Cuffed vs non-cuffed endotracheal tubes for pediatric anesthesia

Pediatric Anesthesia 2009

19 (Suppl. 1): 46–54

doi:10.1111/j.1460-9592.2009.02998.x

Pro-Con Debate

Cuffed vs non-cuffed endotracheal tubes for pediatric anesthesia U N C U F F E D TU BE A D V O C A T E S : TO N I W E B E R Zentrum fu¨r Kinderana¨sthesiologie Deutsches Kinderherzzentrum Sankt Augustin, Germany

CUFFED TUBE ADVOCATES: N A D E` G E S A L V I M D , G I L LE S O R L I A G U E T

MD PhD

De´partement d’Anesthe´sie Re´animation Chirurgicale, Universite´ Paris Descartes, Paris Cedex, France

MODERATOR: ANDREW WOLF Bristol Royal Hospital for Sick Children, Bristol, UK

Introduction The physician undertaking pediatric anesthesia or management of the critically ill child in the pediatric intensive care unit (PICU) has great potential to cause harm to the child. Over many years, routine management of the pediatric airway has become a relatively safe undertaking and this has been achieved through the worldwide development of the speciality of pediatric anesthesia and intensive care. Any future development needs to acknowledge the large body of developmental work from past that has provided reproducible safe practice. Change must not be for change itself, and at the forefront of our practice must be the desire to provide optimized care that is evidence-based as far as possible. New techniques should be evaluated and adopted only if there is substantial evidence that innovation will be beneficial in the widest sense. This includes not only direct patient benefit but also the wider medicoeconomic arguments. The ‘pro and con’ for the direct medical benefits of cuffed vs uncuffed tubes in children remain finely poised, but the medicoeconomic arguments are irrifutable: cuffed tubes remain many times more expensive than uncuffed tubes and are likely remain so. On this basis alone it can be hard to justify the routine use of the cuffed tube provided equipoise between the two techniques remain. In contrast, on an individual basis there may

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be strong arguments in favor of selecting a cuffed tube provided there is justification. While enthusiasts of the cuffed tube continue to promote their potential benefits, the majority of pediatric anesthetists worldwide continue to safely use the uncuffed tube on a daily basis and find it hard to justify the large extra costs needed to change their practice when the benefits remain largely unproven. In this, the first in a new series of pro– con debates in Paediatric Anaesthesia we will examine the arguments for and against their use from the perspective of two expert views, with the goal that this will help the reader make up their own mind of whether to reconsider their current practice.

Uncuffed tubes should continue to be used in pediatric anesthesia Toni Weber Deutsches Kinderherzzentrum Sankt Augustin, Arnold Janssen Str. 29, D 53757 Sankt Augustin, Gemany A cornerstone of good medicine is maintaining safety, simplicity, and effective practice. Ignoring these basic principles can lead to unforseen problems which may not be immediately obvious. Examples of how development may lead to unforeseen complications lie in the highly regulated aircraft industry. An aircraft is a highly complex device, but  2009 The Authors Journal compilation  2009 Blackwell Publishing Ltd

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it can also be regarded as the total the sum of many simple effective solutions. When the new generation of mainly computer-assisted civil airplanes were introduced in the late 1980s it met with substantial critisism of the new so called fly by wire philosophy (invented to reduce cockpit personnel), which led to substantial changes at the human–machine interface. Those changes led to a series of unforeseen events and incidents (1). However until 1994, not a single cause of an accident could be adressed to the machine itself. The reasons for critical incidents were in general problems at the human–machine sytem interface. Similarly in modern anesthesia: the elaborate equipment and monitoring systems have been designed to make our job easier and safer. However, the underlying technology and the machine–human interface is necessarily more complex especially in the need to add advanced skills such as ultrasonography (for transesophageal echocardiography or central line placement). This, like the example with the aircraft industry may lead to errors at the interface in that while the machine and human work correctly at an individual level, errors of decision may be made from misinturpretation at the interface. The development of the cuffed pediatric endotracheal tube into pediatric practice, has added a relatively new and ‘simple’ feature to an established piece of anesthetic equipment. The change to the device is in itself minor and has precedent in the long-term use of cuffed endotracheal tubes (ETT) in adults, but the application within pediatric anesthesia leads to quite complex changes in the ‘interfaces’ between patient, ventilator, and the anesthetist. Key concerns include: 1. The need to use a smaller internal diameter (ID) tube in order to place the cuff, 2. The need for additional monitoring and adjusting of cuff pressure 3. The potential morbidity from the cuff by pressure, 4. The potential for innapropriate tube placement or cuff herniation. Intubation with an ETT (whether cuffed or uncuffed) that is too large can lead to laryngeal damage, tracheal damage and sublottic stenosis with significant long-term morbidity which in the most extreme cases may require tracheostomy and laryngeal or tracheal reconstruction. Initially high pressure applied on the mucosa from an oversized

