A respiratory system includes a pressurized gas source coupled to a nebulizer containing a medicament. The nebulizer is connected to a breathing unit. A pressure sensitive switch detects negative pressure at the breathing unit due to inspiration and opens to provide pressured gas flow to the nebulizer. The pressure sensitive switch is configured to close prior to the end of inspiration. Residual medicament disposed in the system is cleared from the system and delivered to the patient during the remainder of the inspiration cycle. A compressor provides positive pressure to aid delivery of medicaments to the patient.
