CONTENTS

• Management of aspiration itself:
  • Risk factors for aspiration
  • Investigation
  • Prevention
• Aspiration syndromes:
  • Aspiration pneumonitis
  • Aspiration pneumonia
  • Lung abscess ➡️
  • Lipoid pneumonia
  • Foreign body aspiration
  • Aspiration-induced interstitial lung disease
  • Aspiration bronchiolitis ➡️
• Questions & discussion

abbreviations used in the pulmonary section: 8

• ABPA: Allergic bronchopulmonary aspergillosis 📖
• AE-ILD: Acute exacerbation of ILD 📖
• AEP: Acute eosinophilic pneumonia 📖
• AFB: Acid-fast bacilli
• AIP: Acute interstitial pneumonia (Hamman-Rich syndrome) 📖
• ANA: Antinuclear antibody 📖
• ANCA: Antineutrophil cytoplasmic antibodies 📖
• ARDS: Acute respiratory distress syndrome 📖
• ASS: Antisynthetase syndrome 📖
• BAL: Bronchoalveolar lavage 📖
• BiPAP: Bilevel positive airway pressure 📖
• CEP: Chronic eosinophilic pneumonia 📖
• CF: Cystic fibrosis 📖
• COP: Cryptogenic organizing pneumonia 📖
• CPAP: Continuous positive airway pressure 📖
• CPFE: Combined pulmonary fibrosis and emphysema 📖
• CTD-ILD: Connective tissue disease associated interstitial lung disease 📖
• CTEPH: Chronic thromboembolic pulmonary hypertension 📖
• DAD: Diffuse alveolar damage 📖
• DAH: Diffuse alveolar hemorrhage 📖
• DIP: Desquamative interstitial pneumonia 📖
• DLCO: Diffusing capacity for carbon monoxide 📖
• DRESS: Drug reaction with eosinophilia and systemic symptoms 📖
• EGPA: Eosinophilic granulomatosis with polyangiitis 📖
• FEV1: Forced expiratory volume in 1 second 📖
• FVC: Forced vital capacity 📖
• GGO: Ground-glass opacity 📖
• GLILD: Granulomatous and lymphocytic interstitial lung disease 📖
• HFNC: High flow nasal cannula 📖
• HP: Hypersensitivity pneumonitis 📖
• IPAF: Interstitial pneumonia with autoimmune features 📖
• IPF: Idiopathic pulmonary fibrosis 📖
• IVIG: Intravenous immunoglobulin 📖
• LAM: Lymphangioleiomyomatosis 📖
• LIP: Lymphocytic interstitial pneumonia 📖
• MAC: Mycobacterium avium complex 📖
• MCTD: Mixed connective tissue disease 📖
• NIV: Noninvasive ventilation (including CPAP or BiPAP) 📖
• NSIP: Nonspecific interstitial pneumonia 📖
• NTM: Non-tuberculous mycobacteria 📖
• OHS: Obesity hypoventilation syndrome 📖
• OP: Organizing pneumonia 📖
• OSA: Obstructive sleep apnea 📖
• PAP: Pulmonary alveolar proteinosis 📖
• PE: Pulmonary embolism 📖
• PFT: Pulmonary function test 📖
• PLCH: Pulmonary Langerhans cell histiocytosis 📖
• PPFE: Pleuroparenchymal fibroelastosis 📖
• PPF: Progressive pulmonary fibrosis 📖
• PVOD/PCH Pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis 📖
• RB-ILD: Respiratory bronchiolitis-associated interstitial lung disease 📖
• RP-ILD: Rapidly progressive interstitial lung disease 📖
• TNF: Tumor necrosis factor
• UIP: Usual interstitial pneumonia 📖

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risk factors for aspiration

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The prevalence of aspiration may increase with age. Numerous factors increase the frequency and volume of aspiration, as listed below. Patients may often have several causes of aspiration (e.g., neurodegenerative disorder plus sedation). Microaspiration during sleep is very common, occurring in perhaps about half of normal people. (9149581)

acute disturbance of consciousness 

• Intoxication:
  • Drug overdose.
  • Alcoholism.
  • Sedatives.
• Seizure.
• Encephalopathy.
• Peri-intubation aspiration.

