Bronchoalveolar Lavage and Protected Specimen Bronchial Brushing

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W14 Bronchoalveolar Lavage and Protected Specimen Bronchial Brushing

Lillian L. Emlet

image Before Procedure

Indications

• Diagnosis of pneumonia:

• Viral, bacterial, fungal, mycobacterial, Pneumocystis carinii pneumonias
• Quantitative cultures for ventilator-associated pneumonias
• Infiltrates in an immunocompromised host

• Evaluation of diffuse lung infiltrates
• Suspected pulmonary hemorrhage
• Suspected malignancies
• Both bronchoalveolar lavage (BAL) and protected specimen bronchial brushing (PSB) use quantitative culture techniques to differentiate between airway colonization and true pulmonary infection.6,15

Contraindications

• Acute respiratory distress syndrome with hypoxemia

• May cause de-recruitment of noncompliant severe air space disease
• Watch for cardiac arrhythmias, hypoxemia, bronchospasm.

• Bronchopleural fistula

• May not be able to return adequate specimen for analysis

Equipment

• Flexible fiberoptic bronchoscope
• Sterile saline
• Vacuum suction source
• Suction tubing
• Syringes: 10 mL, 20 mL, or 60 mL slip-tip
• Sterile collection trap
• Lidocaine, 1% to 2% for topical anesthesia if needed
• Procedural conscious sedation medications if needed
• Burman airway or oral airway
• Supplemental oxygen
• Endotracheal bronchoscope attachment

image Anatomy

• If performed on native airway, first structure identified is epiglottis and vocal cords.
• Next landmark is trachea and identification of the carina.
• Right and left main bronchi are identified, and location of desired BAL specimen is obtained by identification of majority of purulent material or by correlation to side on chest x-ray where greatest infiltrate exists.10
• If there is a question of which lobe is to be sampled, the posterior portion of the right lower lobe should be sampled first. Autopsy studies indicate that pneumonia in intensive care unit (ICU) patients often involve this lobe.16,23–25
• To obtain the BAL, the bronchoscope is advanced to the farthest segment of the affected bronchus until it cannot advance any farther.

image Procedure: Bronchoalveolar Lavage

• Obtain informed consent, including process for topical anesthesia of airways and/or conscious sedation.
• Prepare for conscious sedation and monitoring with telemetry monitoring, continuous pulse oximetry, intermittent blood pressure cuff measurement, and supplemental oxygen (via nasal cannula or nonrebreather mask or ventilator).
• Prepare with bronchodilators for patients at risk of bronchospasm, and topicalize airways with 2% lidocaine via atomizer.
• Review chest radiograph to identify ideal location of BAL. Right middle lobe or lingual preferred in supine patient, with also right lower lobe for most direct path of aspiration.
• Prepare bronchoscope, collection trap, tubing, and sterile saline.
• Anesthetize vocal cords in nonintubated patients and carina in intubated patients with 2% lidocaine (5 mg/kg maximum).
• Avoid suctioning prior to obtaining BAL specimen to avoid specimen contamination.
• Advance bronchoscope until wedged in desired subsegmental bronchus.
• Flush 20 mL sterile saline, watching flow of saline into distal airways and blanching of tissues.
• Obtain sample immediately after wash, watching for return of lavage specimen into collection trap.
• Slight repositioning of bronchoscope tip can allow better fluid return.
• Intermittent pulsing of suctioning can reduce distal airway collapse.
• Repeat 20 mL sterile saline wash as necessary to obtain adequate sample (usually 30-50 mL, which is usually 40% to 70% recovery of total instilled volume).
• Higher aliquots can be used (usually 120 mL in 3-6 aliquots).10,11

• Estimated alveolar surface area distal to the wedged bronchoscope is 100 times greater than the peripheral airway.
• Fluid return of the BAL can affect the validity of results, and small returns may contain only diluted material from the bronchus rather than the alveoli, resulting in false negatives.12

• Patients with highly collapsible airways, including chronic obstructive pulmonary disease (COPD) patients; amount of negative pressure applied via the bronchoscope to aspirate sample can limit the amount of sample returned and may give rise to a false-negative result.
• Sensitivity of BAL is 73% and specificity is 82%41

image Procedure: Protected Specimen Bronchial Brushing

• Same as bronchoalveolar lavage except use of an endobronchial catheter wedged in the tracheobronchial tree
• The brush is rubbed against areas of infection and then removed from the procedure port of the bronchoscope.
• The brush is then aseptically cut into a measured volume of sterile diluent (usually 1 mL of sterile saline).7,11
• Double-lumen catheter brush system with distal occluding plug or single-sheathed or telescoping plugged catheter tips7–9
• Quantitative cutoff is 103 colony-forming units per milliliter (CFU/mL)
• Sensitivity of PSB 89% (95% confidence interval [CI], 87%-93%) and specificity 94% (95% CI, 92%-97%).39,40

image After Procedure

Postprocedure Care

• Observation of patients until fully recovered from conscious sedation, with continuous monitoring
• Ventilated patients are placed on 100% FIO2 during procedure and weaned back to prior FIO2 as tolerated. Derecruitment is possible and may require recruitment maneuvers.
• Specimen handling:

• For PSB, the brush should be aseptically cut into 1 mL of sterile saline.7,11
• For BAL, the specimen container should be sent for analysis within 30 minutes, although refrigeration can prolong transport and analysis.13,14

• Specimen should be obtained before new antibiotics are administered.

