Review question
Most surgical procedures may require general anaesthesia (a medically-induced state of unconsciousness in which a person feels nothing). Tracheal tubes (a device that is inserted into the windpipe to maintain a person's airway) play a vital role in the surgery. A mechanical ventilator is often needed to keep the patient breathing during anaesthesia. This is a machine that helps a person to breathe in oxygen and to breathe out carbon dioxide. There are two types of tracheal tubes: one is cuffed, with a balloon at the end of the tube providing proper tracheal sealing and preventing the stomach contents from getting into the lungs. The other is uncuffed, with no balloon. This review focuses on the different effects of cuffed and uncuffed tubes on children of up to eight years old during general anaesthesia.
Background
Children have a smaller and more fragile airway than adults. Their larynx is funnel shaped with the narrowest portion occurring at the cricoid cartilage.There is a belief that the risks of windpipe and voice box injuries in children are higher with the use of cuffed tubes, although this assumption is not based on current evidence.
The disadvantages of using an uncuffed tube are an increase in air leakage around the tube, making it difficult to ensure that the child is breathing adequate amounts of oxygen. In addition, the measurement of tidal volume (the normal volume of air displaced between breathing in and out, whether or not by mechanical ventilation) is compromised. It seems reasonable to suppose that cuffed tubes would be more likely to fit the trachea at the first attempt, whereas uncuffed tubes may require more attempts.
Study characteristics
This review includes trials involving 2804 children up to eight years old, undergoing general anaesthesia. The trials assessed two types of cuffed tubes: conventional and Microcuff™ tubes (the latter consisting of a different type of balloon with low pressure levels that is more suitable for children's windpipes).
The primary outcome was postextubation stridor. This is a potentially serious problem resulting from the narrowing of the airway and can be identified by a high-pitched noise following removal of the tube. Other factors assessed were the need to exchange the tube for another; to put the tube back in; to use drugs such as epinephrine (adrenaline) or corticosteroid (an anti-inflammatory); and to admit a child to an intensive care unit to treat stridor; the cost of medical gas per child; and the ability to deliver appropriate volumes of oxygen.
Key results
Two trials (involving 2734 children) measured postextubation stridor and found no difference between the groups. The need to exchange tubes for others was 93% lower in the cuffed ETT group. One trial involving 70 children showed that cuffed tubes reduced the amount of anaesthetic gases required, and consequently the cost involved.
Quality of evidence
The quality of evidence was low to very low, as there were problems with the study designs. Comparisons between cuffed and uncuffed tubes need to be interpreted with caution. Further studies are needed to evaluate the benefits and risks of the two types of tubes.
Conclusion and future research
Several gaps remain in the information available around this question. Large, well-conducted clinical trials should clarify factors such as the ability of these tubes to provide adequate amounts of oxygen, and the respiratory complications that occur with the wide use of cuffed tubes in children.
Implications for practice
We are unable to draw definitive conclusions about the comparative effects of cuffed or non-cuffed endotracheal tubes in children undergoing general anaesthesia. Our confidence is limited by risks of bias, imprecision and indirectness. The lower requirement for exchange of tubes with cuffed ETTs was very low-quality evidence, and the requirement for less medical gas used and consequent lower cost was low-quality evidence. In some cases, tracheal re-intubation is required to guarantee an open airway when adequate oxygenation is difficult after removal of the tube, for a variety of reasons including stridor, muscle weakness or obstruction. No data were available to permit evaluation of whether appropriate tidal volumes were delivered.
Implications for research
Large randomized controlled trials of high methodological quality should be conducted to help clarify the risks and benefits of cuffed ETTs for children. Such trials should investigate the capacity to deliver appropriate tidal volume. Future trials should also address cost effectiveness and respiratory complications. Such studies should correlate the age of the child with the duration of intubation, and with possible complications. Studies should also be conducted in newborn babies. Future research should be conducted to compare the effects of the different types or brands of cuffed tubes used worldwide. Finally, trials should be designed to perform more accurate assessments and to diagnose the complications encountered with cuffed compared to uncuffed ETTs.
Since the introduction of endotracheal intubation in paediatrics, uncuffed endotracheal tubes (ETTs) have been the standard of care for children under eight years old, based on the presumption that complications, particularly postoperative stridor, are higher with cuffed ETTs. The major disadvantages of uncuffed ETTs cited for this shift in procedure include the difficulty in achieving tidal volumes due to leakage around an uncuffed ETT. To seal the airway adequately, uncuffed tubes may need to be exchanged for another tube with a larger diameter, which sometimes requires several attempts before the appropriate size is found. Uncuffed tubes also allow waste anaesthetic gases to escape, contributing significantly to operating room contamination and rendering the anaesthetic procedure more expensive. Our review summarizes the available data, to provide a current perspective on the use of cuffed versus uncuffed endotracheal tubes in children of eight years old or less.
To assess the risks and benefits of cuffed versus uncuffed endotracheal tubes during general anaesthesia in children up to eight years old.
We searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS and Google Scholar databases from their inception until March 2017. We also searched databases of ongoing trials, and checked references and citations. We imposed no restriction by language.
We included randomized and quasi-randomized controlled trials in which the effects of using cuffed and uncuffed tubes were investigated in children up to eight years old undergoing general anaesthesia. We excluded studies conducted solely in newborn babies.
We applied standard methodological procedures, as defined in the Methodological Expectations of Cochrane Intervention Reviews (MECIR).
We included three trials (2804 children), comparing cuffed with uncuffed ETTs. We rated the risks of bias in all three trials as high. Outcome data were limited. The largest trial was supported by Microcuff GmbH, who provided the cuffed tubes used. The other two trials were small, and should be interpreted with caution. Based on the GRADE approach, we rated the quality of evidence as low to very low.
Two trials comparing cuffed versus uncuffed ETTs found no difference between the groups for postextubation stridor (risk ratio (RR) 0.93, 95% confidence interval (CI) 0.65 to 1.33; 2734 children; quality of evidence very low). However, those two trials demonstrated a statistically significantly lower rate of endotracheal tube exchange in the cuffed ETT group (RR 0.07, 95% CI 0.05 to 0.10; 2734 children; quality of evidence very low).
One trial with 70 participants found that costs per case were lower in the cuffed ETT group (mean difference (MD) EUR 19.0 lower; 95% CI 24.23 to 13.77 lower; quality of evidence low), since the higher cost of the cuffed tubes may be offset by the savings made with anaesthetic gases.
No clear evidence emerged to suggest any difference between cuffed and uncuffed tubes for outcomes such as the need to treat postextubation stridor with tracheal re-intubation (RR 1.85, 95% CI 0.17 to 19.76; 115 children; 2 trials; quality of evidence very low), epinephrine (RR 0.70, 95% CI 0.38 to 1.28; 115 children; 2 trials; quality of evidence very low) or corticosteroid (RR 0.87, 95% CI 0.51 to 1.49; 102 children; 1 trial; quality of evidence very low), or need for intensive care unit (ICU) admission to treat postextubation stridor (RR 2.77, 95% CI 0.30 to 25.78; 102 children; 1 trial; quality of evidence very low).
None of the trials included in this review evaluated the ability to deliver appropriate tidal volume.