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Airway management 

Airway management
Chapter:
Airway management
Author(s):

Jeremy Hull

, Julian Forton

, and Anne Thomson

DOI:
10.1093/med/9780199687060.003.0063
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The paediatric airway

  • Respiratory failure may rapidly progress to hypoxic cardiopulmonary arrest in children. The outcome of a properly managed respiratory arrest is good. The outcome of a cardiorespiratory arrest is poor.

Resistance to laminar airflow is inversely proportional to the fourth power of the airway radius. Airflow resistance and work of breathing therefore increase exponentially with small reductions in the airway radius. The paediatric airway, in particular, is compromised by relatively small amounts of oedema.

  • Resistance to turbulent airflow is inversely proportional to the fifth power of the airway radius. Turbulent airflow may be minimized by keeping the child calm and quiet.

  • Posterior displacement of the tongue may cause severe airway obstruction in children, as the tongue is proportionally larger than in adults and the position of the larynx is more cephalad.

The spontaneously breathing child with respiratory distress

Alert children should be left to take a comfortable position. The semi-conscious or unconscious child who is breathing spontaneously may experience an upper airway obstruction as a result of the loss of pharyngeal muscle tone and posterior displacement of the tongue. Airway patency should be optimized, using the head tilt–chin lift manoeuvre (or the jaw thrust if a cervical spine injury is suspected).

Oxygen

Oxygen should be delivered to all children with respiratory difficulty. If spontaneous ventilation is effective, oxygen may be given by an oxygen mask, nasal cannulae, or a head-box. Humidified oxygen should be given as soon as possible to prevent airway obstruction from dried secretions.

Oxygen may be delivered by:

  • a simple face mask;

  • a face mask with a reservoir bag;

  • a Venturi mask;

  • nasal cannulae;

  • a head-box.

These devices are discussed in Airway management Chapter 56.

Airway adjuncts

Oropharyngeal airway (Guedel airway)

  • An oropharyngeal airway is designed to hold the tongue away from the posterior pharyngeal wall and is indicated in the spontaneously breathing unconscious patient where airway patency cannot be maintained with normal positional manoeuvres.

  • An oropharyngeal airway should be avoided in a conscious or semi-conscious child, as it may cause gagging and vomiting.

  • The Guedel airway consists of a flange, a bite block, and an ergonomic curved body, designed to hold the tongue anterior to the oropharynx when correctly sited.

  • The airway provides an air channel and suction access through the mouth.

  • Sizing the oropharyngeal airway is essential, as a poor fit will exacerbate the obstruction. If the oropharyngeal airway is too large, the epiglottis is pushed down, obstructing the glottic opening, and laryngeal structures may be damaged. If the airway is too small, the tongue will be pushed posteriorly into the oropharynx, thereby worsening the obstruction.

  • The correct size can be estimated by measuring the oropharyngeal airway against the face. If flange is positioned at the mouth, the tip of the airway should just reach the angle of the jaw. Airway sizes vary from 4 cm to 10 cm. Guedel airways are size/colour-coded (sizes range from 000 to 4).

  • An oropharyngeal airway should be inserted, using a tongue depressor. If this is unavailable, in the older child, the airway may be inverted for insertion and rotated back 180° to its proper orientation, as it enters the posterior oropharynx.

Nasopharyngeal airway

  • A nasopharyngeal airway provides a conduit for airflow between the nares and the posterior oropharynx. Nasopharyngeal airways are available in sizes 12 F to 36 F, but a shortened soft ETT is commonly used. A 3 mm ETT corresponds approximately to the calibre of a 12 F nasopharyngeal airway and will fit down the nasopharynx of a term infant.

  • Nasopharyngeal airways are usually used in the non-acute setting, in the management of infants with an upper airway obstruction secondary to micrognathia and other structural abnormalities of the oropharynx.

  • Nasopharyngeal airways also have a role in acute resuscitation and may be better tolerated than oropharyngeal airways in semi-conscious children with airway compromise.

  • The correct length for a nasopharyngeal airway can be estimated as the distance from the tip of the nose to the tragus of the ear. A term infant is likely to need a 6–6.5 cm tube.

  • Before inserting the nasopharyngeal airway, drip 1 mL of 1% lidocaine down the larger nostril. Lubricate the nasopharyngeal airway with lidocaine gel, and advance it in an inferoposterior direction, perpendicular to the face and along the floor of the nasopharynx. Laceration may cause bleeding from the nasal mucosa or adenoidal tissue. The tube is too large if the skin of the nostril remains blanched.

