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Pulmonary aspiration

Pulmonary aspiration

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Pulmonary aspiration is the entry of material (such as pharyngeal
Human pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...

 secretion
Secretion
Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, the substance may have a certain function, rather than being a waste product...

s, food or drink, or stomach contents) from the oropharynx
Oropharynx
The Oropharynx reaches from the Uvula to the level of the hyoid bone.It opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the two palatine arches, is the palatine tonsil....

 or gastrointestinal tract into the larynx
Larynx
The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

 (voice box) and lower respiratory tract
Lower respiratory tract
The term lower respiratory tract refers to the portions of the respiratory system from the trachea to the lungs.Lower respiratory tract infections can be the cause of several serious illnesses, including pneumonia....

 (the portions of the respiratory system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...

 from the trachea
Vertebrate trachea
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...

 (windpipe) to the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s). A person may either inhale
Inhalation
Inhalation is the movement of air from the external environment, through the air ways, and into the alveoli....

 the material, or it may be delivered into the tracheobronchial tree
Tracheobronchial tree
The tracheobronchial tree is the structure from the trachea, bronchi, and bronchioles that forms the airways that supply air to the lungs. It is within the neck and the chest. The structure looks like a tree because the trachea splits into the right and left mainstem bronchi, which "branch" into...

 during positive pressure ventilation. When pulmonary aspiration occurs during eating and drinking, the aspirated material is often colloquially referred to as "going down the wrong pipe."

Consequences of pulmonary aspiration range from no injury at all, to chemical pneumonitis
Chemical pneumonitis
Aspiration pneumonitis or chemical pneumonitis is inflammation of the lung caused by aspirating or inhaling irritants. It is sometimes called a "chemical pneumonia", though it is not infectious...

 or pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

, to death within minutes from asphyxia
Asphyxia
Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...

tion. These consequences depend in part on the volume, chemical composition, particle size, presence or absence of infectious agents, and underlying health status
Comorbidity
In medicine, comorbidity is either the presence of one or more disorders in addition to a primary disease or disorder, or the effect of such additional disorders or diseases.- In medicine :...

 of the person. In healthy people, aspiration of small quantities of material is common and rarely results in disease or injury. People with significant underlying disease or injury, especially hospitalized patients, are at greater risk for developing respiratory complications
Complication (medicine)
Complication, in medicine, is an unfavorable evolution of a disease, a health condition or a medical treatment. The disease can become worse in its severity or show a higher number of signs, symptoms or new pathological changes, become widespread throughout the body or affect other organ systems. A...

 following pulmonary aspiration because of certain factors such as depressed level of consciousness
Altered level of consciousness
An altered level of consciousness is any measure of arousal other than normal. Level of consciousness is a measurement of a person's arousability and responsiveness to stimuli from the environment. A mildly depressed level of consciousness may be classed as lethargy; someone in this state can be...

 and impaired airway defenses (gag reflex and/or respiratory tract antimicrobial defense system
Respiratory tract antimicrobial defense system
The respiratory tract antimicrobial defense system is a layered defense mechanism which relies on components of both the innate and adaptive immune systems to protect the lungs and the rest of the respiratory tract against inhaled microorganisms....

).

As the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

 of the right main bronchus
Right main bronchus
The right main bronchus is a bronchus of the respiratory system. It is wider, shorter, and more vertical in direction than the left...

 is more vertical and of slightly wider diameter than that of the left
Left main bronchus
The left main bronchus is smaller in caliber but longer than the right, being nearly 5 cm long...

, aspirated material is more likely to end up in this bronchus or one of its subsequent bifurcations.

Risk factors


Risk factors for pulmonary aspiration include conditions which depress the level of consciousness (such as traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...

, alcohol intoxication, drug overdose
Drug overdose
The term drug overdose describes the ingestion or application of a drug or other substance in quantities greater than are recommended or generally practiced...

, and general anesthesia
General anaesthesia
General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...

). A decreased gag reflex, upper esophageal sphincter
Upper esophageal sphincter
The upper esophageal sphincter refers to the superior portion of the esophagus.Unlike the lower esophageal sphincter, it consists of striated muscle and yet, is not under conscious control. Opening of the UES is triggered by the swallow reflex...

 and lower esophageal sphincter tone, gastroesophageal reflux
Gastroesophageal reflux disease
Gastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...

