Aspiration of a foreign body

Aspiration of a foreign body is a spontanneous and undesirable entry of a foreign body into the airways during inspiration. According to consistency of the inhaled object, it is possible to distinguish between aspiration of solid substances, liquids, emulsions and gases. The presence of a "foreign", unphysiological substance in the airways leads directly or indirectly to the development of pneumonia, i.e., aspiration pneumonia. The most frequent causes of aspiration pneumonia include aspiration of the contents of the mouth by small children, aspiration of the stomach contents in patients with gastroesophageal reflux (GER), swallowing disorders (interestingly, the act of swallowing involves 5 nerves of the head and 26 muscles), neurological disorders and structural abnormalities (cleft palate, oesophageal artresia,tracheoesophageal fistula including the so-called H–type, malrotation, achalasia).

Aspiration causes a complex patophysilogical process. Destructive changes of the pulmonary parenchyme resulting from foreign body aspiration differ from destructive changes caused by infectious agents since they include structural destruction, degenerative (necrotic) changes of the parenchyme and a decrease in dynamic pulmonary compliance with an impaired respiratory function. Therefore, they are sometimes referred to as pneumonititis.

Mechanism of aspiration
Solitary respiratory tract in the area of HCD appears to be a critical segment in its entirety, but the most serious obstruction is caused by a foreign body lodged in the physiologically most narrow spaces: glottic opening, subglottic region and the carina. The obstruction of HCD may also be caused by external pressure caused by a foreign body lodged in the oesophagus, mainly in the so-called Killian’s dehiscence.

The coordination between swallowing and natural breathing may be disrupted by negative effects, which increase the probability of aspiration and affect various patophysiological levels, i.e. so-called predisposing factors to aspiration:


 * impairment of distal esophageal sphincter (GER, inserted nasogastric tube, gastrostomy, hiatal hernia, cardiopulmonary resuscitation, obstruction of upper respiratory tract, mechanical ventilation with negative pressure, muscular dystrophy, sclerodermia),
 * delayed emptying of the stomach (fear of pain, mechanical intestinal obstruction, peptic gastric ulcer, hypoxia, shock, anaesthesia),
 * an increase in intra abdominal pressure or intra gastric pressure (mecanical intestinal obstruction, ascites, abdominal tumor, peritoneal dialysis, VP shunt with fluid drainage, obesity, depolarising myorelaxation),
 * disorder of natural defenses of upper respitatory tract (hypoxic–ischemic encephalopathy, traumatic brain injury, encefalitis, meningitis, status epilepticus, anaesthetics, intoxication, incoordination of sucking and swallowing, REM sleep phase),
 * anatomic and local factors (vocal cord paralysis, tracheal intubation, tracheostomy, bronchoscopy, lowered laryngeal sensitivity, tracheoesophageal fistula, esophageal diverticulum, mucus accummulation in the pharynx).

Localisation
Finding of a foreign body on examination in the larynx is very rare. A smaller foreign body tends to become lodged in the bronchi (usually in the right bronchus, since the right bronchus is less diverted in the bifurcation and it is wider). A large foreign body leads to patienr’s asphyxiation. The presence of foreign bodies in the bronchi is most frequent in toddlers and in pre-school children. These cases mostly involve food substances, most frequently nuts, carrot pieces, soup bones but also beads, small balls, buttons, etc. Foreign object inhalation occurs when a child bursts into laughter or starts crying with his/her mouth full of food. In the alveoli, tiny substances tend to be found, such as ashes, flour, sawdust, sand.

Clinical presentation
The symptomatology of foreign body aspiration depends on the volume and type of the inhaled material, its pH value, presence of bacteria in the aspirated material and last but not least on the underlying health and immunological profile of the patient before the act of foreign body aspiration. Aspiration has a typical clinical presentation during its initial phase, its progression and development of clinical signs.

The most frequent manifestations of aspiration include recurrent wheezing, apnea, chronic cough and recurrent pneumonia.

Immediately after a foreign body is inhaled, aspiration manifests itself as a coughing attack, which subsides after the foreign body becomes lodged in a specific location. Until that moment, it "travels" between the bronchi and the glottis, and it can be also coughed out. A foreign body wedged in the bronchus usually leads to a creation of a ventil and an emfyzema develops subsequently. When inhaling, the lumen expands and the air circulates behind the foreign body. During inspiration, the bronchi collapse due to foreign body obstruction and are unable to release the air. Inflammation arises around the foreign body, and atelectasis develops.

Initial phase

 * paroxysmal, irritating and persistent cough (a natural defense mechanism with the aim to expel the aspired body),
 * apnea,
 * in blood supply of the face and  the mucous membranes – blood perfusion, folowed by cyanosis,
 * retraction of the chest during inspiration,
 * anxiety and psychomotor agitation.

