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Difficulty Inserting Cuffed Endotracheal Tubes in a Child: A Case Report

Imai, Keiko MD; Doi, Taku MD; Kayashima, Kenji MD

doi: 10.1213/XAA.0000000000000404
Case Reports: Case Report

We experienced difficulty inserting cuffed inner diameter (ID) 4.5- and 5.0-mm endotracheal tubes (ETTs) in a 5-year-old boy. Postoperative ultrasound investigations showed that the internal transverse width of the cricoid cartilage was 8.0 mm. The maximum outer diameter (OD) of the deflated cuff portion of the cuffed ID 4.5- and 5.0-mm ETTs was 8.5 and 9.6 mm, respectively. The OD of an uncuffed ID 5.5-mm ETT was 7.6 mm; this tube passed the cricoid cartilage. Hence, the transverse width of the cricoid cartilage and ETT diameter including cuff folds should be considered when selecting cuffed ETTs.

From the Department of Anesthesia, Japan Community Health Care Organization, Kyushu Hospital, Kitakyushu, Fukuoka, Japan.

Accepted for publication June 28, 2016.

Funding: None.

The authors declare no conflicts of interest.

Address correspondence to Kenji Kayashima, MD, Department of Anesthesia, Japan Community Health Care Organization, Kyushu Hospital, 1-8-1 Kishinoura, Yahatanishi-ku, Kitakyushu, Fukuoka 80, Japan. Address e-mail to

Cuffed endotracheal tubes (ETTs) are increasingly used for pediatric intubation.1 Size and diameter of the glottis,2 subglottis,3 and cricoid cartilage2,3 play important roles in selecting the appropriate pediatric ETT size. In this report, we describe a case in which we experienced difficulty inserting 2 differently sized cuffed ETTs through the glottis or subglottis.

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A 5-year-old boy (height, 123 cm; weight, 18.4 kg) was scheduled for adenoidectomy and bilateral ear tube insertion for tympanitis. Written informed consent was obtained from the patient’s parent for publication of this report.

After slow induction of general anesthesia with inhalational sevoflurane and intravenous administration of 0.54 mg/kg rocuronium, a senior resident with 3 years’ experience in anesthesiology and a senior anesthesiologist with 7 years’ experience attempted oral tracheal intubation. Observation using a Macintosh size 2 laryngoscope blade (HEINE® Classic+, HEINE Optotechnik GmbH & Co, Herrsching, Germany) revealed a Cormack-Lehane grade of I. A preformed cuffed internal diameter (ID) 5.0-mm ETT (Parker Flex-Tip; Parker Medical, Highlands Ranch, CO) followed by a preformed cuffed ID 4.5-mm ETT (Parker Flex-Tip) could not be inserted because of resistance at the level of the glottis or cricoid cartilage. The anesthesiologists did not exert unusual force to advance the ETT. An uncuffed ID 5.5-mm ETT (Mallinckrodt, Dublin, Ireland) was successfully placed without resistance. Bilateral respiratory sounds were confirmed by auscultation. There were no breath sounds around the uncuffed ID 5.5-mm ETT at 25 cm H2O. Total operating, endotracheal intubation, and anesthesia times were 61, 102, and 129 minutes, respectively. After extubation, ultrasonography revealed the internal transverse width of the cricoid cartilage to be 8.0 mm. A tracheal diameter of 7.8 mm at the level of the sternoclavicular joint was radiographically measured postoperatively. No complications including sore throat or hoarseness were observed postoperatively.





We measured the outer diameter (OD) at the deflated cuff portion of 2 ETTs both with ID 4.5 mm as 8.5 mm (barrel-shaped cuff; Parker) and 7.4 mm (spindle-shaped cuff; Mallinckrodt) by using a sliding caliper while compressing the folds of the deflated cuff with the caliper arms (Figure). The OD 7.4-mm ETT could have passed the cricoid cartilage with an internal transverse width of 8.0 mm in this patient. The Table compares the ODs between cuffed and uncuffed ETTs (with IDs of 4.5, 5.0, and 5.5 mm) (written on the tube and measured with a sliding caliper).

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In the 5-year-old male patient in this report, neither the cuffed ID 5.0-mm nor the cuffed 4.5-mm ETT could pass the glottis or the subglottis, including the cricoid cartilage with an internal transverse width of 8.0 mm because of the presence of the folds of the deflated cuff. We measured the maximum OD of the deflated cuff portion including folds as 8.5 and 9.6 mm for the preformed cuffed ID 4.5- and 5.0-mm Parker ETTs, respectively. The OD of a preformed uncuffed ID 5.5-mm Mallinckrodt ETT was 7.6 mm, and this tube passed the cricoid cartilage with an internal transverse width of 8.0 mm.

