Traditionally, uncuffed endotracheal tubes (ETTs) have been used for artificial ventilation of infants and children. More recently, newer designed high-volume low-pressure (HVLP) cuffed ETTs are being used with increasing frequency in infants from birth. Considering that many paediatric anaesthetists and intensivists are already using cuffed ETTs in infants >3 kg from birth, should neonatologists be doing the same? This review examines the reasons behind the traditional use of uncuffed ETTs and the problems associated with their use; newer HVLP cuffed ETTs and what they can potentially offer neonates; and reviews evidence from studies comparing the use of cuffed and uncuffed ETTs in neonates and small infants.
- Intensive Care
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Traditional teaching has been that cuffed endotracheal tubes (ETTs) should not be used in children under 8–10 years of age because of the fear that they are associated with mucosal injury leading to subglottic stenosis.1–5 This teaching has also extended to neonates.6 However, since the late 1990s, with the advent of the newer polyvinyl chloride (PVC) high-volume low-pressure (HVLP) cuffed ETTs, and then the introduction of the ultrathin polyurethane Microcuff paediatric ETT in 2004, there has been an increase in the use of cuffed ETTs in children from birth, particularly during anaesthesia and for ventilation in paediatric intensive care units (PICUs).7–13
The use of uncuffed ETTs remains the standard practice in neonatal intensive care units (NICUs). However, in surgical NICUs, infants are now sometimes being admitted from theatre with cuffed ETTs in place. The cuff is often deflated, causing problems with ventilation, or the tube is replaced for an uncuffed one, resulting in an unnecessary further intubation. Considering that many paediatric anaesthetists and intensivists are already using cuffed ETTs in infants >3 kg from birth, should neonatologists be doing the same?
The databases PubMed (http://www.ncbi.nlm.nih.gov, 1966–2015), EMBASE (Excerpta Medica dataBASE) via Ovid (http://ovidsp.tx.ovid.com, 1980–2015), Cochrane Central Register of Controlled Trials (http://www.thecochranelibrary.com, through August 2015), CINAHL (Cumulative Index of Nursing and Allied Health Literature) via OVID (http://ovidsp.tx.ovid.com, 1980–August 2015), were searched in May 2015 and repeated in August 2015. The reference lists of eligible studies and review articles were searched to identify additional studies. Reviewers RT and SR conducted the literature search independently. Medline was searched using the following terminologies: (((tube OR tracheal OR endotracheal) AND (cuff OR cuffed)) OR (microcuff)) AND (infant/OR infant, newborn/OR child/OR paediatrics). The other databases were searched using similar terminologies.
The literature searches retrieved 262 potential relevant citations after removing duplicates. Following careful review of the abstracts, 29 reports were selected for inclusion based upon their relevance with regards to: potential advantages and disadvantages of cuffed ETTs; and studies comparing the use of cuffed and uncuffed ETTs in neonates and small infants (n=7).7 ,8 ,10 ,14–17 A further nine relevant reports were found from checking references from the included studies.2 ,11 ,13 ,18–23
Traditional use of uncuffed ETTs
The traditional teaching of using an uncuffed ETT in infants is based upon studies of cadaveric specimens of children (4 months–14 years), which showed that the airway of an infant/child is funnel shaped, and that the narrowest part is the circumferential, non-distensible cricoid cartilage which is circular in shape.3 Therefore, an uncuffed ETT which fits snugly through the cricoid, leaving some space to allow an air leak at a peak inspiratory pressure (PIP) of 20–25 cm H2O should provide a sufficient seal,2 ,3 ,24 making a cuff unnecessary.
Problems with uncuffed ETTs
An uncuffed ETT must be precisely the right size for the individual infant to fulfil requirements of leak and seal.4 There are high ETT exchange8 ,14 ,16 and leak14 ,25–27 rates when using uncuffed ETTs.
The shape of the paediatric airway is not as traditionally taught
Recent research on the paediatric airway refutes traditional teachings. Litman et al28 performed MRIs on 99 sedated unparalysed children (2 months–13 years), Dalal et al29 carried out video-bronchoscopic images on 135 paralysed children (6 months–13 years) and Wani et al carried out CT images on 135 spontaneously breathing children (1 month–114 months).21 All three studies came to similar conclusions: the cricoid is not round, but an elliptical structure with the transverse dimensions being narrower than the anteroposterior dimensions; the narrowest part of the larynx is not the cricoid but the glottis/subglottic region; and the paediatric airway is more cylindrical, like in adults, rather than funnel shaped.
