How to Determine the Length of an ET Tube

Locate the size indication on the ET tube. The outside diameter (OD) and internal diameter (ID) of the ET tube should be clearly marked. ID sizes typically range from 3.5 mm for small infants to 8.5 mm for adult males.

• When discussing the size of an ET tube, the focus is usually on the internal diameter since it determines the air volume delivered during intubation.

Determining ET Tube Length

Refer to the length marking on the ET tube. Smaller ET tubes with smaller inner and outer diameters are designed for individuals with shorter distances between their mouth and trachea. Typically, ET tubes ranging from 7.0 to 9.0 mm in size can be inserted approximately 20–25 centimeters (7.9–9.8 inches) down the throat, although lengths may vary.

• Length markings along the tube indicate how far the tube extends down the throat.
• Some doctors opt to trim ET tubes to specific lengths for individual patients, a practice particularly common in pediatric cases where required lengths can significantly differ.

Select the appropriate ET tube size based on gender and height in adults. ET tube sizes for adults (over 18 years) are typically determined by the patient's sex and height. Females generally use ET tubes sized 7.0 to 8.0 mm, while males use 8.0 to 9.0 mm tubes. Smaller individuals, around 5 feet (1.5 m) tall, typically use the smaller size, while taller individuals, approximately 6 feet (1.8 m) tall, use the larger size.

• Remember, ET tube size corresponds to the tube's internal diameter.

Consider age when selecting an ET tube size for infants and children. Sizing ET tubes for children requires precision due to their smaller size. Determine the appropriate tube size based on the child's age:

• Newborn: 2.5 - 4.0 mm
• Infant under 6 months: 3.5 - 4.0 mm
• Infant between 6 months and 1 year: 4.0 - 4.5 mm
• Child 1 and 2 years: 4.5 - 5.0 mm
• Child over 2 years: Divide the child's age by 4 and add 4 mm

Measure children using a Broselow tape. For a more tailored measurement, use a Broselow tape to gauge a child's size, including the appropriate ET tube size. The Broselow tape utilizes the child's height to determine the size of equipment needed, including the ET tube.

• To use the Broselow tape, lay it alongside the child's body, noting the color block corresponding to their height. Instructions within this color block indicate the appropriate treatment for the child's size.

Introduce the ET tube into the trachea. Position the individual's head neutrally and use a laryngoscope to elevate the tongue and pharynx. Insert the ET tube through the mouth, passing the vocal cords, and reaching the trachea.

• If the individual is not already unconscious, sedation is necessary before ET tube insertion.

Achieve the appropriate depth by aligning the lower depth marker with the vocal cords. While advancing the tube, monitor its progress until it surpasses the vocal cords. Then, ensure that the marking near the tube's end aligns with the vocal cords.

• The marking denotes the standard depth of ET tube insertion into the trachea.

Verify correct placement by aligning the depth marker with the mouth opening. Length indicators are present along the tube's length. In adults, the tube should extend approximately 20 to 25 cm at the mouth corner when properly positioned.

• Proper alignment of the vocal cord mark with the mouth's depth marker indicates correct tube placement.
• Subsequently, healthcare professionals can use this marker to confirm ongoing correct tube positioning.

Inflate the cuff to secure the ET tube. Upon reaching the appropriate depth, inflate the cuff, a balloon at the tube's base, to stabilize it in the trachea. Use a syringe to inject 10 cc of air into the cuff through its port.

• Aside from stabilizing the tube, the cuff prevents liquid entry into the lungs, reducing the risk of aspiration during intubation.

Confirm proper insertion. After administering oxygen through the tube, ensure the chest rises and falls rhythmically. Then, validate the tube's placement, either via X-ray or ultrasound.

• The ET tube tip should be positioned 3–7 centimeters (1.2–2.8 inches) above the tracheal base.
• Avoid advancing the tube beyond the carina, the tracheal division point, to prevent potential damage.

Document the ET tube position to track any shifts. Recording the initial tube position facilitates subsequent checks for displacement. Note the measurement marked on the tube at a specific mouth location, such as the front teeth or lips.

• This documentation aids in verifying proper tube positioning during follow-up assessments.

Attach a CO2 detector to the ET tube. Verify correct tube insertion by employing a CO2 detector. Color change in the detector indicates exhaled CO2, confirming proper oxygenation, as CO2 is a byproduct of respiration only when oxygen is supplied.

• These detectors are single-use, irreversibly changing color upon CO2 detection, typically employed immediately post-intubation.

Monitor air pressure within the ET tube. Once the tube is in place, gauge respiratory pressure using a pressure regulator.

• Monitoring airway pressure aids in preventing tracheal and lung damage.
• Ensure cuff pressure remains within a safe range of 20 to 30 cmH2O.