Aerosol Delivery to Simulated Spontaneously Breathing Tracheostomized Adult Patients With Heated Humidified High Flow Oxygenation.

Background: Heated and humidified high-flow (HHHF) oxygen therapy is frequently used for spontaneous breathing tracheostomized patients when the ventilator is weaned off. However, the efficacy of in-line placement of nebulizer via HHHF remains unclear. We aimed to assess the impact of nebulizer placements, flow settings, and interfaces on aerosol delivery using a vibrating mesh nebulizer with HHHF in a tracheostomized model. Methods: A simulated spontaneous breathing model of a tracheostomized adult with tracheostomy tube size 8.0 mm was utilized. A collecting filter was placed between the tracheostomy tube and the model lung. Albuterol sulfate (2.5 mg/3 mL) was aerosolized via a vibrating mesh nebulizer in-line with HHHF (Airvo2). The aerosol delivery was evaluated with the nebulizer placed distally (near the humidifier) and proximally to the airway, using tracheostomy adapter and tracheostomy collar at gas flows of 15, 30, and 45 L/min. Each condition was tested five times. The drug was eluted from the collecting filter and assayed with ultraviolet spectrophotometry (276 nm). Results: When delivering aerosol via an in-line vibrating mesh nebulizer with HHHF in a tracheostomized model, the inhaled dose increased as flow decreased, regardless of the interfaces and nebulizer placements (all P < .05). With the tracheostomy adapter, distal placement resulted in higher inhaled doses than the proximal placement at all flows (all P < .05). With the tracheostomy collar, inhaled doses were lower with distal placement than proximal placement, except at 15 L/min (21.3 ± 1.9 vs 16.4 ± 2.1%, P = .009). Compared with the tracheostomy adapter, the tracheostomy collar had higher inhaled doses with the vibrating mesh nebulizer placed proximally at 30 and 45 L/min but a lower inhaled dose with the vibrating mesh nebulizer placed distally at 30 L/min. Conclusions: During aerosol delivery via in-line placement of vibrating mesh nebulizer with HHHF in a tracheostomized model, the inhaled dose increased as flow decreased. Distal nebulizer placement resulted in higher inhaled doses than proximal placement with the tracheostomy adapter at all flows and with the tracheostomy collar at 15 L/min.