Airway

REVIEW ARTICLE
Year
: 2021  |  Volume : 4  |  Issue : 3  |  Page : 148--155

Paediatric airway: Challenges for the anaesthesiologist


Sumalatha R Shetty1, Niveditha Karuppiah2,  
1 Department of Anaesthesia and Critical Care, KS Hegde Medical Academy, Mangalore Nitte University, Mangalore, Karnataka, India
2 Department of Anesthesia and Pain Medicine, London Health Sciences Centre and Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada

Correspondence Address:
Dr. Niveditha Karuppiah
Department of Anesthesia and Pain Medicine, London Health Sciences Centre and Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario
Canada

Abstract

The paediatric airway has always been a challenge to both the novice and the experienced airway manager. In this review, we have addressed the challenges of a paediatric airway, especially for the occasional paediatric anaesthesiologist. Children are not small adults and present unique anatomical, physiological and emotional challenges. It is imperative to be aware of these differences and adequately prepare to manage the normal or difficult airway appropriately. In this review, we have analysed recent publications in indexed journals detailing airway challenges in paediatrics and their management. Recent advances and recommendations include the usage of microcuffed tubes, various sizes of supraglottic airways and multiple paediatric-airway friendly videoscopes. Awareness of the differences and how to manage them efficiently is the key to delivery of a safe anaesthetic in small children.



How to cite this article:
Shetty SR, Karuppiah N. Paediatric airway: Challenges for the anaesthesiologist.Airway 2021;4:148-155


How to cite this URL:
Shetty SR, Karuppiah N. Paediatric airway: Challenges for the anaesthesiologist. Airway [serial online] 2021 [cited 2022 May 20 ];4:148-155
Available from: https://www.arwy.org/text.asp?2021/4/3/148/330386


Full Text



 Introduction



The paediatric airway, especially of a neonate or an infant, is a challenge to the anaesthesiologist, particularly when it is not a part of their regular practice. These airways are relatively smaller and differ in many ways from that of an older child or adult.[1],[2] It is essential to be aware of the anatomical and physiological differences of a paediatric airway. The dissimilarity in anatomy and physiology of the airway in this subpopulation predisposes them to many perioperative adverse events. Remembering and clinically applying the fact that oxygenation and not intubation is of paramount importance is the key to successful airway management.

The analysis of paediatric anaesthesia liability from the American Society of Anesthesiologists Closed Claims Project Reports indicates a decrease in respiratory complications from 51% in 1970s to 23% in 1990s. In addition, these adverse events were more common in the 0–3 years age group.[2] The Pediatric Perioperative Cardiac Arrest Registry reports respiratory-related cardiac events to be around 27% of all the perioperative cardiac arrests.[3]

Why is this so? The fact that the child is not a scaled-down adult, particularly in terms of the airway, is not adequately understood. At the same time, the fear of handling a young child and the fear of consequences of airway misadventures in this age group might add to the problem. Difficulties encountered could be due to a multitude of factors which could be patient, surgery or anaesthesia related.

Patient factors could include age, anatomical and physiological differences compared to adults, and congenital deformities.[4] Surgical factors include the type of surgery, airway surgeries and surgical positioning. Anaesthesia-related factors that add to the problems in paediatrics may be the relative inexperience of the anaesthesiologist who might be handling an occasional paediatric case in his/her practice, or the non-availability of necessary and appropriately-sized equipment.

To overcome all these issues and their associated problems, understanding of the anatomy and physiology of the paediatric airway is of utmost importance.

 Paediatric Upper Airway and its Challenges



A child is not a miniature adult, and this becomes even more evident when we examine the paediatric airway. Not only does it differ from the adult airway in size but also in its anatomical and physiological features. These differences add challenge to different stages of airway management that includes bag-mask ventilation and/or intubation, often rendering oxygenation or ventilation inadequate.[5],[6],[7],[8]

 Anatomical Differences in Paediatric Airway



The unique and dissimilar airway features of paediatric airway as compared to the adult airway are listed below [Figure 1].{Figure 1}

Prominent occiputNarrow nostrils (making them obligate nose-breathers)Large tongueFloppy, omega-shaped epiglottisCephalad, angulated larynxNarrow cricoid/subglottic regionSoft airway

The paediatric airway differs from the adult airway in shape and consistency as well. Aspects of paediatric respiratory physiology may also predispose to complications.

