Children have unique characteristics that make them particularly vulnerable to perioperative adverse events. Skilled airway management is a cornerstone of high-quality anesthetic management. The use of hybrid airway techniques is a critical tool for the pediatric anesthesiologist. Point-of-care ultrasonography has an expanding role in airway management, from preoperative assessment of airway pathology and gastric contents to confirmation of tracheal intubation and identification of the cricothyroid membrane. The exciting fields of 3-dimensional printing, artificial intelligence, and machine learning are areas of innovation that will transform pediatric difficult airway management in years to come.
Key points
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Children are particularly vulnerable to adverse events during airway management.
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Understanding how to use hybrid techniques to manage the pediatric airway is critical for the pediatric anesthesiologist.
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Point-of-care ultrasonography, 3-dimensional printing, artificial intelligence, and machine learning are technologies that are bringing innovation to the management of the pediatric difficult airway.
Introduction
Skilled airway management is a cornerstone of high-quality anesthetic management. Respiratory complications remain a frequent cause of anesthetic-related complications in children due to their unique anatomy and physiology. The infant or child with a difficult airway poses even greater challenges for clinicians. New technologies have improved the safety and management of pediatric difficult airways. The use of hybrid airway techniques, point-of-care ultrasonography (POCUS), novel ventilation devices, 3-dimensional (3-D) printing, artificial intelligence, and machine learning are transforming pediatric difficult airway management. This article summarizes the recent scientific literature, introduces novel airway devices and techniques, and highlights areas of innovation that are advancing pediatric difficult airway management forward.
Unique characteristics of the pediatric airway
Children have anatomic characteristics that make airway management potentially challenging. They have a large occiput that naturally flexes the neck while they are lying supine, leading to upper airway obstruction and soft tissue compression. Their large occiput and more cephalad larynx make it challenging to align their oral, pharyngeal, and laryngeal axes during laryngoscopy. Their tongue and tonsils are proportionally larger than their oropharynx, leading to upper airway obstruction. The pediatric epiglottis is stiff, omega-shaped, and difficult to lift to obtain a view of the glottic opening. The cricoid cartilage is the narrowest point of the airway in an infant, increasing the risk of subglottic trauma with endotracheal tube (TT) placement. The trachea and lower airways are small in diameter, leading to exponential increases in airflow resistance when narrowed.
Children also have respiratory characteristics that predispose them to rapid oxygen desaturation during intubation. Their soft chest wall is compliant due to lack of ossification of the rib cage and is prone to collapse during tidal volume breathing under anesthesia, leading to atelectasis and loss of functional reserve capacity. Children consume more oxygen than do adults, leading to rapid oxygen desaturation during apnea. The infant’s parasympathetic system is more fully developed than their sympathetic system, causing infants to respond to hypoxic stress with bradycardia and consequent cardiac arrest.
Incidence and predictors of the pediatric difficult airway
Challenges in airway management are categorized as occurring during mask ventilation, intubation, or supraglottic airway (SGA) placement. Patient characteristics help predict when one of these steps may be difficult. Congenital and acquired abnormalities of the head and neck often are associated with difficult airway management. The Committee on Nomenclature and Classification of Craniofacial Anomalies of the American Cleft Palate-Craniofacial Association has organized anomalies into 5 categories : clefts, synostosis, hypoplasia, hyperplasia, and unclassified—with each of the categories associated with difficult airway management. Large cleft palates are associated with difficulty intubating. Craniosynostosis occurs when there is premature closure of 1 or more cranial sutures. Some of the most common craniosynostosis syndromes include Apert, Pfeiffer, Crouzon, Saethre-Chotzen, Carpenter, and Muenke syndromes and these syndromes are associated with difficult intubation. Examples of syndromes associated with craniofacial hypoplasia include Pierre Robin sequence and Goldenhar syndrome. Ease of intubation tends to improve with age in children with hypoplastic craniofacial dysmorphisms. Mucopolysaccharidoses, including Hunter and Hurler syndromes, and vascular malformations are hyperplastic anomalies associated with difficult airway management.
Difficult Mask Ventilation
The incidence of difficult bag-mask ventilation (DBMV) among healthy children in the 0 to 8-year age range is reported to be 6.6%. This is much higher than the reported incidence of 1.5% of DBMV in adults. Valois-Gomez and colleagues studied a population of 484 children between the ages of 0 to 8 years undergoing elective surgery requiring bag-mask ventilation (BMV) and tracheal intubation. They defined DBMV as the occurrence of greater than or equal to 2 of the following events during BMV: application of continuous positive airway pressure of greater than or equal to 5 cm H 2 O, required use of an oral/nasal airway, need for 2-person ventilation, desaturation less than 95%, and unanticipated need to increase fraction of inspired oxygen. Patient risk factors for DBMV were age less than 1 year and otolaryngology (ear, nose, and throat [ENT]) surgery.
