4. Airway Management in Children
KeywordsUpper airway, childUpper airway obstruction in pediatric anesthesiaPediatric endotracheal tubeSupraglottic airways in childrenPediatric difficult airwayLaryngospasm, managementCuffed tracheal tubes for children
The core airway skills for anesthetists caring for children are face mask ventilation, LMA insertion, laryngoscopy and intubation, and selecting the appropriate sized ETT. Airway management is such an important part of pediatric anesthesia because respiratory complications are the commonest cause of morbidity and mortality in children without cardiac malformations. Respiratory events cause over three quarters of critical incidents and nearly a third of perioperative cardiac arrests. Not surprisingly, airway obstruction leading to hypoxia and bradycardia or asystole is a huge fear for anesthetists who do not routinely look after children. Airway management, especially face mask ventilation, is the most important skill to learn during pediatric training. It is the technique that will be required when there is airway obstruction and hypoxia.
Anesthetized children have airway problems more than cardiovascular problems. As a trainee, to gain more experience with airway management, avoid just inserting an LMA early on in the anesthetic then returning the child to recovery with the LMA in situ as you might with an adult.
4.1 Airway Anatomy
Anatomical differences in infants and children compared to adults and their consequences for clinical practice
Difference in neonate and infant
High metabolic rate
Desaturate quickly during apnea or airway obstruction
Use head ring rather than pillow (Fig. 4.3)
No nasal turbinates
Less resistance to passage of nasal ETT
Soft, compressible floor of mouth in infants
Pressure from anesthetist’s fingers can push tongue against roof of mouth obstructing the airway—be careful to place fingers only on bony structures during airway maneuvers
Obtuse mandibular angle of 140° (adult 120)
Large tongue relative to mouth size
Higher, slightly anterior larynx (vocal cords opposite C3; adult C5)
Tongue closer to roof of mouth and obstruction more likely. Harder to compress tongue with laryngoscope and align visual axes of mouth, pharynx and larynx. Larynx appears to be more anterior at intubation, and forward flexion of neck does not improve laryngeal view
Long, thin U-shaped epiglottis with small amount of cartilage. Broad and fleshy ary-epiglottic folds. Large, mobile arytenoids
Vocal cords angled slightly anterior (adult perpendicular)
Large floppy epiglottis more likely to require physical displacement to view glottis (lift directly with straight blade). More likely to have ETT catch on glottic opening
Supraglottic structures more likely to feature in pathology
Cricoid ring is narrowest part of airway until puberty (adult: glottic opening)
Determines ETT size
Trachea soft and compliant
Collapse of extrathoracic trachea in upper airway obstruction
Ribcage soft and compliant
Indrawing of chest in upper airway obstruction
4.1.1 Nasal Breathing
Most infants are primarily nasal breathers for the first months of life. Their oral airway can easily be obstructed by a relatively large tongue and high epiglottis that may rest against the soft palate, and coordination between the respiratory and pharyngeal muscles is immature. Some neonates and infants can switch to mouth breathing if their nose is occluded (8% of preterm babies, 40% of term babies). Infants easily mouth breath after 3–5 months of age. The nose contributes only 25% of airway resistance in infants, compared to 60% in adults—most of an infant’s airway resistance is in the distal airways. Nevertheless, a young infant whose nose is blocked by secretions or a nasogastric tube may struggle and persist with nasal breathing rather than mouth breath.
Infants can feed and breathe at the same time. This is possible because the larynx is high in the neck, bringing the epiglottis and soft palate together. This and other changes allow milk to enter the esophagus at the same time as air is entering the trachea. Two of the consequences of this anatomy are that young infants breath primarily through the nose and they cannot have articulated speech.
4.1.2 The Pharyngeal Airway
Infants have a collapsible pharyngeal airway due to lax tissues and a small muscular contribution to airway patency. Airway patency improves over the first 8 weeks as muscle coordination matures. Skeletal growth during the first year increases the size of the mandible and maxilla relative to the tongue and further improves airway patency.