• Even a few doses of antibiotics can negate microbiological cultures.
• Quantitative culture techniques of distal pulmonary secretions with minimal or no upper airway contamination6,15
• BAL and PSB culture sensitivities are lowered if antibiotic therapy has already been initiated.50,52,53

• These techniques do not retrospectively identify resolving pneumonia or assess the adequacy of therapy.25,33,54–56

Complications

• Common:

• Cough
• Transient infiltrates that typically resolve in 24 hours
• Transient decrease in PaO2

• Infrequent:

• Transient fever, chills, myalgias

• Serious, rare complications:

• Derecruitment and hypoxemia resulting in intubation and positive pressure ventilation or increase in ventilator requirements

image Outcomes and Evidence

• Quantitative culture techniques are necessary to differentiate infecting organisms from pharyngeal contaminants.1–5

• Significant BAL culture concentrates are at least 105 to 106 CFU/mL.15–20
• Significant PSB culture concentrates are at least 103 bacteria.11
• A small number of false-positive BAL and PSB results can be seen even when using strict criteria to distinguish between airway colonization and deep lung infection of 103 to 104 CFU/mL.57
• False-negative BAL and PSB results occur when:

• Bronchoscopy is performed at an early stage of infection, and bacterial load is not high enough to reach diagnostic significance.
• Specimens are obtained from unaffected segments of lung.
• Specimen processing errors occur.
• Specimens are obtained after initiation of a new class of antibiotics.
• Consider repeat sampling for persistently symptomatic patients with initial negative quantitative concentrations.61

Suggested Reading

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3 Croce MA, Fabian TC, Waddle-Smith L, et al. Utility of Gram’s stain and efficacy of quantitative cultures for posttraumatic pneumonia: A prospective study. Ann Surg. 1998;227:743-751. discussion 751-754

4 Bonten MJ, Bergmans DC, Stobberingh EE, et al. Implementation of bronchoscopic techniques in the diagnosis of ventilator-associated pneumonia to reduce antibiotic use. Am J Respir Crit Care Med. 1997;156:1820-1824.

5 Rello J, Gallego M, Mariscal D, et al. The value of routine microbial investigation in ventilator-associated pneumonia. Am J Respir Crit Care Med. 1997;156:196-200.

6 Niederman MS, Torres A, Summer W. Invasive diagnostic testing is not needed routinely to manage suspected ventilator-associated pneumonia. Am J Respir Crit Care Med. 1994;150:565-569.

7 Wimberley N, Faling LJ, Bartlett JG. A fiberoptic bronchoscopy technique to obtain uncontaminated lower airway secretions for bacterial culture. Am Rev Respir Dis. 1979;119:337-343.

8 Pham LH, Brun-Buisson C, Legrand P, et al. Diagnosis of nosocomial pneumonia in mechanically ventilated patients: Comparison of a plugged telescoping catheter with the protected specimen brush. Am Rev Respir Dis. 1991;143:1055-1061.

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48 Veber B, Souweine B, Gachot B, et al. Comparison of direct examination of three types of bronchoscopy specimens used to diagnose nosocomial pneumonia. Crit Care Med. 2000;28:962-968.

49 Timsit JF, Cheval C, Gachot B, et al. Usefulness of a strategy based on bronchoscopy with direct examination of bronchoalveolar lavage fluid in the initial antibiotic therapy of suspected ventilator-associated pneumonia. Intensive Care Med. 2001;27:640-647.

50 Montravers P, Fagon JY, Chastre J, et al. Follow-up protected specimen brushes to assess treatment in nosocomial pneumonia. Am Rev Respir Dis. 1993;147:38-44.

51 Timsit JF, Misset B, Renaud B, et al. Effect of previous antimicrobial therapy on the accuracy of the main procedures used to diagnose nosocomial pneumonia in patients who are using ventilation. Chest. 1995;108:1036-1040.

52 Souweine B, Veber B, Bedos JP, et al. Diagnostic accuracy of protected specimen brush and bronchoalveolar lavage in nosocomial pneumonia: Impact of previous antimicrobial treatments. Crit Care Med. 1998;26:236-244. (see comments)

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