The large occiput in neonates and smaller children results in flexion of the neck when they are placed supine, increasing the degree of malalignment of the pharyngeal and laryngeal axes.[9] This problem is overcome using a shoulder roll and extending the neck [Figure 2]The large tongue and soft tissues of the upper airway tend to fall back towards the pharyngeal wall and obstruct the airway during mask ventilation. Use of an oropharyngeal airway and employment of the 'triple airway manoeuvre' are often essential to provide an open airway that facilitates oxygenation and ventilation during anaesthetic inductionThe adenoids and tonsils which are generally large occupy much of the already small upper airway and add to airway obstructionThe epiglottis is floppy, omega-shaped and angled into the lumen of the airway making visualisation of the vocal cords difficult. The soft tissues around the epiglottis and laryngeal inlet are soft and prone to compression and distortion with external laryngeal manoeuvres used during intubationThe larynx is higher in children (C2-C3) as compared to adults and descends to the adult level at around 3 years of age.[5] The laryngeal cartilages are also much softer and even minimal external pressure on them can easily distort them and compromise the airway. The higher position of the larynx allows visualisation of the vocal cords better while using a straight blade as compared to a curved blade that is routinely used in adultsThe narrowest part of the airway has been studied in depth, particularly in the paediatric subpopulation. Anatomic studies have confirmed the “funnel” shape of the larynx. Autopsies have revealed that the narrowest portion of the larynx is at the level of the cricoid cartilage. However, in vivo studies with endoscopies and imaging (computed tomography and magnetic resonance imaging) have revealed that functionally, the glottis and subglottis are the narrowest parts as they have a smaller transverse diameter and less compressible soft tissue[6],[10],[11]The trachea is shorter and narrower as compared to adults. Minor movements in position of the head could move the endotracheal tube (ETT) in or out causing endobronchial intubation or accidental extubation, especially in neonates and smaller children. The narrow lumen of the paediatric airway predisposes it to oedema and obstruction. Oedema from trauma resulting in a 2 mm decrease in diameter of the paediatric airway will result in a 75% decrease in cross-sectional area and 16 times increase in resistance to air flow with the associated increased work of breathing [Figure 3][12]Children can have no teeth, loose teeth or even a complete set of teeth which affects the airway management adversely. While no teeth in the younger children can make mask ventilation difficult, baby teeth could be loose and pose a risk of accidental uprooting and aspiration. Hence proper evaluation of dentition is very essential to make sure that this does not happen.[13]{Figure 2}{Figure 3}

 Physiological Differences in Paediatric Airway



The paediatric airway offers many physiological challenges that can predispose the child to hypoxaemia. The chest wall is more complaint and the ribs are more horizontally placed compared to adults. Functional residual capacity (FRC) is lower in children as compared to adults. The oxygen consumption of an infant is higher when compared to adults (6 mL/kg/min vs. 3 mL/kg/min). Even though the tidal volume (per kg body weight) is relatively consistent with that of an adult, children have a higher respiratory rate to achieve the higher minute ventilation that they need. The lower FRC coupled with increased oxygen consumption leads to rapid desaturation during apnoea as seen during laryngoscopy despite adequate preoxygenation.[14]

Airway resistance is governed by Poiseuille's law:

R = 8ƞL/πr4

Where resistance to flow is inversely related to the fourth power of the radius of the airway. Even a small amount of narrowing due to oedema or inflammation of the paediatric airway could have severe consequences on respiratory function. A number of conditions that can result in such narrowing of the airway include diseases within the airway such as haemangiomas or papillomas; aberrant embryological development such as tracheomalacia, laryngomalacia and laryngeal clefts; iatrogenic causes such as vocal cord paralysis and subglottic stenosis, or compression of the airway structures by a mass located outside the airway.[15] Management of these conditions has a common denominator - avoiding airway trauma and subsequent oedema to tissues constituting the airway.

 Syndromes and Airway Challenges



Syndromes are often recognised or identified when children are posted for an associated airway surgery. Some of the syndromes associated with difficult airway are listed in [Table 1] along with airway challenges. These challenges must be addressed case-to-case. Once a thorough airway examination is completed, a stringent but workable airway plan must be formulated for successful management, ideally by a two-person anaesthesiology team.[16],[17],[18],[19],[20],[21],[22]{Table 1}

Syndromes such as Pierre Robin sequence and Goldenhar syndrome could improve and become less challenging as the child grows up. Syndromes in which airways do not improve with age include Treacher Collins, Apert, Beckwith-Wiedemann and various mucopolysaccharidoses-associated syndromes. In addition to these syndromic children, we have another group of paediatric patients who present to us with difficult airways due to situational and environmental reasons. The boisterous child who is curious and fearless tends to be a victim of accidents, self-made or otherwise. It could be accidental burns, chemical/physical trauma or even foreign-body aspiration. An already difficult airway of the child could be further compromised due to these reasons.

