A Formula for Estimating the Appropriate Tube Depth for Intubation

Abstract

An estimation of the appropriate tubing depth for fixation is helpful to prevent inadvertent endobronchial intubation and prolapse of cuff from the vocal cord. A feasible estimation formula should be established. We measured the anatomical length of the upper-airway tract through the oral and nasal pathways on cephalometric radiographs and tried to establish the estimation formula from the height of the patient. The oral upper-airway tract was measured from the tip of the incisor to the vocal cord. The nasal upper-airway tract was measured from the tip of the nostril to the vocal cord. The tracts were smoothly traced by using software. The length of the oral upper-airway tract was 13.2 ± 0.8 cm, and the nasal upper-airway tract was 16.1 ± 0.9 cm. We found no gender difference (p > .05). The correlations between the patients' height and the length of the oral and nasal upper-airway tracts were 0.692 and 0.760, respectively. We found that the formulas (height/10) − 3 (in cm) for oral upper-airway and (height/10) + 1 (in cm) for nasal upper-airway tract are the simple fit estimation formulas. The average error and standard deviation of the estimated values from the measured values were 0.50 ± 0.66 cm for the oral tract and 0.39 ± 0.63 cm for the nasal tract. Thus, considering the length of the intubation marker of each product (DM), we would like to propose the length of tube fixation as (height/10) + 1 + DM for nasal intubation and (height/10) − 3 + DM for oral intubation. In conclusion, the estimation formulas of (height/10) − 3 + DM and (height/10) + 1 + DM for oral and nasal intubation, respectively, are within almost 1 cm error in most cases.

Nasotracheal intubation for airway management during anesthesia

“…This method improves sealing and reduces leakage [68]. Adequate endotracheal tube length can be predicted by using the equations for predicting the adequate tube depths in Japanese patients: (patient's height / 10) -3 + DM (distance between the distal edge of intubation guide mark and the tip, in cm) for oral intubation, and (patient's height / 10) + 1 + DM for nasal intubation [19,69].…”

Predicting dog tracheal diameter and length: A tool for improved intubation

“…However, there are only a few specific formulas developed specifically for dog applications, and only a few studies are available [ 10 , 14 ]. In contrast, in human medicine, especially in pediatrics, multiple formulas have been proposed to predict optimal ETT size and insertion depth [ 15 , 16 ]. Notably, studies in dogs primarily focused on predicting tube size rather than intubation depth [ 10 , 14 , 17 ].…”

Comparison of Chula Formula With Standard 21/23 Rule for Estimation of Orotracheal Tube Depth in Intubated Adult Patients: A Sindh Institute of Urology and Transplantation Experience

“…6,7 ICU physicians use several methods to estimate the proper depth of OTT to prevent OTT placement related complications prior to its confirmation with a chest X-Ray. These include 21/23 rule 8,9 , Chula formula 10 , 20/22 rule 11 , Indian formula 12 , Japanese formula 13 , topographic landmarks method 14 .…”