先生に教えていただいた。New England journal of Medicine, Vol. 344, No. 9, 665-671 の667頁だけの訳文を提出するよういわれました。前回の重要部分はすでにありますのでその前後の訳文をお願いします。お忙しいとこすみません。
results in clearance of the infectious material without sequelae. However, if these mechanical, humoral, or cellular mechanisms are impaired or if the amount of aspirated material is sufficiently large, pneumonia may follow.
Any condition that increases the volume or bacterial burden of oropharyngeal secretions in a person with impaired defense mechanisms may lead to aspiration pneumonia. Indeed, in patients who have had a stroke and are undergoing an evaluation of swallowing, there is a strong correlation between the volume of the aspirate and the development of pneumonia.39 Factors that increase the risk of oropharyngeal colonization with potentially pathogenic organisms and that increase the bacterial load may increase the risk of aspiration pneumonia. The risk of aspiration pneumonia is lower in patients without teeth40 and in elderly patients in institutional settings who receive aggressive oral care41 than in other patients. These risks largely distinguish aspiration pneumonia from community-acquired pneumonia. However, there is much overlap. For instance, otherwise healthy elderly patients with community-acquired pneumonia have a significantly higher incidence of silent aspiration than age-matched controls.42
In patients with aspiration pneumonia, unlike those with aspiration pneumonitis, the episode of aspiration is generally not witnessed. The diagnosis is therefore inferred when a patient at risk for aspiration has radiographic evidence of an infiltrate in a characteristic bronchopulmonary segment. In patients who aspirate while in a recumbent position, the most common sites of involvement are the posterior segments of the upper lobes and the apical segments of the lower lobes (Figure 1
Anteroposterior Radiograph of the Chest, Showing Air-Space Consolidation (Arrows) in the Right Lower Lobe in a Patient Who Had Recently Had a Thrombotic Stroke.
), whereas in patients who aspirate in an upright or semirecumbent position, the basal segments of the lower lobes are usually affected. The usual course is that of an acute pneumonic process, with features similar to those of a typical community-acquired pneumonia. Without treatment, however, these patients have a higher incidence of cavitation and abscess formation in the lungs.43
Risk Factors for Oropharyngeal Aspiration
Patients with neurologic dysphagia, disruption of the gastroesophageal junction, or anatomical abnormalities of the upper aerodigestive tract are at increased risk for oropharyngeal aspiration. The risk of aspiration is relatively high in elderly persons because of the increased incidence of dysphagia and gastroesophageal reflux in this population. In addition, elderly persons frequently receive poor oral care, resulting in oropharyngeal colonization by potential respiratory tract pathogens, including Enterobacteriaceae, Pseudomonas aeruginosa, and Staphylococcus aureus. 41,44,45
In patients with stroke, the prevalence of swallowing dysfunction ranges from 40 to 70 percent.8,9,46-48 Many of these patients have silent aspiration.49 Patients with dysphagia who aspirate are at an increased risk for pneumonia. Among patients who have had a stroke, pneumonia is seven times as likely to develop in those in whom aspiration can be confirmed than in those who do not aspirate.9,50
Assessing the Risk of Oropharyngeal Aspiration
Assessment of the cough and gag reflexes is an unreliable means of identifying patients at risk for aspiration. A comprehensive swallowing evaluation, supplemented by either a videofluoroscopic swallowing study or a fiberoptic endoscopic evaluation, is required. A speech–language pathologist can perform this evaluation at the bedside.51-53 In patients found to be at risk for aspiration, further behavioral, dietary, and medical management to reduce this risk can be initiated. In patients with swallowing dysfunction, a soft diet should be introduced, and the patient should be taught compensatory feeding strategies (e.g., reducing the bite size, keeping the chin tucked and the head turned while eating, and swallowing repeatedly). Tube feeding is usually recommended in patients who continue to aspirate pureed food despite these strategies.
Feeding Tubes and Aspiration Pneumonia
In 1995, more than 121,000 percutaneous endoscopic gastrostomy tubes were placed in Medicare recipients in the United States,54 most commonly because of dysphagia after a stroke.54,55 However, the use of a percutaneous endoscopic gastrostomy tube has not been shown to be superior to the use of a nasogastric tube for preventing aspiration in these patients.