Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow
Studies of flow through the human airway have shown that inhalation time (IT) and secondary flow structures can play important roles in particle deposition. However, the effects of varying IT in conjunction with the respiratory rate (RR) on airway flow remain unknown. Using three-dimensional numeric...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-06-01
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| Series: | Fluids |
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| Online Access: | https://www.mdpi.com/2311-5521/6/6/221 |
| _version_ | 1797530424338022400 |
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| author | Manikantam G. Gaddam Arvind Santhanakrishnan |
| author_facet | Manikantam G. Gaddam Arvind Santhanakrishnan |
| author_sort | Manikantam G. Gaddam |
| collection | DOAJ |
| description | Studies of flow through the human airway have shown that inhalation time (IT) and secondary flow structures can play important roles in particle deposition. However, the effects of varying IT in conjunction with the respiratory rate (RR) on airway flow remain unknown. Using three-dimensional numerical simulations of oscillatory flow through an idealized airway model (consisting of a mouth, glottis, trachea, and symmetric double bifurcation) at a trachea Reynolds number (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula>) of 4200, we investigated how varying the ratio of IT to breathing time (BT) from 25% to 50% and RR from 10 breaths per minute (bpm) corresponding to a Womersley number (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>) of 2.41 to 1000 bpm (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> = 24.1) impacts airway flow characteristics. Irrespective of IT/BT, axial flow during inhalation at tracheal cross-sections was non-uniform for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> = 2.41, as compared to centrally concentrated distribution for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> = 24.1. For a given <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> and IT/BT, both axial and secondary (lateral) flow components unevenly split between left and right branches of a bifurcation. Irrespective of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>, IT/BT and airway generation, lateral dispersion was a stronger transport mechanism than axial flow streaming. Discrepancy in the oscillatory flow relation <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula>/<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><msup><mi>o</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula> = 2 <i>L</i>/<i>D</i> (<i>L</i> = stroke length; <i>D</i> = trachea diameter) was observed for IT/BT ≠ 50%, as <i>L</i> changed with IT/BT. We developed a modified dimensionless stroke length term including IT/BT. While viscous forces and convective acceleration were dominant for lower <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>, unsteady acceleration was dominant for higher <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>. |
| first_indexed | 2024-03-10T10:28:45Z |
| format | Article |
| id | doaj.art-e0ff1ca1c5234357bb98346f9f14ad08 |
| institution | Directory Open Access Journal |
| issn | 2311-5521 |
| language | English |
| last_indexed | 2024-03-10T10:28:45Z |
| publishDate | 2021-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Fluids |
| spelling | doaj.art-e0ff1ca1c5234357bb98346f9f14ad082023-11-21T23:49:10ZengMDPI AGFluids2311-55212021-06-016622110.3390/fluids6060221Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway FlowManikantam G. Gaddam0Arvind Santhanakrishnan1School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078, USASchool of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078, USAStudies of flow through the human airway have shown that inhalation time (IT) and secondary flow structures can play important roles in particle deposition. However, the effects of varying IT in conjunction with the respiratory rate (RR) on airway flow remain unknown. Using three-dimensional numerical simulations of oscillatory flow through an idealized airway model (consisting of a mouth, glottis, trachea, and symmetric double bifurcation) at a trachea Reynolds number (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula>) of 4200, we investigated how varying the ratio of IT to breathing time (BT) from 25% to 50% and RR from 10 breaths per minute (bpm) corresponding to a Womersley number (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>) of 2.41 to 1000 bpm (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> = 24.1) impacts airway flow characteristics. Irrespective of IT/BT, axial flow during inhalation at tracheal cross-sections was non-uniform for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> = 2.41, as compared to centrally concentrated distribution for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> = 24.1. For a given <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula> and IT/BT, both axial and secondary (lateral) flow components unevenly split between left and right branches of a bifurcation. Irrespective of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>, IT/BT and airway generation, lateral dispersion was a stronger transport mechanism than axial flow streaming. Discrepancy in the oscillatory flow relation <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula>/<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><msup><mi>o</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula> = 2 <i>L</i>/<i>D</i> (<i>L</i> = stroke length; <i>D</i> = trachea diameter) was observed for IT/BT ≠ 50%, as <i>L</i> changed with IT/BT. We developed a modified dimensionless stroke length term including IT/BT. While viscous forces and convective acceleration were dominant for lower <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>, unsteady acceleration was dominant for higher <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>W</mi><mi>o</mi></mrow></semantics></math></inline-formula>.https://www.mdpi.com/2311-5521/6/6/221high-frequency oscillatory ventilationHFOVinhalation timerespiratory flow |
| spellingShingle | Manikantam G. Gaddam Arvind Santhanakrishnan Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow Fluids high-frequency oscillatory ventilation HFOV inhalation time respiratory flow |
| title | Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow |
| title_full | Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow |
| title_fullStr | Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow |
| title_full_unstemmed | Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow |
| title_short | Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow |
| title_sort | effects of varying inhalation duration and respiratory rate on human airway flow |
| topic | high-frequency oscillatory ventilation HFOV inhalation time respiratory flow |
| url | https://www.mdpi.com/2311-5521/6/6/221 |
| work_keys_str_mv | AT manikantamggaddam effectsofvaryinginhalationdurationandrespiratoryrateonhumanairwayflow AT arvindsanthanakrishnan effectsofvaryinginhalationdurationandrespiratoryrateonhumanairwayflow |