Preventive measures are still the best strategy Aspiration syndromes: Pneumonia and pneumonitis key words: Aspiration, Pneumonitis, Pneumonia

While the risk factors for aspiration pneumonia are similar to those for aspiration pneumonitis, the 2 syndromes have different presentations. Aspiration pneumonia tends to occur in older patients or in those with neurological diseases, and the aspiration is not usually witnessed. Aspiration pneumonitis is more likely to occur in patients undergoing anesthesia or in those with acute drug and alcohol overdoses, and the aspiration is often witnessed. The workup may include bedside assessment of the cough and gag reflexes, chest radiography, videofluoroscopic imaging, or fiberoptic endoscopy. Empiric antibiotic therapy should be avoided in most patients with pneumonitis; however, antibiotics may be indicated for those at high risk for bacterial colonization of oropharyngeal and gastric contents who have fever, increasing sputum production, or new infiltrates or for those who fail to improve within 48 hours. (J Respir Dis. 2007;28(9):370-385) Aspiration is defined as the misdirection of oropharyngeal or gastric contents into the larynx and lower respiratory tract.1 This can result in a wide spectrum of clinical syndromes depending on host factors, the type and amount of the material aspirated, and the frequency of aspiration. Although aspiration occurs during normal sleep, mucociliary defense mechanisms and cough reflexes usually clear the airways and prevent pulmonary complications from occurring.1-3 If these mechanisms are impaired or absent, chemical pneumonitis from acidic gastric fluid, infection from aspirated bacterial pathogens, and airway obstruction from particulate matter may result.4 The purpose of this review is to focus on the clinical manifestations, diagnosis, and treatment of aspiration pneumonitis and aspiration pneumonia. While these 2 terms are often used interchangeably, they represent 2 separate and distinct clinical syndromes.ASPIRATION PNEUMONITIS Aspiration pneumonitis is defined as the inhalation of regurgitated gastric contents that results in acute chemical lung injury.2 Normally, gastric contents are sterile because of the acidic suppression of bacterial growth. Therefore, lung injury from aspiration pneumonitis is usually not a consequence of bacterial infection. However, in patients receiving acid suppression therapy (antacids, proton pump inhibitors, H2 blockers) or enteral feeding, bacterial colonization of the normally sterile gastric contents may occur and infection may play a role. Gastric contents may be liquid or particulate matter, and aspiration may result from passive regurgitation or active vomiting of gastric contents in patients who do not have the protection of upper airway reflexes.5 In a healthy, conscious person, the lower esophageal sphincter tone and upper airway reflexes prevent aspiration of gastric contents into the respiratory tract.6 With altered levels of consciousness, as occurs with drug overdose, seizures, or the use of anesthetics, these reflex mechanisms are impaired and aspiration may take place. The aspiration event is usually acute and may be witnessed. In 1946, Mendelson first described this aspiration syndrome in obstetric patients who were in labor; the event is widely recognized as a potential complication of anesthesia during the perioperative and postoperative periods.3,5,7 The clinical response to aspiration of gastric contents depends on the type of material aspirated. Mendelson described 2 separate clinical syndromes. The first syndrome is the inhalation of particulate matter that can cause airway obstruction and asphyxiation. Smaller particles may lead to distal atelectasis, granulomatous inflammation, pulmonary edema, or the nidus for abscess formation.6 The second syndrome is the chemical damage to lung tissue that can result from sterile but acidic gastric fluids. The amount of damage depends on the volume and pH of the aspirate, with larger volumes and lower pH having more deleterious effects.5 Damage from acidic fluid occurs in 2 phases. The first phase occurs within 1 to 2 hours, when the direct toxic effects of the acidic fluid