Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Aspiration pneumonitis and aspiration pneumonia
Respiratory · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
!
Time-critical presentation
Witnessed large-volume aspiration with hypoxaemia, bronchospasm, airway obstruction, shock or reduced consciousness requires immediate airway and critical-care assessment. Suction visible material, support oxygenation and ventilation, but do not perform blind airway sweeps or give automatic antibiotics for chemical pneumonitis.
Overview
Separate sterile chemical aspiration pneumonitis from bacterial aspiration pneumonia, stabilise acute lung injury, treat infection proportionately, and reduce recurrence through swallowing, oral-care and person-centred feeding decisions.
Aspiration describes material crossing below the vocal cords, but its consequences vary. Acid and particulate matter can cause abrupt sterile alveolar injury, bronchospasm and hypoxaemia. Repeated microaspiration of colonised oropharyngeal material, particularly with dysphagia and impaired cough, can produce bacterial pneumonia. Both may coexist, and the initial label should be revisited as the trajectory becomes clear.
Older adults, people with neurological or learning disability, head and neck disease, reduced consciousness and dependence for feeding may present without fever or marked leucocytosis. Management must include the cause of aspiration. Texture modification, tube feeding or stopping oral intake has burdens and imperfect evidence, so capacity, consent, nutrition, hydration and goals of care belong in the decision.
Key points
Practice
Two practice questions
Your practice draft is saved in this browser.
Question 1 of 2
0 correct
RespiratoryOriginal SBA
Witnessed aspiration
A postoperative adult vomits while drowsy and develops immediate hypoxaemia and bilateral dependent shadowing. There was no preceding infection. What is the best initial antimicrobial decision?
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Aspiration pneumonitis is an acute chemical injury, often after witnessed large-volume gastric aspiration in a person with
reduced consciousness
; aspiration pneumonia is infection after aspiration of bacteria-rich secretions.
The distinction is temporal and clinical, not established by procalcitonin: pneumonitis can improve over 24–48 hours with support, whereas persistent or later fever and deterioration suggest secondary infection.
Assess swallowing impairment, consciousness, neurological disease, frailty, reflux, dentition, sedative medicines, feeding dependence and the patient's baseline communication and goals.
Chest radiography can miss aspiration pneumonia; CT is appropriate when the film is inconclusive and the diagnosis or a complication remains important.
Do not give prophylactic antibiotics after uncomplicated chemical aspiration. Treat established aspiration pneumonia using local microbiology guidance; co-amoxiclav is a reasonable common initial choice.
Routine extra anaerobic cover is not recommended; include it when putrid sputum, severe dental disease, lung abscess or empyema makes anaerobic infection credible.
BTS suggests five total days when aspiration pneumonia is improving clinically, with IV-to-oral switch only when swallowing and absorption are safe.
Prevent recurrence with speech and language therapy assessment, twice-daily tooth/tongue/palate brushing, medication review, positioning and individualised feeding decisions; tubes do not eliminate aspiration.
Aetiology
01
Impaired consciousness
Seizure, intoxication, anaesthesia, stroke or severe illness weakens airway protection and permits gastric contents to enter the lower respiratory tract.
02
Swallowing dysfunction
Neurological disease, frailty, oesophageal disorders and head or neck pathology cause recurrent microaspiration of saliva, food or refluxed material.
03
High gastric burden
Vomiting, bowel obstruction, reflux and enteral feeding increase the volume or acidity available for a witnessed macroaspiration event.
04
Oral microbial burden
Poor dentition and oral hygiene increase the bacterial inoculum aspirated into dependent lung, particularly in dependent or institutional care.
Pathophysiology
1
Material enters distal lung
Failure of airway protection delivers acidic gastric contents, food particles or colonised oropharyngeal secretions into dependent bronchopulmonary segments.
2
Chemical injury
Acid and particulate material directly damage epithelium, provoking rapid sterile inflammation, capillary leak and bronchospasm in aspiration pneumonitis.
3
Bacterial infection
Aspirated colonised secretions may establish pneumonia, especially when clearance is impaired, with a more evolving infective syndrome.
4
Impaired gas exchange
Inflamed, collapsed or consolidated alveoli create ventilation-perfusion mismatch and can progress to diffuse acute lung injury.
Clinical features and red flags
Chemical pneumonitisRed flag
Abrupt cough, wheeze, hypoxaemia and bilateral or dependent infiltrates within hours of a witnessed large gastric aspiration, usually during reduced consciousness, anaesthesia or vomiting.
Aspiration pneumonia
Subacute fever, cough, breathlessness, delirium or functional decline in a person with dysphagia or impaired airway protection, often with dependent focal consolidation.