ongoing neurological disorder

• Stroke.
• Traumatic brain injury.
• Multiple sclerosis.
• Neuromuscular weakness causing swallowing impairment (e.g., myasthenia gravis).
• Degenerative neurologic disease:
  • Alzheimer disease.
  • Parkinson disease.
  • Amyotrophic lateral sclerosis.

laryngeal dysfunction

• Recent intubation and/or feeding tube placement.
• Vocal fold paralysis.
• History of radiation.
• Prior neck surgery.

esophageal disorders

• Achalasia.
• Esophageal stricture or web.
• Esophageal dysmotility.
• Esophageal diverticula (e.g., Zenker diverticulum).

gastric disorders 

• GERD (gastroesophageal reflux disease).
• Gastroparesis.
• Gastric outlet obstruction.
• Morbid obesity, pregnancy.

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investigation of aspiration

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patient history

• How is your swallowing?
• Do you have difficulty eating any foods? (Difficulty with liquids suggests neurologic dysfunction). (Murray 2022)
• Any coughing or choking when eating?
• Does it hurt to swallow?
• Do food or pills get stuck?
• Do you regurgitate? (if so, what material?)
• Do you have heartburn? (Murray 2022)
• Do you have hoarseness?

bedside examination

• Tongue weakness, deviation, or fasciculation may suggest a neurological etiology.
• Dental issues may interfere with the ability to chew and form a bolus of food prior to swallowing. (Murray 2022)
• Evaluate the soft palate movement while the patient says “ahhhh.” Palatal asymmetry or paralysis suggests dysfunction of cranial nerves 9/10, which may interfere with normal swallowing. 📖
• Hoarseness may suggest vocal cord paresis, or dysfunction of cranial nerves 9/10.
• (Cough or gag reflexes are unreliable and unhelpful.)

flexible laryngoscopy

• Flexible laryngoscopy may evaluate for:
  • Structural or anatomic abnormalities (e.g., mass or tumor).
  • Vocal cord dysfunction.
  • Pooling of secretions.
• Flexible endoscopic evaluation of swallowing (FEES) involves direct visualization of the pharynx after swallowing. Frank aspiration may be revealed (in terms of fluid within the vocal cords), but the actual oral or esophageal phases of swallowing cannot be directly visualized with this test (so aspiration can be missed).

modified barium swallow (MBS), aka video fluoroscopic swallow study

• Fluoroscopy is utilized to observe the oral, pharyngeal, and esophageal phases of swallowing.
• This test must be distinguished from a barium swallow or barium esophagogram (which focuses on the esophagus and stomach, rather than the act of swallowing).
• Often done in conjunction with a speech-language pathologist.

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prevention of aspiration

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treatment of any causes

• Avoidance of sedating medication.
• Treatment of gastroparesis (e.g., with prokinetic medications).
• Gastroesophageal reflux may respond to conservative measures (e.g., avoidance of eating prior to sleep, avoiding certain types of food).

dysphagia diets & maneuvers

• Specialized diets and coaching with swallowing may be helpful.
• Speech and language pathology services may help guide this intervention.
• Available data suggests that thickened liquids don't actually affect the incidence of pneumonia. (18378947) Likewise, a multicomponent intervention including improved dental hygiene didn't affect the risk of pneumonia. (25520333)

tube feeding?

• Tube feeding may be utilized to provide nutrition transiently, in the context of an acutely recoverable event (e.g., acute stroke).
• Tube feeding is not beneficial in the context of dementia. Evidence has shown that tube feeding does not prevent aspiration pneumonia, prolong survival, or improve quality of life within this context. (10527184) 

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aspiration pneumonitis

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basics

• Aspiration pneumonitis is an acute lung injury from aspiration.
• This seems to be driven by chemical pneumonitis (e.g., due to gastric acid, pepsin, and bile acids).
• Large volume aspiration of gastric contents may cause DAD (diffuse alveolar damage).