The cricoid being elliptical means that when an uncuffed tube is inserted into the non-circular lumen of the cricoid to give a reasonable seal, the pressure exerted on the lateral walls of the cricoid is unknown and could be considerable.4
ETTs which are too tight
Upon insertion of an ETT, standard anaesthetic practice is to demonstrate a leak at a PIP of 20–25 cm H2O to ensure the ETT is not too tight.2 ,3 ,24 However, this is rarely done in neonatal practice. It is also quite a common conception in neonates to be happy with no leak as this improves ventilation. It has been shown that ETTs which are too tight can cause airway damage in infants and children.1 ,30 ,31
ETTs with a large leak
Minimising the ETT leak provides: more efficient ventilation; maintenance of positive end expiratory pressure; maintenance of constant minute ventilation, stabilising gas parameters; more reliable respiratory monitoring; and decreases risk of pulmonary aspiration.2 ,4 ,30
Brinsmead et al26 studied uncuffed ETT leaks in their NICU and found that there was a large leak of >25% on 19% of occasions and in 27% of patients at some point. Dorsey et al14 found a clinically significant ETT leak in 19.4% of infants (0–2 years) with burns who had uncuffed ETTs in their study. Mahmoud et al27 showed that 42.3% of all neonates studied with an uncuffed ETT experienced a leak of >40% at some point. Leak varies with time,26 ,27 position,26 ,32 level of sedation/muscle relaxation,33 and with change in compliance of the lungs.25
Tidal volume (VT)-targeted ventilation is commonly used in neonates.34 VT measurement and control become inaccurate in the presence of substantial airway leak.25 ,27 ,34 Although newer ventilators now offer leak compensation, Keszler claims that this is an imperfect solution given the large fluctuation in the ETT leak over time and that auto-triggering and failure to breath-terminate in flow-cycled modes are likely to occur with substantial ETT leaks.34
Cuffed ETTs for neonates and infants
Over 15 years ago, several authors suggested using the newer HVLP PVC cuffed ETTs in infants and children <8 years of age.2 ,7–9 The use of a cuffed ETT allows adjustment of the cuff to enable adequate sealing of the airway with an estimation of the pressure exerted on the tracheal mucosa.
Shortcomings of older HVLP cuffed ETTs
When the adequacy of the design of readily available PVC cuffed ETTs was investigated by Weiss et al,23 they found that there was a marked variation between ETTs from different manufacturers with regards to: outer diameter; cuff diameter; position of the cuff with regards to the ETT tip; presence of a depth marking; and distance from the depth marking to the tube tip. They concluded that most cuffed ETTs were poorly designed and that a better designed cuffed ETT was required.23
The Microcuff ETT
In 2004, to address the above issues with older HVLP cuffed ETTs, the Microcuff Paediatric ETT was introduced. The Microcuff ETT is a HVLP cuff made of ultrathin polyurethane, which is thought to improve sealing characteristics, allowing shorter cuffs.35 There is no Murphy eye which allows a more distal placement of the cuff (figure 1). It has an appropriate intubation depth mark which has been shown to allow adequate placement of the ETT with a cuff-free subglottic zone and without the risk of endobronchial intubation.36 The polyurethane cuff also avoids the formation of longitudinal folds and channels which prevents fluid leakage and potentially avoids irritation of the mucosa.18
The MicrocuffETT has been shown to require significantly lower cuff sealing pressures in children than other tracheal tube brands.35 Dullenkopf et al19 reported on tracheal sealing with the Microcuff ETT in 500 infants and children (birth–16 years) and showed that in 95% of patients, the trachea was sealed with a cuff pressure of <15 cm H2O (mean 9.7 cm H2O).
Advantages of using cuffed ETTs
Cuffed ETTs potentially offer the advantages of: lower rate of ETT leak; improved ventilation; less reintubations to find the correct ETT size; a smaller ETT through the delicate cricoid; less ventilator-associated pneumonia/aspirations; and the use of less anaesthetic and other gases.
Decreased reintubation rates
A number of studies have reported significantly reduced reintubation rates to find the correct ETT size when using cuffed ETTs. Khine et al8 showed reintubation rates of 0% with cuffed ETT use compared with 30% with uncuffed ETT use in infants (0–2 years) (p<0.0001). Dullenkopf et al37 showed that the tube exchange rate with cuffed ETTs was only 1.6% in 500 children (birth–16 years). Salgo et al38 showed a reintubation rate of 2.6% with cuffed ETT use in 150 children (birth–5 years). Weiss et al16 showed reintubation rates of 2.1% with cuffed ETTs and 30.8% with uncuffed ETTs in 2246 children (birth–5 years) (p<0.0001). Dorsey et al14 showed reintubation rates of 7.2% with cuffed ETTs and 37.6% with uncuffed ETTs in burns patients aged 0–10 years.
Although these studies show impressively reduced rates of reintubation with cuffed ETTs in infants and children, there is no data exclusively for the neonatal population.
Lower clinically significant air leak/improved ventilation
This has not been studied in great detail. Dorsey et al14 reported clinically significant air leaks at a rate of 1.8% with cuffed ETTs and 27% with uncuffed ETTs in 228 intubation events in 145 burns patients (0–10 years) (p=0.003).
Decreased rates of aspiration and ventilator-associated pneumonia
Gopalareddy et al39 sampled ETT aspirates in 27 patients (4 months–19 years) undergoing ventilation in a PICU. The group with cuffed tubes had a lower incidence of aspirates positive for pepsin than the uncuffed group (53% vs 100%, p<0.05).
Dullenkopf et al18 found in vitro that the Microcuff ETT was significantly better than other brands in preventing fluid leakage past the cuff.
Miller et al20 found that in adults (n=3207), the polyurethane cuffed ETT is associated with significantly decreased rates of ventilator-associated pneumonia (p=0.032).
Decreased fresh and volatile gas use
A number of studies have shown significantly reduced rates of fresh and volatile gas consumption with cuffed ETT use, which decreases patient cost and pollution of the atmosphere8 ,17 (see section Studies comparing cuffed versus uncuffed ETTs, below). This could be particularly relevant with nitric oxide use in neonates.
Murat et al reported a dramatic decrease in pollution due to volatile agents since cuffed ETTs were introduced to their paediatric anaesthetic department. The concentrations of sevoflurane and N2O decreased from 48.1 ppm and 192 ppm in June 1997 to 0.3 ppm and 29.4 ppm in December 1999, respectively.9
Theoretically, may cause less airway damage
For cuffed ETTs, a smaller diameter tube (0.5 mm less than uncuffed ETT) is selected which does not wedge within the delicate cricoid and could make intubation less traumatic. The cuff makes its seal in the trachea where there are U-shaped cartilages and a muscular dorsal wall which allow for some distension, in contrast with the rigid cricoid ring where the uncuffed ETT makes its seal.
Inflating the cuff may ease the tube tip away from the anterior wall reducing tube tip damage2 and cause less movement of the ETT in the airway. There is also less exposure to repeated intubations to find the right sized ETT.
Potential disadvantages of using cuffed ETTs
Smaller internal diameter causing increased resistance and potential for ETT blockage
One of the main concerns of cuffed ETTs is the requirement to use an ETT smaller than the uncuffed equivalent. This increases the tube resistance, particularly in the smaller sizes, which could lead to higher ventilator pressure requirements and harder work of breathing on weaning from the ventilator. The smaller diameter ETT could also lead to increased episodes of tube blockage and more difficult suctioning. To date, there are no studies looking at cuffed versus uncuffed ETTs in these respects.
Increased airway damage
For some, there remains a concern that the use of cuffed ETTs in infants and children could be causing damage.
Murat9 reported on their use of cuffed ETTs for anaesthesia in 904 patients <1 year old and had no respiratory complications which could be attributed to the ETT. No studies comparing cuffed and uncuffed ETTs in infants and children have found a difference in postextubation stridor7 ,8 ,10 ,14 ,16 (see section below, Studies comparing cuffed versus uncuffed ETTs), however, airway problems have not been studied well in the longer term.
Holzki1 warns of the risks of using cuffed ETTs in children <8 years. He presented a case series of laryngoscopically documented injuries from uncuffed and cuffed ETTs in infants and children. He comments that the most common injury is from a too-large uncuffed ETT, causing the injury in 92% patients.1 However, Holzki et al40 show trauma secondary to overinflated cuffs causing circular necrosis leading to cicatricial subglottic stenosis. They also show documentation of trauma seen from the cuff being inflated in the larynx and from the sharp shoulder of certain cuffed ETTs where the cuff joins the ETT shaft. They criticise studies of cuffed versus uncuffed ETTs in children for not having any endoscopic evidence to substantiate their recommendations.40
Holzki et al40 also claim that stridor is not a validated measure in screening for airway injuries. They suggest that in many instances, significant airway damage may only present sometime later as scar tissue forms and is not always associated with postextubation stridor. They provide documentary evidence of cases of severe airway damage in children who did not have postextubation stridor.41
Sathyamoorthy et al42 reported on three neonates who were intubated with Microcuff ETTs for surgical procedures and had significant postextubation stridor. The first neonate was an ex-28 week preterm infant who at 8 weeks age (36 weeks corrected) and 2.6 kg was intubated with a 3.0 mm Microcuff ETT. The second infant was an ex-30 week preterm infant who at 6 weeks of age (36 weeks corrected) and 2.8 kg was intubated with a 3.0 mm Microcuff ETT. The third infant was a term infant weighing 4 kg who at 3 weeks of age was intubated with a 3.5 mm Microcuff ETT. None of the three patients underwent a leak check or had cuff pressure monitoring. In all three patients, the most likely explanation for the postextubation stridor was that the cuffed ETT size was inappropriately large.43 The manufacturer does not recommend the Microcuff ETT for infants below 3 kg. The manufacturer recommends the 3.0 mm Microcuff ETT for infants 3 kg and ≤8 months of age and the 3.5 mm Microcuff ETT only for infants ≥8 months of age.