Silent aspiration
Recurrent chest infection, wet voice, coughing with meals, weight loss or unexplained oxygen desaturation may occur without a remembered choking event; absence of cough does not exclude aspiration.
Airway obstruction or severe lung injuryRed flag
Stridor, unilateral absent air entry, visible particulate material, escalating oxygen need, shock or reduced consciousness requires immediate airway and critical-care help.
Complicated infectionRed flag
Putrid sputum, persistent sepsis, cavitation or pleural fluid suggests anaerobic infection, lung abscess or empyema and changes both duration and source control.
Investigations
01Witness and swallowing historyFirst step
Why
Distinguish abrupt chemical aspiration from infective microaspiration and identify recurrence risks.
Interpretation and limitations
Record timing, volume, consciousness, vomiting, feeding, cough effectiveness, sedatives and neurological disease; no single history element is completely sensitive.
02Chest radiograph
Why
Look for dependent consolidation, oedema-like shadowing and complications.
Interpretation and limitations
A normal film does not exclude aspiration pneumonia; BTS notes CT detects some cases missed by radiography. Distribution depends on body position, not invariably the right lower lobe.
03Oxygenation and blood gas
Why
Assess acute lung injury and ventilatory failure.
Interpretation and limitations
Escalating oxygen, hypercapnia, acidosis or fatigue requires critical-care review. Prescribe 94–98% for most or 88–92% when hypercapnic failure risk applies.
04Microbiology and inflammatory tests
Why
Support bacterial diagnosis and narrow therapy in severe or non-responsive infection.
Interpretation and limitations
Obtain sputum and blood cultures when feasible; procalcitonin performs poorly for separating pneumonitis from pneumonia and should not override clinical trajectory.
05
Differential diagnosis
01
Community-acquired pneumonia
Pneumonia without aspiration risk or a compatible event may be ordinary community infection; anatomical distribution alone cannot prove aspiration.
02
Cardiogenic pulmonary oedema
Rapid hypoxaemia and bilateral opacities overlap with chemical pneumonitis, but cardiac findings and hydrostatic congestion favour oedema.
03
Pulmonary embolism
Sudden dyspnoea, hypoxaemia and fever can follow embolism; thromboembolic risk and probability-led imaging discriminate when aspiration evidence is weak.
04
Inhaled foreign body
Focal wheeze, unilateral collapse or a choking episode suggests retained solid material requiring airway evaluation rather than aspiration syndrome alone.
05
Acute respiratory distress syndrome
Diffuse permeability injury may be a complication of aspiration or arise from another insult; the syndrome requires its broader clinical framework.
Management
01ImmediateManage witnessed macroaspirationFirst stepAbrupt respiratory deterioration during vomiting, feeding, anaesthesia or reduced consciousness.+
1Call for airway help, position safely, suction visible oral or tracheal material, provide target-based oxygen and support ventilation; bronchoscopy is considered for persistent large particulate obstruction, not routine lavage.
2Assess severity with observations and gas exchange, obtain imaging when stable, and treat bronchospasm or shock through the appropriate acute pathway.
3Withhold prophylactic antibiotics when the presentation is uncomplicated chemical pneumonitis; reassess closely over 24–48 hours for improvement or emerging bacterial infection.
02InfectionTreat aspiration pneumoniaPersistent or progressive infective syndrome with compatible aspiration risk and imaging.+
Complications
01
Acute respiratory failure
Extensive chemical inflammation or consolidation can cause severe hypoxaemia, fatigue and need for ventilatory support, and potentially prolonging treatment and functional recovery.
02
Acute respiratory distress syndrome
Widespread epithelial and endothelial injury may produce non-cardiogenic alveolar oedema, shunt and prolonged critical illness, with severity determined by its extent and the patient's underlying reserve.
03
Lung abscess
Necrotising infection after aspiration can cavitate, particularly with poor dentition, delayed clearance or an obstructed bronchus.
04
Empyema
Infection may extend through the visceral pleura into a loculated infected effusion requiring drainage, creating an additional need for recognition and targeted treatment.
05
Recurrent aspiration
Uncorrected swallowing, consciousness or feeding problems lead to repeated inflammation, bronchiectasis, malnutrition and further admissions, creating an additional need for recognition and targeted treatment.
Monitoring and follow-up
Trend oxygen requirement, respiratory rate, temperature, haemodynamics, consciousness and cough effectiveness during the first 24–48 hours.
A rapidly improving course without bacterial features supports pneumonitis and avoidance of antibiotics; later fever or deterioration warrants reassessment for secondary pneumonia.
If antibiotics are used, review cultures, route and spectrum at 48 hours and consider stopping after five days when clinically stable.
Monitor oral intake, hydration, weight and adherence to the agreed swallow plan; texture changes can reduce fluid and calorie intake.
Audit mouth care, positioning and medication changes with carers because prevention fails when recommendations are not practical in the person's setting.
Special situations
Pneumonitis is not early pneumonia
Both can cause fever, leucocytosis and infiltrates. A witnessed high-volume event with abrupt hypoxaemia and early improvement favours chemical injury; antibiotics do not neutralise acid.
Procalcitonin cannot settle it
BTS found poor performance for distinguishing aspiration pneumonia from non-infective pneumonitis in critically ill patients, so trajectory and context remain central.
Feeding tubes do not abolish risk
Reflux, saliva and colonised secretions can still be aspirated, and enteral feeding may increase cephalad reflux. Route decisions require benefits, burdens and goals.
Anaerobes are selective
Routine additional anaerobic cover is unnecessary, but putrid sputum, major periodontal disease, abscess and empyema are meaningful exceptions.
Prevention includes the mouth
Regular mechanical cleaning reduces bacterial burden. Foam swabs do not clean teeth effectively and can themselves create an aspiration hazard.
Common pitfalls
01
Giving antibiotics automatically after every witnessed aspiration event.
02
Using a normal chest radiograph to exclude aspiration pneumonia in a high-risk patient.
03
Keeping a person nil by mouth indefinitely without multidisciplinary review of nutrition, hydration, capacity and goals.
04
Adding metronidazole routinely despite no abscess, empyema, putrid sputum or severe dental disease.
05
Assuming a feeding tube prevents aspiration of saliva or refluxed gastric contents.
Swallow assessment
Why
Define a safer feeding plan and the mechanism of recurrent aspiration.
Interpretation and limitations
Start with bedside speech and language therapy assessment; videofluoroscopy or fibreoptic endoscopic evaluation can demonstrate aspiration but one negative study cannot exclude episodic events.
1
Take appropriate cultures without delaying treatment, then select an oral or IV antibiotic through current local microbiology guidance, commonly an amoxicillin-based or co-amoxiclav regimen.
2Do not add anaerobic therapy routinely; ensure anaerobic activity for putrid sputum, severe periodontal disease, abscess or empyema and seek infection advice for severe disease.
3Switch IV to oral only when the patient is improving and can swallow or receive medication safely; if stable, complete five total days, extending only for complications or slow response.
03PreventionReduce the next aspirationAny suspected aspiration pneumonia or recurrent aspiration event.+
1Request speech and language therapy review, assess cough and positioning, and agree texture or route changes with dietetics, the person and carers rather than imposing indefinite nil by mouth.
2Provide oral examination and twice-daily brushing of teeth, tongue and palate with a soft toothbrush and non-foaming toothpaste; treat dental disease and oral candidiasis.
3Review sedatives, antipsychotics, opioids, anticholinergic burden, reflux and feeding technique; document capacity, best interests and palliative goals where decisions carry major burdens.
04Non-responseReopen the diagnosisNo clinical improvement or deterioration despite initial management.+
1Check whether this is oedema, pulmonary embolism, ARDS, airway obstruction or another infection rather than simply broadening antibiotics.
2Review microbiology and obtain CT or pleural ultrasound to identify abscess, empyema or an obstructing lesion.
3EscalationEscalate to respiratory, infection, critical-care and swallowing teams as indicated; source-control complications need procedural treatment.
Key medicines and prescribing safety3 treatments · regimens, roles and cautions+
Covers common aerobic oral and enteric organisms and provides anaerobic activity when aspiration pneumonia is established.
Co-amoxiclav for aspiration pneumonia
A typical community oral regimen is 500/125 mg three times daily for 5 days; use the locally approved IV regimen when severe or swallowing is unsafe.
Do not prescribe for isolated chemical pneumonitis. Check penicillin allergy, renal function and hepatic history, then narrow from cultures and extend only for documented complication.
Provides treatment when a beta-lactam is unsafe, with spectrum chosen for severity and local resistance.
Alternative in immediate penicillin allergy
Select a fluoroquinolone, macrolide, tetracycline or other local alternative at its current BNF dose after microbiology and patient-specific review.
Fluoroquinolones have disabling adverse-effect warnings, QT and interaction risks; doxycycline is unsuitable in pregnancy. Add metronidazole only if anaerobic risk is high and the chosen agent lacks activity.
Treats hypoxaemia during pneumonitis or pneumonia while the airway and lung injury are managed.
Medical oxygen
Titrate to SpO2 94–98% for most adults or 88–92% in those at risk of hypercapnic respiratory failure, with urgent blood gases when indicated.
Oxygen does not remove aspirated material or treat infection. Repeat gases after changes in people at hypercapnic risk and escalate ventilatory support when tiring.