngeal muscles move food into the esophagus, the epiglottis covers the larynx, the vocal cords close, and the upper esophageal sphincter relaxes. Pharyngeal swallowing initiates peristaltic waves in the esophagus that carry the bolus through a relaxed lower esophageal sphincter (LES) to the stomach. The LES then closes to minimize gastroesophageal reflux.
b. Aerodynamic filtration—nose, mouth, and larynx—filter particles greater than 10 µm in diameter.
c. Mucociliary clearance: removes particles 2 to 10 µm in diameter.
d. Alveolar detoxification: alveolar macrophage and neutrophil nonspecific killing for particles <2 µm in diameter.
e. Cough: provides clearance when mucociliary clearance is inadequate.
f. Immunologic mechanisms: These augment the nonimmunologic mechanisms listed above.
2. Factors predisposing to aspiration in critically ill patients.
a. Translaryngeal intubation: Swallowing impairment persists after extubation but usually improves within days to a week.
b. Tracheostomy: interferes with proper laryngeal elevation necessary for glottic closure. Inflated balloon can obstruct esophagus.
c. Enteral feeding tubes: can cause vagally induced LES relaxation and also prevent mechanical closure of the LES.
d. Large residual volumes in stomach: Exact volume is unknown, presumed to be approximately 200 mL.
C. Diagnosis.
1. Diagnostic tests available for aspiration are listed in Table 46-2.
D. Treatment.
1. Mendelson syndrome: Aspiration of gastric contents may cause the development of acute respiratory distress syndrome (ARDS). Management of ARDS is described in Chapter 40.
2. Foreign body aspiration.
a. Particles that do not totally obstruct the trachea can be removed by bronchoscopy.
