Brazilian Journal of Anesthesiology
Brazilian Journal of Anesthesiology
Original Investigation

Comparison of four formulas for nasotracheal tube length estimation in pediatric patients: an observational study

Comparação de quatro fórmulas para estimativa do comprimento do tubo nasotraqueal em pacientes pediátricos: um estudo observacional

Ashkan Taghizadeh Imani, Mehrdad Goudarzi, Niloufar Shababi, Behrang Nooralishahi, Alireza Mohseni

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Correct endotracheal intubation results in better ventilation, prevents hypoxia and its possible damages, such as brain injury, and minimizes attempts for re-intubation. Up to now, several formulas have been published to estimate nasotracheal intubation tube length. This study aims to compare the accuracy of different suggested formulas to find the one that better estimates the tube insertion distance.

This cross-sectional retrospective study was carried out in 102 (51 female, 51 male) children who underwent cardiac surgery under general anesthesia. Inclusion criteria were correct nasotracheal intubation according to the postintubation chest X-ray (CXR). The estimated tracheal tube length was calculated by four different formulas. Pearson’s correlation coefficient was used to find the correlations between the estimated length of each formula and the correct nasotracheal tube length. Also, linear regression was used to obtain a formula to estimate nasotracheal tube length by weight, height, and age.

The formula L = 3*tube size+2 had the best correlation with tube length (r = 0.81, confidence Interval: 0.732–0.878, p-value < 0.001). Among demographic variables, height had the highest correlation coefficient with the tube length (r = 0.83, confidence Interval: 0.788–0.802, p-value < 0.001). Therefore, considering the height as an independent variable and tube length as a dependent variable, using linear regression, the following formula was achieved for determining tube length: Nasotracheal tube length = 0.1*Height+7.

The formula L = 3*tube size+2 and the new suggested formula in this study can be used to estimate nasotracheal tube length in children under 4 years old. However, these formulas are only guides and require confirmation by auscultation and CXR.


Intubation,  Intratracheal,  Pediatric,  Infant,  Child,  Anesthesia



A intubação endotraqueal correta resulta em melhor ventilação, previne a hipóxia e seus possíveis danos, como lesão cerebral, e minimiza as tentativas de reintubação. Até o momento, várias fórmulas foram publicadas para estimar o comprimento do tubo de intubação nasotraqueal. Este estudo visa comparar a precisão de diferentes fórmulas sugeridas para encontrar aquela que melhor estima a distância de inserção do tubo.


Este estudo retrospectivo transversal foi realizado em 102 (51 meninas, 51 meninos) crianças submetidas a cirurgia cardíaca sob anestesia geral. Os critérios de inclusão foram intubação nasotraqueal correta de acordo com a radiografia de tórax (RX) pós-intubação. O comprimento estimado do tubo traqueal foi calculado por quatro fórmulas diferentes. O coeficiente de correlação de Pearson foi utilizado para encontrar as correlações entre o comprimento estimado de cada fórmula e o comprimento correto do tubo nasotraqueal. Além disso, a regressão linear foi usada para obter uma fórmula para estimar o comprimento do tubo nasotraqueal por peso, altura e idade.


A fórmula L=3*tamanho do tubo+2 teve a melhor correlação com o comprimento do tubo (r =0,81, intervalo de confiança: 0,732–0,878, valor p < 0,001). Entre as variáveis demográficas, a altura apresentou o maior coeficiente de correlação com o comprimento do tubo (r=0,83, Intervalo de Confiança: 0,788–0,802, valor p < 0,001). Portanto, considerando a altura como variável independente e o comprimento do tubo como variável dependente, por meio de regressão linear, obteve-se a seguinte fórmula para determinação do comprimento do tubo: comprimento do tubo nasotraqueal=0,1*Altura+7.


A fórmula L=3*tamanho do tubo+2 e a nova fórmula sugerida neste estudo podem ser utilizadas para estimar o comprimento do tubo nasotraqueal em crianças menores de 4 anos. No entanto, estas fórmulas são apenas guias e requerem confirmação por ausculta e radiografia torácica.


Intubação; Intratraqueal; Pediátrico; Infantil; Criança; Anestesia


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