Cuffed tracheal tubes in children - things have changed.

Whether cuffed tubes should be routinely used in infants and small children has been extensively discussed in the past. However, opinions and recommendations were not based on scientific evidence but rather on empiricism. The basic function of a tracheal tube is to provide a reliable connection between the patient’s lung and the bag or ventilator. Ideally, this connection should be leak-proof without causing undue pressure to laryngeal or tracheal structures. If this connection is not reasonably tight or sealed, constant minute ventilation, precise respiratory monitoring and capnography, low fresh gas flow and prevention of pulmonary aspiration are not possible. In an emergency situation and in patients with severe lung disease good sealing becomes even more important. Traditional teaching for the last 50 years was that in children under 8–10 years of age, this sealing should be obtained with an uncuffed tracheal tube that would slip easily through the cricoid and leave some space for an air leak at 25 cm H2O airway pressure. Without any real evidence, cuffed tubes were not considered appropriate for children, in contrast with adults. This teaching was based on the idea that the cricoid, the narrowest part of the pediatric airway up to 8 years, would be a circular structure (1). A tracheal tube fitting snugly through the cricoid and leaving an air leak at an inspiratory pressure of about 25 cm H2O would provide sufficient sealing without a cuff (2). To fulfill both requirements (leak and seal) an uncuffed tube must have precisely the correct size for that particular child. Because this claim is difficult to fulfill in daily practice, many different formulas for tube size selection have been put forward and despite these a high tube exchange rate to find an appropriately fitting tube is usual (3). When a correct sized tube cannot be found, anesthetists have the dilemma to accept an uncuffed tube with a large gas leak or to insert an oversized tracheal tube. Oversized uncuffed tracheal tubes exert undue pressure on the laryngeal structures and are well known as the main cause of laryngeal injury from tracheal intubation (3,4). Large air leakage with uncuffed tracheal tubes results in unreliable ventilation and oxygenation, imprecise capnography and lung function testing, high gas flow consumption, environmental pollution of anesthetic gases, as well as pulmonary aspiration (3). Nevertheless, in the last 50 years pediatric anesthetists have accepted, to live with the shortcomings of uncuffed tubes in children and have taught these myths to their junior colleagues without question. Things have changed! Newer investigations in children revealed, that the cricoid lumen is not a round but mostly an ellipsoid structure (5). If a round uncuffed tracheal tube is inserted into the noncircular lumen of the cricoid, to give a reasonable seal (cricoidal sealing ), considerable pressure on the lateroposterior walls of the cricoid occurs. The air leak at an inspiratory pressure of 25 cm H2O, supposed to prevent excessive mucosal pressure can arise exclusively from the anterior part of the cricoid lumen. Thus when an uncuffed tube reasonably seals the trachea and has a leak, the pressure exerted on some parts of the cricoid mucosa is unknown and may still be excessive. In cuffed tracheal tubes a smaller diameter is selected which does not wedge within the delicate cricoid and the airway is sealed within the trachea using a cuff (tracheal sealing). In contrast with cricoid sealing , tracheal sealing with a high-volume low-pressure (HVLP) cuff allows to estimate and adjust precisely Correspondence to: Markus Weiss, Department of Anaesthesia, University Children’s Hospital, Steinwiesstrasse 75, CH 8032 Zurich, Switzerland (email [email protected]). Pediatric Anesthesia 2006 16: 1005–1007 doi:10.1111/j.1460-9592.2006.02071.x