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tube or an inapropriately used tube cuff leads to local ischemia followed by deep ulceration of the perichondrium or even into the cartilage. This leads to secondary submucosal collagen formation and scar tissue which emerges from maturing and thickened connective tissue. Subsequently a slow contraction from the scar tissue results giving rise to glottic or subglottic stenosis. Some areas appear more vulnerable than others and a particular at risk area is the inner surface of the cricoid cartilage, in the area of the posterior lamina (2),. Additional risk factors for this pathology include duration of intubation (longer than 25 days), repeated intubations and excessive movement of the patient. Comorbidity such as sepsis, infection, chronic illness, or chronic inflammatory disease may also influence the outcome (2). The nature of the pathophysiological process is supported by an earlier neonatal study published 11 years earlier which also describes progressive changes within clearly defined areas in the larynx associated with intubation (3). While the authors doubted that prolonged intubation alone produced subglottic stenosis they did conclude that severe damage to the laryngeal cartilage is an early complication of the intubation procedure together with other individual patient factors. One of the obviously avoidable factors is excessive mucosal pressure either from an over-large uncuffed endotracheal tube (UTT) or an inflated cuff in a cuffed endotracheal tube (CTT). The overall incidence of intubation trauma in the pediatrics is significant with the vast majority of problems (82%) being ascribed, based on endoscopic examination, to an excessively large ETT rather than the intubation procedure itself (4). Longer-term, the incidence of subglottic stenosis has been reported as between 0 and 8% (5–7) with a large series of 3 000 critically ill patients having prolonged intubation without any developing aquired subglottic stenosis. The adoption of a CTT does not protect the patient from airway trauma. Over a 10 year period (1987– 1997) Holzki reported four severe laryngeal injuries caused by CTT on the basis of a screening program documenting postintubation stridor of clinical relevance. Four years later the same author reported six similar lesions in 1 year (8). Concerns have also been raised about the potential for tube misplacement. The distance from glottis to carina is relatively short

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and the design of some cuffed tubes has been such that when the cuff is correctly placed just below the vocal cords, the tip of the tube is already at the carina (9). Meticulous selection of the ETT remains the mainstay of good practice with intellegent use of formulae based on age. The traditional formulae of 4 + age ⁄ 4 has given way to 4.5 + age ⁄ 4 which may reflect the increased growth profile of contemporary children and the reduced wall thickness of modern ETT compared to the historic rubber tubes.(the tube size refers to the intenal tube diameter). It is also worth noting that the formula does only apply from age 2 years and above. In practice, the formulae acts only as a guide in that the more experienced practitioner effectively reduces the number of attempts of intubation by simply visualizing the glottic opening at the first laryngoscopy and then estimate the right tube size, a technique which is widely and effectively adopted in our institution. A recent study comparing cuffed and uncuffed tubes in pediatric practice noted a 23% reintubation rate in the uncuffed group (10). However, selection of the initial tube size was based on a formula alone and this does not reflect realistic clinical practice: An added complexity is that even today not all ETT have the same wall thickness. For example the outer diameter of a Portex ID 3.5 is 4.8 mm and in contrast the outer diameter of a Vygon 3.5 ID is 5.1 mm. It could be argued that this becomes less important if a cuffed tube is being used, but this in itself introduces an additional problem. In general, the cuffed tube selected for intubation will be smaller than the uncuffed tube because cuffed tubes are manufactured with thicker walls and the cuff ‘adds’ the additional diameter to form the seal with the trachea. As a result choosing a cuffed tube necessitates using a tube with a smaller ID. While this may be of less relevance in the older child it has been pointed out that the difference of a 3.0 mm tube compared to a 4 mm tube represents a three-fold increase in airway resistance leading to potential problems increased work of breathing and the problems with retenion of secretions and even airway occlusion (11). In the long history of the UTT the potential disadvantages of undersized tubes have been well documented. These include variable airleak, difficulties in effectively ventilating the patient with lung

