Its main cause is laryngomalacia,7 which tends to disappear within the first year and therefore does not usually require endoscopic revision, except in the cases of parental anxiety. In the cases of atypical presentation, biphasic character, prolonged persistence, suffocation crisis, eating difficulties, association with syndromes or malformations, history of intubation or diagnosis of severe laryngitis in children under the age of 6 months, a complete exploration is recommended8 as there may be anatomical, congenital or acquired anomalies9 (strong recommendation; high-quality evidence).

The existence of respiratory symptoms and/or recurrent or persistent radiological images can be associated with the presence of an unnoticed foreign body. Under these circumstances, RB has a high rate of false negatives. In contrast, FB has a diagnostic exactitude of 100%. Therefore, if a diagnosis is mistaken, it is recommended to first perform FB10 (strong recommendation; high-quality evidence). Once extracted, FB can be very useful for confirming the absence of residues or of fragmented material, as occurs in the case of nuts.

FB is recommended in cases of difficult-to-control wheezing bronchitis, especially in small children, associated with asymmetries upon auscultation and/or radiological alterations11 as they could be due to a foreign body or structural anomalies of the tracheobronchial wall12 (strong recommendation; high-quality evidence).

Hemoptysis is an uncommon and alarming symptom. In the absence of a known explanation (otorhinolaryngological infections or bronchiectasis), FB is required11 (strong recommendation; high-quality evidence). The most frequent causes are problems related with artificial airways, tracheostomies, primary alveolar hemorrhage, congenital vascular anomalies and infectious or inflammatory endobronchial pathologies, while tumors are the exception.13

Persistence of more than 6 weeks, together with unexplained symptoms, makes FB recommendable14 (weak recommendation; high-quality evidence). The most frequent findings are mucus plugging, foreign bodies, extrinsic compression in cases of congenital cardiopathy,15,16 inflammatory granulation tissue or endobronchial tuberculosis.17,18

Middle lobe syndrome is a relatively frequent entity in pediatrics due to the anatomical characteristics of this bronchus. The observation of bacterial growth, a predominance of neutrophils in the bronchoalveolar lavage and evolution towards bronchiectasis in more than 50% of children with non-atopic wheezing19 has renewed interest in this syndrome.20 It has been proposed that the syndrome, if it cannot be resolved with treatment, indicates a study with FB21 (strong recommendation; high-quality evidence).

When its presence is not associated with congenital or post-infectious causes, localized hyperlucency requires carrying out FB as there may be air trapping due to a valvular mechanism, which is usually secondary to an intrinsic obstruction (foreign body, bronchomalacia,22 granulation tissue) or extrinsic compression due to adenopathies, vessels that are aberrant, anomalous and/or increased in size, or congenital or acquired mediastinal masses23 (strong recommendation; high-quality evidence).

FB is essential for the diagnosis of problems that arise during in/extubation and for monitoring and following patients with tracheostomy25 (strong recommendation; high-quality evidence). The most frequent findings are laryngeal edema, subglottic stenosis and tracheobronchial granulation tissue secondary to trauma caused by endotracheal tubes and cannulae or by repeated aspirations.26

Phonatory abnormalities: abnormal or persistent, aphonic crying can be due to the unilateral paralysis of a vocal cord generally associated with trauma during birth, hydrocephalus or post-operative cardiopathy, juvenile papillomatosis or aspiration during birth. The association with stridor warrants carrying out FB with a complete examination of the airway28 (strong recommendation; high-quality evidence). Other situations indicating FB include: persistent cough without diagnosis by non-invasive techniques (as it may be due to entities such as bacterial malacia or bronchitis.)29 and the evaluation of injury secondary to burns or inhalation of toxic substances.30

FB is widely used in researching lung infiltrates that are unclarified, localized or diffuse, with interstitial, alveolar, miliary or nodular pattern, when diagnosis is not possible by means of other less-invasive methods (strong recommendation; high-quality evidence).

FB can be useful for resolving atelectasis due to the retention of secretions or mucus plugging. The percentage of radiological re-expansion is variable, generally no higher than 50%. In cystic fibrosis31 (weak recommendation; low-quality evidence) or in plastic bronchitis (moderate recommendation; low-quality evidence) endoscopic lavage and aspiration can be indicated together with the instillation of mucolytics32 (MESNA or DNasa).33 In alveolar proteinosis, repeated BAL is the recommended treatment34 (strong recommendation; high-quality evidence).

