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← Respiratory indexChapter sections
Purpose and principlesIndications, selection and cautionsMethod and interpretationClinical next stepsProcedure and medicine safetyRisks, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Bronchoscopy, sputum studies and respiratory microbiology

Respiratory · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Time-critical presentation

Stabilise hypoxaemia, major haemoptysis, severe bronchospasm, tension pneumothorax, sepsis and threatened airway obstruction before pursuing a diagnostic specimen. During or after bronchoscopy, new respiratory distress, chest pain, haemodynamic instability, substantial bleeding or reduced consciousness requires immediate ABCDE assessment, senior endoscopy support and the locally rehearsed complication pathway.

Purpose and principles

Choose and handle respiratory samples intelligently, understand what bronchoscopy can answer, and translate laboratory results into safe clinical decisions without mistaking detection for disease.

Respiratory microbiology is a chain from bedside question to specimen, transport, laboratory method and clinical interpretation. Failure at any link can produce a confident-looking but misleading answer. A purulent sample from a patient with bronchiectasis may reflect chronic airway colonisation, whereas the same organism in a new lobar pneumonia with systemic illness may be causative. Conversely, antibiotics, low organism burden and poor sampling can make a true infection culture-negative.

Flexible bronchoscopy is not a single test. Inspection can identify tumour, bleeding, foreign material or airway distortion; washing samples airway secretions; bronchoalveolar lavage samples a defined distal segment; brushing and biopsy obtain cellular or tissue material. The clinician should specify the target, anticipated specimens and required containers before starting, because histology, cytology, routine bacteriology, mycobacterial culture, fungal studies and flow cytometry are not interchangeable.

Indications, selection and cautions

Sample-dependent lower respiratory infectionRed flag

Severe pneumonia, treatment failure, immunosuppression, unusual exposure, cavitation or recurrent infection makes microbiological definition more valuable. Ask what organism class matters and collect the least invasive high-quality sample that can answer it.

Possible pulmonary tuberculosisRed flag

Chronic cough, weight loss, fever, night sweats, haemoptysis, compatible imaging or epidemiological risk should trigger the local TB pathway, appropriate respiratory precautions and specifically labelled mycobacterial specimens rather than ordinary bacterial culture alone.

Focal lesion requiring tissue

An endobronchial abnormality, central mass, unexplained collapse or suspicious lymphadenopathy may require bronchoscopy, biopsy or EBUS-directed nodal sampling after CT-based planning. Cytology alone may not provide architecture or molecular material.

Diffuse or opportunistic processRed flag

Diffuse infiltrates in an immunocompromised patient may justify early specialist bronchoalveolar lavage for bacterial, viral, fungal or pneumocystis testing, balanced against oxygenation, bleeding risk and whether a safer sample is available.

Post-bronchoscopy complicationRed flag

New hypoxaemia, wheeze, haemoptysis, pleuritic pain, fever, hypotension or reduced consciousness can represent bronchospasm, bleeding, pneumothorax, sedation toxicity or infection. Assess immediately rather than dismissing symptoms as expected recovery.

Method and interpretation

  1. 01
    Fresh sputum microscopy, culture and susceptibilityFirst step
    Why
    Identify plausible bacterial pathogens and guide narrower treatment.
    Interpretation and limitations
    Judge epithelial contamination, inflammatory cells, organism burden, prior antibiotics and clinical syndrome. Growth may represent colonisation, especially in structurally abnormal airways; susceptibility supports drug selection but does not prove causation.
  2. 02
    Mycobacterial smear, nucleic-acid testing and culture
    Why
    Investigate suspected tuberculosis or non-tuberculous mycobacterial disease.
    Interpretation and limitations
    Request the dedicated pathway and serial respiratory samples as advised locally. Smear informs bacillary burden but is not species-specific; molecular tests can accelerate identification and selected resistance information, while culture remains important for confirmation and susceptibility.
  3. 03
    Chest CT with airway and lesion review
    Why
    Define the target and safest diagnostic sampling strategy.
    Interpretation and limitations
    Map a focal lesion, lymph nodes, cavitation, bronchiectasis, mucus plugging or diffuse pattern before invasive sampling. Imaging can redirect sampling to sputum, pleural fluid, percutaneous biopsy, EBUS or another higher-yield route.
  4. 04
    Bronchial washing or bronchoalveolar lavage
    Why
    Sample airway secretions or a selected distal lung segment.

Clinical next steps

01SputumObtain an interpretable respiratory sampleFirst stepA lower respiratory infection question where microbiology could change management.+
  1. 1Define the syndrome and request: routine bacterial culture, mycobacteria, fungi, viral testing or cytology need distinct instructions and sometimes different containers.
  2. 2Before antimicrobials when clinically safe, ask the patient to rinse the mouth, take deep breaths and expectorate lower-airway sputum directly into a labelled sterile pot.
  3. 3Record site, time, current antimicrobials, immune status and key exposures; transport promptly according to the receiving laboratory handbook.
  4. 4When the report returns, review sample quality and whether the organism fits the illness before narrowing, stopping or changing therapy with local guidance.
02BronchoscopyPlan an answer-focused bronchoscopyNon-invasive testing is insufficient and an invasive result is likely to alter care.+

Procedure and medicine safety

Suppress airway sensation and cough to permit safe examination and sampling.