Difficult Tracheal Intubation
Valois-Gomez and colleagues determined the incidence of difficult tracheal intubation in children to be 1.2% and defined difficult tracheal intubation as the presence of greater than or equal to 2 of the following: Cormack-Lehane laryngoscopic view grade III or grade IV; greater than 3 attempts at intubation; intubation time greater than 5 minutes in total (sum of all attempts between the time the operator holds the laryngoscope until the TT passes the cords and the position is verified by auscultation and positive EtCO 2 ); and presence of desaturation less than 95%. The incidence of difficult intubation in children is similar to the incidence reported in adults of 1.8%.
Heinrich and colleagues found a similar incidence (1.35%) of difficult direct laryngoscopy (DL) in pediatric patients ages 0 to 18 years old. They analyzed a cohort of 11,219 pediatric patients undergoing anesthesia over a 5-year period and found patient age less than 1 year, American Society of Anesthesiologists physical status class III or IV, Mallampati score class III or IV, and low body mass index as risk factors associated with difficult DL. In the cohort, infants had the highest incidence of difficult DL (5%), followed by neonates (3.2%). The study also found that patients undergoing pediatric cardiac or oromaxillofacial surgery have a high incidence of difficult laryngoscopy—potentially explained by the finding that congenital heart defects often are associated with craniofacial dysmorphisms.
Difficult Supraglottic Airway Device Placement
SGAs, including laryngeal mask airways (LMAs), may be used as the primary airway device during general anesthesia or as a secondary technique during rescue and emergency airway management. SGAs are indicated for rescue ventilation in pediatric difficult airway algorithms when mask ventilation or tracheal intubation is difficult or impossible. In a retrospective study of 11,910 anesthetic cases in pediatric patients less than 18 years old, Mathis and colleagues identified that LMAs failed to rescue the airway in 0.86% of attempts. Risk factors for LMA failure were patient age less than 2 years old, ENT procedures, inpatient status, prolonged surgical duration, airway abnormalities, and room-to-room transport with an LMA in place.
Complications during pediatric difficult airway management
A relatively high rate of severe critical events occurs during anesthetic management of children. The Anaesthesia Practice in Children Observational Trial (APRICOT), a prospective observational study of children less than 15 year old undergoing 31,127 anesthetic procedures across 261 hospitals in Europe, found that the incidence of perioperative severe critical events was 5.2%. The incidence of respiratory critical events, including laryngospasm, bronchospasm, bronchial aspiration, and postanesthesia stridor, was 3.1%. Severe critical events occurred more often in children who were considered difficult to intubate. This finding was corroborated by a study from the Pediatric Difficult Intubation Collaborative. The group analyzed 1018 difficult pediatric tracheal intubation encounters across 13 children’s hospitals and showed that 20% of pediatric patients with difficult intubations experienced perioperative complications, including cardiac arrest, hypoxemia, laryngospasm, and airway trauma ; 3% of these children had severe complications, including 1% having cardiac arrest. Children with unanticipated difficult airways had an even higher incidence of cardiac arrest, at a 3% rate. Complications during difficult tracheal intubation were associated with the following risk factors: weight less than 10 kg, short thyromental distance, multiple tracheal intubation attempts (>2), and persistent DL attempts (≥3). Important takeaways from these studies are that the anesthetic management of a child less than 10 kg and with a short thyromental distance requires particular attention and preparation for a suspected difficult airway. Additionally, for children at risk of difficult tracheal intubation, each intubation attempt should be treated as a critical intervention and the number of DL and intubation attempts should be limited.
Devices and techniques for the pediatric difficult airway
Oxygenation for the Pediatric Difficult Airway
Hypoxemia is one of the most common complications associated with pediatric difficult airway management. In both adult and pediatric populations, oxygen delivery during tracheal intubation attempts reduce the incidence of hypoxemia. Oxygen may be delivered during intubation while patients are kept spontaneously ventilating or while they are apneic.
Apneic oxygenation is a concept first described by Martin Holmdahl in 1956. During apnea, oxygen is taken up from the alveoli due to the differential rate between alveolar oxygen absorption and carbon dioxide excretion, producing a mass flow of gas from the upper respiratory tract into the lungs. Apneic oxygenation may be delivered in a variety of ways, including via nasal cannula, modified nasopharyngeal airway, modified oral Ring-Adair-Elwyn (RAE) TT, or heated humidified high-flow nasal cannula (HHHFNC) ( Fig. 1 ).
