Data from: Imposed work of breathing for flow meters with in-line versus flow-through technique during simulated neonatal breathing

Background: The ability to determine airflow during nasal CPAP (NCPAP) treatment without adding dead space or resistance would be useful when investigating the physiologic effects of different NCPAP systems on breathing. The aim of this study was to investigate the effect on pressure stability of different flow measuring devices at the in-line and flow-through position, using simulated neonatal breathing. Methods: Six different flow measure devices were evaluated by recording pressure changes and imposed work of breathing for breaths with 16 and 32 ml tidal volumes. The tests were performed initially with the devices in an in line position and with 5 and 10 L/min using flow through technique, without CPAP. The flow meters were then subsequently tested with an Infant Flow CPAP system at 3, 5 and 8 cm H2O pressure using flow through technique. The quality of the recorded signals was compared graphically. Results: The resistance of the measuring devices generated pressure swings and imposed work of breathing. With bias flow, the resistance also generated CPAP pressure. Three of the devices had low resistance and generated no changes in pressure stability or CPAP pressure. The two devices intended for neonatal use had the highest measured resistance. Conclusion: The importance of pressure stability and increased work of breathing during non-invasive respiratory support are insufficiently studied. Clinical trials using flow-through technique have not focused on pressure stability. Our results indicate that a flow-through technique might be a way forward in obtaining a sufficiently high signal quality without the added effects of rebreathing and increased work of breathing. The results should stimulate further research and the development of equipment for dynamic flow measurements in neonates.

研究背景：在探究不同经鼻持续气道正压通气（nasal CPAP, NCPAP）系统对呼吸的生理学影响时，无需额外增加死腔（dead space）或阻力（resistance）即可测定经鼻CPAP治疗期间气流的方法具有重要应用价值。本研究旨在利用模拟新生儿呼吸，评估不同流量测量装置分别置于串联（in-line）和通流（flow-through）位置时对压力稳定性的影响。

研究方法：本研究共评估6种不同的流量测量装置，通过记录潮气量（tidal volume）为16 ml与32 ml的呼吸周期内的压力变化及附加呼吸功（imposed work of breathing）完成测试。初始测试时，装置以串联位置安装，采用通流技术，分别设置偏流量（bias flow）为5 L/min与10 L/min，且未施加CPAP。随后，采用婴儿流量CPAP系统，以通流技术分别在3、5、8 cm H2O的压力下对上述流量计进行测试。通过图形化方式对比各装置的记录信号质量。

研究结果：测量装置的阻力会引发压力波动（pressure swings）并附加呼吸功。当存在偏流时，该阻力还会影响CPAP压力水平。其中3种装置的阻力较低，未对压力稳定性或CPAP压力产生明显改变。两款专为新生儿设计的装置测得的阻力最高。

研究结论：无创呼吸支持过程中，压力稳定性与呼吸功增加的相关研究仍不够充分。采用通流技术开展的临床试验尚未关注压力稳定性问题。本研究结果表明，通流技术有望在避免重复呼吸（rebreathing）与附加呼吸功增加的额外影响的前提下，获得足够高的信号质量。上述结果将为新生儿（neonates）动态流量测量（dynamic flow measurements）设备的进一步研发与相关研究提供激励与方向。