Children with oral or facial tumours constitute another group that requires us to manage their airways either during surgery or on a daily basis. Cystic hygroma is a fluid-filled sac due to blockage in the lymphatic system. These are mostly located in the head-and-neck area. It may occur on its own or as part of a genetic syndrome with other features such as in Turner syndrome or Down syndrome. The large swelling can obstruct the airway causing problems during induction and intubation.

 Airway Equipment



Paediatric airway equipment needs to be available in a spectrum of sizes due to the anatomical changes that occur as the child grows. Almost all airway equipment are available in varying sizes for use in paediatrics. However, these are not commonly available in non-paediatric care centres.

 Facemask



Different varieties of facemasks are available for the paediatric age group. Starting from the anatomical face mask with minimal dead space, coloured and scented facemasks are now available. The clear cushioned face mask gives us a window to observe misting and detect upper airway obstruction (inadequate mouth opening, tongue fall or obstruction at the mouth). Any regurgitation can also be noted with these masks.

 Nasal/Oral Airways



When selecting to use an airway in children (particularly in the younger age group), it is better to use an oral airway compared to nasal airway. The paediatric age group is prone to have enlarged and at times inflamed adenoids which could bleed. Appropriate-sized airways should be used as these by themselves may cause obstruction or trauma and oedema of the air passage.

 Endotracheal Tubes



After many decades of debate regarding the use of cuffed versus uncuffed ETTs for paediatric patients, we presently advocate the use of microcuffed ETTs.[23] The advantages provided by cuffed ETTs outweigh those provided by uncuffed ones. Some advantages include a lesser number of laryngoscopies, the ability to adjust leak with changes in compliance, use of low fresh gas flows and reduced risk of aspiration. It also provides reliable end-tidal CO2 (ETCO2) and tidal volume measurements, making it possible for fine adjustments in ventilation. The ability to practice low-flow anaesthesia also decreases operation theatre pollution. Simultaneously, one must remember the chances of increased airway resistance and increased work of breathing due to smaller diameter of the ETTs. Adjustments in the cuff pressure with constant monitoring of the same will be essential, particularly if nitrous oxide is being used.

Various formulae have been developed and studied for choosing the correct size of ETT. The Cole formula, i.e., ([age/4] +4) is used for calculating the correct size of uncuffed ETT in children. With advances in ETT design and the increasing use of cuffed tubes, other formulae have been developed for calculation of tube size. These include the Khine formula ([age/4] +3) and the Duracher formula ([age/4] +3.5).[24],[25] The Duracher formula is more commonly used with changes of the material used in cuff design and the increasing use of microcuffed tubes.

 Supraglottic Airways



Not all children or surgical procedures require endotracheal intubation. Certain procedures and airway challenges may be addressed with the use of supraglottic airways (SGA). There are several types of SGAs available in the market with similarities in the overall purpose and construction. One can use SGAs as a primary airway device or a rescue device in a difficult airway situation.

The choice of SGAs is often based on weight. Newer designs allow for use in premature and small for age neonates. However, they may be displaced more easily and not provide adequate seal. The size selection and recommended maximum volume in the cuff must be strictly adhered to.[8],[26],[27]

The SGA can also be used as a conduit to insert an appropriate-sized ETT in difficult airway situations. The SGA may get dislodged and not seat properly in smaller children, especially in neonates. The epiglottis might fold over and obstruct the airway if the SGA is pushed in deeper and cause the inability to ventilate adequately, sometimes mimicking laryngospasm. Careful insertion and constant vigilance are of paramount importance in small children.

 Laryngoscopes



Laryngoscopes with straight or curved blades and videoscopes and stylets of various designs are available for use in paediatric patients.[28] Straight blades are preferred to curved blades as it facilitates better visualisation of the paediatric larynx and helps elevate the epiglottis directly. However, it could damage the soft mucosa of the epiglottis. Straight blade designs include the popular Miller blade, Wis blade and the Seward blade [Figure 4]. The curved blade is used as in adults where the tip of the blade is placed in the vallecula and the epiglottis lifted indirectly. This is commonly chosen by the occasional paediatric anaesthesiologist. The curved blade creates more pressure on the soft tissues and needs more manoeuvreing to obtain a good laryngeal view. Laryngoscope handles are variable in sizes and lengths and can be used according to provider comfort, keeping in mind that lesser pressure should be used while handling a paediatric airway.{Figure 4}

There are many videoscopes that have been adapted from the adult airway cart to suit the needs of the paediatric airway.[29] This includes both rigid and flexible scopes and stylets which allow direct and indirect visualisation of the glottic opening. Flexible scopes are a valuable part of the difficult airway cart in paediatrics as well.