clinical manifestation

• Symptoms begin within ~1-5 hours of the aspiration event.
  • Unlike most other aspiration syndromes, aspiration pneumonitis is often preceded by a well-defined aspiration event (e.g., seizure, drug overdose, head trauma, aspiration during intubation or procedural sedation).
• Manifestations may include:
  • Dyspnea.
  • Cough.
  • Wheezing.
  • Fever.
  • Hypoxemic respiratory failure (including ARDS).
  • Systemic inflammatory response with hypotension.
• Symptoms range from minimal to dramatically severe:
  • Small-volume aspiration of material with neutral pH may be asymptomatic.
  • Large-volume aspiration of acidic material may cause ARDS and hypotension (Mendelson syndrome). (20993766)

radiology

• Chest radiograph shows abnormalities rapidly (within ~2 hours).
• Three general patterns are described: (Fishman 2023)
  • (1) Extensive bilateral consolidation.
  • (2) Widespread patchy infiltrates, especially involving the dependent areas of the lung.
  • (3) Focal consolidation that is usually localized to one or both lung bases.
• Infiltrates often tend to occur in a dependent location:
  • Recumbent aspiration often involves apical segments of lower lobes and posterior segments of upper lobes.
  • Upright aspiration often involves basal segments of lower lobes.
• Chest radiograph usually improves within a few days (unless aspiration pneumonitis leads to ARDS or pneumonia).
  • 💡 Rapid radiographic improvement is often a useful clue to the presence of aspiration, rather than a true bacterial pneumonia (which rarely resolves within 1-2 days).

treatment

• Bronchodilators may be reasonable for patients with significant wheezing.
• Antibiotics:
  • Initiating antibiotics shortly following an aspiration event to prevent the development of pneumonia is not usually recommended.
  • For patients with clinical deterioration over 1-2 days, it may be impossible to clearly determine whether there is a component of superimposed pneumonia. In this context, initiation of antibiotics is reasonable.
  • Procalcitonin may lack adequate performance in this context to differentiate between sterile aspiration versus aspiration pneumonia. (30267280, 21283001)
• Bronchoscopy:
  • Bronchoscopy is not generally indicated.
  • It might be tempting to perform a lavage in efforts to remove aspirated material. However, this is not recommended. (Fishman 2023) Lavage will push the aspirated material deeper into the lungs – which may make matters even worse.
  • If large airway obstruction due to particulate material is suspected, then bronchoscopy is indicated. (Fishman 2023)

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aspiration pneumonia

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definition?

• “Aspiration pneumonia” is a nebulous term, because the vast majority of pneumonias are caused by aspiration (other routes would include hematogenous seeding of the lungs, or inhalation of airborne pathogens). Healthy people often experience microaspiration during sleep, which although usually benign, causes most community-acquired pneumonias.
• There is no rigorous definition of what “aspiration pneumonia” actually means. It generally refers to pneumonia caused by abnormally severe aspiration (e.g., a witnessed macroaspiration event during intubation, or a patient who clearly has pathological dysphagia with aspiration).

clinical presentation of aspiration pneumonia

• The clinical presentation is largely the same as that of other types of bacterial pneumonia.
• Compared to aspiration pneumonitis:
  • (1) Aspiration pneumonia takes longer to develop after a defined aspiration event.
  • (2) Aspiration pneumonia takes longer to resolve (radiographic changes usually persist for several days).
• Features that may suggest aspiration pneumonia:
  • Repeated episodes of pneumonia.
  • Dependent portions of the lung tend to be involved (discussed below).

radiology

• Dependent portions of the lung are often involved, although this depends on body position when aspiration occurs. For patients aspirating in a supine position, the posterior segments of the upper lobes and apical segments of the lower lobes are often involved. (Fishman 2023)
• Lung necrosis with subsequent abscess formation may be more common than with most community-acquired pneumonias (lung abscess is discussed further here 📖).

treatment

• Treatment is general similar to that of community-acquired pneumonia. 📖
  • Anaerobic coverage is not required. Antibiotic selection will depend on the clinical context (e.g., community-acquired versus hospital-acquired).
• Prevention:
  • Anti-aspiration measures described above may be helpful. 📖
  • The ability of oral hygiene to prevent pneumonia is controversial.

