Chapter 69: Aspiration-Related Pulmonary Disorders

INTRODUCTION

Aspiration is defined as the misdirection of oropharyngeal or gastric contents into the larynx and lower respiratory tract.² An assortment of pulmonary syndromes may occur following aspiration depending on the quantity and nature of the aspirated material, the chronicity of aspiration, and the nature of the host’s defense mechanisms and the host’s response to the aspirated material. The most important syndromes include “aspiration pneumonitis” or Mendelson’s syndrome, which is a chemical pneumonitis caused by the aspiration of gastric contents, and “aspiration pneumonia,” an infectious process caused by the aspiration of oropharyngeal secretions colonized by pathogenic bacteria.² While there is some overlap between these two syndromes, they are distinct clinical entities.² The distinction between these two syndromes is based largely on clinical criteria (Table 69-1). Although gastric biomarkers for aspiration are increasingly available (e.g., pepsin, amylase, lipid-laden macrophages), none has been clinically validated.^3–5 Serum procalcitonin and other inflammatory markers are unable to distinguish aspiration pneumonitis from aspiration pneumonia.⁶ The administration of antibiotics is central to the management of aspiration pneumonia, while the treatment of aspiration pneumonitis is largely supportive.² In addition to aspiration pneumonitis and aspiration pneumonia, a variety of pulmonary conditions result from chronic recurrent occult aspiration, most notably “diffuse aspiration bronchiolitis.”⁷ Other aspiration syndromes include airway obstruction, lung abscess, exogenous lipoid pneumonia, chronic interstitial fibrosis, and Mycobacterium fortuitum pneumonia. This chapter focuses on the pathophysiology, clinical features, and management of aspiration pneumonitis, aspiration pneumonia, and diffuse aspiration bronchiolitis.

ASPIRATION PNEUMONITIS

Aspiration pneumonitis is best defined as acute lung injury ...