Endotracheal Tube Depth
We all know that airway management is a critical skill for those of us who care for pediatric patients in the acute environment! Due to conditions like severe respiratory illness (ex, asthma), acute trauma (ex, pulmonary contusion), or acute metabolic derangements (ex, DKA) children may benefit from endotracheal intubation. We must, however, remember, that in our efforts to help the child we must first do no harm, and the act of intubation has a large potential for inducing harm. One of the most important aspects of endotracheal intubation is proper positioning of the ETT. Let us take a moment to review Endotracheal Tube Depth.
Endotracheal Tube Depth: Do No Harm
- Unrecognized ETT misplacement (too high/too low) occurs frequently in Ped ED. [Miller, 2016]
- Low placement (i.e., mainstrem bronchus) is the most common misplacement!
- Younger patients and female patients are particularly at risk.
- Unrecognized ETT misplacement leads to complications!
- Inadequate / difficult ventilation
- Significant atelectasis
- Potential for unnecessary procedures (ex, misinterpretation of their being a pneumothorax leading to chest tube)
Endotracheal Tube Depth: Anticipate
- When planning to intubate, remind yourself of the proper positioning of the ETT
- Distal tip of the ETT should be between:
- The thoracic inlet and
- The carina.
- The ETT should be positioned and measured at the central incisor / alveolar ridge.
- Do not measure at the lip.
- Anticipate that this will be more challenging to achieve in children, particularly infants.
- Shorter tracheal length = less room for error
- The length from the vocal cords to the carina can vary between 5cm and 9 cm.
- Head / neck position plays a role!
- Neck extension will cause the ETT to move cephalad: potentially leading to extubation!
- Neck flexion will cause ETT to move toward carina: potentially going into mainstem bronchus!
Endotracheal Tube Depth: Estimate
- There are several formulas that can help estimate the depth in centimeters of the ETT.
- Personally, I am always a little leery any time there are multiple formulas to answer a question… (see Traumatic LP CSF Evaluation)
- Also, sadly, in the heat of the moment… doing complex calculus is not my strongest skill…
- Formulas can be useful to estimating initial tube placement, but their performance is variable for each individual patient.
- Age-based or height-based formulas are based on population statistics.
- Your individual patient may be outside the mean of that population!
- Most formulas are less accurate for children < 3 years of age. [Koshy, 2016]
- PALS Estimation
- For children > 1 year
- [Age (in years) / 2] + 12 (for oral ETT)
- Frequently leads to malpositioned ETT [Koshy, 2016; Lau, 2006]
- Internal Diameter Estimation
- 3 x ID of ETT
- Ex: 4.0 ETT => Depth = 12 cm
- Only used for ETT 3.0 or greater.
- Only predicted accurate placement in ~59% of cases. [Koshy, 2016]
Endotracheal Tube Depth: Auscultate?
- ETT placement confirmation has typically begun with auscultation of breath sounds.
- Equal / symmetric bilateral breath sounds would seem to suggest aeration from above the carina.
- The problem is that ETT’s with a Murphy eye can generate bilateral breath sounds even in the setting of a mainstem bronchial intubation.
- Bilateral breath sounds does not exclude mainstem intubation. [Verghese, 2004]
Endotracheal Tube Depth: Confirm!
- Chest Xray are traditionally used to confirm ETT position.
- Pros: CXR has been found to be superior to over formulas or other estimations. [Koshy, 2016]
- Cons: CXR is time consuming to obtain.
- Palpation of the trachea has been used to help determine ETT position. [Gamble, 2014]
- During intubation, another practitioner places 3 fingers on trachea with inferior finger at the sternal notch.
- The ETT is slowly advanced into the airway and positioned via external palpation.
- This was found to be superior to estimation formulas.
- Ultrasound can help you “see” the ETT position!
- An ultrasound probe positioned at the sternal notch can help locate the ETT. [Chowdhry, 2015; Chou, 2015; Tessaro, 2015]
- Much more readily available than CXR!
Moral of the Morsel:
- Your successful placement of the ETT through the cords is only the beginning of the airway management!
- Don’t celebrate too early! You have now placed the patient in a precarious position!
- Ensure that the ETT is appropriately positioned!
- Anticipate and Estimate, but Confirm!!!
- If there is any change in the child’s condition, Re-CONFIRM appropriate position of the ETT!
- Bring your Ultrasound to the bedside! Looking is better than listening!!