Limits...
Imposed Work of Breathing for Flow Meters with In-Line versus Flow-Through Technique during Simulated Neonatal Breathing.

Donaldsson S, Falk M, Jonsson B, Drevhammar T - PLoS ONE (2015)

Bottom Line: 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.The quality of the recorded signals was compared graphically.The results should stimulate further research and the development of equipment for dynamic flow measurements in neonates.

View Article: PubMed Central - PubMed

Affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT

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.

No MeSH data available.


Related in: MedlinePlus

In-line and flow-through position.With the in-line position the flow meter simply records patient breathing but dead space will be increased. In the flow-through position the flow meter records the breathing offset by the added bias flow. If the bias-flow is not constant a second flow meter is needed to measure the bias-flow offset. If the bias flow is sufficient the volume of the flow meter will not add to dead space.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4507850&req=5

pone.0133432.g001: In-line and flow-through position.With the in-line position the flow meter simply records patient breathing but dead space will be increased. In the flow-through position the flow meter records the breathing offset by the added bias flow. If the bias-flow is not constant a second flow meter is needed to measure the bias-flow offset. If the bias flow is sufficient the volume of the flow meter will not add to dead space.

Mentions: Infants are sensitive to the addition of extra dead space and the resulting CO2 increase will affect breathing. There are two positions where flows can be measured (Fig 1). The in-line position (I) measures breathing directly, with the flow meter attached to the endotracheal tube or patient interface. The volume of the measuring device will add to dead space. The in-line position has been the standard technique used in studies reporting results from neonatal resuscitation and pulmonary function testing [1, 5, 6]. The flow-through position (II) measures breathing after a bias-flow has been added between the measuring device and the patient [7]. The volume of the measure device does not add to dead space if the bias flow is high enough to prevent re-breathing. The main disadvantage with this technique is that it is technically more difficult because the added bias flow has to be subtracted. The subtraction makes the flow-trough position sensitive to non-constant bias flow and drift of the flow meter. Modern adult and pediatric ventilators use flow-through techniques when they measure flow on the expiratory limb of a breathing circuit. The flow-through technique using a constant bias-flow was first described by Rigatto and Brady [8] and has been used in spontaneously breathing infants in several studies.


Imposed Work of Breathing for Flow Meters with In-Line versus Flow-Through Technique during Simulated Neonatal Breathing.

Donaldsson S, Falk M, Jonsson B, Drevhammar T - PLoS ONE (2015)

In-line and flow-through position.With the in-line position the flow meter simply records patient breathing but dead space will be increased. In the flow-through position the flow meter records the breathing offset by the added bias flow. If the bias-flow is not constant a second flow meter is needed to measure the bias-flow offset. If the bias flow is sufficient the volume of the flow meter will not add to dead space.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507850&req=5

pone.0133432.g001: In-line and flow-through position.With the in-line position the flow meter simply records patient breathing but dead space will be increased. In the flow-through position the flow meter records the breathing offset by the added bias flow. If the bias-flow is not constant a second flow meter is needed to measure the bias-flow offset. If the bias flow is sufficient the volume of the flow meter will not add to dead space.
Mentions: Infants are sensitive to the addition of extra dead space and the resulting CO2 increase will affect breathing. There are two positions where flows can be measured (Fig 1). The in-line position (I) measures breathing directly, with the flow meter attached to the endotracheal tube or patient interface. The volume of the measuring device will add to dead space. The in-line position has been the standard technique used in studies reporting results from neonatal resuscitation and pulmonary function testing [1, 5, 6]. The flow-through position (II) measures breathing after a bias-flow has been added between the measuring device and the patient [7]. The volume of the measure device does not add to dead space if the bias flow is high enough to prevent re-breathing. The main disadvantage with this technique is that it is technically more difficult because the added bias flow has to be subtracted. The subtraction makes the flow-trough position sensitive to non-constant bias flow and drift of the flow meter. Modern adult and pediatric ventilators use flow-through techniques when they measure flow on the expiratory limb of a breathing circuit. The flow-through technique using a constant bias-flow was first described by Rigatto and Brady [8] and has been used in spontaneously breathing infants in several studies.

Bottom Line: 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.The quality of the recorded signals was compared graphically.The results should stimulate further research and the development of equipment for dynamic flow measurements in neonates.

View Article: PubMed Central - PubMed

Affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.

ABSTRACT

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.

No MeSH data available.


Related in: MedlinePlus