  • The ideal position is for the tip of the nasopharyngeal tube to lie just behind the edge of the soft palate (in children with intact palates). A laryngoscope may be used to visualize the tip of the nasopharyngeal airway, as it advances beyond the soft palate. It should then be withdrawn, until it just disappears from view. In a child with a cleft palate, the tip of the tube is sited at the estimated position where the intact palate would have reached. Irritation of the vocal cords, epiglottis, and vagal nerve from a long tube may cause reflex coughing, vomiting, and laryngospasm.

  • If an ETT is used as a nasopharyngeal airway, the 15 mm diameter adapter must be firmly re-inserted into the shortened tube to prevent an accidental advancement beyond the nostril. For children with chronic nasopharyngeal airway insertion, the shortened ETT may be sutured to the wings, which can be neatly fixed to the face with tape (or the ETT cut, so that the extruding end forms two wings).

  • When the tube is first placed, there are likely to be lots of secretions, and regular assessment of the patency with suctioning is necessary. Secretions will settle. If an infant feeds with the tube in situ, milk will initially reflux up the tube. With time, most infants learn to feed with the tube in position, with little milk reflux. Withdrawing the tube back slightly (0.5 cm) during feeds may be helpful.

  • CPAP may be administered via a nasopharyngeal airway in cases of severe upper airway obstruction.

Suction

  • A suction force of 80–120 mmHg is required to adequately remove secretions from the airway. Wall-mounted vacuum suction units provide an airflow of 30 L/min, corresponding to a maximum suction force of 300 mmHg. Portable units do not provide comparable suction power but are easy to transport.

  • Flexible plastic suction catheters may be used to suction thin secretions from the upper airway, oropharyngeal airways, nasopharyngeal airways, and ETTs. Large-bore rigid catheters (e.g. yankauer catheter) are more effective for thick secretions, blood, and vomitus in the oropharynx.

  • Suctioning should be performed with a sterile technique. It may produce vagal-induced bradycardia and should always be performed with adequate monitoring. Patients should be pre-oxygenated, and each suction attempt should not exceed 5 s. Flexible suction catheters should not be inserted >1 cm beyond the end of an ETT, as trauma to the carina or bronchi may cause significant granulation tissue. Suction should only be applied on withdrawing the catheter.

Respiratory failure or arrest

In the case of respiratory failure, basic life support should be commenced:

  • open the AIRWAY;

  • support BREATHING;

  • assess CIRCULATION.

Bag–valve–mask ventilation

Ventilation face masks need to create an airtight seal, if the administration of high oxygen concentrations and assisted pressure ventilation are to be effective. Bag–valve systems can also be used with an oropharyngeal or nasopharyngeal airway.

When sizing the mask, the correct size should reach from the bridge of the nose to the cleft of the chin, forming a tight seal around both the mouth and nose, but without compression of the eyes. The mask volume should be small, particularly in infants, so that rebreathing of exhaled gases is minimized.

Bag size and tidal volume

  • The tidal volume should be 10–15 mL/kg and should dictate which size of bag to use. Neonatal size bags (250 mL) are generally inadequate for a term infant.

  • Lung compliance may be assessed during bag–mask ventilation. This is most easily done when the size of the bag is appropriate for the child. A sudden decrease in lung compliance should alert the user to the possibility of airway displacement, airway obstruction, or a pneumothorax.

Airway positioning

  • The mask is held on the face with one hand, which also positions the airway correctly with a head tilt–chin lift manoeuvre (the second hand compresses the ventilation bag). In infants, the mandible is supported with the base of the middle finger without pressure. In older children, fingers 3–5 are placed on the ramus of the mandible and used to lift the jaw forward.

  • Ventilation is usually most effective for infants and toddlers with the head in a neutral position, without hyperextension of the neck, but it may be necessary to gently move the head and neck to determine the position of maximum airway patency and optimum mask ventilation. Hyperextension of the neck may cause airway obstruction in infants and should be avoided. In children >2 years, the airway patency may be improved by placing a small support (e.g. a folded towel) under the head and neck.

  • If ventilation is ineffective, re-assess the face mask seal, the airway position, and the need for suction, and check the equipment.

Nasogastric tube

  • An NG tube should be passed, as gastric dilatation is common with mask ventilation, may precipitate vomiting and aspiration, and will prevent optimal ventilation.

  • Gastric inflation and regurgitation in an unconscious child may be minimized by applying pressure to the cricoid cartilage with the thumb and index finger (the Sellick procedure) to occlude the oesophagus.

Self-inflating bag–valve–mask ventilation

Ventilation may be supported, with or without an oxygen supply, as the elastic recoil of the bag results in spontaneous reinflation between administered breaths, irrespective of whether or not there is a pressurized oxygen supply in the circuit.

