Humidity, Aerosol Therapy & Bland Aerosol

Humidification

Bypassing the upper airway removes the body's humidifier; the circuit must replace it.

• An artificial airway requires at minimum 30 mg/L of water vapor at 30–34°C; the natural airway delivers 44 mg/L at 37°C at the carina.
• Heat and moisture exchangers are passive, cheap, and add dead space — contraindicated with thick or bloody secretions, hypothermia, large leaks, low tidal volumes, or minute ventilation above ~10 L/min.
• Heated wire humidifiers reduce condensate; without them, water collects in the tubing and causes auto-triggering and a drainage hazard.
• Signs of inadequate humidity: thick secretions, mucus plugging, rising airway resistance. Signs of excess: excessive condensate, thin copious secretions, and infection risk from the water reservoir.