An Experimental and Numerical Investigation of CO2 Distribution in the Upper Airways During Nasal High Flow Therapy

Hove, S. C. Van; Storey, J. R.; Adams, Cletus Fiifi; Dey, Koustav; Geoghegan, Patrick; Kabaliuk, Natalia; Oldfield, S. D.; Spence, Callum; Jermy, Mark; Suresh, V.; Cater, John

doi:10.1007/s10439-016-1604-8

Cited by 30 publications

(29 citation statements)

References 31 publications

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“…Note how this falls to 0.04% (atmospheric CO 2 concentration) when NHF of 30 L/min is applied. This indicates a reduction in re-inspired dead space CO 2 by NHF, which is in line with findings by Spence, et al [23] and Van Hove, et al [22] that NHF promotes mixing and flushes dead space CO 2 . In Figure 3b and Figure 3c The average EtCO 2 (of 120 capnograms) for each waveforms (in both IE1-group and IE2-group) have been presented in Figure 4.…”

Section: Resultssupporting

confidence: 91%

“…The fall in EtCO 2 (≈ 20%) upon the application of 30 L/min of NHF supports the report that NHF improves mixing and reduces the proportion of CO 2 in re-inspired dead space air [9,22,23]. The present data suggests that breathing flow waveforms of different patterns, but similar in tidal volume, period and I:E ratio show statistically significant differences in EtCO 2 .…”

Section: Discussionsupporting

confidence: 89%

“…In the setup, a rigid upper airway model (3D-printed in acrylic, Visijet EX200) - Figure 2a -of an anonymous 44 year male adult (previously used by Spence, et al [25] and Van Hove, et al [22]) was connected to a piston pump. A CO 2 source was connected to the barrel of the piston pump via a rotameter.…”

Section: Methodsmentioning

confidence: 99%

“…In the remainder [21], the flow pattern was presented as a plot of tidal volume versus time which was numerically integrated to yield flow rate versus time plot after acquisition. Together with a healthy adult breathing flow waveform, which was previously used by Van Hove, et al [22] and Spence, et al [23] five waveforms were used in all.…”

Section: Waveform Collectionmentioning

confidence: 99%

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Effect of variation in the COPD breathing flow pattern on end-tidal CO2 tension: An in vitro study

Adams¹,

Jermy²,

Geoghegan³

et al. 2017

Med Clin Arch

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Aim: The goal of this work was to find out if the variation in breathing flow pattern alone (without change in tidal volume and respiratory rate) changes the end-tidal CO 2 tension (EtCO 2 ) enough to affect the health of a patient. The influence of I:E ratio on EtCO 2 was also investigated. Method:Four breathing flow patterns belonging to different individuals diagnosed with COPD were collected from the literature. These were scaled to the same tidal volume, respiratory rate and I:E ratio, leaving shape as the only varying parameter. A programmable piston pump was used to reproduce the breathing flow patterns in an anatomically correct adult upper airway model (3D printed in acrylic, Visijet Ex200). CO 2 was simultaneously bled into the pump chamber at steady rate to mimic metabolic CO 2 production, followed by the measurement of EtCO 2 with and without 30 L/min of nasal high flow therapy. Results:Breathing flow patterns varying in shape but not in tidal volume, respiratory rate and I:E ratio can produce statistically significant differences in EtCO 2 . The variability in EtCO 2 was however found to be small (1 -2%) and unlikely to be physiologically relevant. A 35% fall in I:E ratio corresponded to a 2% rise in EtCO 2 . 30 L/min of NHF reduced EtCO 2 by approximately 20%. Conclusion:Shape alone can cause a statistically significant difference in EtCO 2 however the difference in EtCO 2 is small. A 35% reduction in I:E ratio results in a 2% rise in EtCO 2 .