Post-aspiration phase, i.e., signs of acute respiratory distress

 * mixed dyspnea, stridor and wheezing,
 * tachypnea,
 * vocal changes,
 * cyanosis,
 * quantitative disorders of consciousness,
 * hemodynamic instability,
 * findings during chest auscultation: asymmetry, wheezing, impaired inspirium, impaired breathing and others (up to 40 % of patiens who present with aspiration of an anorganic body have normal physiological findings on examination, unlike patients who present with aspiration of an organic body, out of which only 13 % have normal physiological findings on examination),
 * unexplicable night fevers and/or night sweats,
 * purpulent sputum,
 * night wheezing and/or cough.

Aspiration should be strongly suspected in patients presenting with asthma-like symptomatology, patients irresponsive to standard treatment and patients whose symptomatology is not directly related to the presence of allergens, physical effort or pulmonary infarction. Recurrent pneumonia often affects patients with foreign body aspiration suffering from neorological disorders or patients with recurrent pulmonary microaspirations (e.g., related to GER). Chronic cough (i.e., cough lasting for more than 3 weeks) may be the only symptom of aspiration. After its initial manifestation, aspiration may become oligosymptomatic or even asymptomatic for a period of several hours, days or even weeks until the recurrence of symptoms.

Diagnostics
The examination of a patient with suspicion of aspiration aims at its rapid and reliable identification. It is necessary to identify patients with a high risk of aspiration (by means of a detailed and targeted anamnesis, detailed clinical and neurological examination, continuous monitoring of respiratory functions and ECG) as well as continuous monitoring of clinical symptoms. Typical presentation includes breathing through the nose (nasal breathing), besides wheezing, crackles tend to be present, as well as retraction, alternatively grunting and cyanosis. A valuable aspect is evaluation of the dynamics of changes, i.e., blood supply, the quality of cough, respiratory distress, stridor, wheezing, breathing frequency and auscultatory findings. The essential laboratory tests to be performed include arterial blood gas analysis, monitoring of measurement of the arterial oxygen saturation (SaO2), FBC+differential., inflammatory markers (importance is given to the dynamics of changes). Complementary tests include overall IgE (immunoglobulin E) and prick tests; and/or RAST (radioallergosorbent assay testing) if eosinophylic esophagitis or gastritis is suspected, which can show reactions to common food groups.

Chest X-ray
Chest X-ray represents a routine diagnostic method. The finding of an emphysema with a mediastinal shift to the opposite side indicates ventil mechanism of an abstruction with a foreign body. The presence of atelectasis with mediastinal shift to the affected side indicates aspiration with a complete obstruction of the bronchus in a a given part of the lungs resulting in resorbtion of the air.

The most frequent X-ray findings include emphysematous changes, followed by the presentation of atelectasis, a normal radiograph, and consolidation. Sensitivity of the X-ray imging techique and its propensity to detect aspiration also depends on the time frame of its implementation. If the X-ray is performed more than 24 hours following aspiration, positive findings tend to be more frequent. On the other hand, it has been shown that if X-raz imaging was performed less than 24 hours following aspiration, up to 30 % of children with a subsequently diagnosed aspiration had a negative (normal) radiological finding when endoscopy was performed. An X-ray image without a finding of aspiration does not exclude the possibility of aspiraton!

Bronchoscopy
Diagnostic bronchoscopy performed when a finding of a foreign body is proved also fulfills a therapeutic function. The decision to perform an endoscopy is based on a suggestive anamnesis (paroxysmal coughing), on a positive RTG finding and according to findings of a performed physical examination (differences between the sides of lungs detected during ausculcation). Children younger than 3 years of age tend to have foreign bodies diagnosed much more frequently in the right main bronchus. Up to two thirds of aspirated bodies are represented by nuts of various types. In case of chronic microaspirations, it is instrumental to perform the procedure of bronchoscopy and bronchoalveolar lavage BAL, which reveals the finding of lipophagy. A modern diagnostic method consists in the assay of pepsins during the procedure BAL.

Further examination procedure
An ultrasound examination of the digestive tract is performed in order to assess gastric distension, presence of GER, intestinal content and motility and build-up of fluid in the abdomen, i.e., ascites. Native abdominal X-ray performed in a standing position provides information about the content of intenstines, levels of fluid in intestinal lumen, position of nasogastric probe (tube). Bacteriological examination of available samples is performed, including aerobic and anaerobic sputum cultivation, pleural fluid, a blood culture test and gastric aspirate. It is also recommended to perform pulmonary function tests and in specific cases also sweat chloride tests. A barium swallow test may reveal anatomic defects such as a hiatal hernia, malrotation, pyloric stenosis, antral or duodenal algae. All these abnormalities might predispose a patient to GER. Gastro-esophageal scintigraphy, often called “milk scan“, is a radionuclid imaging technique, which may confirm aspiration into the lungs (although its specificity and sesitivity among GER diagnostic procedures is not high). Measuring pH over the course of 24 hours is considered the “gold standard“ of diagnostic procedure for determining the presence of GER. In case of uncertainty, lung inhalation scintigraphy might be helpful, if available. Esophagogastroduodenoscopy with biopsy may reveal infiltration with eosinophilia.

