What is the role of HACOr (Hospitalized Acute COPD score) scoring in assessing patients with respiratory failure or severe respiratory distress, particularly those with chronic obstructive pulmonary disease (COPD), pneumonia, or heart failure?

HACOR Score: A Validated Tool for Predicting Noninvasive Ventilation Failure

The HACOR score is a validated bedside scoring system that predicts noninvasive ventilation (NIV) failure in patients with acute respiratory failure, including those with COPD, and should be calculated at NIV initiation and serially at 1-2 hours, 12 hours, and 24 hours to guide decisions about early intubation. 1

What is the HACOR Score?

The HACOR score is a simple risk stratification tool that incorporates five readily available clinical parameters 1:

• Heart rate (beats/minute)
• Acidosis (assessed by pH)
• Consciousness (assessed by Glasgow Coma Scale)
• Oxygenation (assessed by PaO₂/FiO₂ ratio)
• Respiratory rate (breaths/minute)

Scores range from 0 to 27, with higher scores indicating higher risk of NIV failure, defined as requiring intubation or death during NIV 2, 1.

Predictive Performance in COPD Patients

Timing and Cutoff Values

The HACOR score demonstrates excellent predictive power when assessed serially during NIV treatment in COPD patients 1:

• At 1-2 hours of NIV: Area under the curve (AUC) = 0.90, with optimal cutoff >5 points (sensitivity 84%, specificity 79%) 1
• For early NIV failure (<48 hours): AUC = 0.91-0.96, demonstrating particularly strong predictive ability 1
• HACOR score >5: Associated with 50% NIV failure rate across multiple cohorts 1

Clinical Implications for COPD

In COPD patients with HACOR score >5 after 1-2 hours of NIV, early intubation (<48 hours) is associated with decreased hospital mortality compared to delayed intubation (odds ratio 0.15,95% CI 0.05-0.39) 1. This finding is critical because COPD patients admitted to ICU with severe community-acquired pneumonia have higher mechanical ventilation rates and ICU mortality compared to non-COPD patients 3.

Application in Non-COPD Respiratory Failure

The HACOR score maintains high predictive accuracy in non-COPD patients with acute-on-chronic respiratory failure and respiratory acidosis (pH <7.35, PaCO₂ >45 mmHg) 2:

• At initiation: Cutoff value 7 (sensitivity 68%, specificity 61%) 2
• After 1-2 hours: Cutoff value 5 (sensitivity 90%, specificity 85%) 2
• After 12 hours: Cutoff value 4 (sensitivity 82%, specificity 91%) 2
• After 24 hours: Cutoff value 2 (sensitivity 100%, specificity 76%) 2

This includes patients with sleep apnea-hypopnea syndrome, chronic thoracic sequelae, bronchiectasis, chest wall deformity, and obesity-hypoventilation syndrome 2.

Use in Acute Hypoxemic Respiratory Failure

High-Flow Nasal Oxygen (HFNO)

The HACOR score has been adapted to predict HFNO failure in acute hypoxemic respiratory failure 4:

• At 1 hour: Cutoff >6 points provides 81% sensitivity, 91% specificity, with 85% diagnostic accuracy 4
• HACOR score <6 after 1 hour: Indicates <15% risk of HFNO failure 4
• Overall diagnostic accuracy: Exceeds 87% when assessed at 1,12,24, or 48 hours of HFNO 4

Moderate to Severe ARDS

In patients with moderate to severe ARDS (PaO₂/FiO₂ ≤150 mmHg), the change in HACOR score (△HACOR) after 1-2 hours identifies treatment responders 5:

• △HACOR >1 point improvement: Defines responders with lower NIV failure rate (36% vs 72%) and lower 28-day mortality (32% vs 47%) compared to non-responders 5
• Delayed intubation in ARDS: Associated with increased mortality, making early identification of NIV failure critical 5

Mortality Prediction

Beyond predicting NIV failure, the HACOR score predicts in-hospital mortality in patients with acute respiratory failure 6:

• At 24 hours: HACOR score >5 is independently associated with increased mortality (RR 2.39,95% CI 1.60-3.56), even after adjusting for age and Sequential Organ Failure Assessment score 6
• Serial measurements: Non-survivors consistently have higher HACOR scores at all time points (initiation, 1 hour, 24 hours) compared to survivors 6

Clinical Implementation Algorithm

Step 1: Calculate HACOR at NIV/HFNO Initiation

Document baseline score to establish risk stratification 1.

Step 2: Reassess at 1-2 Hours

This is the most critical time point for decision-making 1, 4:

• HACOR >5 in COPD or NIV patients: High risk of failure, consider early intubation 1
• HACOR >6 in HFNO patients: High risk of failure, consider escalation to NIV or intubation 4
• △HACOR >1 point improvement in ARDS: Patient responding well, continue current therapy 5

Step 3: Continue Serial Monitoring

Reassess at 12 and 24 hours to identify delayed deterioration 2, 1.

Step 4: Act on High-Risk Scores

Do not delay intubation in patients with persistently elevated or worsening HACOR scores, as delayed intubation increases mortality 1, 5.

Important Caveats

Population-Specific Considerations

The HACOR score has been validated primarily in patients with hypercapnic respiratory failure and COPD 1. While it shows utility in non-COPD populations 2 and hypoxemic failure 5, 4, external validation shows lower AUC (0.71) compared to derivation cohorts 1, suggesting performance may vary across different patient populations.

Limitations in Complex Patients

The evidence does not specifically address HACOR score performance in patients with severe comorbidities such as heart failure, which is present in 20-70% of COPD patients and can mimic acute exacerbations 3. In patients with multiple comorbidities, clinical judgment must supplement the HACOR score, as these patients may require different thresholds for intubation 3.

Integration with Other Assessment Tools

While the HACOR score provides objective risk stratification, it should be used alongside comprehensive COPD severity assessment tools such as the BODE index (BMI, airflow obstruction, dyspnea, exercise capacity) 3, 7 and consideration of exacerbation history 3. The GOLD multidimensional assessment framework emphasizes that spirometry alone does not capture disease severity 3, 7, and the same principle applies to the HACOR score—it is one component of comprehensive patient evaluation.