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(exogenous) lipoid pneumonia

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basics

• Lipoid pneumonia is an inflammatory lung disease caused by aspiration of mineral oil or other oily substances.

epidemiology

• Lipoid pneumonia is most common among elderly patients, or patients with impaired swallowing.
• Sources of lipoid material:
  • Oil-based laxatives (e.g., mineral oil, castor oil, paraffin oil). (31812209)
  • Oil in foods or nutritional supplements (e.g., olive oil, cod liver oil).
  • Nasal application of oil-based products (e.g., petroleum jelly).
  • Excessive lip balm use, flavored lip gloss.
  • Crack cocaine mixed with petroleum jelly.
  • Tracheostomy or endotracheal tube lubrication with oil-based products. (33447286)
  • Occupational exposure to paraffin or other oily materials (e.g., spray paints and machinery lubricants). (35921455)

clinical presentation

• Severity varies, from asymptomatic to acute respiratory failure. The most common clinical presentation is an insidious onset of nonspecific dyspnea or cough. (34366046)
• The most common symptoms are:
  • Cough, which may be productive (64%).
  • Dyspnea (50%).
  • Fever (38%).
  • Weight loss (34%).
  • Pleuritic chest pain may occur.
• Overall, lipoid pneumonia may present as:
  • Chronic cough.
  • Nonresolving pneumonia.
  • Lung cancer mimic.

radiology 

• 💡 Radiological abnormalities are generally disproportionately dramatic as compared to clinical findings. (27144799)
• Focal dense consolidation(s) are the most common finding:
  • Distribution often involves the lower lobe(s), often in a dependent distribution.
  • Classically, a low-density consolidation may be seen (discussed further: 📖).
  • Consolidated areas may persist for years, even in the absence of ongoing lipid aspiration.
• Ground-glass opacities may also be seen, often combined with septal thickening to create a crazy-paving pattern.
• Other features that may be seen:
  • Nodules.
  • Masses may occur that are positive on PET scan, mimicking malignancy. (27144799)
  • Lymphadenopathy.

invasive diagnosis

• Bronchoscopy with bronchoalveolar lavage:
  • BAL fluid can appear milky or oily (sometimes with fat globules floating on the surface). Serial lavage may reveal an increasingly cloudy return, mimicking pulmonary alveolar proteinosis. (27144799)
  • Lipid-laden macrophages are usually the key finding (discussed further here: 📖)
  • Differential cell count may reveal neutrophils, lymphocytes, eosinophils, or a mixed inflammatory pattern. (35921455)
  • Smear and culture for bacteria, fungi and acid-fast bacilli (AFB) should be sent. There is an association between lipoid pneumonia and opportunistic superinfection (especially nontuberculous mycobacterial infection, discussed further below). (31812209)
• Lung biopsy may reveal chronic granulomatous pneumonitis with masses of foamy (lipid-laden) macrophages and foreign-body giant cells.

differential diagnosis of foamy macrophages: 📖

treatment

• Avoidance of further exposure to exogenous lipoid substances is the primary treatment.
  • Anti-aspiration measures should be taken, as discussed above: 📖
  • Cessation of exposure causes improvement in ~85% patients, but some patients may continue to deteriorate. (27144799)
• Steroid:
  • There is no high-level evidence that steroid is effective.
  • Steroid may be considered for patients with acute, severe pneumonitis.
  • For patients with subacute or chronic symptoms, discontinuation of further exposure to lipoid material is generally sufficient (without steroid therapy).
• Nontuberculous mycobacterial infection:
  • Lipoid pneumonia has been associated with rapidly growing nontuberculous mycobacterial infections (especially M. fortuitum, M. chelonae, and M. abscessus). This may be due to impaired immune function by lipid-laden macrophages. (31812209) Especially for patients with lipoid pneumonia who aren't responding to other therapies, the possibility of infection with nontuberculous mycobacteria should be considered. (Murray 2022)

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foreign body aspiration

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epidemiology

• Risk factors are largely reflective of the same risk factors of aspiration in general: 📖
• Foreign bodies can be found nearly anywhere: (31019795)
  • Trachea (3%).
  • Right main bronchus (5%).
  • Right upper lobe bronchus (3%).
  • Bronchus intermedius (23%).
  • Right middle lobe bronchus (4%).
  • Right lower lobe bronchus (27%).
  • Left main bronchus (18%).
  • Left upper lobe bronchus (4%).
  • Left lower lobe bronchus (14%).

