A bench study of oxygen (O2) delivery during non-invasive ventilation (NIV)

Abstract

Introduction: Children who are on non-invasive or invasive ventilator support long term usually are ventilated in room air. However some children need supplemental O2 which is usually administered by adding it into some part of inspiratory arm of the circuit. Current portable ventilators do not measure delivered O2 concentration. In this bench study we determine the O2 concentrations delivered during NIV using different test conditions. Methodology: A Philips Respironics Inc. Trilogy 100 machine delivered CPAP and Bilevel pressures with an O2 flow input at the machine end to a Maquet test lung (“mask end”) fitted with 3 different levels of leaks [Respironics Swivel passive exhalation port (high), Whisper Swivel II (medium) and passive exhalation outlet (low)] and tested each setting with two tubing (2 m) diameters of 15 mm and 22 mm. An O2 concentration monitor (Teledyne Analytical Instruments, MX300) measured O2 percent (%) just prior to the test lung. A baseline, calibrated, room air O2 level was established prior to each measurement and the maximum value after a 3 minute steady state in O2 value was measured at the mask for CPAP (5, 10, 15, 20 cmH2O), and bilevel pressures IPAP/EPAP (10/5, 15/5, 20/5, 15/ 10, 20/10 and 25/10) using ventilation rates of 15 and 35 bpm. Results: During CPAP (22 mm tubing), the O2 concentration at CPAP 5cmH2O (3.96 litres/min flow) vis-à-vis 20cmH2O (10.75 litres/min flow) for 1, 5 and 10 L/min O2 are: 24.4%, 39% and 65.2% vs. 22.4%, 28.5% and 40%, respectively. There was no significant difference in O2 concentration delivered via 15 mm compared to 22 mm tubing in similar testing conditions during CPAP. During Bilevel ventilation, with 22 mm tubing, a higher O2 concentration was seen with 15 bpm compared to 35 bpm. There was significant difference in O2 concentration between 15 to 35 bpm at 25/10 (highest) and at 10/5 (lowest). The difference in O2 concentrations with 15 mm tubing was smaller than 22 mm tubing for all O2 flow rates and ventilator rates. Conclusions: Higher CPAP pressures require higher flow which in turn resulted in reduced O2 delivered at patient end. During bilevel ventilation, the O2 concentration delivered to the patient is influenced by the pressures used, ventilator rate and circuit tubing size.L6195254392017-12-08 <br />