Show Summary Details
Page of

Lower airway samples 

Lower airway samples
Chapter:
Lower airway samples
Author(s):

Jeremy Hull

, Julian Forton

, and Anne Thomson

DOI:
10.1093/med/9780199687060.003.0068
Page of

PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2016. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

Subscriber: null; date: 23 October 2019

Induced sputum

  • This method is used for collecting lower airway secretions, both for the identification of infection and for assessing the cellular content. It is generally used when children are unable to spontaneously expectorate sputum. Although it is more commonly used in adults and older compliant children, it can be used in infants.

  • Ideally, the child will brush their teeth and rinse out their mouth prior to the procedure to minimize upper respiratory tract contamination.

  • Salbutamol (five puffs via a spacer) is given to minimize bronchoconstriction.

  • Hypertonic saline (3–7%) is given, either with a jet or an ultrasonic nebulizer, using a face mask or mouthpiece, to induce coughing. Typically, the nebulization is continued for 15–20 min. Cooperative children can be encouraged to cough and to expectorate sputum into a specimen pot. For infants, a session of physiotherapy is carried out, using chest percussion, and sputum is then collected from the nasopharynx by suctioning.

  • The expectorate can be analysed for cell counts, soluble mediators, and for pathogens by PCR and culture.

Non-bronchoscopic lavage

  • Non-bronchoscopic BAL is generally used in intubated patients to collect lower respiratory secretions for culture or cytology. It is usually performed in acutely unwell patients on paediatric ICU but may be performed under short elective anaesthesia.

  • Sterile technique should be used.

  • If the child is lightly sedated or anaesthetized, 1 mL of 1% lignocaine is instilled into the trachea via the ETT to minimize coughing.

  • Pre-oxygenation with high inspired oxygen concentrations for a few minutes will reduce any desaturation in children with unstable lung disease.

  • An 8 F end-hole suction catheter is passed through the ETT, until a wedge in a small airway is established. This is likely to be in the right lower lobe. It is important to use appropriate end-hole catheters. Side-hole catheters will not work, and cutting these catheters to produce a single end-hole will leave sharp edges that will damage the airway.

  • A volume of 1 mL/kg of normal saline is instilled into the suction catheter, followed by 5 mL of air, to clear the tube of fluid. The fluid can then either be aspirated using wall suction into a suction trap (usually via a 3-way tap) over 10–20 s, using negative pressures of 100–150 mmHg, or aspirated back into the syringe. The procedure is repeated to collect three sequential samples that are analysed separately. For more details on BAL fluid analysis, see Lower airway samples Chapter 64.

Early morning gastric aspirates

  • Infants and young children do not expectorate respiratory secretions and tend to swallow them instead. Aspiration or lavage of the gastric contents is the best approach to obtaining respiratory secretions for culture. Early morning gastric aspirates or lavage taken before gastric emptying are favoured, as the sample taken will represent an accumulation of secretions from overnight.

  • The procedure is performed principally for MTB culture. Children with primary tuberculous chest disease produce few organisms, and sampling accumulated secretions increases the likelihood of obtaining organisms for culture. The use of induced sputum is an alternative.

  • An NG tube should be passed. The child should be kept nil by mouth on waking up in the morning. Overnight feeds in infants should be omitted. Before the child gets out of bed, and ideally shortly after waking, gastric contents are aspirated via the NG tube. If <5 mL can be aspirated, 10–20 mL of sterile water is instilled and re-aspirated. Specimens should be delivered immediately to the laboratory for Ziehl–Neelsen staining and culture.

Further information

Zar HJ, Hanslo D, Apolles P, Swingler G, Hussey G (2005). Induced sputum versus gastric lavage for microbiological confirmation of pulmonary tuberculosis in infants and young children: a prospective study. Lancet 365, 130–4.Find this resource: