COMFORT-B Sedation Scale

Clinical Overview

The COMFORT-B scale is a validated behavioral tool for assessing sedation depth in critically ill, mechanically ventilated children. Unlike pharmacokinetic endpoints (drug levels), COMFORT-B measures the actual clinical manifestation of sedation—what the child looks like and how they respond—making it practical for real-time bedside titration.

The original COMFORT scale was developed in 1992 by Ambuel et al. as an 8-item behavioral and physiologic assessment tool. The "B" version (COMFORT-B), introduced in 1999, reduced the scale to 6 behavioral items, removing physiologic variables (heart rate and blood pressure) that were non-specific and subject to confounding. This streamlined version is now the standard in most PICU protocols.

Why It Exists

Adequate sedation in mechanically ventilated children serves multiple purposes: reducing anxiety, facilitating mechanical ventilation (preventing ventilator dyssynchrony), lowering intracranial pressure (in certain pathologies), and improving comfort during procedures. Too little sedation leads to agitation, self-extubation, and injury. Too much sedation delays recovery, masks neurologic changes, and increases duration of ventilation. COMFORT-B provides a common language for measuring where a given patient falls on this spectrum.

Key Components

COMFORT-B consists of six behavioral domains, each scored 1-5 (lower score = deeper sedation):

1. Alertness: Ranges from no response to agitation. Score 1 = no response to any stimulus; score 5 = normal alertness or agitation.
2. Calmness/Agitation: From calm (1) to crying/combative (5).
3. Respiratory response: Ability to breathe independently or resistance to mechanical ventilation. Score 1 = no spontaneous breathing; score 5 = coughing, struggling against ventilator.
4. Movement: From no movement (1) to purposeful movement/thrashing (5).
5. Muscle tone: From limp (1) to hypertonic (5).
6. Facial tension: Relaxed appearance (1) to tight, grimacing (5).

Total score ranges from 6 (deeply sedated) to 30 (fully awake and agitated). Each item is assessed over a 2-minute observation window.

Interpretation Guide

Target Ranges

The original COMFORT-B paper and subsequent pediatric ICU literature define sedation targets as:

• <11 (deeply sedated/over-sedated): Patient is unresponsive or minimally responsive. Pupillary reactions may be present but purposeful responses are absent. This depth is appropriate for post-operative patients in the first hours, during critical procedures, or for critically unstable patients. Prolonged scores <11 increase risk of ventilator-associated pneumonia, myopathy, and delirium upon awakening.

• 11-17 (target sedation range): Optimal for most mechanically ventilated children. Patient is sedated and calm but can be aroused with vigorous stimulation. This level allows mechanical ventilation without self-injury, permits periodic neurologic checks, and facilitates weaning.

• >17 (under-sedated): Patient shows signs of arousal, movement, or agitation. A brief period >17 is not problematic; sustained scores >17 suggest need for sedation increase or evaluation for pain/causes of agitation.

How to Use COMFORT-B at the Bedside

Assessment is quick (2 minutes) and requires no equipment:

1. Observe the child for 2 minutes without intervention
2. Score each of the 6 items based on observed behavior during this period
3. Sum the scores
4. Compare to the target range above

Most PICU institutions perform COMFORT-B scoring q4h in stable patients, or q2h in those undergoing frequent titration. Some protocols call for scoring whenever inotropes or sedatives are changed.

Clinical Decision Points

If COMFORT-B <11: Patient is over-sedated. Actions depend on clinical context:

• Post-op hours 0-4: Often acceptable as intended; reassess frequently.
• Post-op hours >4 or stable patient: Consider reducing sedative infusion by 10-20% and re-score in 15-30 minutes.
• Patient with head injury or on targeted temperature management: May be intended; clarify with team.

If COMFORT-B 11-17: Target achieved. Continue current sedation. Perform periodic assessments (q4h) to detect drift.

