Clinical Implications of Penetration Aspiration Scale and Function of Dysphagia Assessment and Rehabilitation Services
A high Penetration Aspiration Scale (PAS) score significantly increases the risk of aspiration pneumonia, with PAS scores ≥3 associated with a 4-fold higher risk of developing aspiration pneumonia even when following liquid thickening recommendations. 1
Penetration Aspiration Scale (PAS) and Clinical Significance
The Penetration Aspiration Scale is an 8-point scale that objectively measures the depth of airway invasion during swallowing and the patient's response to this invasion:
| Score | Description |
|---|---|
| 1 | Material does not enter the airway |
| 2 | Material enters the airway, remains above vocal folds, and is ejected |
| 3 | Material enters the airway, remains above vocal folds, and is not ejected |
| 4 | Material enters the airway, contacts vocal folds, and is ejected |
| 5 | Material enters the airway, contacts vocal folds, and is not ejected |
| 6 | Material enters the airway, passes below vocal folds, and is ejected |
| 7 | Material enters the airway, passes below vocal folds, and is not ejected despite effort |
| 8 | Material enters the airway, passes below vocal folds, and no effort is made to eject |
Clinical Implications of PAS Scores:
- PAS ≥3 (penetration-aspiration): Significantly associated with aspiration pneumonia development (OR 4.03) 1
- Higher PAS scores: Correlate with increased risk of respiratory complications
- PAS score 3: Particularly concerning as it indicates material remains in the airway without ejection 1
- Silent aspiration (PAS 8): Material passes below vocal folds without triggering protective reflexes - particularly dangerous as patients show no outward signs of aspiration
Risk Factors Associated with High PAS Scores
Several clinical factors increase the likelihood of penetration-aspiration:
- Vocal fold paralysis: Increases risk (OR 1.99) 1
- Impaired laryngeal sensation: Significantly increases risk (OR 5.01) 1
- History of aspiration pneumonia: Strong predictor (OR 2.90) 1
- Poor performance status: Associated with aspiration pneumonia development (OR 1.85) 1
- In Parkinson's disease: Delayed pharyngeal swallow (OR 7.47) and reduced hyolaryngeal excursion (OR 5.13) are significant predictors 2
Dysphagia Assessment and Rehabilitation Services (DARS)
DARS are specialized multidisciplinary services that assess, diagnose, and manage swallowing disorders. Their key functions include:
1. Comprehensive Assessment
- Instrumental evaluation: Videofluoroscopy (VSE) or fiberoptic endoscopic evaluation of swallowing (FEES) to directly visualize swallowing physiology and identify silent aspiration 3
- Testing with various consistencies: Evaluating swallowing safety with different liquid viscosities (thin, mildly thickened, moderately thickened) 1
- Delivery method assessment: Testing different delivery methods (spoon, cup) during instrumental evaluation 3
2. Intervention Planning
- Liquid modification recommendations: Based on PAS scores with different viscosities 1, 3
- Postural techniques: Implementing chin-tuck, head rotation, or other compensatory postures that can eliminate aspiration in up to 77% of patients 3
- Swallowing maneuvers: Teaching techniques like effortful swallow and multiple swallows to improve bolus control 3
3. Rehabilitation
- Exercise programs: Strengthening swallowing muscles through specialized exercises 3
- Biofeedback: Using electromyography and electrical stimulation to improve swallowing function 3
4. Monitoring and Follow-up
- Regular reassessment: Tracking changes in swallowing function over time
- Adjusting recommendations: Modifying diet and liquid consistency based on progress
Management Algorithm Based on PAS Scores
PAS 1-2 (Normal/Minimal risk):
- Regular diet as tolerated
- Regular monitoring
PAS 3-5 (Moderate risk):
- Implement liquid thickening (nectar-thick/mildly thickened)
- Consider postural techniques (chin-tuck)
- Swallowing exercises
- Monitor hydration status
PAS 6-8 (Severe risk):
- More aggressive liquid thickening (honey-thick/moderately thickened)
- Consider alternative feeding methods if aspiration persists
- Intensive swallowing therapy
- Close monitoring for aspiration pneumonia
Practical Recommendations
- Liquid thickening: Thicker liquids significantly reduce penetration-aspiration rates (thin: 32.9%, mildly thickened: 21.1%, moderately thickened: 14.3%) 1
- Delivery method: Spoon delivery provides better control and slower transit than cups or straws 3
- Screening tools: EAT-10 score >15 has 71% sensitivity for predicting aspiration risk 4
- Regular monitoring: Particularly important for patients with poor performance status, history of aspiration pneumonia, or PAS scores ≥3 1
Important Caveats
- Instrument differences: FEES tends to show higher (more severe) PAS scores than videofluoroscopy for the same swallows (mean difference 1.15 points) 5
- Thickening disadvantages: Excessive thickening can increase pharyngeal residue, reduce palatability, and decrease fluid intake 3
- Bolus volume effect: Larger liquid volumes significantly increase penetration-aspiration risk (γ = 0.71) 2
By understanding the clinical implications of PAS scores and utilizing DARS effectively, clinicians can significantly reduce the risk of aspiration pneumonia and improve quality of life in patients with dysphagia.