Bronchiolitis in infants under 12 months produces a heterogeneous mixed obstructive-restrictive lung disorder with variable regional time constants.
Key Physiological Equations & Formulas
- Respiratory Time Constant in Bronchiolitis: $$\tau_{obstructive} > 0.5-0.8\text{ s}$$ Obstructed bronchioles require prolonged exhalation to empty, predisposing to air trapping.
Practical Clinical Pearls & Bedside Rules
- High-Flow Nasal Cannula (HFNC) First-Line: Start HFNC at 2 L/kg/min (up to 20-30 L/min) to generate 2-4 cmH2O PEEP and wash out nasopharyngeal dead space.
- Invasive Indications: Severe exhaustion, recurrent apnea, or worsening acidosis (pH < 7.20 with PaCO2 > 65-70 mmHg) despite optimal non-invasive support.
Initial Settings & Clinical Titration Protocol
| Parameter | Recommended Initial Setting | Titration Goal / Safety Threshold |
|---|---|---|
| Ventilator Rate | 20-30 bpm | Avoid high rates that cause breath-stacking. |
| PEEP | 5-8 cmH2O | Stents open small floppy bronchioles during expiration. |
Bedside Troubleshooting & Red Flags
Warning
Mucus Plug Occlusion: Sudden desaturation and loss of tidal volume in PC mode is almost always an acute mucus plug. Perform prompt inline suction and saline lavage.
Key Takeaways & Summary
- Always evaluate patient synchrony and physiological response before changing ventilator parameters.
- Maintain lung-protective strategies to minimize driving pressure ($\Delta P$) and mechanical power.
- Continuously reassess liberation and extubation readiness on daily morning rounds.