Evaluation of a new recommendation for improved cuffed tracheal tube size selection in infants and small children

BACKGROUND: The purpose of this study was to evaluate a new recommendation for tracheal tube size selection using second-generation Microcuff paediatric endotracheal tubes (PETs) with optimized outer diameter (OD) of the distal tube. METHODS: With Ethics Committee approval, patients aged from birth to 5 years, requiring general anaesthesia with orotracheal intubation, were included. Tracheal tube sizes were selected as follows: internal diameter (ID) 3.0 mm, birth (if > or =3 kg) to <6 months; ID 3.5 mm, 6 to <18 months; ID 4.0 mm, 18 months to <3 years; ID 4.5 mm, 3 to <5 years. Tracheal tubes with the cuff not inflated were classified as too large if no air leak was obtained at an airway pressure of < or =20 cmH2O. Post-intubation stridor requiring therapy was noted. RESULTS: Three hundred and fifty children were studied. Nine tracheal tubes (2.6%) were too large and had to be exchanged: in patients requiring tracheal tubes of ID 3.0 mm and 3.5 mm, three and four tracheal tubes, respectively, and, in patients requiring tracheal tubes of ID 4.0 mm and 4.5 mm, one tracheal tube in each group. In three patients (0.9%), post-intubation stridor occurred which required therapy. CONCLUSION: The new recommendation presented for the use of second-generation Microcuff PETs with improved OD to ID ratio allows the selection of cuffed tracheal tubes with larger IDs than previously recommended for small children without increased need for tracheal tube exchange or increased incidence of post-intubation stridor in these age groups.     

A weight-based formula for tracheal tube size in children

Objective:  Age (in years) of the child has conventionally been used in formulae to estimate the tracheal tube (TT) size. The objective of this retrospective study was to test a weight-based formula (WBF) for uncuffed oral TT in children and compare it with the conventional age-based formula (ABF).
Methods:  The patient's age, weight, and size of TT internal diameter (ID) were recorded. For comparative analysis, the actual TT size used was compared with predicted TT size, calculated using both the standard ABF [ID = age (years)/4 + 4 mm] and the WBF [ID = weight (kg)/10 + 3.5 mm].
Results:  The Pearson's correlation coefficient for age and actual TT size used was 0.77 (95% CI: 0.74–0.80) and between weight and actual TT used was 0.70 (95% CI: 0.66–0.74). The ABF correctly predicted 51.3% of TT sizes while the WBF correctly predicted 44.8% of TT sizes ( P  = 0.01). The measures of agreement between the actual and predicted TT size were 0.35 and 0.27 for the ABF and WBF respectively. The difference between the percentages of paired predictions for the ABF and WBF was statistically significant ( P  < 0.001) suggesting that, when correctly predicting the actual tube size used, the WBF functions for a different subset of the patient cohort than the ABF.
Conclusions:  This study suggests that in this patient cohort, the WBF is statistically inferior to the conventional ABF. However, our findings also suggest that the WBF may correctly predict TT sizes in a subset of patients in whom the ABF is inaccurate.     

Prediction of tracheal tube size in children using multiple variables

BACKGROUND: Tracheal tube (TT) size selection in children is important to avoid complications. Formulae utilizing age and physical characteristics to predict appropriate tube size are not entirely predictive. METHODS: Using an automated anaesthesia record keeper database, the anaesthetic records of 8504 children, aged up to 7 years, who required tracheal intubation, were reviewed. Age, height and weight data were related to TT size. The total number of patients whose age, height and weight were independently available was 8396, 3929 and 7823, respectively. The number having all three variables was 3814. A linear regression analysis was performed for patients with all three variables and for each variable individually. RESULTS: Tracheal tube size is best predicted using multivariate analysis and, for any child aged up to 7 years, is represented by the formula: 2.44 + (age x 0.1) + (height x 0.02) + (weight x 0.016). Formulae utilizing these variables individually are also reviewed. CONCLUSIONS: Prediction of TT size is best accomplished using multiple variables. Further prospective study is suggested.     

Novel use of neonatal cuffed tracheal tube to occlude tracheo-oesophageal fistula

The use of a cuffed tracheal tube is described to occlude the leak through a tracheo-oesophageal fistula (TOF) in a neonate and prevent gastric dilatation during positive-pressure lung ventilation.     