disease or allowing atelectasia, environmental contamination of anesthetic gasses, risk of aspiration, and difficulty in accurate masurement of endtidal CO2 concentration. Despite these potential problems, the use of the uncuffed pediatric endotracheal has remained popular and with the many years of usage pediatric anesthetists have learnt to overcome these shortcomings effectively. While tight fitting tubes confer benefit in patients with critical ventilation (such as pulmonary hypertension) the safe pressure in the child with cardiac compromise remains unknown. Dullenkopf suggested that cuff pressures below 25–30 cm H2O should be accepted (12) in children with a compromised cardiovascular system, but this was not evidence-based and accepting a leak brings in to question the whole issue of whether a cuffed tube should have been used In our institution with a large pediatric surgical and cardiac service we use a throat pack on occasions to reduce the number of repeated intubations with uncuffed tubes to below 5–10% which allows good control of advanced ventilatory modes with modern ventilators that can adjust for leaks. Many of the studies on cuffed vs uncuffed tubes are undertaken by enthusiasts and the conclusions of these studies are open to critisism and claims of bias. For example Deakers (13) compared two groups of children in an intensive care enviroment were the patients intubated with an uncuffed tube had a mean of 2.5 years of age while the children intubated with a CTT have been a mean of 8.1 years old. In the paper of Khine in which the outcome measure was postintubation stridor (10) the intubation time was just about an hour, the number of neonates was not mentioned and it could be argued that there was substantial study bias in terms of meticulous control of cuff pressure and tube position. Up to the year 2005 there was only one randomized and controlled trial on cuffed vs cuffed tubes (10). Most of the other available studies have concentrated on postextubation stridor which does not appear to be related to incidence of subglottic stenosis (14,15). The sheer numbers of manufacturers making cuffs, the types of design of cuff (high-volume lowpressure vs standard design), the lack of standardization of the tube design have been very confusing. In one study by Weiss a total of 15 tube types from four different manufacturers were tested which adds significant confusion (16) and discouragement to try

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this out in clinical practice. The authors concluded at the time that most tubes were poorly designed particularly in the younger age group and that a lot more work was needed. Not surprisingly, a majority of pediatric anesthetists interviewed in a recent UK survey felt that minimal benefit could be gained from cuffed tubes (17). More interestingly, all of the responding anesthetists and 45% of the intensivists reported that they did not routinely monitor the intracuff pressure, when using a cuffed tube. Similar results were reported in a 2001 European study by Orliaguet (18). Cuff pressures do not remain static due to temperature effects, gas exchange and local factors including cuff movement, muscle relaxation, and anesthetic depth. Increasing cuff pressure promotes mucosal damage while reduced pressure can allow leak. Modern cuff design may reduce complications but meticulous pressure monitoring is mandatory. No doubt, an endoscopically positioned, cuffed tube with closely monitored control of cuff pressure and tube movement would be unlikely to cause difficulties. Moreover, for individual clinical situations particularly in intensive care there might be clear benefit, but in a rapid turnover operating list with healthy patients this might not be a feasible or sensible option. The cuffed tube, while intrinsicaly safe, suffers from increased complexity and a bewildering variety of manufactured options that requires additional patient ⁄ equipment physician interphase. Under pressurized working conditions errors whose adverse consequences may lie dormant within the system may become manifest when combined with other factors They are most likely to be spawned by those whose activities are removed in both time and space from the direct control interface: designers, high level decision makers contruction workers, managers, and maintenance personnel (19). Indeed a recent survey among California anesthesiologists had witnessed a critical incident in which patient safety was compromised owing to pressure on the anesthesiologist (20). In conclusion, while pediatric airway itself has not changed, efforts have been made to achieve better control of the airway and reduced airway manipulation through development of a pediatric cuff. Despite potential advantages of the CTT they are yet to prove themselves against a technique that has

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a safety and reliability record over over 40 years. CTT also have disadvantages, with a smaller margin of safety (9) and a requirement for precise positioning. Undoubtedly they have a place in pediatric anesthesia but with their increased cost, added complexity and the continuing problems associated with applying cuffed tubes in the youngest infants, they remains a selective tool for the older child.