, full stomach, as well as obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

 and pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 can all increase the risk of aspiration in the semiconscious. Tracheal intubation
Tracheal intubation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...

 or presence of a gastric tube
Nasogastric intubation
Nasogastric intubation is a medical process involving the insertion of a plastic tube through the nose, past the throat, and down into the stomach.-Uses:...

 (for example, a feeding tube
Feeding tube
A feeding tube is a medical device used to provide nutrition to patients who cannot obtain nutrition by swallowing. The state of being fed by a feeding tube is called gavage, enteral feeding or tube feeding...

) may also increase the risk.

Particle-related


Pulmonary aspiration of particulate matter may result in acute airway obstruction which may rapidly lead to death from arterial hypoxemia
Hypoxemia
Hypoxemia is generally defined as decreased partial pressure of oxygen in blood, sometimes specifically as less than or causing hemoglobin oxygen saturation of less than 90%.-Distinction from anemia and hypoxia:...

.

Acid-related


Pulmonary aspiration of acidic material (such as stomach acid
Gastric acid
Gastric acid is a digestive fluid, formed in the stomach. It has a pH of 1 to 2 and is composed of hydrochloric acid , and large quantities of potassium chloride and sodium chloride...

) may produce an immediate primary injury caused by the chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 of acid with lung parenchyma
Parenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...

, and a later secondary injury as a result of the subsequent inflammatory response
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

.

Bacterial


Pulmonary aspiration is often followed by bacterial pneumonia
Bacterial pneumonia
Bacterial pneumonia is a type of pneumonia caused by bacterial infection.-Sign and symptoms:*Fever*Rigors*Cough*Dyspnea*Chest pain*Pneumococcal pneumonia can cause Hemoptysis-Gram positive:...

. Community-acquired
Community-acquired pneumonia
Community-acquired pneumonia is a term used to describe one of several diseases in which individuals who have not recently been hospitalized develop an infection of the lungs . CAP is a common illness and can affect people of all ages. CAP often causes problems like difficulty in breathing, fever,...

 aspiration pneumonia
Aspiration pneumonia
Aspiration pneumonia is bronchopneumonia that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents...

 is usually caused by anaerobic bacteria
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...

, whereas hospital-acquired
Hospital-acquired pneumonia
Hospital-acquired pneumonia or nosocomial pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48–72 hours after being admitted. It is usually caused by a bacterial infection, rather than a virus....

 aspiration pneumonia is more often caused by mixed flora, including both aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

 and anaerobic bacteria.

Prevention


The lungs are normally protected against aspiration by a series of protective reflexes such as coughing and swallowing
Swallowing
Swallowing, known scientifically as deglutition, is the process in the human or animal body that makes something pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration...

. Significant aspiration can only occur if the protective reflexes are absent (in neurological disease, coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...

, drug overdose
Drug overdose
The term drug overdose describes the ingestion or application of a drug or other substance in quantities greater than are recommended or generally practiced...

, sedation
Sedation
Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure...

 or general anesthesia). In intensive care, sitting patients up reduces the risk of pulmonary aspiration and ventilator associated pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

.

Measures to prevent aspiration depend on the situation and the patient. In patients at imminent risk of aspiration, tracheal intubation
Tracheal intubation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...

 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
First aid
First aid is the provision of initial care for an illness or injury. It is usually performed by non-expert, but trained personnel to a sick or injured person until definitive medical treatment can be accessed. Certain self-limiting illnesses or minor injuries may not require further medical care...

 and CPR classes), so that any vomitus produced by the patient will drain out their mouth instead of back down their pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...

. Some anesthetists will use sodium citrate (to neutralize the stomach's low pH) and Metoclopramide or Domperidone (pro-kinetic agents, to empty the stomach).

People with chronic neurological disorder
Neurological disorder
A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord, or in the nerves leading to or from them, can result in symptoms such as paralysis, muscle weakness, poor coordination, loss of sensation, seizures,...

s, for example, after a stroke, are less likely to aspirate thickened fluids
Thickened fluids
Thickened fluids are often used for people with dysphagia, a disorder of swallowing function. The thicker consistency makes it less likely that an individual with dysphagia will aspirate while they are drinking...

.

The location of abscess
Abscess
An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...

es 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 posterior segment of the right upper lobe, or the posterior basal segment of the right upper lobe. If one is lying on the left, it goes to the lingula
Lingula of left lung
The human left lung, unlike the right, contains no middle lobe. However, the term lingula is used to denote a projection of the upper lobe of the left lung that serves as the homologue. Some sources define the lingula as a distinct lobe...

.

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