Pulmonary aspiration overview

In medicine, aspiration is the entry of secretions or foreign material into the trachea and lungs. The patient may either inhale the material, or it may be blown into the lungs during positive pressure ventilation or CPR. As the right main bronchus is more vertical and of slightly wider lumen than the left, aspirated material is more likely to end up in this branch or one of its subsequent bifurcations.

The lungs are normally protected against aspiration by a series of “protective reflexes” such as coughing and swallowing. Significant aspiration can only occur if the protective reflexes are absent (in neurological disease, coma, drug overdose, sedation or general anesthesia). In intensive care, sitting patients up reduces the risk of pulmonary aspiration and ventilator associated pneumonia.

If enough material enters the lungs, the patient may simply drown. However, small volumes of gastric acid contents can fatally damage the delicate lung tissue. Even small volumes of aspirated food may lead to bronchopneumonia infection. Chronic aspiration may lead to bronchiectasis and may cause some cases of asthma.

The location of abscesses caused by aspiration depends on the position one is in. If one is sitting or standing up, the aspirate ends up in the posterior basal segment of the right lower lobe. If one is on one’s back, it goes to the superior segment of the right lower lobe. If one is lying on the right side, it goes to the superior segment of the right middle lobe, or the posterior basal segment of the right upper lobe. If one is lying on the left, it goes to the lingula.

Measures to prevent aspiration depend on the situation and the patient. In patients at imminent risk of aspiration, endotracheal intubation by a trained health professional provides the best protection. A simpler intervention that can be implemented is to lay the patient on their side in the rescue position (as taught in first aid and CPR classes), so that any vomitus produced by the patient will drain out their mouth instead of back down their pharynx.

People with chronic neurological disorders, for example, after a stroke, are less likely to aspirate thickened fluids.

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