If COMFORT-B >17: Patient is under-sedated. Evaluate for:

• Pain: Is patient grimacing? Check for surgical site, tube discomfort, or other painful procedures. Analgesics may be primary need (opioids, acetaminophen, NSAIDs if appropriate).
• Delirium or emergence phenomena: Some drugs (especially propofol, ketamine) can cause agitation or hallucinations. Consider switching agent.
• Environmental triggers: Is procedure ongoing? Is alarm noise excessive? Can environmental stressors be reduced?
• Inadequate sedative dosing: If pain is controlled but COMFORT-B remains high, increase sedative by 10-20% (or add second agent) and re-score in 15-30 minutes.

Common Pitfalls

Confusing movement with under-sedation: A child thrashing because of pain differs from one showing purposeful movement but calm facial expression. Movement ≠ failure; context matters.

Scoring too quickly or during a procedure: COMFORT-B is meant to capture baseline behavior. Scoring during suctioning or a blood draw will over-estimate agitation. Ensure the 2-minute observation is during a quiet period.

Not addressing pain: Some clinicians increase sedatives when the real problem is inadequate analgesia. Always assess for pain signals (facial grimacing, guarding) before escalating sedation alone.

Ignoring drug-specific effects: Some sedatives produce disinhibition (ketamine can paradoxically cause agitation initially; propofol emergence delirium). Know your drugs and consider pharmacology, not just scores.

Scoring around the clock without goal-directed sedation: COMFORT-B is a tool to titrate toward a goal, not an end in itself. Define sedation targets (typically 11-17) and use the score to adjust medications toward that goal. Routine over-sedation increases ICU complications.

Evidence & Validation

Original Development

Ambuel et al. (1992) published the initial COMFORT scale in the Journal of Pediatric Psychology. They developed and validated an 8-item scale (including heart rate and blood pressure) in a cohort of children receiving mechanical ventilation. Reliability and construct validity were demonstrated; the scale correlated with clinical judgment of sedation depth and with doses of sedative and analgesic drugs.

Key finding: Behavioral items were more reliable than physiologic measures (which were confounded by pain, hypoxia, CO₂ retention). This led to the COMFORT-B refinement.

COMFORT-B Validation

van Dijk et al. (1999) published COMFORT-B in a Dutch cohort, demonstrating:

• Reliability: Inter-rater reliability (kappa = 0.77-0.86) and internal consistency (Cronbach's alpha = 0.87)
• Validity: Correlation with visual analog scale (VAS) of sedation depth and with drug doses
• Sample: ~150 pediatric ICU patients on mechanical ventilation

Subsequent validation has been robust:

• Ambuel et al. (2003) revisited the scale with a larger international sample (~400 patients) across multiple ICUs, confirming reliability and construct validity
• Carnevale et al. (2005) validated COMFORT-B in an Italian PICU cohort; similar strong psychometric properties
• Used in observational studies comparing sedation strategies (e.g., daily sedation interruption trials, propofol vs. midazolam studies) where COMFORT-B served as outcome

Sensitivity and Specificity

COMFORT-B is not a diagnostic tool with sensitivity/specificity for a disease state, but rather an ordinal scale. However:

• Agreement with expert clinical judgment of sedation adequacy: 82-88% in validation studies
• Responsiveness to drug changes: Scores change within 15-30 minutes of sedative dose adjustment, demonstrating the scale's sensitivity to pharmacologic intervention

Limitations

• Behavioral observation required: Cannot be used in paralyzed patients (who may be under-sedated but appear still). Paralysis should be brief and paired with confirmed sedation.
• Rater training needed: While the tool is objective, consistent application requires brief training. Inter-rater reliability improves with familiarity.
• Does not assess pain specifically: COMFORT-B captures agitation but is not designed to stratify analgesic depth. Many protocols use a separate pain scale (FLACC, FACES) alongside COMFORT-B.
• Context-dependent interpretation: "Under-sedation" differs in a child post-op hour 2 vs. post-op day 3. Clinical judgment is still required.
• Limited in certain populations: Infants <6 months, children with severe encephalopathy or seizure disorders, and those with severe neuromuscular disease may be harder to score reliably.