The future of the cuffed endotracheal tube

It has been traditionally taught that only uncuffed endotracheal tubes (ETTs) should be used for intubation in children younger than 8, or even 10, years old. However, recent literature suggests that the advantages of using uncuffed ETTs in children may be just another myth of paediatric anaesthesia. Using an uncuffed ETT does allow a tube of larger internal diameter to be used, minimizing resistance to airflow and the work of breathing in the patient who is breathing spontaneously. However, this advantage does not hold for ventilated patients, for whom ventilator settings can be adjusted to provide optimal airflow. Longer duration of intubation and a poorly fitted ETT are risk factors for mucosal damage, whether the ETT is cuffed or uncuffed. Furthermore, a properly sized, positioned, and inflated modern (low-pressure, high-volume) cuffed ETT can offer many advantages over an uncuffed ETT, including greater ease of intubation, better control of air leakage, lower rate and better control of flow of anaesthetic gases, and decreased risk of aspiration and infection.     

Postal survey of cuffed or uncuffed tracheal tubes used for paediatric tracheal intubation

A postal survey of the use of cuffed or uncuffed tracheal tubes for tracheal intubation in children and infants was performed to investigate the criteria used for deciding the choice of tube and the manner of inflating the cuff in the case of use of a cuffed tracheal tube (CTT). From 200 questionnaires despatched, replies were received from 130 paediatric anaesthesiologists (response rate 65%). In paediatric practice, the CTT was routinely used by 25% of respondents for more than 80% of their patients, while more than 37% of respondents use them in less than 20% of the cases. The three main criteria used for inflating a cuff were: (i) the presence of a leak, (ii) the type of surgery associated with the presence of a leak and (iii) the patient's age associated with the type of surgery and the presence of a leak. These criteria were specified, respectively, by 32%, 24% and 18% of the respondents. The cuff was inflated in response to a leak in 18% of the cases and as a response to a pressure manometer in 15% of the cases. Few paediatric anaesthesiologists use a cuffed tracheal tube routinely for tracheal intubation in children, and fewer actually use a pressure monitoring device, while it is suggested that the cuff pressure should be monitored in case of CTT.     

A pressure regulator for the cuff of a tracheal tube

A regulator is described for the maintenance of a constant pressure difference above airway pressure during positive pressure ventilation in a cuffed tracheal tube. It comprises a tubular threshold valve which is powered by the anaesthetic gas supply source to a breathing system. The valve is interposed between the anaesthetic gas supply machine and the breathing system creating a pressure differential. The upstream pressure is transmitted to the pilot tube supplying the cuff of a tracheal tube via an upstream connection. The valve is suitable only for breathing systems that require a constant gas supply. The regulator was evaluated during anaesthesia, using a modified Mallinkrodt Hi-Lo jet ventilation tube to obtain simultaneous pressure measurements within the cuff and the lumen of the tracheal tube. A greater pressure was demonstrated in the cuff than in the airway and the two traces were approximately parallel throughout the respiratory cycle. The device should prevent excessive cuff inflation pressure and solves the problem of forgetting to let the cuff down before extubation.     

Cuff compliance of pediatric and adult cuffed tracheal tubes: an experimental study

BACKGROUND: Tracheal mucosal damage related to tracheal intubation has been widely described in pediatric and adult patients. High volume-low pressure cuffs (HVLPC) are being advertised as safe to avoid this particularly unpleasant complication. Compliances of these supposed pediatric and adult HVLPC are not mentioned by manufacturers and still remain unknown. METHODS: The compliance of HVLPC was measured in vitro and defined as the straight portion of the pressure-volume curve. Cuff pressure was measured after incremental 0.1 ml filling volumes of air for sizes 3.0-8.0 of internal diameter of Rüsch and Mallinckrodt tracheal tubes. Compliances were assessed in air and in a rigid tube. The filling volume to achieve a 25-mmHg intracuff pressure was also measured. RESULTS: In air, each 0.1 ml step almost linearly increased cuff pressure by 1 mmHg (size 8.0) to 9 mmHg (size 3). In air, the volume needed to maintain a cuff pressure < 25 mmHg was small for sizes 3-5.5 (0.35-2 ml). The 25 mmHg inflated cuff volume and compliance were decreased within a rigid tube, especially for adult sizes. In a rigid tube simulating a trachea, the compliances of almost every Rüsch tracheal tube were statistically higher than those of the Mallinckrodt. CONCLUSION: We conclude that the tested tracheal tube cuffs have low compliance and cannot be defined as high volume-low pressure.     