Topical lidocaine for flexible bronchoscopy

Use the lowest effective topical dose by the locally approved bronchoscopy protocol, recording cumulative administration throughout the procedure.

Dose limits vary with formulation and patient factors; calculate all routes cumulatively. Toxicity can cause neurological symptoms, arrhythmia or cardiovascular collapse, and topical anaesthesia does not replace careful sedation monitoring.

Provide conscious sedation and anxiolysis while retaining purposeful response and ventilation.

Titrated intravenous midazolam procedural sedation

Give incremental intravenous doses only by trained staff under the current local sedation protocol, using less in frailty or respiratory vulnerability.

Respiratory depression, hypotension and prolonged sedation are more likely with opioids, older age and organ impairment. Continuous observation, oxygenation monitoring, airway skills and immediate access to reversal and resuscitation equipment are essential.

Reverse excessive benzodiazepine sedation while airway and ventilation are actively supported.

Flumazenil for clinically important benzodiazepine effect

Administer titrated intravenous reversal according to the local emergency medicines protocol when benzodiazepine sedation is causing clinically significant compromise.

Its effect may wear off before the sedative, so recurrent depression requires observation and sometimes repeat treatment. Seizures can occur in dependent patients or mixed overdose; it is not a substitute for airway management.

Risks, monitoring and follow-up

  • During bronchoscopy record consciousness, respiratory rate, oxygen saturation, pulse and blood pressure at locally specified intervals, with ECG and capnography according to risk and policy.
  • After bronchoscopy confirm stable physiology, adequate ventilation, recovery from sedation, controlled pain or bleeding and an appropriate escort and discharge plan before transfer.
  • Track every specimen to a named clinician and review date, including late mycobacterial, fungal, cytological and histological reports after the initial bacterial result.
  • For treated infection, monitor clinical trajectory, oxygen requirement, inflammatory response and antimicrobial toxicity rather than using culture clearance as the only endpoint.
  • Reconcile positive results with previous microbiology and imaging; repeated isolation of the same organism may signal chronic airway disease requiring specialist review rather than serial empirical antibiotics.

Special situations

The request determines the test

Writing only 'culture' can miss mycobacteria, fungi, viruses or cytology. State the syndrome and suspected organism class, and contact the laboratory before collecting unusual or high-risk samples.

Anatomical labelling changes meaning

A BAL from a radiologically involved segment is not equivalent to pooled secretions. Record the exact bronchial segment so a positive or negative result can be reconciled with imaging.

Detection is not invasion

Sensitive molecular methods can detect nucleic acid from organisms that are colonising or no longer viable. Clinical syndrome, sample type, burden and host response remain essential.

Tissue adequacy is strategic

Modern cancer care may require morphology, immunohistochemistry and molecular testing. A small diagnostic sample can still be inadequate for treatment selection, so plan acquisition with the downstream question in mind.

Negative tests revise probability

A negative result is most reassuring when the correct lesion was sampled with an appropriate method before treatment. Otherwise it may mainly document a sampling limitation.

Common pitfalls

  1. 01

    Sending saliva as sputum and treating any cultured organism as the cause of pneumonia.

  2. 02

    Failing to request mycobacterial or fungal testing because routine bacterial culture was ordered.

  3. 03

    Performing bronchoscopy without first deciding what result would change management or whether CT suggests a safer route.

  4. 04

    Applying one antithrombotic interruption rule to lavage, brushing, endobronchial biopsy and transbronchial biopsy despite different bleeding risks.

  5. 05

    Calling a non-diagnostic biopsy benign without reconciling specimen adequacy and radiological pre-test probability.

  6. 06

    Losing ownership of delayed culture, susceptibility, cytology or histology results after the patient leaves the procedure unit.

Practice

Two practice questions

Your practice draft is saved in this browser.

Question 1 of 2
0 correct
RespiratoryOriginal SBA

Interpreting a sputum isolate

A clinically stable adult with established bronchiectasis submits sputum during a mild increase in cough. Culture grows an organism also present in several previous stable samples. What is the best interpretation and next step?

Choose one answer, then submit
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Sources and review status5 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.

  • BTS Flexible bronchoscopy quality standardsProcedure governance, consent, safety and quality standards.
  • BTS Bronchoscopy and pleural procedure safety standardsNational safety-standard framework for invasive respiratory procedures.
  • UKHSA Standards for microbiology investigationsNational laboratory algorithms and specimen-processing principles.
  • NICE NG122 Lung cancer diagnosis and stagingCT-led selection of diagnostic and staging investigations.
  • NICE NG250 Pneumonia recommendationsCurrent national principles for microbiological testing and antimicrobial review.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

UK antimicrobial choices depend on syndrome, severity, local resistance, allergy, renal function and microbiology advice. Stable national principles are to sample promptly where useful, treat immediately when delay is dangerous, review at the earliest reliable result, narrow or stop therapy when appropriate, and follow separate infection-control and notification pathways for diseases such as suspected pulmonary tuberculosis.

