Cuffed Endotracheal Tubes in Children: Size Does Matter!

Abstract

March 15, 2017 • Volume 8 • Number 6 cases-anesthesia-analgesia.org 127 Copyright © 2017 International Anesthesia Research Society DOI: 10.1213/XAA.0000000000000448 The use of a cuffed endotracheal tube (ETT) has become standard of care in pediatric anesthesia. This applies even to neonates and infants and increasingly to pediatric intensive care medicine.1 The main advantage of using cuffed ETTs in children is the markedly reduced tube exchange rate to find an appropriately sized ETT with a smooth fit and a good seal of the pediatric airway when compared with uncuffed ETTs.2 Fundamental advances in the understanding of the pediatric upper airway anatomy and the availability of newer cuffed pediatric ETTs have changed the old historical practice to seal the pediatric airway using an uncuffed ETT just fitting into and/or slightly deforming the elliptical shaped cricoid (cricoidal sealing).3,4 This is in contrast to the use of a slightly smaller-sized cuffed ETT with a thin high-volume low-pressure (HVLP) cuff that allows the smooth passage through the vulnerable larynx and to gently seal the pediatric airway within the less susceptible trachea (tracheal sealing). Sealing the pediatric airway by means of a cuff within the trachea allows the anesthesiologist to compensate for the problem of age-related and individual variations of subglottic size within a certain age group of children. Both can result in high ETT exchange rates, insufficient sealing of the airway, and pressure-related lesions within the larynx when using uncuffed ETTs.2–5 With the use of modern pediatric cuffed ETTs, exchange rates range from 0% to 2.1% with a median cuff inflation pressure of about 10 cm H2O. This sufficiently seals the trachea without increasing the incidence of postextubation stridor. Postextubation stridor as a scientifically valid outcome measure for assessing the pediatric airway injury after endotracheal intubation has been vehemently criticized.9 Endoscopic data in children aged from birth to 6 years, however, did not reveal increased airway injury in children after short-term endotracheal intubation with a cuffed ETT when compared with children without earlier airway instrumentation.10 Many of the airway alterations so far attributed to endotracheal intubation were found in children who had never undergone intubation before. Endoscopic results of prolonged endotracheal intubation with uncuffed and cuffed ETTs in pediatric intensive care patients are expected for 2017 (ClinicalTrials.gov NCT02350933). It must be emphasized that the above-mentioned benefits and safety of cuffed ETTs in children are only achieved if careful endotracheal intubation, confirmation of an air leak with the cuff not inflated, cuff pressure limitation to a maximum of 20 cm H2O, strictly evidence-based selection of ETT size, and the use of an ETT designed to fit the pediatric anatomy are guaranteed.11 The case report by Imai et al12 in this issue of A&A Case Reports documents the considerable dimensional differences between similarly sized cuffed pediatric ETTs from different manufacturers, and the lack of knowledge and information regarding appropriate selection of cuffed ETT size, both resulting in difficulties and even failure to insert a cuffed pediatric ETT. Historically, the selection of uncuffed ETTs in pediatrics was based on their outer diameter (OD).13 In the past, very experienced pediatric anesthesiologists used their knowledge of OD differences between ETTs from different manufacturers when exchanging an inappropriately sized ETT to adjust for the individual pediatric airway anatomy. Today, however, the size of ETTs is internationally defined by its internal diameter (ID), and the ID is used in the age-adjusted selection of an ETT in pediatric patients.14 Although the ID of a specific ETT has to be within a certain manufacturing tolerance, there are considerable differences in the OD of pediatric ETTs because of differences in the wall thickness of pediatric tracheal tube ETTs, not only between ETTs from different manufacturers, but also between ETTs from the same manufacturer.15 However, for the selection of an appropriately sized ETT, the OD is more important than the ID in predicting uncomplicated passage of the ETT through the larynx. Although listing of the OD on the ETT package insert and the ETT surface is required by medical equipment regulations, even the experienced anesthesiologist caring for a child is rarely aware of these subtle differences. Hospitals may change ETT brands for logistic or financial reasons. The accompanying changes in ETT dimensions are not routinely communicated to the medical staff. Moreover, anesthesiologists rarely know age-adjusted laryngeal dimensions of pediatric patients. At present, ultrasound assessment of airway dimensions is more of a research tool than routine practice before endotracheal intubation. It may be helpful in patients with suspected or known subglottic narrowing (eg, in patients with Down syndrome). Lack of knowledge about variations in OD of ETTs at comparable ID has caused serious airway damage in children.16 The use of oversized cuffed ETTs (by selection or choice of manufacturer) is considered the likely cause of most cases of postextubation stridor and severe laryngeal damage observed in children after intubation with a cuffed ETT.1,17 The introduction of HVLP cuff ETTs has increased the effective OD of a cuffed ETT, making insertion more difficult, at times even impossible, particularly in pediatric patients. This was systematically investigated many years ago. Considerable differences between low-volume highpressure and HVLP cuff ETTs were shown.18 The large cuff bulk of conventional HVLP pediatric ETTs resulted in the recommendation to decrease the calculated ID by 1.0 mm From the Department of Anesthesia, University Children’s Hospital, Zurich, Switzerland; and Department of Pediatric Anesthesia, a Medical Faculty, University of Zurich, Switzerland.