Bronchoscopy can act as a guideline for intubation in cases of craniofacial anomalies and polymalformative syndromes,35 or in selective bronchial intubation (strong recommendation; high-quality evidence).

Although there are publications that endorse the good performance of FB,36,37 it is usually a complicated procedure in small children. In these patients, RB is preferred as it offers the advantages of general anesthesia, assisted ventilation, larger instruments and a greater variety of accessories38 (strong recommendation; high-quality evidence). The ideal procedure would be to initiate with FB, which allows for greater reach in the exploration and the identification of the foreign body, extraction with RB, and a final revision with FB in order to rule out a residual foreign body.10 In some cases in which the clinical and/or radiological information is conclusive, the procedure may be directly initiated with RB.10

FB can be of use in the peri-operative management of tracheoesophageal fistulas,39 both isolated or recurrent, as it allows for its identification and canalization, facilitating the surgical approach40 (weak recommendation, low-quality evidence). In other techniques such as bronchial permeabilization or the placement of prosthesis, the small size of the FB can be either a complication or an impediment, and therefore RB should be used41 (strong recommendation; high-quality evidence).

These are the most frequent. Compression and/or topical adrenalin are sufficient for its control.

These may be due to causes inherent of the procedure and patient, or to the excess or deficit of sedation. FB increases the resistance of the airway which, together with sedation, can motivate hypoxemia and hypercapnia, which can persist 15–20min after the exploration. BAL and prolonged aspiration maneuvers, mainly in newborns and infants, favor alveolar collapse and increase its risk. Due to vagal irritation, or in children with bronchial hyperreactivity, there may also be some degree of bronchospasm. These changes can attenuated by maintaining a stable hemodynamic situation, choosing instruments of the proper size, previously administering bronchodilators and supplemental oxygen, optimizing the sedation-anesthesia and performing the procedure quickly.42

These may be related with not enough sedation or the instillation of topical anesthesia.

Also related with the choice of bronchoscope of improper size or forcing the way through a stenotic area, causing edema, hypersecretion and greater obstruction.

Aspiration and brushing or biopsies usually cause small transitory hemorrhages facilitated by the existence of granulation tissue, tumors, bronchiectasis or hemorrhagic diathesis. Severe hemorrhage is exceptional, and can be associated with overly vascularized endobronchial lesions, which are rare in children, BAL in patients with coagulation disorders and especially transbronchial biopsy.

In general, hemorrhaging will let up spontaneously in a few minutes, but in cases of severe hemorrhage, lavage with cold physiological saline solution can be of use (5ml aliquots) or with adrenalin at 1/20 000–1ml of adrenalin at 1/1000, diluted in 20ml of physiological saline solution (strong recommendation; low-quality evidence). If the hemorrhage persists, it is recommended to place the patient in lateral decubitus, with the bleeding lung in a declining position, and to insert the bronchoscope in a segmental or subsegmental bronchus, aspirating continuously for 3–5min in order to produce a collapse of the distal bronchial walls (strong recommendation; low-quality evidence). On rare occasions, compression is needed with a 3 Fr Fogarty catheter or selective guided intubation. In these cases, RB could be necessary to explore the area of the bleeding and to aspirate the large clots. In one study, it has been suggested that the endobronchial instillation of pro-coagulation substances, such as tranexamic acid, can be effective, although the evidence for its recommendation is still limited43 (weak recommendation; low-quality evidence).

Pneumothorax is a rare complication although it can occur with transbronchial biopsy. In other cases, the misuse of the bronchoscope (uncontrolled pressure with the tip, abrupt movements, especially if there is coughing, or using either O2 or pressured air through the working channel) could cause them.44

Fever is frequent, appearing in up to 15% of the procedures, especially if BAL had been carried out. It is related with the release of cytokines or with transitory bacteriemia, mainly in immunosuppressed patients. More rarely, FB could give rise to infectious complications, both for the patient (dissemination to healthy areas of the lung or transmission of contaminated material from a previous exploration) as well as for the health-care professional (transmission of M. tuberculosis).

• -

  Biopsy forceps: the most often used are alligator forceps and they are used in bronchial as well as transbronchial biopsies. There are other models with smooth edges, with a central needle, fenestrated or not, revolving or swinging. All these are shown in Table 4.

  Table 4.

  Biopsy Forceps Available for Pediatric Bronchoscopes.