Key points

  • Begin with a clinical question: routine bacterial culture, tuberculosis or non-tuberculous mycobacteria, fungal disease, viral infection, cytology, diffuse lung disease or an endobronchial lesion require different samples and laboratory handling.
  • Collect sputum before antimicrobials when this is safe, but never delay treatment of severe infection merely to obtain a perfect sample.
  • A good lower-respiratory specimen is freshly expectorated after mouth rinsing into the correct sterile container; saliva and delayed transport reduce interpretability.
  • Microscopy, culture and susceptibility must be interpreted beside sample quality, prior antibiotics, airway disease, immune status and the distinction between colonisation and invasive infection.
  • Bronchoscopy permits airway inspection, bronchial washing, bronchoalveolar lavage, brushing and biopsy; each has a different diagnostic yield and risk profile.
  • CT should usually define the target and the least invasive useful sampling route before bronchoscopy for suspected malignancy or focal disease.
  • Negative sputum or bronchoscopy results do not exclude malignancy, tuberculosis or infection when pre-test probability remains high; review whether the correct site and tests were sampled.
  • Request mycobacterial or fungal studies explicitly and alert the laboratory to unusual exposures, immunosuppression and high-consequence pathogens because routine culture does not answer every question.
  • Consent covers the intended procedures, sedation plan, alternatives and material risks; use the procedural checklist and verify antithrombotic, allergy and fasting instructions locally.
  • Do not prescribe an antibiotic simply because an organism is reported: decide whether it explains the syndrome, then use local susceptibility and antimicrobial guidance.
Interpretation and limitations
Interpret organism detection with the sampled segment, immune state and method. BAL differential cell counts may support a clinicoradiological diagnosis but are rarely diagnostic alone; lavage is not a substitute for tissue when architecture matters.
  • 05
    Endobronchial brushing, biopsy or EBUS-guided sampling
    Why
    Obtain cellular or tissue material from a defined lesion or node.
    Interpretation and limitations
    Confirm that histology, cytology, microbiology and molecular requirements were communicated before sampling. A non-diagnostic specimen may reflect access or adequacy rather than benign disease and must be reconciled with imaging probability.
  • 06
    Pre-procedure oxygenation, blood count and haemostasis review
    Why
    Estimate procedural and sedation risk before bronchoscopy.
    Interpretation and limitations
    Testing is individualised to procedure and comorbidity rather than ordered reflexively. Review antiplatelets, anticoagulants, platelets, oxygen requirement, ventilation risk, allergies and relevant imaging against local bronchoscopy standards.
    1. 1Review CT, differential diagnosis and alternatives, then agree the airway target and exact specimens with respiratory, radiology, pathology and microbiology teams as needed.
    2. 2Assess fitness, oxygenation, airway and bleeding risk; reconcile antithrombotics and medicines using the local procedure-specific policy rather than a generic interruption rule.
    3. 3Obtain informed consent, complete the safety checklist, confirm personnel and rescue equipment, and use the locally authorised topical anaesthesia and sedation plan.
    4. 4Label each specimen at the bedside with its anatomical site and requested discipline, then document findings, complications, recovery criteria and responsibility for results.
    03Result reviewTranslate detection into a clinical decisionA respiratory culture, molecular result, cytology or biopsy report becomes available.+
    1. 1Verify the specimen type, site, quality, collection timing and tests actually performed before reading the organism or pathology headline.
    2. 2Classify the result as explanatory disease, possible contributor, colonisation or contamination using symptoms, imaging, inflammation, immune state and previous cultures.
    3. 3Act on urgent findings, infection-control duties and critical pathology; use local antimicrobial susceptibility advice and seek microbiology or pathology clarification where discordant.
    4. 4Document treatment, follow-up and outstanding cultures explicitly because mycobacterial and fungal results may mature after discharge or transfer.
    04DeteriorationRespond to bronchoscopy complicationsNew physiological instability during the procedure or recovery period.+
    1. 1Stop the procedure, call for help and perform ABCDE with oxygen, monitoring, suction and airway support appropriate to the clinical problem.
    2. 2Identify likely mechanism: sedation-related hypoventilation, bronchospasm, bleeding, pneumothorax, arrhythmia or another acute event; deploy the rehearsed local emergency pathway.
    3. 3EscalationEscalate to anaesthesia, critical care, interventional radiology or surgery when needed and obtain chest imaging promptly for suspected pneumothorax without delaying lifesaving treatment.
    4. 4Record the event, interventions and post-procedure observation plan, then communicate clearly to the patient and receiving clinical team.
    Authoring stateComplete draft
    Clinical stateAwaiting review
    JurisdictionUnited Kingdom