4.1.3 The Larynx and Cricoid Cartilage
The larynx is higher in the neck of neonates and infants, making it appear more anterior at laryngoscopy.
Airway trauma from intubation in a young child may cause edema and post extubation stridor in the short term, and subglottic stenosis in the long term.
4.2 Assessment of the Airway
Older children can be assessed as an adult would be, although the Mallampati score and thyromental distance tend not to be used because they are not validated in children. History is usually non-specific in routine cases, although symptoms of obstructive sleep apnea (OSA) may indicate adenotonsillar hypertrophy and more difficult mask ventilation. Younger children may not cooperate with a formal examination. Instead, they are observed for abnormalities of mouth opening and neck movement. Children differ from adults in that a child who is difficult to intubate will usually look difficult to intubate, whereas adults who are difficult to intubate may look normal. However, the unexpected difficult airway does exist and preparations for it need to be taken for any anesthetic.
The most important observation of the airway in children is the jaw size. A small jaw (retrognathia or micrognathia ) gives less space between the tongue and soft palate for a clear airway and less space to compress the tongue during laryngoscopy. It is the reason babies with Robin sequence can be difficult to intubate.
Micrognathia is a common and important indicator of intubation difficulty. It makes direct laryngoscopy difficult because there is little room for the blade to compress the tongue and give a direct line-of-sight view of the vocal cords.
4.3 Upper Airway Obstruction
Anatomical differences predispose children to upper airway obstruction, and hypoxia may develop quickly because they have a high oxygen consumption and smaller oxygen reserve (lower functional residual capacity (FRC), higher closing volume).
4.3.1 Signs of Upper Airway Obstruction
Signs of upper airway obstruction in children
Signs of upper airway obstruction
Inspiratory stridor and prolonged inspiration
Rocking chest and abdomen during breathing
Use of accessory muscles:
– Tracheal tug
– Flaring nostrils
– Intercostal chest retractions
Tachypnea and tachycardia
Anxious and restless initially, lethargic later
Indrawing of the chest wall occurs during obstruction, especially in young children who have pliable, cartilaginous rib cages. Obstruction also causes a rocking paradoxical movement of the chest and abdomen—the abdomen moves outwards from descent of the diaphragm while the chest collapses inwards from negative intrapleural pressure. As obstruction worsens, the work of breathing increases and accessory muscles become active with flaring of the nostrils and tracheal tug. Initially, an awake child with airway obstruction is tachypneic and tachycardic. Eventually the child may tire and respiratory effort fades. Infants and neonates rapidly fatigue and may develop apneic episodes as a result of airway obstruction.
4.3.2 Site of Upper Airway Obstruction During Anesthesia in Children
In sedated or anesthetized children, loss of muscle tone in the airway reduces patency and narrows the entire upper airway. Most obstruction, however, is at the level of the soft palate and the epiglottis. In contrast, upper airway obstruction in adults occurs at the level of the base of the tongue from loss of tone in the genioglossus muscle. At either age, resistance during inspiration generates a negative airway pressure and worsens airway collapse.
4.4 The Mask Airway and Mask Ventilation
Many adult techniques are applicable for the management of a child’s airway. Always actively manage the child’s airway to learn the best way to obtain a clear airway in that child and to detect airway obstruction within a breath or two. Active airway management means holding the rebreathing bag and moving your hand gently with each breath, assisting the breathing and providing continuous positive airway pressure (CPAP) if needed.
4.4.1 Face Masks
Children have large cheeks and a relatively small nose bridge, resulting in their face being in one plane. This allows masks with a soft, flat cuff to form a seal—even a circular shape such as the Laerdal silicone resuscitation mask can be used. The cuff should be neither too soft nor too hard—soft enough to conform to facial contours, but not so soft that forming a seal is difficult and not so hard that the mask does not conform to the face. Adults have a more prominent nose bridge, and a contoured mask is needed to form a seal. Teenagers have a prominent nose bridge and may need an adult mask.