  Diameter, mm	Characteristics
  1a	Round, smooth edgeOval, smooth, disposableOval, alligator
  1.2b	Oval spoon, mouse-tooth
  1.5a	Oval, smooth, disposableDentate spoon
  1.8a	Round, smooth edgeOval, sooth, fenestrated, disposableOval, smooth, fenestrated, disposable, with a needleDentate spoon
  2b	Re-usableFenestrated, mouse-toothed alligatorRound, fenestrated with/without needleOval, fenestratedOval, fenestrated alligatorDisposableOval, fenestratedOval, fenestrated with needleOval, fenestrated alligatorOval, fenestrated alligator with needle

  a

  Refers to the diameter of the forceps.

  b

  Refers to the diameter of the working channel.
• -

  Brushes: used for bronchial cytology studies and to test signs of inflammation, infection and malignancy.

• -

  Transbronchial aspiration needles: used for diagnosing lung nodules or lesions near the bronchial tree. They are not frequently used in children.

• -

  Accessories for extracting foreign bodies: although the standard norm is not to extract foreign bodies with FB, it is useful to have the equipment available in order to recover either small fragments or those from more distal areas that are not accessible with the rigid bronchoscope. There are 3 models: mini-forceps, forceps and extraction baskets (Table 5).

  Table 5.

  Accessories for the Extraction of Foreign Bodies With Flexible Bronchoscope.

  Diameter, mm	Characteristics
  1a	Helical basket, 4 wires
  1.2b	Helical baskets, 3 and 4 wires3-pronged forcepsWire loop
  1.3a	Basket, 6 wires
  1.5a	Handle
  1.8a	Helical basket, 4 wiresMouse-toothed forcepsV forceps3-pronged forceps
  2b	Basket, 4 wiresV forcepsMouse-toothed forcepsRubber forceps

  a

  Refers to the diameter of the forceps.

  b

  Refers to the diameter of the working channel.
• -

  Balloon catheter: used to plug hemorrhagic lesions.

• -

  Endotracheal tube adapter: used in intubated patients to allow for simultaneous ventilation.

BAL allows for the evaluation of the cell and biochemical constituents of the epithelial surface of the lower respiratory tract or the presence of microorganisms, by means of the instillation and later aspiration of liquid in one or several lung segments.

Chest radiographs and, if possible, computed tomography in order to outline the most ideal segment for BAL. In certain patients, platelet count higher than 60 000/mm3 and Quick index >50%.

If bacteriological studies are going to be ordered, BAL should be done first, before exploring the bronchial tree, avoiding aspirating secretions with the aim of impeding, or reducing the contamination of the suction channel by the oropharyngeal flora (strong recommendation; low-quality evidence). Likewise, lavage should be done before other techniques (biopsy, brushing or needle aspiration) that could cause hemorrhages and affect the results. Refrain from the instillation of topical anesthesia in the segment for lavage, as this could inhibit bacterial growth.

In children with localized lung lesions, BAL should be performed in the most affected segment or lobe. In diffuse disease, any place may be chosen, although the most appropriate segments are the middle lobe (ML) and the lingula, both due to their accessibility and easy impaction of the bronchoscope as well as the greater recovery of the liquid instilled as it is favored by the pull of gravity (strong recommendation; high-quality evidence). In infants, one of the most accessible areas is the right lower lobe.

Sterile isotonic saline is used, at room temperature or at 37°C to diminish the cough reflex.44 It is introduced through the bronchoscope channel with a syringe, followed by the instillation of sufficient air in order to completely empty it. Afterwards, the liquid that was introduced is aspirated by either manual or mechanical aspiration through a circuit made up of several interconnected recipients between the working channel and the aspiration, applying an intermittent negative pressure between −25 and −100mmH2O (strong recommendation; low-quality evidence). Excessive negative pressure should be avoided as it could lead to the collapse of the distal airway, impeding the recovery of the liquid.

Children <20kg: a total of 3ml/kg, divided into 3 equal fractions; children ≥20kg: aliquots of 20ml, up to a total final volume of 3ml/kg (strong recommendation; low-quality evidence).

The volume instilled and the volume recovered both should be recorded. A recovery of 40% with few epithelial cells is accepted, although some authors48 admit ≥10%. In healthy children, between 43% and 85% of the volume introduced can be recovered, although the first sample is usually clearly less than the remainder. The first aliquot is considered the bronchial sample. It has more neutrophils and less lymphocytes than the remainder. For this reason, it should be separated from the rest for microbiological cultures, unless it is necessary to analyze specifically the cell component in bronchial inflammatory processes like asthma. The other aliquots offer comparable results, and therefore can be joined in one container. The processing of the liquid obtained should be done within 4h, and until processing it should be kept at 4°C to favor cell viability.

