TY - JOUR T1 - Effect of the Anatomic Reservoir on Low-Flow Oxygen Delivery Via Nasal Cannula: Constant Flow Versus Pulse Flow With Portable Oxygen Concentrator JF - Respiratory Care SP - 1199 LP - 1209 DO - 10.4187/respcare.02878 VL - 59 IS - 8 AU - Steven Zhou AU - Robert L Chatburn Y1 - 2014/08/01 UR - http://rc.rcjournal.com/content/59/8/1199.abstract N2 - BACKGROUND: The FIO2 for a nasal cannula with constant flow (CF) depends on the anatomic reservoir (AR), which is affected by changes in frequency and end-expiratory flow. Conversely, pulse flow (PF) devices do not require the AR. The purpose of this study was to compare the FIO2 delivered by a nasal cannula supplied by CF via oxygen tank with that delivered by PF delivered via portable oxygen concentrator. Hypotheses were (1) a lung model of COPD with non-zero end-expiratory flow decreases FIO2 for CF more than for PF, and (2) CF and PF perform differently in terms of FIO2 delivery, despite having equivalent settings. METHODS: Normal and COPD lung models were simulated (IngMar Medical ASL 5000) using published human data: normal: breathing frequency = 15 breaths/min, Rin = 4 cm H2O · s · L–1, Rout = 4 cm H2O · s · L–1, C = 60 mL · cm H2O–1, tidal volume (VT) = 685 mL, Pmax = 11.95 cm H2O, increase = 33%, and release = 28; COPD: breathing frequency = 20 breaths/min, Rin = 12 cm H2O · s · L–1, Rout = 25 cm H2O · s · L–1, C = 66 mL · cm H2O–1, VT = 685 mL, Pmax = 24.52 cm H2O, increase = 35%, and release = 23%. CF was 1–5 L/min. Portable oxygen concentrators used were Solo2 (Invacare), XPO2 (Invacare), FreeStyle (AirSep), Focus (AirSep), One G3 (Inogen), and LifeChoice ActivOx (Inova Labs). RESULTS: CF produced significantly higher FIO2 at all settings for normal lungs but lower for COPD lungs compared with Solo2. COPD reduced the FIO2 for CF but had a smaller variable effect for PF. Data show there is no equivalency between PF setting and CF rates for the portable oxygen concentrators tested. CONCLUSIONS: CF oxygen delivery via a nasal cannula is significantly reduced by elimination of the AR in a model of COPD, yielding clinically important decreases in FIO2. PF (delivered with a portable oxygen concentrator) is relatively unaffected. This study supports the recommendation that clinicians and caretakers should titrate the PF setting to each patient's unique oxygen requirements. ER -