FFS: Aspiration

Aspiration is the inhalation of oropharyngeal or gastric contents into the lungs. Less commonly, foreign substances (e.g. water, hydrocarbons) may be aspirated, but these are considered distinct clinical entities.

Aspiration is often occult — especially in:

  • Elderly nursing home residents
  • Patients with decreased consciousness (e.g. overdose, seizures)

A witnessed aspiration event is rarely observed. Clinicians must maintain a high index of suspicion.

Consequences of Aspiration

ConditionDefinitionKey Features
Aspiration pneumonitisAcute chemical injury from gastric acidSymptoms within hours; typically no infection
Aspiration pneumoniaSecondary bacterial infection following aspiration eventSymptoms usually ≥48 hrs post-event; may not be witnessed

In practice, the distinction is often unclear. Management decisions are based on clinical judgement.

Pathophysiology

Mechanisms of Aspiration
  • Vomiting (active process)
  • Regurgitation (passive process)
  • External sources: near-drowning, hydrocarbons
Severity Determinants
  • Nature of aspirate:
    • pH < 2.5 increases risk of severe pneumonitis
    • Particulate or infected material worsens injury
  • Volume: ≥0.3 mL/kg (≈20–25 mL in adults)
  • Patient comorbidities

Risk Factors

CategoryExamples
Airway reflex impairment↓ Consciousness (e.g. drugs, seizures), neuromuscular disease, dementia
↑ Gastric volume/pressureRecent meals, delayed gastric emptying, obstruction
Dysphagia pathologyTracheo-oesophageal fistula, achalasia, strictures, oesophageal tumours
IatrogenicNGTs, tracheostomy, bag-valve masking in unfasted patients

Clinical Features

Aspiration is frequently occult. Suspect aspiration in any patient with:

  1. Predisposing risk factor
  2. History of vomiting/choking
  3. Acute respiratory symptoms

Presentations

  • Abrupt respiratory distress: cough, wheeze, crepitations, cyanosis
  • Occult collapse in elderly, particularly with stroke or dementia
  • Status epilepticus, OD, intoxication → silent aspiration

Investigations

Bloods
  • FBC, U&Es, glucose, CRP
  • ABG/VBG and lactate as indicated
ECG
  • Routine for unwell patients, though not specific
CXR
  • May be normal in early/low-volume aspiration
  • Changes: patchy opacities, usually gravity-dependent
  • Most affected lobes:
    • Right lower lobe (most common)
    • If supine: posterior upper/lower lobes
    • If upright: basal lower lobes, right middle lobe, lingula
CT Chest
  • More sensitive than CXR
  • Common findings:
    • Tree-in-bud nodules (airway impaction)
    • Ground-glass opacities
    • Consolidation ± atelectasis
    • Airway plugging

Management

Aspiration Pneumonitis
ActionDetails
AirwayClear oropharynx; suction
OxygenationNP/mask/rebreather; intubation if hypoxic or unable to protect
AntibioticsNot routinely required unless severe/unwell/aspirated food

If uncertain, err on the side of treating with antibiotics due to high risk of secondary infection (~25%).

Aspiration Pneumonia
ActionDetails
OxygenationAs above
AntibioticsRequired

Empirical regime:

  • Ceftriaxone + Metronidazole
    • Particularly if periodontal disease, putrid sputum, necrotising pneumonia, or abscess
Steroids
  • No proven benefit in either pneumonitis or pneumonia

Appendix 1

aspiration pneumonia
Anteroposterior Radiograph of the Chest, Showing
Air-Space Consolidation (Arrows) in the Right Lower Lobe in a
Patient Who Had Recently Had a Thrombotic Stroke. NEJM

References

FOAMed

Resources

Fellowship Notes

Dr James Hayes LITFL Author Medical Educator

Educator, magister, munus exemplar, dicata in agro subitis medicina et discrimine cura | FFS |

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