January 29, 2026 With the collaboration of Prof. José Roquette What is aspiration pneumonia? This is a bacterial infection that develops after substances foreign are inhaled or aspirated into the lungs , such as: Saliva; Secretions from the upper airways; Food; Stomach contents; Small objects. Under normal circumstances, when substances like these reach the oropharynx, that is, the area of the throat at the back of the mouth, one of two things happens: Either the swallowing reflex is triggered and they are swallowed, as will generally happen with saliva and food; The cough reflex and/or the gag reflex are triggered and they are expelled through the mouth, as happens if we choke on something, cough up phlegm, or vomit. If, for some reason, these reflexes did not function properly, foreign substances can enter the lower airways. Thus, they reach the lungs and cause aspiration pneumonia. Why do bacteria that cause infection develop? Generally, saliva, food, secretions, and other foreign substances that cause aspiration pneumonia are not sterile . They contain bacteria, some of which are even part of the normal digestive flora, others that may be contaminants. When foreign substances enter the lungs, a defense reaction involving inflammation is triggered . In addition, there may be: Irritation, direct tissue damage, or blockages , mainly with solid substances and gastric contents; Interference with the gas exchanges in the alveoli, as occurs with liquids. With all this, the lungs become weaker and more vulnerable to infections , and the bacteria carried by foreign substances find favorable conditions for their multiplication, triggering pneumonia. What if the aspirated substances are sterile? In that case, they may only cause inflammation, and it will be aspiration pneumonitis . However, aspiration pneumonitis is less frequent because, in addition to the aspirated substances rarely being sterile, the aspiration of foreign substances leaves the lungs vulnerable and this favors an infection. Are there people at higher risk of aspiration pneumonia? Yes, aspiration pneumonia is more common in people who have, for example : Difficulty swallowing This group includes people with neurological and neuromuscular diseases, usually in advanced stages, when reflexes no longer function correctly and the coordination between the mechanisms of swallowing and breathing correctly, protecting the airways, is compromised. This can happen in stroke (cerebrovascular accident), Parkinson's disease, dementia, multiple sclerosis, amyotrophic lateral sclerosis, among others. Decreased state of consciousness For example, in alcohol or drug intoxication, during recovery from anesthesia or sedation, or with seizures. In these circumstances, one should not eat or drink due to the increased risk. Young children Their reflexes are not yet fully developed. Especially infants due to the type of feeding, and those with severe reflux. Elderly Reflexes become less effective with aging. They often have other diseases that weaken them. Gastroesophageal reflux Particularly when they lie down and sleep after a large meal, because the gastric contents of the reflux can be aspirated. Dental problems and/or poor oral hygiene These situations increase the load of microorganisms present in the mouth. Bedridden people , due to the horizontal posture that favors misroute into the airway. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
