What is the role of the Cormack-Lehane (C-L) score in predicting difficult intubation in pediatric patients?

COPUR Score in Pediatric Airway Assessment

The COPUR (Colorado Pediatric Airway Score) is an independent predictor of difficult intubation in infants and should be incorporated into preoperative airway assessment alongside BMI, best oropharyngeal view (BOV), and tragus-to-mouth angle (TMA) measurements. 1

What is the COPUR Score?

The COPUR score is a validated pediatric-specific airway assessment tool that emerged from prospective research examining anthropometric predictors of difficult intubation in infants with apparently normal facial and neck features. 1

• In multivariate analysis, COPUR was identified as one of four independent predictors of difficult intubation (alongside BMI, BOV, and TMA), demonstrating its clinical utility in the pediatric population. 1
• The score addresses a critical gap in pediatric airway management, as traditional adult scoring systems like the Macocha score have not been validated in children. 2

Clinical Context: Why Pediatric-Specific Prediction Matters

Risk factors for complicated intubation must be distinguished from predictive factors for difficult intubation in children, as these are fundamentally different concepts. 2

Difficult Intubation Risk Factors in Pediatric ICU:

• History of difficult intubation (OR 1.83,95% CI 1.02-3.29) 2
• Signs of upper airway obstruction (OR 1.91,95% CI 1.09-3.35) 2
• Younger age, low weight, inadequate sedation/neuromuscular blockade (in univariate analysis only) 2

Complicated Intubation Risk Factors:

• Hemodynamic instability 2
• Respiratory failure 2
• Operator inexperience 2

The distinction matters because complications occur in approximately 20% of non-severe cases and 3-6% of severe cases in the PICU, including cardiopulmonary arrest, unrecognized esophageal intubation, severe hypotension, and direct airway injury. 2

How COPUR Compares to Other Pediatric Airway Scores

Cormack-Lehane (C-L) Score:

• The C-L score describes laryngoscopic view quality (Grades 1-4), with Grades 3 and 4 indicating difficult visualization where the glottis is not seen. 3
• C-L is a descriptive tool used during laryngoscopy, not a preoperative predictor. 3
• In multivariate analysis, C-L score predicted difficult facemask ventilation but was analyzed separately from intubation difficulty predictors. 1

Modified LEMON Criteria:

• Recent multicenter data (2025) shows the modified LEMON criteria have poor performance in pediatric emergency patients: sensitivity 41% (95% CI 25-59%), specificity 73% (95% CI 69-77%). 4
• The negative predictive value was 95%, meaning it's better at ruling out difficult intubation than identifying it. 4
• Standards individualized for pediatric patients based on age and physical characteristics are needed, as adult-derived criteria perform poorly. 4

Anthropometric Measurements with COPUR:

The 2024 study identified specific measurements that complement COPUR: 1

For Difficult Intubation:

• Hyomental distance in neutral position (HMDn): specificity 83.8% 1
• Hyomental distance in extension (HMDe): specificity 76.7% 1
• Thyromental distance (TMD): sensitivity 89.2% 1
• Sternomental distance (SMD): sensitivity 75.7% 1
• Ratio of height to SMD (RHSMD): sensitivity 70.3% 1

For Difficult Facemask Ventilation:

• Tragus-to-mouth angle (TMA): sensitivity 86.7% 1
• Sternomental distance (SMD): specificity 80% 1

Practical Application Algorithm

Step 1: Preoperative Assessment

Measure and document: 1

• BMI
• COPUR score
• Best oropharyngeal view (BOV)
• Tragus-to-mouth angle (TMA)
• Sternomental distance (SMD)
• Hyomental distances (neutral and extension)
• Thyromental distance
• Mouth opening
• ASA physical status

Step 2: Risk Stratification

High-risk features requiring advanced preparation: 2, 1

• Elevated COPUR score with abnormal BMI
• History of difficult intubation (OR 1.83)
• Signs of upper airway obstruction (OR 1.91)
• Poor BOV or limited mouth opening
• Abnormal TMA measurements

Step 3: Equipment and Personnel Preparation

All pediatric ICU patients must be considered at risk for complicated intubation. 2

• Have both Miller straight and Macintosh curved blades immediately available, as both provide equivalent visualization and switching blades improves success after initial failure. 2, 5
• Prepare videolaryngoscopy as first-line for anticipated difficult airways or after failed direct laryngoscopy, as it significantly enhances first-attempt success. 5
• Limit direct laryngoscopy to maximum 2 attempts by the most senior practitioner, then transition to videolaryngoscopy or alternative techniques. 5, 6

Step 4: Intubation Strategy

Preservation of oxygenation and cardiovascular stability throughout the procedure is mandatory. 2

• First attempt success rates have improved to 42% in recent multicenter data when following systematic approaches. 6
• Persistence with direct laryngoscopy beyond 2 attempts is associated with severe complications and should be avoided. 6
• Severe complications decreased from 3.2% to 1.8% when rapid transition to advanced techniques was implemented. 6

Critical Pitfalls to Avoid

Do not persist with direct laryngoscopy after 2 failed attempts, as this is a modifiable risk factor associated with nearly 50% of severe complications including cardiac arrest. 6

Do not rely solely on adult-derived prediction scores like modified LEMON in pediatric patients, as sensitivity is only 41% in this population. 4

Do not assume normal facial features exclude difficult intubation risk, as the COPUR score was specifically developed for infants with apparently normal airways who still had 38.1% incidence of difficult intubation. 1

Do not underestimate the importance of adequate sedation and neuromuscular blockade, as inadequate pharmacologic preparation was associated with difficult intubation in univariate analysis. 2

Do not proceed without distinguishing between risk factors for difficult intubation versus complicated intubation, as these require different management strategies. 2