HHHFNC is technique that originally was used in neonatology as a mode of respiratory support for premature infants, decreasing the need for tracheal intubation. Cool dry gas delivered through nasal cannula at flows greater than 2 L/min quickly dry nasopharyngeal and oropharyngeal mucosa and is not well tolerated in young children. HHHFNC heats gas to body temperature and humidifies it to greater than 99% relative humidity, allowing for comfortable delivery of gas flow rates matching or exceeding a patient’s inspiratory flow rate. This technique is used during adult difficult airway management to prolong the apneic time postinduction and is referred to as transnasal humidified rapid-insufflation (THRIVE). THRIVE also has been described to be effective in delaying hypoxia in children during apnea after induction of anesthesia. Humphreys and colleagues showed that children who received THRIVE doubled their time to desaturation to 92%. The flow rates used by Humphreys and colleagues are shown in Table 1 . Anesthesiologists should consider delivering supplemental oxygen during difficult airway management of a child to reduce the risk of hypoxemia, using one of the numerous options available.
| Weight | Flow Rate |
|---|---|
| 0–15 kg | 2 L/kg/min |
| 15–30 kg | 35 L/min |
| 30–50 kg | 40 L/min |
| >50 kg | 50 L/min |
Videolaryngoscopy
Videolaryngoscopy (VL) allows the larynx to be visualized indirectly via a camera at the end of a laryngoscope blade. As opposed to DL, where the oral, pharyngeal, and laryngeal axes must be aligned to view the glottis, VL with a camera and video cable allows the operator to see around curves. An ever-increasing number of VL systems continue to be developed, including standard blades and hyperangulated options.
Standard blade videolaryngoscopes
Standard blade VLs have a similar shape and size to conventional Miller and Macintosh blades with the addition of a camera at the tip of the blade. The 2 main techniques for standard blade VL use are (1) traditional VL and (2) video-assisted DL. Video-assisted DL is a technique where the laryngoscopist performs DL and has the back-up of the VL in the setting where DL is challenging. The application of this technique is increasingly popular in medical education. A trainee is able to perform DL with the VL, with an instructor looking on at the video screen, giving real-time feedback and coaching. , This technique has been useful particularly in teaching learners the intubation technique for neonates and infants, a population known to have a higher incidence of DBMV and difficult tracheal intubation and prone to rapid oxygen desaturation during airway management.
Hyperangulated videolaryngoscopes
There are several hyperangulated VLs available for use in children. Hyperangulated VLs cannot be used to perform standard DL because of the blade’s acute angle, typically between 55° and 90°. A common problem with hyperangulated blades is a phenomenon called view-tube discrepancy, or when a good view of the glottis is obtained but there is difficulty advancing the TT into the trachea. The inherent angle of the blade, curvature of the styletted TT, and potentially challenging patient anatomy all contribute to this difficulty of advancing the TT into the trachea. Zhang and colleagues conducted a prospective observational study of 225 GlideScope (Verathon; Bothell, Washington)-guided intubations in children less than 6 years of age and determined that 58% of attempts had technical difficulties, with the most common difficulty being “view-tube discrepancy.” Technical difficulty was most likely to occur when the TT was advanced between the arytenoid cartilages just beyond the vocal cords. The TT often would catch on the arytenoid cartilage. Clockwise rotation of the TT was the most helpful maneuver to resolve this issue. The overall success rate of tracheal intubation with this technique was 98%, with first-attempt success rate of 80%.
Channeled VLs are a subset of hyperangulated VLs that have a guidance channel for a TT to be integrated into the blade of the scope. The potential benefit of channeled VLs is that when a view of the glottis is obtained, advancing the TT through the channel theoretically leads the tip of the tube through the glottic opening. Channeled devices, however, also have been associated with view-tube discrepancy. Table 2 shows commonly used pediatric videolarygoscope systems.
| Hyperangulated | Nonangulated | |||||
|---|---|---|---|---|---|---|
| Manufacturer | Neonatal/Infant | Pediatric | Teen | Neonatal/Infant | Pediatric | Teen |
| GlideScope a (Verathon) | + | + | + | Forthcoming | Forthcoming | + |
| C-MAC b (Karl Storz, El Segundo, California) | +/− | + | + | + | + | + |
| McGrath c (Medtronic, Minneapolis, Minnesota) | − | − | + | + | + | + |
| Airtraq d (Teleflex, Morrisville, North Carolina) | + | + | + | − | − | − |
| Truview PCD (Truphatek, Netanya, Israel) | + | + | + | − | − | − |
| UE Scope (UE Medical Devices, Newton, Massachusetts) | − | + | + | + | − | − |
| King Vision d (Ambu, Columbia, Maryland) | + | + | + | − | − | − |
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