基于循证的气管插管全麻导管拔除管理方案的构建与应用

目的提高麻醉护士拔管护理的规范性和麻醉护理质量。方法检索数据库,获取临床实践指南、证据汇总、推荐实践、系统评价等证据等级较高的文献,拟定气管导管拔除方案初稿,通过专家会议法对方案进行补充修正,最终确立PACU全麻患者气管导管拔除护理管理方案并应用于102例麻醉苏醒拔管患者,并与应用前的104例患者比较拔管效应。结果方案应用后,拔管后患者的呼吸系统异常情况发生率显著低于应用前,患者报告咽喉痛程度及对PACU有记忆率显著高于应用前(P0.05,P0.01);PACU麻醉护士除拔管后严密观察病情外,其余行为明显改善(均P0.01)。结论以循证为依据构建的PACU全麻患者气管导管拔除护理管理方案切实可行,可以提高临床麻醉护理质量。     

Predictors of postoperative sore throat in intubated children

Background: The incidence of postoperative sore throat (POST) following intubation is not well defined in the pediatric population. The etiology is multifactorial and includes impairment of subglottic mucosal perfusion and edema as a result of the pressures exerted by cuffed or uncuffed tubes. Aim: To determine the incidence of, and risk factors for, POST in intubated children undergoing elective day‐case surgery. Methods: Five hundred patients aged 3–16 years were studied prospectively. Endotracheal tube (ETT) choice (cuffed or uncuffed) was left to the anesthetist. The cuff was inflated either until loss of audible leak or to a determined pressure using a cuff manometer. The research team then measured the cuff pressure (CP). POST incidence and intensity was determined by interviewing patients prior to discharge from the same day procedure unit. Chi‐square testing and stepwise logistic regression were used to determine the predictors of POST. Results: Of the 111 (22%) children developed a sore throat, 19 (3.8%) a sore neck, and 5 (1%) a sore jaw. 19% of patients with cuffed ETTs complained of sore throat compared with 37% of those intubated with an uncuffed ETT. The incidence of POST increased with CP; 0–10% at 0 cmH₂O, 4% at 11–20 cmH₂O, 20% at 21–30 cmH₂O, 68% at CP 31–40 cmH₂O, and 96% at CP >40 cmH₂O. The ETT CP and use of uncuffed ETTs were univariate predictors of POST. Conclusions: Children intubated with uncuffed ETTs are more likely to have POST. ETT CP is positively correlated with the incidence of POST. When using cuffed ETTs, CP should be routinely measured intraoperatively.     

Comparison of tracheal tube cuff diameters with internal transverse diameters of the trachea in children

BACKGROUND: In this study, we evaluated the ratio of the cuff diameters of the Microcuff paediatric tracheal tube (Microcuff PET, Weinheim, Germany) to fluoroscopically measured internal transverse tracheal diameters in children from birth to adolescence. METHODS: With Institutional Ethics Committee approval and parental consent, we measured the internal transverse tracheal diameters from fluoroscopy images in children undergoing cardiac catheterization requiring general anaesthesia with oro-tracheal intubation. Minimal tracheal sealing pressures were assessed at standardized respirator settings. Internal transverse tracheal diameters were compared with cuff diameters at 20 cmH2O cuff pressure. Linear regression analysis was employed to assess the correlation of tracheal diameters with age, height and weight, and to assess the correlation of the cuff/tracheal diameter ratio with sealing pressures. For all tests, P < 0.05 was considered to be statistically significant. RESULTS: One hundred and forty-five patients were studied (62 girls; 83 boys). Transverse tracheal diameters correlated well with age (r = 0.890; P < 0.0001), height (r = 0.900; P < 0.0001) and weight (r = 0.882; P < 0.0001). Tracheal sealing pressures ranged from 4 to 18 cmH2O. The ratio of the tracheal tube cuff diameter to the internal transverse tracheal diameter ranged from 1.06 in tubes with internal diameters of 6.0 and 4.5 mm to 2.01 in a tube with an internal diameter of 3.5 mm (median, 1.43), and did not correlate with tracheal sealing pressures (r = 0.021, P = 0.7999). CONCLUSIONS: The residual diameters of the Microcuff paediatric tracheal tube cuffs were sufficient to cover the measured internal transverse tracheal diameters of children from birth to adolescence. This allowed the internal tracheal mucosal surface to be draped and the trachea to be sealed at very low cuff pressures.     

Choice of tracheal tube size for children: finger size or age-related formula?

A study was undertaken to compare the size of tracheal tube used for paediatric anaesthesia derived from either the diameter of the distal phalanx of the little or index finger, or from a standard formula (age in years/4 + 4.5 mm). The results showed that the diameter of the terminal phalanx was a poor predictor of the external diameter of the tube that provided the best fit. The mean (SD) diameters were 9.34 (1.02), 10.24 (1.23) and 7.56 (0.97) mm for the little finger, index finger and tracheal tube providing 'best fit', respectively. The formula provided a better correlation with the internal diameter of the chosen tracheal tube. The mean (SD) figures were 5.61 (0.75) and 5.70 (0.67) mm for the formula and the chosen tracheal tube, respectively. The use of the diameter of the terminal phalanx of either the little or the index finger is an unreliable measurement for the prediction of tracheal tube size in paediatrics.