Aspiration has to do with the inhalation of foreign substances into the respiratory tract, then to the lungs. The aspiration can be a substance from the Gastrointestinal Tract, which can be from the esophagus, or stomach, which will then move to the go to the airway. The foreign content can also be oropharyngeal secretion where there is a secretion from the oral cavity or from the pharyngeal area which should go to the esophagus but rather, they go to the trachea or larynx and then into the airway. This can also be from foreign bodies from the outside environment which would move to the airways, rather than going to the esophagus and then to the stomach.
These aspirations occur as a result of decreased cough or a gag reflex which is usually mitigated by neuromuscular activities, or by the central nervous system. If there is damage to centers such as the vagus nerve, glossopharyngeal nerve, and the accessory nerve that controls cough and gag reflex as a result of a disease, or a trauma, inhibiting the areas where the nerves are to be innervating and sending action potentials to, then this can lead to aspiration. It could also occur as a result of Central nervous system depression as a result of a drug intake, or sedation, and could be as a result of a neuromuscular junction disorder causing an inability to form a gag reflex or cough to remove the foreign body from the airway. Gastrointestinal motility disorders such as achalasia can also be a cause and a mechanical closure of the glottis such as using G-tubes, as well as an opening between the gastrointestinal tract (esophagus) and the trachea such as a tracheoesophageal fistula can lead to the movement of foreign particles into the trachea instead of heading to the esophagus. In post-term neonates, meconium fluid aspiration is at a high rate and this can get stuck in the airways as their gag reflexes are not properly developed.
When patients aspirate as a result of any of the causes, it can lead to a stuck in the proximal airways leading to infiltration and inflammation of the mucosal causing a cough reflex. This could lead to a disruption of the lower airway known as wheezing, and upper airways known as Stridor. The obstruction is common in the right bronchus, compared to the left bronchus leading to decrease breath sounds in the affected lung. The blockage to the airways would lead to partial breathing causing less air to get in and out, causing an hyperexpansion of the part of the lungs being obstructed. In complete obstruction, air would be prevented from getting in, leading to the collapse of the lungs. When there is a blockage, patients usually present with an ipsilateral mediastinal and trachea shift. Patients with obstruction will present with evidence of cyanosis including bluish coloration of the lip, fingers, and mucus membrane as airflow is blocked and the air is prevented from getting into the body leading to hypoxemia.
Patients can also develop aspiration of the oral pharyngeal secretion which is basically the gastrointestinal contents such as gastric acids and microorganisms into the airway leading to irritation and inflammation and leading to an increased risk of infection. This can lead to a cough, bronchospasm, receptor irritation, and the release of cytokine which would lead to fever becoming suggestive of aspiration pneumonia and aspiration pneumonitis. This can lead to Acute respiratory distress syndrome (ARDS) and Lung Abscesses. In the case of ARBS, as aspiration pneumonia starts to increase, it leads to diffuse alveoli damage leading to severe hypoxemia. In Lung abscesses, anaerobes start to cause the lungs to warn out area of the infection the causing complication and abscesses such as lung abscess. With Meconium aspiration, post-term neonates have a clog in their airways which is not matured leading to hyperinflation of the lung affected as it is filled with meconium and not allowing air to leave. This can lead to air leaking into the pleural cavity and the mediastinum. , , ,
Diagnosing, the signs and symptoms of the patients from the physical examination is a good way to start. The patient presents with a cough, stridor, cyanosis, wheezing, ipsilateral mediastinal and trachea shift, breath sounds, fever, or lung abscess. This is a good sign to tell that there is a blockage but to be sure, a bronchoscopy should be done to find the obstruction. Chest X-ray and CT scan can be done. Obstruction is usually more common in the right lung than in the left lung, affecting the upper segment of the right lower lobe, as well as the basal or posterior segment of the right lower lobe when standing as a result of gravity. In cases where the foreign body isn't visible then the signs of the type of obstruction should be considered. In the case of a full obstruction, there is a collapse of the lungs, if the obstruction is a partial one, then it would lead to hyperinflation of the area of the obstruction.
If after bronchoscopy, the foreign body is seen, then it can be removed but in cases where the patient is choking, showing signs of cyanosis, coughing, and silent chest decreased breath sound, then a chest or abdominal thrusting will help to push the obstruction out if it is foreign. If the patient has pneumonitis the underlying cause should be treated, supportive treatment should be given, oxygen should be given if they are not properly getting air, and bronchodilators if there are bronchospasm. In the case of pneumonia, ARDS and Lung abscess should be looked for. Antibiotics such as clindamycin and amoxicillin-clavulanate for anaerobic infections. Sputum culture is used to guide the use of the antibiotics toward the area where it is affected.
Image Reference
Image 1 || Wikimedia commons || Broncoscopia terapeutica.