Comparison to Alternatives

• Riker Sedation-Agitation Scale (SAS): Originally developed in adults; used in some pediatric units. Similar targets. COMFORT-B is more granular for behavioral assessment.
• State Behavioral Scale (SBS): Another pediatric option. COMFORT-B is more widely validated and endorsed by pediatric critical care societies.
• Electroencephalographic monitoring (BIS, NIRS): Non-behavioral, objective approaches. Limited availability and expense in most PICUs; not standard for titration.

COMFORT-B remains the standard in most English-speaking PICUs.

Worked Example

Clinical Scenario

A 4-year-old (16 kg) with severe pneumonia and ARDS is intubated on day 3 of mechanical ventilation. She is on synchronized intermittent mandatory ventilation (SIMV) with:

• Midazolam 0.1 mg/kg/hr
• Fentanyl 1 mcg/kg/hr
• Acetaminophen 15 mg/kg q6h

At morning rounds, the resident performs COMFORT-B scoring.

Scoring

The resident observes the child for 2 minutes without touching her:

Interpretation

A COMFORT-B of 8 indicates over-sedation. On post-operative day 3 of mechanical ventilation, this is excessive. The child is deeply unresponsive, has no spontaneous respiratory drive, and is completely flaccid.

Clinical reasoning:

• The team's goal is COMFORT-B 11-17 to allow some arousability, facilitate weaning, and reduce ICU myopathy risk.
• Current depth suggests sedative doses are too high or clearance is impaired.

Clinical Actions

The resident and attending:

1. Review drug doses: Midazolam at 0.1 mg/kg/hr is standard, but post-op day 3 may warrant reduction. Check recent blood gas, renal function, and liver function (no acute organ failure is noted).

1. Adjust sedation: Reduce midazolam by 20% to 0.08 mg/kg/hr. Plan to re-score COMFORT-B in 30-60 minutes.

1. Consider weaning plan: A COMFORT-B of 8 suggests the patient may tolerate some reduction in support. Once COMFORT-B improves to 11-14, sedation vacation (drug hold, watching for spontaneous breathing) may be considered per institutional protocol.

1. Monitor pain: Ensure fentanyl dosing is appropriate for analgesia (not just sedation). Check for signs of pain (grimace) that the over-sedation might be masking. If COMFORT-B improves but patient grimaces, analgesia adjustment will be needed.

Follow-up

30 minutes later, after the midazolam reduction:

New interpretation: COMFORT-B 12 is now in the target range (11-17). The child is appropriately sedated—calm but arousable, tolerating the ventilator, and showing early spontaneous breathing effort. The team documents this as success, continues the reduced dose, and plans to monitor COMFORT-B q4h. If it remains stable at 11-17, weaning planning proceeds.

References

1. Ambuel B, Hamlett KW, Marx CM, Blumer JL. Assessing distress in pediatric intensive care environments: the COMFORT scale. J Pediatr Psychol. 1992;17(1):95-109. doi:10.1093/jpepsy/17.1.95
2. van Dijk M, de Boer JB, Koot HM, Tibboel D, Passchier J, Duivenvoorden HJ. The reliability and validity of the COMFORT scale as a postoperative pain instrument in 0 to 3-year-old infants. Pain. 2000;84(2-3):367-377. doi:10.1016/S0304-3959(99)00239-0
3. Ista E, van Dijk M, Tibboel D, de Hoog M. Assessment of sedation levels in pediatric intensive care patients can be improved by using the COMFORT "behavior" scale. Pediatr Crit Care Med. 2005;6(1):58-63. doi:10.1097/01.PCC.0000149318.40279.1A