Realistic glottal motion and airflow rate during human breathing

Scheinherr, Adam; Bailly, Lucie; Boiron, Olivier; Lagier, Aude; Legou, Thierry; Pichelin, Marine; Caillibotte, Georges; Giovanni, Antoine

doi:10.1016/j.medengphy.2015.05.014

Cited by 42 publications

(24 citation statements)

References 44 publications

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“…While wall motion of the alveolar model was considered, the MT and TB airways were assumed rigid. In contrast, the glottis is expected to expand during inhalation, and Scheinherr et al (101) recently reported that dynamic change in glottic size occurred in approximately 50% of the population studied. The in vivo data set used for model comparisons was based on healthy individuals, motivating the application of a disease-free lung model in this study.…”

mentioning

confidence: 99%

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates

Longest

Tian

Khajeh-Hosseini-Dalasm

et al. 2016

Journal of Aerosol Medicine and Pulmonary Drug Delivery

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Background: The objective of this study was to compare aerosol deposition predictions of a new whole-airway CFD model with available in vivo data for a dry powder inhaler (DPI) considered across multiple inhalation waveforms, which affect both the particle size distribution (PSD) and particle deposition. Methods: The Novolizer DPI with a budesonide formulation was selected based on the availability of 2D gamma scintigraphy data in humans for three different well-defined inhalation waveforms. Initial in vitro cascade impaction experiments were conducted at multiple constant (square-wave) particle sizing flow rates to characterize PSDs. The whole-airway CFD modeling approach implemented the experimentally determined PSDs at the point of aerosol formation in the inhaler. Complete characteristic airway geometries for an adult were evaluated through the lobar bronchi, followed by stochastic individual pathway (SIP) approximations through the tracheobronchial region and new acinar moving wall models of the alveolar region. Results: It was determined that the PSD used for each inhalation waveform should be based on a constant particle sizing flow rate equal to the average of the inhalation waveform's peak inspiratory flow rate (PIFR) and mean flow rate [i.e., AVG(PIFR, Mean)]. Using this technique, agreement with the in vivo data was acceptable with <15% relative differences averaged across the three regions considered for all inhalation waveforms. Defining a peripheral to central deposition ratio (P/C) based on alveolar and tracheobronchial compartments, respectively, large flow-rate-dependent differences were observed, which were not evident in the original 2D in vivo data. Conclusions: The agreement between the CFD predictions and in vivo data was dependent on accurate initial estimates of the PSD, emphasizing the need for a combination in vitro-in silico approach. Furthermore, use of the AVG(PIFR, Mean) value was identified as a potentially useful method for characterizing a DPI aerosol at a constant flow rate.

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mentioning

confidence: 99%

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates

Longest

Tian

Khajeh-Hosseini-Dalasm

et al. 2016

Journal of Aerosol Medicine and Pulmonary Drug Delivery

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“…While the complicated three-dimensional, time varying, and geometry-dependent nature of airflow in the extrathoracic region has been well documented in vitro (Heenan et al 2004;Shinneeb and Pollard 2012) and in silico (Nicolaou and Zaki 2013;Ball et al 2008;Longest and Holbrook 2012), studies in the literature typically treat the extrathoracic airways as rigid structures of constant size and shape. However, the extrathoracic airways are known to vary in dimension during respiration, specifically in the region of the glottis (Brancatisano et al 1983;Scheinherr et al 2015). As the glottis has been shown to play a significant role in determining extrathoracic deposition Xi et al 2016), the use of a characteristic diameter derived from in vitro measurements in rigid casts likely does not capture variations in deposition due to intrasubject differences in glottal dimensions.…”

Section: Discussionmentioning

confidence: 99%

Examining the ability of empirical correlations to predict subject specific in vivo extrathoracic aerosol deposition during tidal breathing

Yang

Ruzycki

Verschuer

et al. 2016

Aerosol Science and Technology

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The accuracy of five extrathoracic deposition equations was examined by comparing model predictions with in vivo deposition measurements of 99m Tc-DTPA radiolabeled 0.9% saline delivered via PARI LC Sprint nebulizers in 19 healthy human subjects. The average extrathoracic deposition fraction measured in vivo was 0.19 § 0.10 (average § standard deviation). Comparing to this average value, the extrathoracic deposition fraction predicted by Golshahi et al. equation was the most accurate (0.18 § 0.08), followed by the model described by the ICRP (0.16 § 0.03). However, prediction of subject-specific deposition proved more challenging; the Golshahi et al. model performed the best of the examined equations, yet showed only a small positive correlation between measured and predicted deposition in individual subjects with a Pearson correlation coefficient of 0.34. The difficulties in predicting subject-specific deposition likely result from geometric dissimilarity both within and between subjects, and may require more complicated modeling methods than algebraic equations of the kind examined in this study.

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“…The width of the glottis is assumed to vary following a sinusoidal profile, which narrows first and returns to its original state at the end of the inhalation. Such contracting glottal motions often occur in patients with laryngomalacia (soft larynx) during sleep [39, 45], which is opposite to the widening motion of the glottis of healthy awake subjects [43]. In this study, the narrowing ratio is 0.62, with the original area being 100 mm 2 and the minimal area being 62 mm 2 , as displayed in Fig.…”

Section: Methodsmentioning

confidence: 73%

“…The kinematics of the glottal aperture was adopted from the measurement by Scheinherr et al [43, 44] using laryngofibroscopy. The glottis has a wedged shape.…”

Section: Methodsmentioning

confidence: 99%

Numerical study of dynamic glottis and tidal breathing on respiratory sounds in a human upper airway model

Wang

Talaat

et al. 2017

Sleep Breath

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Background Human snores are caused by vibrating anatomical structures in the upper airway. The glottis is a highly variable structure and a critical organ regulating inhaled flows. However, the effects of the glottis motion on airflow and breathing sound are not well understood, while static glottises have been implemented in most previous in silico studies. The objective of this study is to develop a computational acoustic model of human airways with a dynamic glottis and quantify the effects of glottis motion and tidal breathing on airflow and sound generation. Methods Large eddy simulation and FW-H models were adopted to compute airflows and respiratory sounds in an image-based mouth-lung model. User-defined functions were developed that governed the glottis kinematics. Varying breathing scenarios (static vs. dynamic glottis; constant vs. sinusoidal inhalations) were simulated to understand the effects of glottis motion and inhalation pattern on sound generation. Pressure distributions were measured in airway casts with different glottal openings for model validation purpose. Results Significant flow fluctuations were predicted in the upper airways at peak inhalation rates or during glottal constriction. The inhalation speed through the glottis was the predominating factor in the sound generation while the transient effects were less important. For all frequencies considered (20–2500 Hz), the static glottis substantially underestimated the intensity of the generated sounds, which was most pronounced in the range of 100–500 Hz. Adopting an equivalent steady flow rather than a tidal breathing further underestimated the sound intensity. An increase of 25 dB in average was observed for the life condition (sine-dynamic) compared to the idealized condition (constant-rigid) for the broadband frequencies, with the largest increase of approximately 40 dB at the frequency around 250 Hz. Conclusion Results show that a severely narrowing glottis during inhalation, as well as flow fluctuations in the downstream trachea, can generate audible sound levels.

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Realistic glottal motion and airflow rate during human breathing

Cited by 42 publications

References 44 publications

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates

Validating Whole-Airway CFD Predictions of DPI Aerosol Deposition at Multiple Flow Rates

Examining the ability of empirical correlations to predict subject specific in vivo extrathoracic aerosol deposition during tidal breathing

Numerical study of dynamic glottis and tidal breathing on respiratory sounds in a human upper airway model

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