According to Motoyama’s formula for calculating the appropriate size for a cuffed tube (size [mm internal diameter] = [age/4 in years] + 3.5 = 4.75 for a 5-year-old),4,5 the ID 4.5-mm ETT should have been suitable in this 5-year-old patient. In addition, although intubation with the initially selected cuffed ID 5.0-mm ETT was unsuccessful in this patient, application of Cole’s formula (size [mm internal diameter] = [age/4 in years] + 4 = 5.25 mm for a 5-year-old)5 indicates that an uncuffed ID 5.0-mm ETT should have been appropriate in this patient. Many preformed ETTs are not well suited for routine use in small children because of the problem of endobronchial intubation.6 The preformed uncuffed ID 5.5-mm ETT used in the present patient is designed for a child aged 6 years or older, and use of this ETT might have resulted in endobronchial intubation in this patient.

An air leak should be present at a peak airway pressure of 15 to 25 cm H2O.4 There were no breath sounds around the ETT at 25 cm H2O; thus, an ETT one size smaller might have been appropriate. However, no resistance was felt during insertion in this patient and the cuff-leak test may be unreliable in children. An ETT air leak pressure ≥30 cm H2O measured in nonparalyzed critically ill children before extubation or for the duration of mechanical ventilation was common and did not predict an increased risk of extubation failure.7

In children, Microcuff (Halyard Health Inc, Alpharetta, GA) ETTs have been used as follows: ID 4.5 mm in patients with an average height of 107 cm and age of 4.8 years, and ID 5.0 mm in patients with an average height of 122 cm and age of 6.8 years.8 The present patient was 123 cm tall, which is equivalent to the height of a 7-year-old Japanese boy in Japan. This factor was taken into account by the anesthesiologists in the selection of a relatively large ETT.

Available cuffed and uncuffed ETT sizes differ among manufacturers. In our department, we usually choose Parker cuffed or uncuffed ETTs because of the shape of the soft tip. For ear, nose, and throat surgery, we prefer to use a cuffed ETT to prevent secretions and blood from entering the trachea. It should be noted that larger-than-expected cuffed ETTs with their intralaryngeal cuff position in children may cause mucosal damage and inflammatory reactions within the larynx. The tube cuff is likely to be situated within the larynx when placed in accordance with insertion depth formulas or radiological criteria, as used for uncuffed tracheal tubes in children.9 The ETT cuff shape has been well investigated for successful pediatric intubation.5 However, the maximum OD of the deflated cuff portion may not have been carefully considered in pediatric anesthesia. Larger volume cuffs (eg, Parker Flex-Tip) may form bigger folds than smaller ones (eg, Mallinckrodt or Microcuff) when deflated. The Microcuff consisting of an ultrathin (0.01 mm) cuff that does not form folds5 has not been introduced in our department. Microcuff use may resolve the problem of folds when choosing appropriate pediatric cuffed ETTs.

We could not distinguish whether the resistance occurred at the glottis or the entrance of the cricoid cartilage during the first and second intubation attempts because of the unknown distance between the glottis and the entrance to the cricoid cartilage in this patient. The anterior portion of the glottic ligaments attaches to the thyroid cartilage. In contrast, the posterior portion of the glottic ligaments attaches to the arytenoid on the posterior portion of the cricoid ring. The posterior portion of the cricoid ring is higher than the anterior portion. The subglottic area is defined as the area extending from the lower surface of the true glottis to the lower surface of the cricoid cartilage. The distance between the 2 structures averaged 8.4 mm in 56 children with a median weight of 10.7 kg and might have been 9.6 mm in this 5-year-old boy.10

Measurement based on video laryngoscopy in 128 children with a mean age of 5.9 years revealed that the glottis (mean cross-sectional area [CSA] of 30 mm2) rather than the cricoid cartilage (49 mm2) was the narrowest portion of the pediatric airway. However, more mobile, expandable vocal cords may function to enlarge the glottic opening more than the cricoid cartilage.2 Computed tomography measurement in 220 children with a mean age of 48 months showed that the mean anteroposterior diameter and transverse width of the subglottis were 9.2 and 7.5 mm, respectively (CSA of 17.3 mm2); those of the cricoid cartilage were 8.5 and 8.3 mm, respectively (CSA of 17.6 mm2). Laryngeal edema can affect the measurement of the cricoid cartilage on ultrasonography. In the present patient, the absence of postextubation stridor does not exclude the possibility of a certain amount of laryngeal edema, and the ultrasonographically measured internal transverse width of the cricoid cartilage after extubation might have been affected by laryngeal edema generated by 3 intubation attempts.

In clinical practice, we can ultrasonographically measure the internal width of the cricoid cartilage instead of the transverse diameters of the glottis. Hence, the internal width of the cricoid cartilage obtained using ultrasonography or computed tomography may help in ETT selection.

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We are grateful to the following manufacturers for the provision of sample endotracheal tubes: Parker Medical (Parker Flex-Tip), Mallinckrodt, and Halyard Health (Microcuff).

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Name: Keiko Imai, MD.

Contribution: This author helped complete the manuscript.

Name: Taku Doi, MD.

Contribution: This author helped complete the manuscript.

Name: Kenji Kayashima, MD.

Contribution: This author helped complete the manuscript.

This manuscript was handled by: Hans-Joachim Priebe, MD, FRCA, FCAI.

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