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May 1997
Comparison of cuffed and uncuffed endotracheal tubes in young children during anesthesia.
Khine HH, Corddry DH, Kettrick RG, Martin TM, McCloskey JJ, Rose JB, Theroux
MC, Zagnoev M;
Anesthesiology 1997; 86: 6217-31.
[ see abstract below ]
Khine et al compared the safety and complications of using cuffed vs. uncuffed endotracheal tubes in 488 children ranging in age from the neonate to 8 years. The groups appeared to be evenly matched regarding weight, duration of intubation, and type of procedure but the patients in the uncuffed group tended to be slightly younger (p = 0.05).
The authors used the commonly applied Cole formula for selection of the uncuffed endotracheal tubes and a modification of that formula for cuffed endotracheal tubes. The authors found a significantly smaller incidence of reintubation to place an acceptable size endotracheal tube, a decrease in operating room pollution, a lower fresh gas flow to maintain ventilator bellows inflation, and an equivalent incidence of post-intubation croup.
This is an interesting study because it proves something I have thought for many years, i.e. the size of the tube (cuffed or uncuffed) is not as important as the assurance that, regardless of which type of endotracheal tube is used, there must be a leak around the tube to ensure that the tube is not tight. In order to accomplish this, a compensation is needed, hence the modified formula which, on average, resulted in insertion of an endotracheal tube 1 full mm diameter smaller.
The adequacy of the leak must also be frequently checked during the anesthetic especially if nitrous oxide is used; the authors accomplished this by using a pressure relief adaptor for cuffed endotracheal tubes. One major flaw in this study was how the population less than 2 years was managed. It has been my practice to use a size 3.0 for a newborn, a 3.5 for a 6 month-old, a 4.0 for a one year-old, a 4.5 for the 18 month-old, and a 5.0 for a 2 year-old and then follow the classic Cole formula 4 + age/4.
These investigators used what I would consider to be relatively large uncuffed endotracheal tubes in the children in the newborn to 1 year age group (size 4.0 down to the newborn) so I am not surprised that 41 patients in this age group required placement of a smaller endotracheal tube.
I am equally concerned about advocating the use of a 3.0 cuffed endotracheal tube in this age group because this will quite often be tight; there likely would be no leak in children 3 months of age or less. I am quite astounded that the authors were satisfied that there was a leak with cuffed endotracheal tubes in this neonate/infant population.
I was also surprised at the relatively high rate of post intubation croup, which was the same in both cuffed and uncuffed patients (no age distribution provided) and nearly the same as a prior study by Koka et al where some tubes were described as having no leak. This suggests to me that perhaps the younger population in both groups had tight fitting endotracheal tubes thus resulting in an equivalent rate of post intubation croup.
The practitioner should understand that the work of breathing will be significantly increased with a proper sized cuffed tube compared to a similarly appropriately sized uncuffed endotracheal tube because the internal diameter will be smaller in the uncuffed group by 1 full millimeter. Thus the use of cuffed endotracheal tubes is practical only when controlled ventilation is to be used.
In conclusion, I would urge practitioners to be aware that there are many factors which cause laryngeal/tracheal trauma, which can lead to transient (croup) or more permanent injury (subglottic stenosis). Since these complications generally relate to tightness of endotracheal tube fit (compromised mucosal blood flow), trauma (too large an endotracheal tube, excessive neck movement), and other factors such as infection, blood pressure, and oxygenation, we as the individuals in control of the airway must be meticulous in paying attention to the size endotracheal tube, whether it is cuffed or uncuffed.
There must be a leak between 20 and 40 cm water peak inflation pressure and this is best measured by placing a stethoscope over the larynx and slowly pressurizing the circuit. One cannot rely on the "feel" of the bag because often it is the system's pressure pop-off that is relieving pressure, and not a leak around the endotracheal tube. In addition, one cannot place a cuffed tube and then over-pressurize the cuff.
Unfortunately, even with all this attention to detail, there likely will still be patients who develop post-intubation croup. I don't know which is worse, several intubations with small endotracheal tubes with increasing size until the proper leak is achieved, or intubation with too large cuffed endotracheal tube and having to go down in size. My personal bias is to continue to use uncuffed endotracheal tubes. I am less concerned with the theoretic worry of violating NIOSH regulations which have never been validated.
Return to the Current Literature Review Front Page, or read the abstract:
ABSTRACT
Background: Uncuffed endotracheal tubes are routinely used in young children. This study tests a formula for selecting appropriately sized cuffed endotracheal tubes and compares the use of cuffed versus uncuffed endotracheal tubes for patients whose lungs are mechanically ventilated during anesthesia.
Methods: Full-term newborns and children (n=488) through 8 yr of age who required general anesthesia and tracheal intubation were assigned randomly to receive either a cuffed tube sized by a new formula [size(mm internal diameter) = (age/4) + 3], or an uncuffed tube sized by the modified Cole's formula [size(mm internal diameter) = (age/4) +4].
The number of intubations required to achieve an appropriately sized tube, the need to use more than 2 1 . min -1 fresh gas flow, the concentration of nitrous oxide in the operating room, and the incidence of croup were compared.
Results: Cuffed tubes selected by our formula were appropriate for 99% of patients. Uncuffed tubes selected by Cole's formula were appropriate for 77% of patients (P greater than 0.001). The lungs of patients with cuffed tubes were adequately with 2 1 . min-1 fresh gas flow, whereas 11% of those with uncuffed tubes needed greater fresh gas flow (P less than 0.001).
Ambient nitrous oxide concentration exceeded 25 parts per million in 37% of cases with uncuffed tubes and in 0% of cases with cuffed tubes (P less than 0.001). Three patients in each group were treated for croup symptoms (1.2% cuffed; 1.3% uncuffed).
Conclusions: Our formula for cuffed tube selection is appropriate for young children. Advantages of cuffed endotracheal tubes include avoidance of repeated laryngoscopy, use of low fresh gas flow, and reduction of the concentration of anesthetics detectable in the operating room. We conclude that cuffed endotracheal tubes may be used routinely during controlled ventilation in full-term newborns and children during anesthesia.
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