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This document contains information that is supplementary to an article that appeared in informed, September 2001 Vol 7 No 4, which is available online at www.ices.on.ca.The educational materials herein are believed to be valid as of September 1, 2001 except where noted. Clinical decisions must always be individualized and ICES assumes

no liability for use of these materials by patients or health professionals.

Endotracheal tube choice

informedPlusS U P P L E M E N TA R Y T O O L S A N D I N F O R M A T I O N T O A S S I S T Y O U I N Y O U R P R A C T I C E

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Institute for Clinical Evaluative Sciences (ICES), G1 06, 2075 Bayview Avenue, Toronto, ON M4N 3M5

Phone: (416) 480-4055, Extension 3890 Internet: http://www.ices.on.ca E-mail: informed@ices.on.ca

7422

Endotracheal Intubation: tube sizing recommendations

Adapted from: Roberts: Clinical Procedures in Emergency Medicine 3rd Edition. 1998, WB Saunders, New York. Accessed May 11, 2001 from http://home.mdconsult.com/das/book/body/0/644/190.html

Laryngoscope considerations

Two basic blade designs: curved (MacIntosh) and straight (Miller and Wisconsin), each with advantages and disadvan-tages. Slight variations in technique follow from the choice of blade: the tip of the straight blade goes under the

epiglottis and lifts it directly, whereas the curved blade fits into the vallecula and indirectly lifts the epiglottis via the

hypoepiglottic ligament to expose the larynx.

The straight blade is usually a better choice in pediatric patients, in those with an anterior larynx or a long floppy epiglottis,and in those whose larynx is fixed by scar tissue. It is less effective in those with prominent upper teeth (breakage is

possible). Straight blade use is also associated with increased laryngospasm due to stimulation of the superior

laryngeal nerve.

The wide curved blade, generally preferred in adult intubation, helps keep the tongue retracted from the field andleaves more room for passing the tube. Some clinicians report the curved blade requires less forearm strength than

the straight blade.

Caveat

Unstable cervical spine injury is a relative contraindication to direct laryngoscopy

Endotracheal (E/T) tubes

Standard plastic E/T tubes are about 30 cm in length. Tube sizing is based on internal diametermeasured in mm, andrange from 2.0 to 20.0 mm in increments of 0.5 mm. The outer diameter is 2 and 4 mm larger than the internal. Size is

printed on the tube, as is a scale in cm for determining the distance along the tube from the tip. Standard tube cuffs are

high-volume and low-pressure. Correct cuff inflation can be determined by slowly injecting air into the cuff until no air

leak is audible when the patient is being bagged (generally 5-8 mL of air, so use a 10 mL syringe); you can also be guided

by the tension of the pilot balloon, as slight compressibility with gentle external pressure indicates adequate inflation for

most clinical situations. Capillary blood flow is compromised in the tracheal mucosa when the pressure exceeds 30 mm

Hg. No cuffs are used in children.

Adult men: usually 7.5 to 9.0 mm tube.

Adult women: usually 7.0 to 8.0 mm tube. In general, do not use tubes smaller than these, especially in patients withCOPD who may be difficult to wean from the respirator due to excessive airway resistance from a small tube. Note: in

emergency intubations, many clinicians prefer to use a slightly smaller tube initially, then replace with a larger tube

later if necessary. The exception is the burn patient where as large a tube as is possible should be placed because

swelling may prohibit tube placement later. When intubating nasally, use a slightly smaller tube (by 0.5 to 1.0 mm).

In infants and children: this formula is a highly accuratemethod for determining correct tracheal tube size:

The old saw: using the width of the nail of the little finger is sufficiently accurate as a guide, and is more precise than

finger diameter. In a child, the smallest airway diameter is at the cricoid ring, not the vocal chords as in adults. Tubes

that hold up after passing the chords should be replaced with the next smaller size. Children under the age of eight aretubed with an uncuffed tube; therefore, good tube size is important to provide a good tube seal.

4 + age (years)

4TUBE SIZE =

Correction date:

November 19, 2001

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