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Section: Resultssupporting

confidence: 91%

Section: Discussionsupporting

confidence: 89%

Section: Methodsmentioning

confidence: 99%

Section: Waveform Collectionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of variation in the COPD breathing flow pattern on end-tidal CO2 tension: An in vitro study

Adams¹,

Jermy²,

Geoghegan³

et al. 2017

Med Clin Arch

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“…However gas mixing (CO 2 washout), flow and resistance can be studied using computational fluid dynamics (CFD) [7]- [18] or experimental methods using cast or 3D printed model airways [8] [19]- [24]. Accurate physical airway models are essential to these approaches.…”

Section: Introductionmentioning

confidence: 99%

Strategies for Segmenting the Upper Airway in Cone-Beam Computed Tomography (CBCT) Data

Kabaliuk¹,

Nejati²,

Loch³

et al. 2017

OJMI

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The wide availability, low radiation dose and short acquisition time of ConeBeam CT (CBCT) scans make them an attractive source of data for compiling databases of anatomical structures. However CBCT has higher noise and lower contrast than helical slice CT, which makes segmentation more challenging and the optimal methods are not yet known. This paper evaluates several methods of segmenting airway geometries (nares, nasal cavities and pharynx) from typical dental quality head and neck CBCT data. The nasal cavity has narrow and intricate passages and is separated from the paranasal sinuses by thin walls, making it is susceptible to either over-or under-segmentation. The upper airway was split into two: the nasal cavity and the pharyngeal region (nasopharynx to larynx). Each part was segmented using global thresholding, multi-step level-set, and region competition methods (the latter using thresholding, clustering and classification initialisation and edge attraction techniques). The segmented 3D surfaces were evaluated against a reference manual segmentation using distance-, overlap-and volume-based metrics. Global thresholding, multi-step level-set, and region competition all gave satisfactory results for the lower part of the airway (nasopharynx to larynx). Edge attraction failed completely. A semi-automatic region-growing segmentation with multi-thresholding (or classification) initialization offered the best quality segmentation. With some minimal manual editing, it resulted in an accurate upper airway model, as judged by the similarity and volumetric indices, while being the least time consuming of the semi-automatic methods, and relying the least on the operator's expertise.

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The Safety and Efficacy of Transnasal Humidified Rapid‐Insufflation Ventilatory Exchange for Laryngologic Surgery

et al. 2020

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Objectives: Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) is an intraoperative ventilatory technique that allows avoidance of tracheal intubation (TI) or jet ventilation (JV) in selected laryngologic surgical cases. Unimpeded access to all parts of the glottis may improve surgical precision, decrease operative time, and potentially improve patient outcomes. The objective of this prospective, randomized, patient-blinded, 2-arm parallel pilot trial was to investigate the safety and efficacy of THRIVE use for adult patients undergoing nonlaser laryngologic surgery of short-to-intermediate duration. Methods: Twenty adult, American society of anesthesiology class 1-3 patients with body mass index (BMI) < 35 kg/m 2 were randomly assigned to either an experimental THRIVE group or active comparator conventional ventilation group (TI or supraglottic high-frequency JV [SHFJV]). Primary outcomes included intraoperative oxygenation, anesthesia awakening/ extubation time, time to laryngoscopic suspension, number of intraoperative suspension adjustments, and operative time. Secondary patient outcomes including postanesthesia and functional patient recovery were investigated. Results: Compared to TI/SHFJV, THRIVE use was associated with significantly lower intraoperative oxygenation (SpO 2 93.0 AE 5.6% vs. 98.7 AE 1.6%), shorter time to suspension (1.8 AE 1.1 minutes vs. 4.3 AE 2.1 minutes), fewer suspension adjustments (0.4 AE 0.5 vs. 1.7 AE 0.9), and lower postoperative pain scores on recovery room admission (1.3 AE 1.9 vs. 3.7 AE 2.9) and discharge (0.9 AE 1.3 vs. 2.7 AE 1.8). The study was underpowered to detect other possible outcome differences. Conclusion: We confirm the safe intraoperative oxygenation profile of THRIVE for selected patients undergoing nonlaser laryngologic surgery of short-to-intermediate duration. THRIVE facilitated surgical exposure and improved early patient recovery, suggesting a potential economic benefit for outpatient laryngologic procedures. The results of this exploratory study provide a framework for designing future adequately powered THRIVE trials. Trial Register: ClinicalTrials.gov (NCT03091179).

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An Experimental and Numerical Investigation of CO2 Distribution in the Upper Airways During Nasal High Flow Therapy

Cited by 30 publications

References 31 publications

Effect of variation in the COPD breathing flow pattern on end-tidal CO2 tension: An in vitro study

Effect of variation in the COPD breathing flow pattern on end-tidal CO2 tension: An in vitro study

Strategies for Segmenting the Upper Airway in Cone-Beam Computed Tomography (CBCT) Data

The Safety and Efficacy of Transnasal Humidified Rapid‐Insufflation Ventilatory Exchange for Laryngologic Surgery

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