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.