A pre-formed paediatric orotracheal tube designed based on anatomical measurements

Derivation and validation of a formula for paediatric tracheal tube size using bootstrap resampling procedure

BACKGROUND AND AIMS

The accuracy of age-, length- and weight-based formulae to predict optimal size of uncuffed tracheal tubes (TTs) in children varies widely. We determined the accuracy of age, length and weight in predicting the size of TT in Indian children, and derived and validated a formula using the best predictor.

METHODS

In the derivation phase, 100 children aged 1-8 years undergoing general anaesthesia and tracheal intubation with an uncuffed tube were prospectively studied. The correct size of the TT used was confirmed using the leak test. A bootstrap resampling procedure was used to estimate the accuracy of the predictors (age, weight, or length alone; length and age; length and weight; and length, weight and age). The best predictor was used to derive a formula (Paediatric Tube Size Predictor, PTSP) to calculate the size of TT. The accuracy of PTSP was tested in 150 children of the same age group in the validation phase.

RESULTS

Length (L (in meters), R 2 = 0.61) was the best single predictor of the size of TT and was used to derive the PTSP as internal diameter = 3L + 2.5. In the validation phase, the PTSP predicted the size of TT correctly in 75% of children. Re-intubation was associated with a higher incidence of respiratory morbidity than one-time tracheal intubation.

CONCLUSION

Length of the child predicts the size of an uncuffed TT better than age and weight. The PTSP formula based on length correctly predicts the size of uncuffed TT in 75% of children.

Do pediatric patients undergoing cardiac surgeries require larger-size cuffed endotracheal tubes? A prospective study

BACKGROUND

There is a controversy over using either smaller- or larger-size endotracheal tubes (ETT) in children undergoing cardiac surgery, and some anesthesiologists prefer to use ETT sizes different from the formula-based sizes. The aim of the present study was to compare proper-size cuffed ETT in children undergoing cardiac vs noncardiac surgeries.

METHODS

In an observational prospective study, 80 children planned to undergo noncardiac elective surgeries (NCS group) and 80 children scheduled for cardiac surgeries (CS group) were recruited. For intubation, initial cuffed ETT size was calculated based on the following formula: Tube size (mm ID) = age (year)/4 + 3.5. The estimated ETT size for each age group and the size of final utilized tubes for each age range were recorded.

RESULTS

Patients of tube sizes 4.5, 5, and 5.5 in the CS group were of lower age, weight, height, and body surface area compared with the patients of the same tube sizes in the NCS group (P < 0.05). The compatibility of the predicted vs actual required tube sizes was more in the NCS group compared to the CS group (72.5% vs. 56.2%; P = 0.02). Additionally, the cases with underestimated tube sizes were significantly more in the CS group compared with the NCS group (38.8% vs. 18.8%, P = 0.01).

CONCLUSION

Children undergoing cardiac surgeries in relation to their age and body size do require larger-size ETTs compared with the children scheduled for noncardiac surgeries.

The design of pediatric tracheal tubes

Differences in the anatomy and physiology of the young child necessitate specialist equipment and anesthetic equipment is constantly evolving. We will review the factors influencing the design of pediatric tubes and highlight those areas of special interest. There have been pleas for more standardization of tube markings, as this would help with positioning of tubes, especially in small babies, and there are recent advances in this area. Anesthetists need to be aware that there are important differences between tubes so that they take this into account when choosing an appropriate tube. In addition, developments in the design of cuffed tubes are increasingly being used both for routine care and specialist surgery.

A comparison of three methods for estimating appropriate tracheal tube depth in children

BACKGROUND

Estimating appropriate tracheal tube (TT) depth following tracheal intubation in infants and children presents a challenge to anesthesia practitioners. We evaluated three methods commonly used by anesthesiologists to determine which one most reliably results in appropriate positioning.

METHODS

After IRB approval, 60 infants and children scheduled for fluoroscopic procedures requiring general anesthesia were enrolled. Patients were randomly assigned to one of three groups: (1) deliberate mainstem intubation with subsequent withdrawal of the TT 2 cm above the carina ('mainstem' method); (2) alignment of the double black line marker near the TT tip at the vocal cords ('marker' method); or (3) placement of the TT at a depth determined by the formula: TT depth (cm) = 3 x TT size (mmID) ('formula' method). TT tip position was determined to be 'appropriate' if located between the sternoclavicular junction (SCJ) and 0.5 cm above the carina as determined by fluoroscopy. Risk ratios were calculated, and data were analysed by the chi-square test accepting statistical significance at P < 0.05.

RESULTS

The mainstem method was associated with the highest rate of appropriate TT placement (73%) compared with both the marker method (53%, P = 0.03, RR = 1.56) and the formula method (42%, P = 0.006, RR = 2.016). There was no difference between the marker and formula methods overall (P = 0.2, RR = 1.27). Analysis of age-stratified data demonstrated higher success with the marker method compared with the formula method for patients 3-12 months (P = 0.0056, RR = 4.0).

CONCLUSIONS

Deliberate mainstem intubation most reliably results in appropriate TT depth in infants and children.

Estimation of the length of nasotracheal tube to be introduced in children

The formula 10.5 + (weight[kg]/2) showed a predictive capacity of 0.8939 to estimate the length (cm) of endotracheal tube to be introduced through the nasal route in 99 children between newborn and 4 years old. In a validation study, the formula maintained a high level of concordance with the true values: 0.9370.

Evaluation of a new method for determining tracheal tube length in children

Most paediatric tracheal tubes are marked in centimetres from the tip. In 105 children, nasotracheal tube length was set at the level of the vocal cords such that all 3.0 and 3.5 mm internal diameter tubes were placed with the 3 cm mark at the cords, all 4.0 and 4.5 tubes were set at 4 cm at the cords and all 5.0 and 5.5 tubes were set at 5 cm at the cords. Subsequent chest X ray showed that 79% of the tracheal tubes were in the ideal midtracheal position, one tube was marginally short and 20% of the tubes were marginally long. Neither bronchial intubation nor accidental extubation occurred in any subject. This is an effective method to determine tracheal tube length which may be used for both oral and nasal intubation.

Intubation guide marks for correct tube placement. A clinical study

The tracheas of 140 adult patients were intubated with either TFX or Portex tracheal tubes. Guide marks were printed at variable distances proximal to the tube cuffs, and during intubation the guide mark was positioned at the level of the vocal cords. The distance between the bevel end of the tube and the carina was determined with a fibreoptic bronchoscope. The mean distance between the tip of the tracheal tube and the carina varied between 3.7 and 4.1 cm with the head in the neutral position. The tip of the tracheal tube approaches the carina by a mean distance of 0.5 cm when the head is moved from the extended position to the neutral position. It is recommended that a guide mark be placed 2.5 cm from the proximal end of the cuff in tubes used for adult males and 2.25 cm in tubes used for adult females. The use of guide marks is a simple, safe and reliable method for correct tracheal tube placement.