The use of cuffed ETTs
The smallest manufactured Microcuff ETT is 3.0 mm internal diameter and is recommended for infants ≥3 kg. There is no generally accepted guideline as to how to manage the cuff and practice varies enormously.11 There are differing methods used to decide whether and how much to inflate the cuff, the maximum cuff pressure to be used and how often to check cuff pressures.11
The most common method used to inflate the cuff is until the leak just disappears at a PIP of 20–25 cm H2O.10 ,38 ,44 It is generally accepted that a cuff pressure of >20 cm H2O should not be used12 ,16 ,35 as though not known, 20 cm H2O is thought to be the capillary perfusion pressure in the trachea of small children (it is known to be 25–30 cm H2O in adults45). Dullenkopf et al37 concluded that if the cuff pressure was held <20 cm H2O there was no increased airway morbidity with a rate of postextubation croup requiring therapy of 0.4%.
It is clear that cuff pressures should be checked.22 ,44 ,46 ,47 Bernet et al48 showed that small amounts of inflated air led to a rapid increase in cuff pressure and volume. Cuff pressure has been shown to change with head position,49 N2O use22 and altitude on transport.47 How often the cuff pressure is checked varies greatly.11 Cuff pressure inflation and monitoring is generally done with a handheld manometer with a syringe set-up (figure 2). There have been suggestions of set-ups for continuous pressure monitoring.50 ,51
Studies comparing cuffed versus uncuffed ETTs
Studies comparing cuffed versus uncuffed ETT use in neonates
There are no studies which compared the use of cuffed versus uncuffed ETTs solely in neonates and/or small infants.
Studies of short-term cuffed versus uncuffed ETT use in anaesthesia
There are three randomised controlled trials (RCTs)8 ,16 ,17 and one retrospective review14 which compared the short-term use of cuffed versus uncuffed ETTs during anaesthesia for surgical procedures in children. These studies included some neonates and infants, but breakdown of data was limited (table 2).
Studies of the use of cuffed versus uncuffed ETT for longer-term ventilation in PICU
There are two published non-randomised studies7 ,10 and one unpublished RCT (conference proceedings of which the full peer reviewed publication is awaited)15 which compared cuffed versus uncuffed ETTs in the PICU setting in children. These studies included neonates and infants, but data breakdown was limited (table 3).
Since the advent of new HVLP cuffed ETTs, they are being used with increasing frequency from birth. Cuffed ETTs offer the advantages of a more controllable leak improving ventilation, a decreased need to reintubate to find the correct sized tube, decreased fresh and anaesthetic gas use and potentially decreased airway damage. There is mounting evidence for the safety of the use of cuffed ETTs in infants and small children for short-term ventilation during anaesthesia with regards to short-term outcomes. However, the use of cuffed ETTs for longer-term ventilation in the intensive care setting, efficiency of ventilation and longer-term outcomes is poorly studied.
Since there is no real experience of cuffed ETT use in neonates in the NICU, it would seem pertinent to carry out smaller pilot studies evaluating the usefulness and safety of cuffed ETTs in this setting prior to embarking upon a costly large RCT. Our group is currently carrying out a pilot RCT comparing cuffed versus uncuffed ETTs in newborns >3 kg and infants up to 3 months of age in the intensive care setting (Trial ID ACTRN12615000081516 https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=367700).
Contributors RT and SR searched for relevant articles. RT drafted the manuscript. SR and CM critically reviewed the manuscript.
Funding RT is the recipient of a Telethon (Western Australia) Research Fellowship to conduct research involving cuffed endotracheal tubes in neonates.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.