The case for cuffed tracheal tubes in routine pediatric anesthesia Nade`ge Salvi M.D., Gilles Orliaguet MD. Ph.D. De´partement d’Anesthe´sie Re´animation Chirurgicale, Universite´ Paris Descartes, Paris Cedex, France Until the end of past decade, the use of uncuffed tracheal tubes (UTT) was the rule for endotracheal intubation in children under 8 years of age during pediatric anesthesia and in the pediatric intensive care unit (PICU). In fact, two surveys have shown that UTT were, until recently, preferred in routine practice in children by some pediatric anesthesiologists (18,21). Three major arguments were cited in favor of this choice. Firstly, the use of a UTT was supposed to reduce the risk of laryngeal mucosa injury and thus the risk of secondary subglottic stenosis. Secondly, the use of a cuffed tracheal tube (CTT) was not required because of anatomic considerations, such as a narrow subglottic region of the trachea. Thirdly, the choice of a CTT requires the use of a tube with a smaller internal diameter, leading to higher respiratory airway pressures, as well as an increased work of breathing and risk of tube obstruction. But these latter arguments were only relevant when children breathed spontaneously during anesthesia with ether or in the neonatal intensive care unit. Recent studies have shown that the use of CTT was safe in pediatric anesthesia as well as in PICU (10,22), leading to a larger use of CTT by many teams. Indeed, endotracheal intubation with a CTT presents many advantages. This review will describe these advantages and the reasons why we have chosen to routinely use CTT in our department. The use of an adapted size of CET is not associated with an increased risk of respiratory complications. In a review by James in 2001 he concluded that ‘the little evidence we have is that cuffed tubes are not more dangerous than uncuffed tubes’ (23), and now

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many studies are available that provide evidence of the safety of CTT in children. In their now classical study, in 1997, Khine et al. compared (10) the use of CTT and UTT in pediatric anesthesia. One of their outcomes was the incidence of upper airway symptoms, such as croup, which was regarded as evidence of laryngotracheal injury. They found no more croup in the CTT group as compared with the UTT group during the postoperative period. In another study, Murat (24) evaluated the use of CTT since their introduction in routine practice in 2000 in its department. She showed that respiratory complications in the recovery room were not associated to the use of CTT. A recent study by Duracher et al. (25) evaluated the use of the Khine formula in predicting the correct size of CTT in pediatric anesthesia. Their secondary outcome was the incidence of postintubation respiratory complications. They reported six cases of complications among 204 cases analyzed (2.9%). Three cases required treatment using epinephrine or cortico-steroids. No tracheal reintubation or subglottic stenosis were recorded and there were no long-term complication. The complications were related, in three cases, to the use of CTT of an incorrect predicted size. Moreover, Newth et al. (22) evaluated the safety of CTT in a large cohort of critically ill children hospitalized in a PICU. The primary outcome was the frequency of postextubation croup following long-term tracheal intubation using either a CTT or UTT. They found no difference between the two groups, even in neonates, provided the CTT size was carefully selected and the cuff pressure (Pcuff) of the CTT was monitored and adapted. Finally, even in the emergency settings, the use of a CTT is safe as shown by Meyer et al. (26) In fact; the authors demonstrated that the occurrence of laryngotracheal complications after emergency tracheal intubation in severely injured children was not related to the use of a CTT. In summary, several risk factors for laryngotracheal injury have been identified, including traumatic intubation, prolonged duration of intubation and severe arterial hypotension during laryngoscopy; however the main factor constantly found is the use of an oversized tracheal tube. (26–28) Finally, no study has demonstrated an increased risk of airway complications related to the use of CTT provided a CTT of appropriate size is chosen and the cuff pressure is monitored and adapted.