Pre-hospital procedure
Pokud byla aspirace cizího tělesa přímo pozorována a dítě je při vědomí, podporujeme ho v aktivním kašli. Pokud je kašel neefektivní, dýchání nedostatečné nebo dítě upadne do bezvědomí, pokusíme se o odstranění tělesa. Manuální odstranění cizího tělesa nikdy neprovádíme naslepo, zejm. v hypopharyngu, neboť hrozí zatlačení hlouběji do dýchacích cest. U dítěte v bezvědomí zabezpečíme dýchací cesty tak, že chytíme společně mandibulu (dolní čelist) a čelo a táhneme je směrem nahoru. Pokud vidíme cizí těleso, odstraníme ho!

Manévry na uvolnění dýchacích cest

 * 1) Gordonův manévr pro kojence, který je při vědomí a spontánně dýchá:
 * 2) *Kojence položíme tváří dolů na svoje předloktí tak, že hlava dítěte je níže než jeho tělo, hlavu dítěte držíme za mandibulu a své předloktí si můžeme opřít o své stehno. Následně 5x udeříme dlaní mezi lopatky dítěte. Potom položí zachránce svoji volnou ruku na záda dítěte a držíce ho mezi dvěma rukama jako "sendvič", ho otočí (dítě leží zády na předloktí). Následně provedeme 5 kompresí hrudníku jako při KPR. Postup opakujeme, dokud neodstraníme těleso nebo dokud dítě neztratí vědomí.
 * 3) Heimlichův manévr pro starší dítě, které je při vědomí a spontánně dýchá:
 * 4) *Postavíme se za dítě a obejmeme rukama jeho hrudník. Uděláme "pěst" a tu položíme na břicho dítěte mezi pupek a processus xiphoides. Následně 5 x stlačíme břicho rychlými pohyby směrem nahoru. Nestlačujeme processus xiphoides, neboť by mohlo dojít k vnitřním poraněním.
 * 5) Je-li dítě v bezvědomí, je postup stejný pro všechny věkové skupiny :
 * 6) *Dítě položíme na záda, pokusíme se uvolnit dýchací cesty. Pokud vidíme cizí těleso, odstraníme ho. Pokud ho nevidíme, začneme s umělým dýcháním. Pokud se hrudník zvedá, pokračujeme do příchodu RZP. Pokud se hrudník nezvedá, opakujeme celý dosavadní postup včetně Gordonova/Heimlichova manévru.

Dramatizace provedení Haimlichova manévru na YouTube (anglicky)

Nemocniční postup
Při akutní aspirační epizodě doporučujeme postup po jednotlivých krocích podle závažnosti a dynamiky rozvoje klinických příznaků aspirace. Observace by měla být minimálně 48 hod.

Provádíme odsátí nasopharyngu, zpravidla ukončujeme krmení ústy a zavádíme tenkou nasogastrickou sondu. Poskytneme adekvátní oxygenoterapii, při nutnosti ev. intubaci s následnou UPV. Zajistíme i.v. linku a podáváme tekutiny dle vypočtené denní potřeby. Při wheezingu může přinést zlepšení situace inhalační podání β-2 mimetik. Pro extrakci partikulí je určena rigidní bronchoskopie, doplněná ev. o BAL. Antibiotika neindikujeme paušálně, ale tehdy pokud se objeví teplota, zhoršení klinického stavu, elevace zánětlivých parametrů nebo RTG korelát aspirace na RTG. Pokud je antibiotikum indikováno, podáváme jej zásadně intravenosně a v nejvyšší doporučené dávce. V léčbě aspirační pneumonie jsou doporučovány cefalosporiny II. nebo III. generace, které pokryjí jak grampozitivní mikrofloru z oropharyngu, tak gramnegativy z gastrointestinálního traktu. Nutno předpokládat i možnou přítomnost anaerobní bakteriální flóry, kde doporučovaným antibiotikem jsou linkosamidy (klindamycin), ale pokrytí anaerobní flory není rutinně v iniciální (empirické) léčbě nutné. Při nezlepšení stavu do 48 hod. rozšiřujeme antibiotické spektrum. Efekt kortikoidů nebyl potvrzen klinickými studiemi.

Prevence
Prevence spočívá v identifikaci vysoce rizikové skupiny pacientů. Při zvracení polohujeme pacienta na pravý bok s elevací hrudníku a odsátím nosohltanu, při GER je vhodná elevace trupu, ev. spolu s prokinetikem. U pacientů s oslabenými ochrannými reflexy dýchacích cest se snažíme o co nejnižší aplikaci sedativ a anestetik. Při úplném vymizení ochranných reflexů dýchacích cest je nezbytné pacienta zajistit tracheální intubací. Pro enterální výživu používáme tenké a měkké nasogastrické nebo nasojejunální sondy.

Zdroj

 * HAVRÁNEK, Jiří: Aspirace cizího tělesa.