The size of the facemask should allow the mouth to be slightly open, but not cover the eyes—sit the top part of the cuff on the bridge of the nose and ensure the lower part sits in the mental groove on the chin. If the mask comes up onto the eyes or down onto the chin, it is too big. If an infant is settled with a soother or dummy in its mouth, sometimes a larger mask can be placed over the top of the soother during the early stages of induction, changing to a smaller mask later when the soother is removed.
4.4.2 Opening the Upper Airway
Summary of main airway maneuvers to obtain patent airway in a child
Important airway maneuvers to overcome upper airway obstruction
Head and neck position
Jaw thrust (not just chin lift)
Oral (or nasal) airway
Positioning child on side may help
Gastric distension pushes the diaphragm upwards and inhibits ventilation. Remove the air by inserting a suction catheter through the mouth—suction may or may not be required.
188.8.131.52 Head Position
Positioning for direct laryngoscopy is different in adults and children. Adults are placed in the ‘sniffing’ position (neck flexed, head extended). Children don’t benefit from neck flexion during intubation because their larynx is relatively high. Only extension of the atlanto-axial joint to tilt the head back is needed.
184.108.40.206 Hand Position
Try to hold the mask using a technique that incorporates jaw-thrust. This technique doesn’t force the mouth shut, doesn’t apply pressure to the floor of the mouth, and keeps one hand free for ventilation or CPAP. It avoids the need for a two-handed, two-person technique when difficulties arise.
220.127.116.11 Oral and Nasal Airways
Nasopharyngeal airways are occasionally used as they are better tolerated in the conscious patient. Small, soft nasopharyngeal airways are available, but some are too long if inserted fully with the collar against the nostril. The size of the airway is selected by matching its length to the distance between the nose and tragus of the ear. An alternative to a purpose-made made nasopharyngeal airway is a shortened, age-appropriate ETT taped or pinned in place so that it cannot migrate inwards or outwards, and labelled so that it is not mistaken for a tracheal tube. Position the nasal airway carefully so that it is just below the soft palate, but not touching the epiglottis. They can sometimes cause trauma and bleeding from the nose or adenoids.
CPAP and jaw thrust are the most important maneuvers to learn to maintain an open airway in children.
Tip: To Apply CPAP
Ensure you have an effective mask seal (use finesse, not force!) with one-handed jaw thrust.
Partially close the APL valve and keep the bag tight during the expiratory pause.
Feel the bag & watch the chest for the start of inspiration.
Gently squeeze the bag as soon as inspiration starts.
Squeeze gently, feeling for feedback that air has entered chest. If the bag is squeezed too hard before confirming this, the stomach might inflate.
Once you have the ‘feel’ for airway patency and respiratory rhythm, increase the bag squeeze and pressure support, and start to squeeze slightly before inspiration starts (anticipating when the next breath is about to start).
CPAP requires a circuit that can keep the airway pressure positive during inspiration. Simply closing the APL valve on a circle circuit or kinking the tail of a T-piece circuit does not produce CPAP (Fig. 4.6b). The simplest method in practice is to gently squeeze the rebreathing bag at the very start of inspiration, keeping the bag slightly distended during expiration so that there is minimal lag between the start of the child’s inspiration and the bag producing a positive pressure. This technique is called CPAP, but is probably more correctly a manual form of pressure support ventilation. Some centers use the pressure-support mode of the anesthetic ventilator during induction.