Another advantage of CTT is that the presence of a cuff makes a better seal between the cuff of the CTT and the trachea. The control of an important air leak with a CTT requires only adding air in the cuff instead of performing a new tracheal intubation with a different-sized tube. (29) In the study by Khine et al. (10), 23% of the patients of the UTT group required reintubation vs 1.2% in the CTT group. Avoiding multiple intubations is important because it represent an independent risk factor for laryngeal mucosa injury. In addition, the use of CTT allows reducing air leak around the tube and thus improves several aspects of patients care. Tracheal intubation with a CTT is probably the most reliable mean to ensure adequate positive pressure ventilation. Indeed, tidal volume or airway pressures can be dramatically modified in case of air leak during mechanical ventilation with a UTT, which may in turn compromise gas exchanges potentially leading to many complications (hypoxemia, altered pulmonary artery pressure, excessive variability of PaCO2 etc). In contrast, in the lack of air leak, respiratory parameters, such as tidal volume or airway pressure, are more precisely and consistently obtained, especially in patients with low lung compliance. The use of CTT allows positive end-expiratory pressure (PEEP) to be used reliably. Reduced gas leak also allows techniques such as low fresh gas flow anesthesia in a circle system to be used, with accurate monitoring of inspired and expired gas composition (30). Reducing air leak, particularly if this allows a low flow circle system reduces consumption of volatile agents reduces atmospheric pollution (10) and can lower the cost of anesthesia. The introduction of CTT in routine practice was reported by Murat et al. to reduce sevoflurane and N2O concentrations measured on anesthesiologists in the operating room, from 48.1 ppm and 192 ppm to 0.3 ppm and 29.4 ppm, respectively (24). These results are important if one keeps in mind that the limit tolerates by the American National Institute for Occupational Safety and Health (NIOSH) for N2O exposure is 25 ppm. The last, but not least, argument for the use of a CTT is the decrease in the risk of gastric content aspiration (13, 31), which may be very useful in children with a full stomach (32). In fact, a recent study by Gopalareddy et al. (33) showed that the rate

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of microaspirations, evaluated by gastric pepsin measurement in tracheal aspirates of ventilated children, was lower in the CTT group than in UTT or tracheotomy groups. If a CTT is used special attention is required to prevent induced airway mucosal injury. An appropriately sized tube must be selected of adequate internal diameter (ID). Many formulas are existing and the formula most commonly used is the Khine’s one: cuffed tube size (mm ID) = (age ⁄ 4) + 3 (10). However, a recent study has shown that Khine’s formula underestimated the size of CTT by 0.5 mm. This may lead to a need of reintubation to limit air leaks (25). Duracher et al. proposed the following formula for children older than 1 year of age: cuffed tube size (mm ID) = (age ⁄ 4) + 3.5. Another very important factor to take into account to prevent postintubation laryngeal injury is the outer diameter (OD) of the tube. Several studies by Weiss et al., who analyzed various CTT or UTT in vitro, have shown that for a given ID the OD of the tube may greatly differ from one manufacturers to the other (16,34). (Table 1). So, the choice of an optimal size fitted CTT requires to take into account not only the ID but also the OD. Another challenge seems to be the adequate placement of the cuff relative to the cricoid ring. Simply placing the cuff below the cricoid ring, as suggested by James (23) seems insufficient. Indeed, Weiss et al. recently concluded that ‘most cuffed paediatric tubes are poorly designed, in particular the smallest sizes’ and that the ideally ‘cuffed paediatric tracheal tube should have a

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high-volume-low pressure cuff with a short cuff length, adequate depth markings and not allow the cuff to be inflated in the subglottic region’ (16). More recently Weiss has evaluated a new CET (Microcuff Paediatric Tracheal Tube, Microcuff Endotracheal Tube for Pediatrics: Kimberly-Clark Global Sales Inc, Roswell, GA, USA) and showed that it allows safer placement of the cuff according to the depth marks (35). During general anesthesia, N2O remains still frequently used. Several studies have demonstrated that during anaesthesia using a N2O ⁄ oxygen gas mixture the Pcuff increases because of N2O diffusion into the cuff (36). This problem mainly occurs during the first 105 min (37) and may potentially lead to tracheal damages because of a decrease in the tracheal perfusion pressure (38). In adult patients, a study showed that the mucosal capillary pressure of the trachea ranged 25–30 mmHg (39). In children, the value of this mucosal capillary pressure is unknown, but is probably less because systemic pressure physiologically decreases with decreasing age. Meyer et al. (26) showed that the occurrence of shock at the time of emergency intubation was significantly associated with long-term laryngo-tracheal complications, while the use of cuffed tube was not. Thus, it is of utmost importance to carefully control Pcuff and there are several ways to proceed. In fact, free inflation of the cuff with air and control using pilot balloon palpation results in extremely variable cuff pressure, ranging from 0 to 120 cmH2O in children (37). Therefore several studies have described different ways of filling the cuff in order

