Abstract
BackgroundThe 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.MethodsSix 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.ResultsThe 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.ConclusionThe 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.
Highlights
Measurement of airway flow of a spontaneous breathing infant allows determination of respiratory parameters during respiratory support and forms the basis for lung function testing
The aim of this study is to investigate pressure stability for different flow measuring devices with the in-line and flow-through position, using simulated neonatal breathing
For in-line technique simulations the resistance of Florian and EXHALYSER S generated an increase in pressure swings and imposed work of breathing (WOB) compared to other devices but the absolute differences were small
Summary
Measurement of airway flow of a spontaneous breathing infant allows determination of respiratory parameters during respiratory support and forms the basis for lung function testing. A technique suitable for neonatal use requires minimal resistance and dead space to avoid significant effects on breathing [1, 2]. The quality of the flow recordings needs to be high. The resistance of a flow meter adds to the imposed work of breathing (WOB). This may change the infants breathing pattern and affect measurements. This is of particular concern in studies of imposed work of breathing and for variables that are affected by increased resistance.
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