Validity of three formulas in measuring endotracheal tube insertion depth in children under mechanical ventilation

Abstract

In the process of intubation, inappropriate placement of the endotracheal tube can lead to hypoxemia, aspiration, insufficient ventilation, atelectasis, barotrauma and pneumothorax. The above complications may be difficult for a patient with severe disease to tolerate; especially when inappropriate placement is not detected by the specialist in the initial evaluation and the diagnosis has lasts until the confirmatory chest x ray is performed. This study evaluated the validity of three formulae in measuring the depth of endotracheal intubation in children under mechanical ventilation. Materials and Methods: In this study, 60 children aged 2 months to 12 years who were intubated were studied. Age, height, weight, sex, intubation indication, the number of intubation failures were recorded. Patients were randomly divided into three study groups. Endotracheal tube length for each patient was calculated on the basis of the endotracheal tube length formulas (12 + age (years) / 2; endotracheal tube length * 3; and 5 + height (cm) / 10). The ideal depth of the endotracheal tube based on chest x ray was measured as the median distance between the first thoracic vertebra (T1) and the carina in cm. The distance between the ideal depth of the endotracheal tube and the end location of the endotracheal tube was also measured and recorded. Results: The mean age of the patients was 42.90 months and 58.3% were boys. The most common indication for intubation was pneumonia, along with respiratory distress (33.3%). Considering the difference in endotracheal tube depth between the two values calculated using the formula and chest X-ray equal to 0.5 cm, formula 12 + (2 / age) in 55% of patients, formula 3 * endotracheal tube length in 70% patients and formula 5 + (10 / height) in 85% of patients, were correctly estimated endotracheal tube length. On the other hand, it was observed that in 15%, 45% and 40% of the patients, the formula predicted the correct length of the endotracheal tube for correct intubation without any difference from the chest X-ray. In evaluating the results obtained from the formula and length of the endotracheal tube measured by chest X-ray, it was also observed that the formulas 12 + (2 / age), 3 * length of the endotracheal tube and 5 + (10 / height) were significantly correlated with CXR (rs = 0.966, rs = 0.966 and rs = 0.982; respectively).