clinical presentation

• Aspiration event itself:
  • Foreign body aspiration may follow an obvious event (e.g., choking, witnessed aspiration, or cardiac arrest).
  • However, usually patients don't recall aspiration events.
• Acute dyspnea may occur (if the foreign body occludes a large airway).
• Chronic foreign body may lead to:
  • Chronic cough (with or without sputum production).
  • Persistent wheezing refractory to bronchodilator therapy.
  • Hemoptysis (which can be massive, if a bronchial artery has been eroded).
  • Recurrent pneumonia, which may eventually lead to focal bronchiectasis.
  • Persistent atelectasis.
• Physical examination may reveal:
  • Localized wheezing
  • Focal absence of breath sounds (if there is complete airway obstruction).
  • Stridor (rarely, if the foreign body is in the upper airway).

chest radiograph

• Chest radiograph has a sensitivity of only ~20% for foreign bodies. (33422242) However, this will depend on the specific foreign body in question. Radiopaque objects (e.g., teeth, coins) are easier to detect on chest radiograph.
• Indirect evidence of a foreign body may be seen:
  • Focal atelectasis or post-obstructive pneumonia may be evident. If untreated, eventually this can lead to focal bronchiectasis.
  • If there is a ball-valve phenomena, air trapping may occur leading to focal hyperinflation.

CT scan

• Modern multidetector CT scan has substantially higher sensitivity than chest radiograph, possibly even approaching 100%. (34295390)
• ⚠️ Diagnosing foreign body can be tricky. Techniques that may help include the following:
  • (1) Carefully scroll back and forth while evaluating the patency of the main airways (this is similar to evaluation of pulmonary arteries for pulmonary emboli).
  • (2) Sagittal and coronal views may be extremely helpful (example below).
  • (3) Soft tissue windows may be helpful to look for high-density materials within the airway.
  • (4) Obtain a formal radiology interpretation.
• Inspiratory and expiratory scans may help reveal the presence of occult airway obstruction (which will cause focal air trapping on expiration).
• Chronic foreign body may stimulate a chronic inflammatory reaction with intrabronchial mass formation that can mimic lung cancer. (Walker 2019)

differential diagnosis: foreign body may be confused with:

• Asthma.
• Bronchitis.
• Chronic pneumonia.
• Tumor (granulation tissue may develop over time, the bronchoscopic appearance of a chronic foreign body may resemble malignancy). (34295390)

management

• Flexible bronchoscopy is generally successful at removal of the foreign body (~85%). Various techniques may be used, depending on the nature of the object (e.g., baskets, forceps). If the foreign body can be removed to the upper trachea but there is difficulty removing it, the patient may be asked to cough it out. (Murray 2022)
• Rigid bronchoscopy has a higher success rate than flexible bronchoscopy (>99%). Potential indications for rigid bronchoscopy could include:
  • Failure of flexible bronchoscopy.
  • Anticipated difficulty (e.g., large foreign body).
  • Acute respiratory distress (rigid bronchoscopy may provide more immediate and definitive control of the airway and foreign body). (Murray 2022)
• Potential complications:
  • Central airway obstruction.
  • Hemoptysis.
  • Bronchospasm, hypoxemia.
  • ⚠️ Caution is required when removing sharp objects that could tear or puncture the airway upon removal (e.g., nail, razor blade, fish hook).
• Foreign body removal usually isn't an immediate emergency. For more complex cases, it may be helpful to consult with an interventional pulmonologist.

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aspiration-induced interstitial lung disease

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aspiration as the cause of interstitial lung disease

• Repeated aspiration of small volumes may lead to fibrosis (which can mimic idiopathic interstitial lung disease).
• The lower lobes are usually predominantly involved. Volume loss and coarse reticular infiltrates may occur.
• Aspiration is usually not suspected clinically. Many cases may be diagnosed on the basis of a surgical lung biopsy that reveals food particles in the lung parenchyma. Organizing pneumonia has been associated with aspiration, so this may additionally be seen on pathologic samples.

aspiration plus idiopathic interstitial lung disease

• Aspiration may also aggravate co-existing idiopathic interstitial pneumonia (especially idiopathic pulmonary fibrosis).
• Aspiration may be associated with scleroderma-associated interstitial lung disease (since scleroderma commonly causes esophageal dysfunction).

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questions & discussion

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