Protection of the lungs from oral, nasal, and gastric contaminants is provided by a complex and not always competent set of reflexes that can be disrupted by structural and functional abnormalities, many of which are associated with aging and neurologic disorders. Major and minor episodes of aspiration contribute to the terminal stages of many diseases, and aspiration appears to play a role in a variety of chronic disorders, such as cough, bronchial asthma, bronchiectasis, and pulmonary fibrosis. The pharynx and mouth are used in common for eating, vomiting, and breathing, and food and liquids entering the mouth must be diverted away from the lungs by the epiglottis to avoid flow into the lungs.

Direct connections between the mouth, esophagus, and stomach put the lungs at risk for aspiration during swallowing and regurgitation, and excess gas can be swallowed ( Figure 1). The intimate relationship between the pulmonary and gastrointestinal systems cannot be considered an unmixed blessing. Relationship of the Lungs to the Gastrointestinal Tract

Finger oxygen meter lung dead space