The bag has three valves: the gas intake valve; the mask valve; and an exhalation valve near the mask. During bag compression, the mask valve opens, allowing flow from the bag to the mask, and the gas intake valve closes. During patient exhalation, through the exhalation valve, the valve mask closes, preventing the accumulation of exhaled gases in the bag, and the gas intake valve opens, allowing entrained room air (and/or oxygen, if connected) to refill the bag.

Oxygen supply and reservoir

Oxygen connected to a bag–valve–mask ventilation system at 10 L/min can provide 30–80% oxygen. In older children with larger tidal volumes, the oxygen flow may be rate-limiting, and room air, as well as oxygen, may be entrained into the bag during reinflation. Bag–valve–mask devices, fitted with a reservoir and run with high-flow oxygen at 10–15 L/min, can provide higher oxygen concentrations.

Ventilation pressures

Most self-inflating bags may have a pressure-limited pop-off valve. In situations of poor lung compliance or high airway resistance, high pressures may be necessary for adequate ventilation. A pop-off valve in this situation may limit the tidal volume delivered. The pop-off valve may be twisted closed or the pressure limit altered to an upper limit of 35–40 cmH2O.

Positive end-expiratory pressure

PEEP may be provided by a bag–valve–mask system if a spring-loaded or magnetic ball or disk PEEP valve is sited at bag–valve outlet. PEEP valves only open with compression of the bag and cannot be used in the self-ventilating patient to administer CPAP.

Self-ventilating patients

Bag–valve–mask systems should not be used to deliver oxygen to self-ventilating children. Valves within the system may result in an inadequate oxygen flow if the bag is not compressed with each inspiration.

Anaesthesia ventilation systems

  • An anaesthesia bag (Ayre’s bag, A-bag, Jackson Rees circuit) consists of a standard face mask and a 15–22 mm connector, to which a T-piece is connected. The T-piece has a gas inflow port and an overflow port, leading to a latex reservoir bag with an open tail. High-flow oxygen enters the circuit through the inflow port, and, if the face mask seal is good, it leaves via the overflow port and out of the reservoir bag tail. The reservoir bag is held, with the tail sitting between the fourth and fifth finger. Partial occlusion of the tail increases the resistance to gas flow, and the reservoir bag will inflate. This generates a pressure within the circuit. Compression of the reservoir bag with ongoing resistance at the tail will increase the circuit pressure and generate an inspiratory breath. Maintaining some resistance at the reservoir tail will generate PEEP during expiration. Full occlusion of the tail can generate dangerously high pressures.

  • This is a closed system, so oxygen concentrations are predictable, but, as it is a rebreathing system, flow rates need to be high to wash out exhaled gases. A high flow rate at the wall is needed to ensure that these gases are washed out, even whilst the circuit flow is restricted to generate PEEP during expiration.

  • Run oxygen at 2 L/min in infants, and 4–6 L/min in children.

  • Bag sizes: 500 mL for infants; 1000–2000 mL for children.

  • CPAP can be administered to the spontaneously ventilating patient, using the T-piece, because there are no high resistance flow valves to overcome on inspiration.

Endotracheal airway

  • Endotracheal intubation is the most effective approach to assisted ventilation, as the circuit to the airway is secure, ensuring complete control of ventilation and oxygenation. The tube also protects the airway from potential aspiration of gastric contents.

  • Elective intubation of self-ventilating children is generally after gas induction of anaesthesia, using volatile anaesthetic agents such as halothane or sevofluorane.

  • Rapid sequence induction of anaesthesia is used in the acute setting when children will be at risk of aspiration.

Preparation

  • Call the anaesthetist early.

  • Check the laryngoscope (straight blade age <2 years; curved blade in older children).

  • Check suction is working.

  • ETT sizing: (age in years/4) + 4 (uncuffed, age <8 years; cuffed in older children).

  • Endotracheal length estimate: (age in years/2) + 12.

  • Monitor the heart rate, saturations, and blood pressure. IV access is mandatory.

  • Pre-oxygenate in 100% oxygen, using a self-inflating bag–valve–mask with a reservoir and high-flow oxygen (or an A-bag circuit).

  • Pass an NG tube, and empty stomach contents.

  • Apply cricoid pressure before giving sedative drugs. If there is concern about cervical cord injury, place one hand behind the neck to provide additional support when applying cricoid pressure.

  • Give:

    • atropine (prevents vagal-induced bradycardia during laryngoscopy);

    • a sedative/hypnotic such as a combination of benzodiazepine and opiate or propofol or thiopental (watch for hypotension!);

    • a rapid-onset short-acting muscle relaxant such as suxamethonium.