18.104.22.168 Difficult Facemask Ventilation
Common causes of difficult facemask ventilation in children
Common causes of difficult facemask ventilation
Large tonsils and adenoids; obesity
Inadequate depth of anesthesia or paralysis
Congenital or pathological conditions
Alveolar collapse and reduced compliance
Air in stomach
4.5 The LMA and Other Supraglottic Airway Devices
4.5.1 Classic and Classic-Style LMA
Child weight and recommended LMA size
Weight range (kg)
A clinically acceptable airway is obtained with the LMA in 92–99% of children (similar to adults), but the incidence of partial airway obstruction seen on fiberoptic assessment in children is up to 19% (higher than adults). In infants, the pharyngeal seal is not as good and there is a lower cuff leak pressure compared with older children. Malpositioning is more common with the smaller sizes of LMA, and is usually due to the epiglottis being caught within the LMA. Bilateral jaw thrust by a second person during insertion of the LMA improves positioning. The chest and abdomen sometimes have a rocking movement during spontaneous ventilation due to partial airway obstruction. Despite all of this, a clear airway is usually obtained with an LMA, although it is important to check that the tidal volume is adequate and that the child is not working too hard at breathing. Pressure support ventilation is usual nowadays with modern anesthesia ventilators.
4.5.2 Second Generation LMAs and Other Supraglottic Airway Devices
The first generation LMA is still commonly used in children because of cost, familiarity and good performance in clinical practice. However, there is good evidence second generation devices are superior, with the gastric channel being useful to release trapped air. The pediatric Proseal LMA® (PLMA) does not have the dorsal cuff of the adult sizes, and is not available in single-use versions. The iGel® is effective in infants and children, but there may be a large leak until the cuff warms, softens and conforms to the pharynx. It also has a tendency to migrate outwards, requiring extra taping or repositioning.
4.5.3 Removal of LMAs
LMAs are commonly removed while the child is still deeply anaesthetized. A deeply anaesthetized child in the lateral position usually has a clear airway (unlike adults) and so there is less to gain from leaving the LMA in situ in PACU. Although it is clear awake removal is better in adults, in children it is not so certain and studies point either way, partly because of differences in definitions of ‘awake’, or of complications. There is little difference in the incidence of laryngospasm if the LMA is removed deep or awake in healthy children. However, in children with increased bronchial hyper-reactivity or those with risk factors for respiratory adverse events, deep removal is superior to avoid complications. The experience of PACU staff must be considered before planning to leave the LMA in for later awake removal. If removing deep, the child should be in the lateral position. If awake, the child should be very awake, defined by Archie Brain as being after the onset of swallowing and when the child is either able to open the mouth to command or expel the LMA spontaneously.
There are several blades for direct laryngoscopy available for children. However only two are needed for routine anesthesia in children—the size 1 Miller blade for neonates and infants, and the size 3 (adult) Mac blade for children.
4.6.1 The Miller Blade
Tips for using the Miller blade in infants and neonates
Technique for using the size 1 Miller blade in neonates
Insert blade in right corner of mouth and sweep tongue swept across to the left
Look in the mouth as you gently advance the blade
Get the blade out of the corner of the mouth and have your assistant retract the right corner of the mouth
Lift the epiglottis indirectly and use external laryngeal pressure
The infant Miller blade was first described in 1946 by RA Miller (NOT RD Miller of Miller’s Anesthesia). Free full text of the original description online. Anesthesiol 1946;7: 205.
4.6.2 The MacIntosh Blade
The adult size 3 MacIntosh blade is suitable for children of all ages, including older infants. In small children, only the thin, distal part of the blade is inserted, leaving plenty of room in the mouth. Small MacIntosh blades are available but are only scaled down adult blades without proper adjustment of their proportions. If these small blades are used for intubation, the thick part of the blade is in the mouth and takes up more space. They also have a significant curve requiring more mouth opening and force to obtain a direct line of vision. The size 1 MacIntosh and Miller blades have been shown to give an equivalent view in infants as young as 3 months. Although the Mac blade is tempting to use because it is familiar, the Miller blade is needed for neonates, so it is best to gain experience with it on larger infants as well.
Most children are easy to intubate. If the cords are not clearly seen, resist pulling harder- use external laryngeal pressure (the ‘three-handed’ intubation technique).