Table 1 Measured outer diameters (OD) of paediatric cuffed tracheal tubes according to the internal diameter (ID) of tracheal tubes supplied by different manufacturers ID OD (mm)

Tracheal tube brand

2.5

3.0

3.5

4.0

4.5

5.0

5.5

Sheridan Tracheal Tube cuffed Murphy Sheridan Tracheal Tube cuffed Magill Mallinckrodt TT High-Contour Murphy Mallinckrodt TT High-Contour Murphy P-Serie Mallinckrodt TT Lo-Contour Magill Mallinckrodt TT Lo-Contour Murphy Mallinckrodt TT Hi-Lo Murphy Mallinckrodt TT Safety Flex Portex TT- Profile Soft Seal Cuff, Murphy Ru¨sch Ruschelit Super Safety Clear Magill Ru¨sch Ruschelit Super Safety Clear Murphy

NA NA NA NA NA NA NA NA NA 4.0 NA

4.2 4.3 4.4 4.3 4.5 4.4 NA 5.2 NA 5.1 NA

4.9 NA 4.9 5.0 4.9 5.0 NA 5.5 NA 5.3 NA

5.5 5.5 5.7 5.7 5.7 5.6 NA 6.2 NA 5.9 NA

6.2 NA 6.3 6.4 6.2 6.2 NA 6.7 NA 6.2 NA

6.8 6.9 7.0 6.7 6.9 7.0 6.9 7.2 7.0 6.7 6.7

7.5 NA 7.6 7.7 7.5 7.5 7.5 7.9 7.6 7.2 7.3

Adapted from (18). NA, not available (tubes not produced by manufacturers).  2009 The Authors Journal compilation  2009 Blackwell Publishing Ltd, Pediatric Anesthesia, 19 (Suppl. 1), 46–54

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to prevent both initial as well as secondary cuff overinflation during N2O anesthesia. Tu et al. proposed to fill the cuff with an N2O-oxygen gas mixture and showed that postintubation laryngeal mucosal lesions were less common using this method (38) Combes et al. showed that there were less severe laryngeal mucosal lesions if the cuff was filled with normal saline (36). But they do not recommend this technique because the CET are not designed for that. Anyway, a safe attitude during N2O anesthesia is certainly to monitor the Pcuff continuously and to remove iteratively the gas in excess from cuff to maintain Pcuff around 20 cmH2O (36,37). Another solution is to avoid using N2O during anesthesia. However, avoiding N2O during anesthesia does not prevent the risk of cuff initial cuff overpressure. Indeed, the cuff may be overinflated after free filling immediately after tracheal intubation; therefore initial control of Pcuff is recommended (37). In conclusion, CET can be safely used in pediatric patients and are associated with many advantages. The increased cost of CTT compared to UTT is greatly compensated by the decrease in the reintubation rate, reducing the cost of using different tracheal tubes (at least two), as well as by the reduction in halogenated agents consumption permitted by fresh gas flow anaesthesia. The global risk to benefit balance of using CET seems in favor of CET as compared to UTT. Finally, there is no more argument to avoid routinely using CET in pediatric anesthesia, intensive or emergency care provided a tube with an adequate high-volume low-pressure cuff is selected (40) and some important precautions are carefully respected. These include appropriate choice of a CET size, careful Pcuff monitoring throughout the case and adjustment of this pressure as necessary.