Intubation technique

  • The child should be lying flat. In suspected cervical spine injury, the child is maintained in the neutral position with manual cervical stabilization. Otherwise, in children aged <2 years, the chin is lifted to the sniffing position. In children aged >2 years, the chin is lifted to the sniffing position, and the cervical spine displaced anteriorly with a small pillow placed under the head.

  • Using a laryngoscope in the left hand and standing at the patient’s head, the laryngoscope is placed to the right of the tongue and advanced.

  • Suction may be necessary (yankauer).

  • With a curved laryngoscope, the blade is inserted into the vallecula (which lies between the root of the epiglottis and the base of the tongue). Upward pressure in the direction of the laryngoscope handle elevates the jaw, and the glottic opening becomes visible. A straight laryngoscope is used in younger children, because the epiglottis in this age group is relatively larger. The tip of the straight blade may be placed distal to the epiglottis, which is then displaced with the same upward pressure manoeuvre. Cricoid pressure may help visualize the glottic opening. Care should be taken not to damage the teeth and gums.

  • Insert the ETT gently through the vocal cords under direct vision. With cuffed tubes, the cuff should be placed just below the vocal cords.

  • Remove the laryngoscope; inflate the cuff on cuffed tubes, and check the position of the ETT, looking for symmetrical chest movements and listening for equal breath sounds on auscultation. Monitor the end-tidal CO2, if possible. A simple colour change CO2 detector can be used to confirm the ETT is in the airway.

  • If doubt exists regarding the tube position, deflate the cuff; remove the tube, and re-oxygenate before trying again.

  • Secure the tube. Document the position at the lips. Continue ventilation with a self-inflating bag with oxygen and a reservoir.

  • Confirm the ETT position on CXR.

Cricothyroidotomy

Percutaneous needle cricothyroidotomy may be needed in children with an acute complete upper airway obstruction, although it has rarely been performed successfully in this age group. This temporary surgical airway is sufficient for oxygenation but usually inadequate for ventilation, so ENT surgeons will need to perform a formal surgical cricothyroidotomy. Causes of an acute complete airway obstruction include a foreign body, severe laryngeal infection, severe orofacial injuries, or a laryngeal fracture. Call for anaesthetic and ENT help immediately.

Needle cricothyroidotomy

  • Place a roll of towels under the child’s shoulders to maximally displace the larynx anteriorly (check there is no possibility of cervical injury before extending the neck).

  • Locate the cricothyroid membrane (extending from the thyroid cartilage caudally to the cricoid cartilage). Palpate with the fingernail of the left index finger (the cartilage is only 1 mm wide in infants).

  • Stabilize the trachea with the left-hand middle finger and thumb, whilst locating the cricothyroid membrane with the index finger.

  • Clean with an aseptic swab.

  • Define the path by first introducing a small-bore needle attached to a syringe (20–22-gauge) in the midline, directed 45° caudally (towards the feet). If air is aspirated, repeat the procedure with a cricothyroidotomy cannula-over needle, if available, or a large IV cannula (14- or 16-gauge).

  • Once the membrane is punctured (air is aspirated), remove the needle; advance the cannula caudally, and check air can still be aspirated.

  • Connect high-flow oxygen to the cannula, using a Y connector. Set the flow rate to the child’s age in years. Occlude the outflow limb of the Y connector for 1 s, and assess for chest movement. If there is no chest rise, turn up the oxygen by 1 L/min, until it is observed. Inflate for 1 s, and allow passive deflation for 4 s. If a Y connector is not available, a hole can be made in the oxygen tubing and intermittently occluded.

  • Note the following.

    • Expiration must occur via the upper airway. It cannot occur through the cannula, since the resistance is too high. If the upper airway is completely occluded, the oxygen flow should be reduced to 1–2 L/min, which will provide some oxygenation, but little ventilation.

    • Bag-and-mask devices will be ineffective at driving gas through the cannula. They cannot generate sufficient pressure.

Surgical cricothyroidotomy

  • The risk of injury to vital structures is significant, and this procedure should only be carried out by those with appropriate surgical training, usually an ENT surgeon.

  • The skin is cleaned and infiltrated with local anaesthetic.

  • A small vertical midline skin incision is made.

  • A transverse cricothyroid membrane incision is made.

  • The tract is dilated, and an appropriately sized endotracheal or tracheostomy tube is inserted.

Further information

Advanced Life Support Group (2011). Advanced paediatric life support: the practical approach, 5th edn. Wiley-Blackwell BMJ Books, Oxford. See also: <http://www.alsg.org>.Find this resource: