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Nasal high flow clears anatomical dead space in upper airway models.

Möller W, Celik G, Feng S, Bartenstein P, Meyer G, Oliver E, Schmid O, Tatkov S - J. Appl. Physiol. (2015)

Bottom Line: There was a similar tracer-gas clearance characteristic in the tube model and the upper airway model: clearance half-times were below 1.0 s and decreased with increasing NHF rates.The level of clearance in the nasal cavities increased by 1.8 ml/s for every 1.0 l/min increase in the rate of NHF.The study has demonstrated the fast-occurring clearance of nasal cavities by NHF therapy, which is capable of reducing of dead space rebreathing.

View Article: PubMed Central - PubMed

ABSTRACT
Recent studies showed that nasal high flow (NHF) with or without supplemental oxygen can assist ventilation of patients with chronic respiratory and sleep disorders. The hypothesis of this study was to test whether NHF can clear dead space in two different models of the upper nasal airways. The first was a simple tube model consisting of a nozzle to simulate the nasal valve area, connected to a cylindrical tube to simulate the nasal cavity. The second was a more complex anatomically representative upper airway model, constructed from segmented CT-scan images of a healthy volunteer. After filling the models with tracer gases, NHF was delivered at rates of 15, 30, and 45 l/min. The tracer gas clearance was determined using dynamic infrared CO2 spectroscopy and 81mKr-gas radioactive gamma camera imaging. There was a similar tracer-gas clearance characteristic in the tube model and the upper airway model: clearance half-times were below 1.0 s and decreased with increasing NHF rates. For both models, the anterior compartments demonstrated faster clearance levels (half-times < 0.5 s) and the posterior sections showed slower clearance (half-times < 1.0 s). Both imaging methods showed similar flow-dependent tracer-gas clearance in the models. For the anatomically based model, there was complete tracer-gas removal from the nasal cavities within 1.0 s. The level of clearance in the nasal cavities increased by 1.8 ml/s for every 1.0 l/min increase in the rate of NHF. The study has demonstrated the fast-occurring clearance of nasal cavities by NHF therapy, which is capable of reducing of dead space rebreathing.

No MeSH data available.


Related in: MedlinePlus

Infrared absorption images of expiratory flow through a tube model (TM) of upper airways demonstrate rebreathing from dead space. The images show four stages of filling of the model with exhaled CO2 at (i) peak expiratory flow, (ii) expiratory flow 30 l/min, (iii) expiratory flow 15 l/min, and (iv) end of expiration. A: control demonstrates filling of the TM during the expiration phase without NHF from a cannula. At the beginning of inspiration all gas from the TM will be rebreathed into the lungs. B: NHF from the cannula purges the expired CO2-rich gas from the model and replaces it with fresh air. This results in a reduction of CO2 rebreathing. Breathing through the model demonstrates that the replacement of expired gas with air starts before the end of expiration and that the static conditions used in the experiments led to an underestimation of the speed of dead-space clearance during respiration.
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Figure 2: Infrared absorption images of expiratory flow through a tube model (TM) of upper airways demonstrate rebreathing from dead space. The images show four stages of filling of the model with exhaled CO2 at (i) peak expiratory flow, (ii) expiratory flow 30 l/min, (iii) expiratory flow 15 l/min, and (iv) end of expiration. A: control demonstrates filling of the TM during the expiration phase without NHF from a cannula. At the beginning of inspiration all gas from the TM will be rebreathed into the lungs. B: NHF from the cannula purges the expired CO2-rich gas from the model and replaces it with fresh air. This results in a reduction of CO2 rebreathing. Breathing through the model demonstrates that the replacement of expired gas with air starts before the end of expiration and that the static conditions used in the experiments led to an underestimation of the speed of dead-space clearance during respiration.

Mentions: Figure 2A demonstrates exhalation flow profiles through the TM and visualization of expired CO2. Figure 2B shows clearance of CO2 in the TM during 30 l/min flow through the cannula into the nozzle.


Nasal high flow clears anatomical dead space in upper airway models.

Möller W, Celik G, Feng S, Bartenstein P, Meyer G, Oliver E, Schmid O, Tatkov S - J. Appl. Physiol. (2015)

Infrared absorption images of expiratory flow through a tube model (TM) of upper airways demonstrate rebreathing from dead space. The images show four stages of filling of the model with exhaled CO2 at (i) peak expiratory flow, (ii) expiratory flow 30 l/min, (iii) expiratory flow 15 l/min, and (iv) end of expiration. A: control demonstrates filling of the TM during the expiration phase without NHF from a cannula. At the beginning of inspiration all gas from the TM will be rebreathed into the lungs. B: NHF from the cannula purges the expired CO2-rich gas from the model and replaces it with fresh air. This results in a reduction of CO2 rebreathing. Breathing through the model demonstrates that the replacement of expired gas with air starts before the end of expiration and that the static conditions used in the experiments led to an underestimation of the speed of dead-space clearance during respiration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482836&req=5

Figure 2: Infrared absorption images of expiratory flow through a tube model (TM) of upper airways demonstrate rebreathing from dead space. The images show four stages of filling of the model with exhaled CO2 at (i) peak expiratory flow, (ii) expiratory flow 30 l/min, (iii) expiratory flow 15 l/min, and (iv) end of expiration. A: control demonstrates filling of the TM during the expiration phase without NHF from a cannula. At the beginning of inspiration all gas from the TM will be rebreathed into the lungs. B: NHF from the cannula purges the expired CO2-rich gas from the model and replaces it with fresh air. This results in a reduction of CO2 rebreathing. Breathing through the model demonstrates that the replacement of expired gas with air starts before the end of expiration and that the static conditions used in the experiments led to an underestimation of the speed of dead-space clearance during respiration.
Mentions: Figure 2A demonstrates exhalation flow profiles through the TM and visualization of expired CO2. Figure 2B shows clearance of CO2 in the TM during 30 l/min flow through the cannula into the nozzle.

Bottom Line: There was a similar tracer-gas clearance characteristic in the tube model and the upper airway model: clearance half-times were below 1.0 s and decreased with increasing NHF rates.The level of clearance in the nasal cavities increased by 1.8 ml/s for every 1.0 l/min increase in the rate of NHF.The study has demonstrated the fast-occurring clearance of nasal cavities by NHF therapy, which is capable of reducing of dead space rebreathing.

View Article: PubMed Central - PubMed

ABSTRACT
Recent studies showed that nasal high flow (NHF) with or without supplemental oxygen can assist ventilation of patients with chronic respiratory and sleep disorders. The hypothesis of this study was to test whether NHF can clear dead space in two different models of the upper nasal airways. The first was a simple tube model consisting of a nozzle to simulate the nasal valve area, connected to a cylindrical tube to simulate the nasal cavity. The second was a more complex anatomically representative upper airway model, constructed from segmented CT-scan images of a healthy volunteer. After filling the models with tracer gases, NHF was delivered at rates of 15, 30, and 45 l/min. The tracer gas clearance was determined using dynamic infrared CO2 spectroscopy and 81mKr-gas radioactive gamma camera imaging. There was a similar tracer-gas clearance characteristic in the tube model and the upper airway model: clearance half-times were below 1.0 s and decreased with increasing NHF rates. For both models, the anterior compartments demonstrated faster clearance levels (half-times < 0.5 s) and the posterior sections showed slower clearance (half-times < 1.0 s). Both imaging methods showed similar flow-dependent tracer-gas clearance in the models. For the anatomically based model, there was complete tracer-gas removal from the nasal cavities within 1.0 s. The level of clearance in the nasal cavities increased by 1.8 ml/s for every 1.0 l/min increase in the rate of NHF. The study has demonstrated the fast-occurring clearance of nasal cavities by NHF therapy, which is capable of reducing of dead space rebreathing.

No MeSH data available.


Related in: MedlinePlus