Endotracheal Tube (ETT) Depth and Tidal Volume Calculator
Use in patients over 20 years old.
Adult patients requiring orotracheal intubation.
- ETT depth is measured based on the patient’s front teeth (not the molars).
- Larger tidal volumes may be temporarily required for patients with severe metabolic acidosis.
- Placing the ETT too deeply may cause right mainstem intubation, hypoxemia, and pneumothorax. However, placing the ETT too shallowly may risk injury to the vocal cords and accidental extubation. Standard approaches to verify ETT depth (e.g. bilateral auscultation) are insensitive.
- Use of lower tidal volumes appears to prevent the development of acute respiratory distress syndrome, even in patients who do not have lung injury.
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- ETT position should still be verified with a chest radiograph among patients who will remain intubated for an extended period of time.
- Tidal volume: 6-8 mL/kg ideal body weight (IBW) is generally a safe initial setting, but further ventilator adjustment may be required depending on the adequacy of ventilation and airway pressures.
Endotracheal intubation and mechanical ventilation.
Chest radiograph and measurement of CO2 level (e.g. end-tidal CO2 or blood gas analysis) to confirm ETT position and adequacy of ventilation.
Chula formula: ETT depth = 0.1 * [height (cm)] + 4
- Ideal body weight (IBW), men = 50 kg + 2.3 * [height (in) – 60]
- IBW, women = 45.5 kg + 2.3 * [height (in) – 60]
- Usual tidal volume target = 6-8 mL/kg IBW
The Chula formula was developed and validated by Techanivate and colleagues at King Chulalongkorn Memorial Hospital in Thailand.
These authors prospectively validated the use of this formula among 100 patients in Thailand. Patients were intubated and the ETT placed according to the formula. Subsequently, a bronchoscope was used to determine the relationship among the ETT, carina, and vocal cords:
- The distance between the ETT and carina ranged between 1.9-7.5 cm. No patient was at immediate risk of endobronchial intubation.
- The upper border of the ETT cuff was always >1.9 cm below the vocal cords, avoiding risk of laryngeal trauma or inadvertent extubation.
Original/Primary ReferenceARDSnet investigators. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000; May;342(18): 1301-1308.Techanivate A, Kumwilaisak K, Samranrean S. Estimation of the proper length of orotracheal intubation by Chula formula. J Med Assoc Thai. 2005 Dec;88(12):1838-46
Other ReferencesPulmCrit: Devil in the details: Endotracheal tube depthPak HJ, Hong BH, Lee WH. Assessment of airway length of Korean adults and children for otolaryngology and ophthalmic surgery using a fiberoptic bronchoscope. Korean J Anesthesiol. 2010 Oct;59(4):249-55. doi: 10.4097/kjae.2010.59.4.249. Epub 2010 Oct 21.Hunyady AI, Pieters B, Johnston TA, Jonmarker C. Front teeth-to-carina distance in children undergoing cardiac catheterization. Anesthesiology. 2008 Jun;108(6):1004-8. doi: 10.1097/ALN.0b013e3181730288.
About the Creator
Anchalee Techanivate, MD, is an associate professor in the Department of Anesthesiology at King Chulalongkorn Memorial Hospital of Chulalongkorn University in Bangkok, Thailand.
To view Dr. Anchalee Techanivate's publications, visit PubMed
- Joshua Farkas, MD