Total cell count should be determined (considered valid with >300–500cells/ml) as should the differential formula. Studies on the normal values for children do not include many cases, many of which are not always absolutely healthy, and they have different methodologies (Table 6).49–53

For the diagnosis of bacterial infections, Gram stain, quantitative colony-culture and, in some cases, intracellular bacteria studies should be done. The detection of more than 1% of epithelial squamous cells can indicate an excessive contamination of the sample by oropharyngeal flora. Isolations ≥10 000UFC/ml are considered significant (strong recommendation; high-quality evidence). The detection of microorganisms that do not form part of the usual oropharyngeal flora (M. tuberculosis, Legionella, Nocardia) is always pathological (strong recommendation; high-quality evidence).

Pediatric bronchoscopes are shorter than those used in adults. They measure between 30 and 16cm long with an internal diameter between 3.2mm and 7mm. To these measurements, one must also add the thickness of the wall of the tube, which ranges between 2 and 3mm depending on the manufacturer, to obtain the external diameter. The beveled tip facilitates vision during intubation, and makes for easier passage through the vocal cords and stenosis and for mechanical resection. On its distal third, there are lateral holes, introduced by Killian, that ventilate the contralateral lung.

Some bronchoscope models have different ports of entry on their proximal end designed for different uses. Those of standard size are for connecting respirators and jet ventilation. Others allow for the simultaneous introduction of different types of fiber lasers and aspiration catheters. There are also optics of different thickness that adapt to the working channel.

In addition to the basic apparatus, it is convenient to have a video camera adaptable to the head of the optics. The variety of endoscopic forceps is extensive, but the main ones are: alligator mouth forceps for foreign bodies, universal forceps, spoon-shaped biopsy forceps and grasping forceps for soft foreign bodies.

The patient is positioned in supine decubitus with the bronchoscopist at his/her head. The ideal position for the visualization of the larynx and intubation is the combination of anterior flexion of the neck with hyperextension of the atlanto-occipital joint (flexion–extension or Boyde-Jackson position).

For intubation with the rigid bronchoscope, a laryngoscope can be used, using the standard tracheal intubation technique or directly using the RB; in this case, one may either look directly through the channel of the bronchoscope or use the straight optical viewfinder, which gives a better-quality magnified vision. The bronchoscope is held with the right hand and with the left the mouth is opened, protecting the incisors as well as the soft parts, lips and tongue from injury. The visualization of the arytenoids, with the vocal cords in front and the entrance of the esophagus behind, serves as a reference. In order to pass through the vocal cords, the bronchoscope is rotated on its axis clockwise until its tip coincides with the major axis of the rima glottidis. Once past the separated vocal cords, the rotation is undone. In the previously intubated patient, the point of the bronchoscope slips down on top of the orotracheal tube, using the tube as a guide until the tip comes to the point above the vocal cords; the orotracheal tube is then withdrawn and the RB pushed forward. Lastly, when there is a tracheotomy, the bronchoscope can also be introduced, carrying out what is known as a lower bronchoscopy in order to distinguish it from a translaryngeal or upper bronchoscopy. Once past the glottis, the ventilation system is connected to the lateral connections.

The complications of RB are due to the instrumentation with the bronchoscope itself, the medication used, the ventilation technique, the underlying pathology, the experience of the endoscopist and the type of intervention (extraction of foreign bodies, laser, placement of endoprosthesis, etc.).

The introduction of the bronchoscope can injure teeth and the soft parts of the mouth, the lips and tongue, as they can become caught between the metallic tube and the teeth. During the maneuver, the bronchoscopist must avoid using the incisors as a leverage point in order to elevate the soft tissue and expose the glottis. To prevent this type of injury, a dental protector is used. When the bronchoscope goes through the glottis, there may be damage to the arytenoids or vocal cords. When it enters into the trachea, there may be a cardiovascular response that, in adults, is usually sympathetic-tonic with an increase in the heart rate and blood pressure, but in younger people and in children the response may be vagotonic with bradycardia.

The most frequent complications are related with anesthesia and ventilation. These are hypoxemia, hypercapnia, cardiac arrhythmias and barotrauma.