• Wei Tan, Bing Dai, Dong-Yang Xu, Li-Li Li, and Jie Li.
• Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of China Medical University, Shenyang, China.
• Respir Care. 2022 Jul 1; 67 (7): 807813807-813.

BackgroundThe effect of single- and dual-limb circuits on aerosol delivery during noninvasive ventilation (NIV) in adult models is unclear.MethodsA noninvasive ventilator equipped with a single-limb circuit or an ICU ventilator equipped with a dual-limb circuit was connected to a simulated lung. Ventilator parameters were adjusted to maintain a tidal volume at ∼500 mL. Aerosol deposition with different placements of a vibrating mesh nebulizer and humidification conditions were compared. Additional experiments by using a non-vented mask or a vented mask were compared in the single-limb circuit only. Aerosol was collected by a disposable filter placed between the simulated lung and the head model (n = 3), and measured by ultraviolet spectrophotometry (276 nm).ResultsThe aerosol deposition varied between 4.12 ± 0.22% and 20.75 ± 0.95%. The greatest aerosol delivery during NIV when using a non-vented mask was found when a vibrating mesh nebulizer was placed between the mask and 15 cm from the exhalation port in the humidified single-limb circuit, and 15 cm from the Y-piece in the inspiratory limb of the humidified dual-limb circuit, and no significant difference of aerosol deposition was found between the two optimal positions (20.03 ± 1.48% vs 18.04 ± 0.93%, respectively; P =.042). There was no difference of aerosol delivery in dry versus humidified circuits, except when a vibrating mesh nebulizer was placed at the humidifier inlet in a dual-limb circuit. When using a vented mask, the aerosol deposition was poor (6.56 ± 0.41 ∼ 8.02 ± 0.39%), regardless of vibrating mesh nebulizer positions and humidification types.ConclusionsDuring NIV, the aerosol delivery was optimal when a vibrating mesh nebulizer was placed between the non-vented mask and 15 cm from the exhalation port in the single-limb circuit or 15 cm from the Y-piece in the inspiratory limb of the dual-limb circuit; no significant difference was found between the two optimal placements. Humidification had little effect on aerosol delivery. Aerosol delivery was poor in the single-limb circuit with a vented mask.Copyright © 2022 by Daedalus Enterprises.

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