The CALMS Score for Extubation Success aka Off ETT, NIF (Negative Inspiratory Force), and Leak Distress in the Pediatric ICU

Score of 9 or above: High likelihood of successful extubation.

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Introduction

Extubation is a critical step in the management of pediatric patients in the Intensive Care Unit (ICU). Successfully removing an endotracheal tube (ETT) requires careful assessment to ensure the patient's readiness, thereby minimizing risks of extubation failure and re-intubation. The Nakornping Pediatric Weaning Score, commonly referred to as the CALMS Score, is a validated tool designed to predict extubation success in children. This article provides an in-depth look at the CALMS Score and its application in the Pediatric ICU.

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CALMS Score Components

The CALMS Score comprises five main components, each divided into specific assessment criteria. These components are:

1. CNS Function:
   • Cough Reflex: Evaluates the presence or absence of a cough reflex.
   • Swallowing Reflex: Assesses the patient's ability to swallow.
   • Gag Reflex: Checks for a gag reflex.
   • Consciousness: Measures the patient's level of consciousness, ideally at E4VTM5-E4VTM6.
2. Airway Leak Test:
   • Measures the pressure difference when the cuff is deflated. A value ≤ 25 mmHg indicates readiness.
3. Lung Assessment:
   • Lung Sounds: Ensures lungs are clear upon auscultation.
   • Pco2 Levels: Assesses carbon dioxide levels, with ≤ 50 being optimal.
4. Muscle Function:
   • NIF Test (Negative Inspiratory Force): Evaluates respiratory muscle strength, with a value > -20 mmHg indicating readiness.
   • Muscle Relaxant Use: Notes if muscle relaxants are in use; absence indicates better readiness.
5. Secretion Management:
   • Secretion Status: Ensures that secretions are clear and manageable.

Each criterion is scored 0 or 1, resulting in a total possible score of 10.

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Interpreting the CALMS Score

A higher CALMS Score correlates with a greater likelihood of successful extubation. Research indicates that:

• Score of 9 or above: High likelihood of successful extubation.
• Sensitivity at score 9: 85.2%
• Specificity at score 9: 42.9%
• AUROC: 0.66 (95% CI 0.50-0.83)

Application in the Pediatric ICU

Pre-Extubation Assessment:

1. Perform the CALMS Score assessment.
2. Ensure a score of 9 or higher for extubation readiness.

Monitoring and Support:

1. Proceed with extubation for patients with appropriate scores.
2. Continuously monitor respiratory parameters post-extubation.

Post-Extubation Care:

1. Provide respiratory support as needed (e.g., HFNC).
2. Regularly reassess for signs of respiratory distress.

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Teaching Points: NIF (Negative Inspiratory Force) and Leak Distress

Understanding NIF (Negative Inspiratory Force)

Definition: NIF measures the maximum negative pressure a patient can generate during inspiration against a closed airway. It reflects the strength of the respiratory muscles.

Importance:

• Indicates respiratory muscle strength.
• Helps predict the ability to maintain spontaneous breathing post-extubation.

Normal Values:

• A NIF value of at least -20 cm H2O is generally considered adequate for weaning from mechanical ventilation.

Measurement Process:

1. Ensure the patient is in a comfortable position.
2. Instruct the patient to take a deep breath in against a closed airway.
3. Measure the maximum negative pressure generated.

Clinical Use:

• Used in conjunction with other weaning parameters to assess extubation readiness.
• Particularly useful in patients with neuromuscular diseases or those recovering from prolonged mechanical ventilation.

Understanding Leak Distress

Definition: Leak distress refers to the presence of air leaks around the endotracheal tube, which can affect ventilation efficiency and cause complications.

Assessment:

• Conducted during spontaneous breathing trials or before extubation.
• Involves deflating the cuff of the endotracheal tube and observing for air leak.

Leak Test:

1. Deflate the cuff of the ETT.
2. Observe for the presence of air leaking around the tube.
3. A significant leak indicates adequate airway patency and less risk of post-extubation stridor.

Impact of Leak Distress:

• Significant air leaks can lead to inadequate ventilation.
• Must be addressed to ensure safe extubation.

Management:

• Ensure proper tube size and position.
• Use of medications like steroids to reduce airway swelling if needed.
• Consider re-evaluation and delaying extubation if a significant leak is detected.

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Conclusion

The CALMS Score is a valuable tool in the Pediatric ICU for assessing extubation readiness. Alongside other critical assessments such as NIF and leak tests, it helps ensure safe and effective weaning from mechanical ventilation. Understanding and applying these principles can significantly improve patient outcomes and reduce complications associated with extubation.