Questions and conclusions These two contrasting articles highlight issues that are yet to be resolved with anesthetists who are considering altering their practice. To help this further, the authors have been asked a few key questions (set out below) that may help: 1. At what age ⁄ weight would you change from uncuffed to a cuffed tube and why? TW: For routine purposes I would change to cuffed tubes at an age from 6 years on. That

correlates with an ETT tube ID of 5.5 mm. In very special cases when vigorous control of the airway is mandatory e.g. patients undergoing major laparotomies or children with diminished lung compliance where precise CO2 control is one of the therapeutic principles, I would go down to an age except for 4 years what correlates with a tube size of 5.0 mm ID. The complexity of those special cases would justify the additional effort of additional measures like bronchoscopy to verify the tube position. It should explicitely be accentuated that cuff pressure measurement does not represent an additional measure in patients supplied with a cuffed ETT. It’s clearly standard monitoring in all patients with a cuffed ETT. 2. Given the lack of correlation between postextubation stridor and subsequent laryngeal injury, does this limit any conclusions about cuffed tubes and airway trauma? TW: No I think there are conclusions that can be made. The trauma is not due to the cuff itself, but from the pathologic mechanisms related to the effect of long-term pressure on the laryngotracheal mucosa from an oversized tube or overinflated cuff. In my view this is an intrinsic risk of a cuffed tube. NS ⁄ GO: No. Up to now, there is no evidence that the use of CTT increases the risk of postextubation stridor or of laryngeal injury. 3. Provisional data suggests that in order to eliminate leak with the CTT the initial cuff pressures can be considerably higher than the recommended values and may be sufficiently high to risk mucosal damage. How can this be dealt with on a clinical basis do you accept the leak and leave the pressure no more than recommended? TW: Keeping the observation in mind, that laryngotracheal stenosis and airway injury is an early complication every effort should be made to overcome the problems associated with leak due to sub-optimal positioning and meticulous care with inflation pressure of an inflatable device in the trachea. I am personally very careful and slow when inflating a cuff of a CTT. Furthermore the manometer of the cuff lies directly beside the head of my patients and is part of my continuous monitoring. In case of laryngeal masks (LMA) my philosophy is that the necessity of an inappropriate high inflation pressure of the LMA is a sign of malposition of the

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device that e.g. might be caused by inadequate depth of anesthesia. Of course I would accept a leak and I mentioned that there are several techniques existing from matched respirator settings to such simple tools like a throat pack. NS ⁄ GO: In case of persistent leak despite inflation of the cuff and adjustment of the initial cuff pressure at 20–25 cmH2O using a cuff manometer, which is a rare event using CTT, there are two solutions: • first, to accept the leak and leave the pressure no more than recommended, if adequate mechanical ventilation of the patient is still possible; • secondly, if because of the leak, mechanical ventilation becomes difficult and ⁄ or requires very high fresh gas flow, you may decide to change the tracheal tube for a larger one. Clearly, the use of CTT has many advantages but in order to avoid unnecessary and dangerous hyperinflation of the cuff, the routine use of cuff manometers is mandatory.

Conclusions The application of cuffed tubes into general pediatric anesthesia practice is still in evolution. Progress is being made to standardize the equipment and produce an optimum design. There is a strong case for the application of cuffed tubes in specialist clinical situations such as pediatric intensive care, when lung pathology or airway leak can produce significant problems in terms of ventilation and airway soiling. As a result these tubes are becoming a standard tool due to the problems that are inherent in the design of the uncuffed tube. However, routine use of uncuffed tubes in both pediatric anesthesia and intensive care, has been demonstrated to have an excellent safety record over many years. It is therefore essential that progressing to the more expensive cuffed tube, which requires cuff monitoring and meticulous tube placement, is truly progress. Large scale prospective monitoring of this development is essential to ensure that the balance of risk and benefit together with economic evaluation outweighs the routine use of uncuffed cuffed tubes in pediatric anesthesia. There is also no clear view or data to inform the practitioner as to what age or size of tube is the lower limit for cuffed tube and this clearly requires further work.

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Conflicts of interest The authors have declared no conflicts of interest.

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Accepted 5 March 2009

 2009 The Authors Journal compilation  2009 Blackwell Publishing Ltd, Pediatric Anesthesia, 19 (Suppl. 1), 46–54