Comparison of Age-Based Formula and Ultrasound-Guided Subglottic Diameter Measurement for Endotracheal Tube Sizing

Comparison of Age-Based Formula and Ultrasound-Guided Subglottic Diameter Measurement for Endotracheal Tube Sizing in Single Ventricle Patients

To compare the accuracy of ultrasound-guided subglottic diameter measurement versus age-based formulas in determining the optimal endotracheal tube (ETT) size in pediatric patients with single ventricle physiology and reducing post-extubation complications.

Study Overview

• Status: Recruiting
• Conditions: Endotracheal Tube Wrongly Placed During Anesthetic Procedure
• Intervention / Treatment: Other: Cole's Formula; Device: Ultrasound

Detailed Description

To compare the accuracy of ultrasound-guided subglottic diameter measurement versus age-based formulas in determining optimal ETT size in pediatric patients with single ventricle physiology to avoid post-extubation complications. All legal guardians will provide written informed consent after a full explanation of the study. During the pre-anesthetic evaluation, demographic data, ASA physical status, relevant comorbidities, and a recent echocardiogram confirming single ventricle physiology will be documented. In the operating room, patients will be monitored using standard ASA monitors including ECG, non-invasive blood pressure, pulse oximetry, and capnography, followed by preoxygenation with 100% oxygen. If intravenous access is available, anesthesia will be induced with ketamine, fentanyl, and rocuronium. If IV access is not available, inhalational induction with sevoflurane will be used until IV access is secured, after which fentanyl and rocuronium will be administered. Following induction, ventilation will continue with FiO₂ 100% and sevoflurane 1.5% for 3 minutes.

Patients will be divided into two groups:

Group A (Age-Based Formula):

In neonates and infants under 1 year, a weight-based sizing is used:

• Infants <1 kg (Preterm): 2.5 mm ETT
• Infants 1-2 kg: 3 mm ETT
• Infants 2-3 kg (Full Term): 3-3.5 mm ETT
• Infants >3 kg (3 months to 1 year): 3.5-4 mm ETT

In Infants > 1 year, ETT size will be selected based on the standard formula: Cole's Formula for uncuffed ETT.

ETT ID (mm) = (Age/4) + 4.

Group B (Ultrasound Group):

During mask ventilation, a trained anesthesiologist will perform transverse subglottic diameter measurement using a high-frequency linear ultrasound probe (7-15 MHz). The patient will be positioned supine with mild neck extension. The probe will be placed transversely just below the thyroid cartilage to identify the subglottic airway at the level of the cricoid cartilage. The measured diameter (in mm) will be recorded and used to determine ETT size from the equation:

ETT ID (mm) = Subglottic diameter (mm) × 0.8 To confirm appropriate ETT sizing, all patients will be placed on pressure-controlled mechanical ventilation and a leak test will be performed in both groups. Start with pressure 20-25 cm H₂O, if there is resistance to ETT passage into the trachea or no audible leak or ventilator-detected leak when the lungs are inflated, the tube will be exchanged for one that is 0.5 mm smaller. If a leak is detected, decrease the pressure to 10 cm H₂O. If there's still a detected leak at 10 cm H₂O, the ETT will be exchanged for one that is 0.5 mm larger. If there's no leak at 10 cm H₂O then the ETT is optimal. Tube size will be considered optimal when a tracheal leak is not detected at an inflation pressure between 10-20 cm H₂O with uncuffed tubes.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Nouran Nemr, M.B.B.Ch, M.Sc.; Phone Number: 01008558583; Email: Nourannemr@med.asu.edu.eg
• Study Contact Backup: Name: Mohamed Tolba, MD; Phone Number: 01156622298

Study Locations

• Egypt
  • Abbasseya
    • Cairo, Abbasseya, Egypt, 00202
      • Recruiting
      • Ain Shams University
      • Contact: Nouran Nemr, M.B.B.Ch, M.Sc.; Phone Number: 01008558583; Email: Nourannemr@med.asu.edu.eg

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Pediatric patients (3 months to 8 years)
• Patients with single ventricle physiology
• Scheduled for Glenn or Fontan surgery or cardiac catheterization
• Patients with Glenn or Fontan shunt scheduled for surgery

Exclusion Criteria:

• Refusal of legal guardians
• Emergency surgery
• Patients with tracheostomy tubes
• Recent or active upper respiratory tract infection
• Airway anomalies (e.g. Pierre Robin, Treacher Collins)
• ICU stay due to complications other than that of airway

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Age-Based Formula Group; In neonates and infants under 1 year, a weight-based sizing is used: Infants <1 kg (Preterm): 2.5 mm ETT; Infants 1-2 kg: 3 mm ETT; Infants 2-3 kg (Full Term): 3 - 3.5 mm ETT; Infants >3 kg (3 months to 1 year): 3.5 - 4 mm ETT In Infants > 1 year, ETT size will be selected based on the standard formula: Cole's Formula for uncuffed ETT. ETT ID (mm) = (Age/4) + 4.	Other: Cole's Formula; Subglottic diameter in mm x 0.8
Active Comparator: Ultrasound Group; During mask ventilation, a trained anesthesiologist will perform transverse subglottic diameter measurement using a high-frequency linear ultrasound probe (7-15 MHz). The patient will be positioned supine with mild neck extension. The probe will be placed transversely just below the thyroid cartilage to identify the subglottic airway at the level of the cricoid cartilage. The measured diameter (in mm) will be recorded and used to determine ETT size from the equation: ETT ID (mm) = Subglottic diameter (mm) × 0.8	Device: Ultrasound; Using Ultrasound for accuracy of ETT sizing

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Accuracy of ETT size selection	Accuracy of endotracheal tube size selection measured by the number of ETT attempts required to achieve an appropriate leak test and successful airway placement.	During endotracheal intubation, immediately after induction of anesthesia and neuromuscular blockade (within 10 minutes after induction)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of post-extubation stridor/croup	Occurrence of post-extubation stridor or croup assessed using the Westley croup score.	From extubation until 24 hours post-extubation
Severity of post-extubation croup	Severity of post-extubation croup assessed using the Westley croup score	At 30 minutes, 2 hours, and 24 hours after extubation
Duration of ICU stay related to airway complications	Length of ICU stay due to airway complications such as post-extubation stridor	From ICU admission until ICU discharge, up to 30 days

Collaborators and Investigators

• Sponsor: Ain Shams University

Study record dates

Study Major Dates

• Study Start (Actual): January 1, 2026
• Primary Completion (Estimated): June 30, 2027
• Study Completion (Estimated): June 30, 2027

Study Registration Dates

• First Submitted: April 22, 2026
• First Submitted That Met QC Criteria: May 8, 2026
• First Posted (Actual): May 14, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 8, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Diagnostic Techniques and Procedures; Diagnosis; Diagnostic Imaging; Ultrasonography
• Other Study ID Numbers: FMASU MD353/2025

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No