 Keys to Managing a Normal Paediatric Airway



In addition to the anatomic challenges in a paediatric airway, physiological and psychological challenges also exist. Children have:[4],[29]

Increased resting parasympathetic tone, which leads to bradycardia in response to hypoxiaAn immature respiratory centre and decreased respiratory reservesHigh basal oxygen consumptionHigher number of type two respiratory muscle fibres that are easily fatigableImmature central nervous system (increased sensitivity to drugs and thus prone to oversedation)Behavioural differences – children are more anxious, fearful and uncooperative. A crying and stressed child will make induction more difficult and add to the physiological burden and make them desaturate more quickly.

In preparation for airway management, the operation room should have appropriately-sized equipment and drugs prepared. Premedication is a valuable preparatory step. Positioning is vital, especially in neonates and infants. A roll is placed between the shoulder blades with the extension of the head to align the oral, pharyngeal and laryngeal axes. This position helps overcome the malalignment of axes caused by the large occiput.

Anaesthetic techniques used to achieve induction may be inhalational with sevoflurane, intravenous with ketamine or propofol, or a combination of both techniques. As the priority is to oxygenate the child to ensure safety, preoxygenation plays a major role in the anaesthetic plan. An agitated child makes this essential step next to impossible. Hence the need for a calm and sedate child becomes especially important. The presence of parents during the take-over plays a major role in addressing this issue.

Use of high flow nasal insufflation has been shown to be successful but may not be tolerated by the child. Mask ventilation could be difficult if appropriate age-specific masks are not available. An appropriate size of oral or nasal airway should be used to alleviate upper airway obstruction from the large tongue and other soft tissue. All children must be adequately preoxygenated. The time for laryngoscopy (apnoeic time) must be kept as short as possible keeping in mind the lower reserves and increased demands of oxygen.

Intubation under spontaneous respiration may be preferred in case of difficult airways especially when muscle relaxation is not required. The use of propofol, ketamine, dexmedetomidine, remifentanil and inhalational agents can be used to this end.

 Common Pitfalls in Routine Airway Management



Delay in recognition of upper airway obstruction: Paradoxical chest movement (chest indrawing), tracheal tug and absence of capnographic tracings are early indications of upper airway obstruction. Early recognition is crucial, and a simple manoeuvre such as jaw thrust, with or without the use of oral/nasal airways, should relieve the obstructionInappropriate size of oral or nasal airway: Large tonsil and adenoids may lead to injury and bleedingInadequate depth of anaesthesia during any kind of airway manipulation leads to breath-holding, laryngospasm and struggle with airway obstruction causing rapid desaturationIncidence of laryngospasm is as high as 25% in children and more common than in adults. Laryngeal spasm occurs through multiple mechanisms in children – closure of vocal cords, closure of false vocal cords, folding of the epiglottis, closure of glottic opening and collapse of the soft paraglottic tissues[10]Aggressive bag-mask ventilation with PEEP leads to gastric insufflation which reduces already decreased lung reserves and increases chances of regurgitation and aspirationUse of a styleted ETT, usually in the shape of the blade or a 'hockey stick', is useful in neonates and children as they have an anteriorly placed larynx. The ETT is soft and does not offer the stiffness to manoeuvre the tube into the glottis easily. The largest and stiffest stylet that fits the ETT should be used. However, a recent review showed that there was no difference between using a styleted or a non-styleted ETT.[30]

 Difficult Paediatric Airway Management Protocols



Various associations around the world have created detailed guidelines for the management of anticipated and unanticipated difficult airway management in paediatrics.[31],[32],[33],[34],[35] A detailed description of these guidelines is outside the scope of this review.

The common suggestions include:

Cases should be done by an experienced anaesthesiologistComplete airway assessment and preparation should be done on a case-by-case basisVideolaryngoscopes are recommended as the first line of management for the anticipated difficult airway.[29] This may be both direct or indirect with the use of fibreoptic bronchoscopes recommended where possibleThe main objective is to maintain oxygenation.

 Conclusion



The airway of children varies in anatomy and physiology and hence poses various challenges for airway management. Failure to identify these differences and modify management following adequate preparation on a case-to-case basis can lead to dire consequences. However, awareness of the anatomy and physiology of the paediatric airway with good preparation in the hands of an experienced provider can ensure a safe anaesthetic.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given consent for images and other clinical information to be reported in the journal. The guardian understands that the child's name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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