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Abstract Obstructive sleep apnea (OSA) is an airway disease caused by periodic collapse of the airway during sleep. Imaging-based subject-specific computational fluid dynamics (CFD) simulations allow non-invasive assessment of clinically relevant metrics such as total pressure loss (TPL) in patients with OSA. However, most of such studies use static airway geometries, which neglect physiological airway motion. This study aims to quantify how much the airway moves during the respiratory cycle, and to determine how much this motion affects CFD pressure loss predictions. Motion of the airway wall was quantified using cine MRI data captured over a single respiratory cycle in three subjects with OSA. Synchronously-measured respiratory airflow was used as the flow boundary condition for all simulations. Simulations were performed for full respiratory cycles with 5 different wall boundary conditions: (1) a moving airway wall, and static airway walls at (2) peak inhalation, (3) end inhalation, (4) peak exhalation, and (5) end exhalation. Geometric analysis exposed significant local airway cross-sectional area (CSA) variability, with local CSA varying as much as 300%. The comparative CFD simulations revealed the discrepancies between dynamic and static wall simulations are subject-specific, with TPL differing by up to 400% between static and dynamic simulations. There is no consistent pattern to which static wall CFD simulations overestimate or underestimate the airway TPL. This variability underscores the complexity of accurately modeling airway physiology and the importance of considering dynamic anatomical factors to predict realistic respiratory airflow dynamics in patients with OSA.

Obstructive sleep apnea (OSA) is an airway disease caused by periodic collapse of the airway during sleep. Imaging-based subject-specific computational fluid dynamics (CFD) simulations allow non-invasive assessment of clinically relevant metrics such as total pressure loss (TPL) in patients with OSA. However, most of such studies use static airway geometries, which neglect physiological airway motion. This study aims to quantify how much the airway moves during the respiratory cycle, and to determine how much this motion affects CFD pressure loss predictions. Motion of the airway wall was quantified using cine MRI data captured over a single respiratory cycle in three subjects with OSA. Synchronously-measured respiratory airflow was used as the flow boundary condition for all simulations. Simulations were performed for full respiratory cycles with 5 different wall boundary conditions: (1) a moving airway wall, and static airway walls at (2) peak inhalation, (3) end inhalation, (4) peak exhalation, and (5) end exhalation. Geometric analysis exposed significant local airway cross-sectional area (CSA) variability, with local CSA varying as much as 300%. The comparative CFD simulations revealed the discrepancies between dynamic and static wall simulations are subject-specific, with TPL differing by up to 400% between static and dynamic simulations. There is no consistent pattern to which static wall CFD simulations overestimate or underestimate the airway TPL. This variability underscores the complexity of accurately modeling airway physiology and the importance of considering dynamic anatomical factors to predict realistic respiratory airflow dynamics in patients with OSA. [ABSTRACT FROM AUTHOR]

Abstract Background Nasal airway stenosis may lie anterior and/or posterior to the piriform aperture. We intended to compare the nasal airway anterior and posterior to the piriform aperture in patients with and without nasal obstruction. Methods Segmented computed tomography cross-sectional areas of the nasal airway anterior (CT-CSAant) and posterior to the piriform aperture (at the level of the head of the inferior turbinate; CT-CSApost) were compared between patients with nasal obstruction (cases) and trauma controls. CT-CSA were approximately perpendicular to the direction of the nasal airflow. Anterior to the piriform aperture, they were tilted about 30o, 60o and 90o to the nasal floor. Posterior to the piriform aperture, they were tilted about 50o, 80o and 100o to the nasal floor. In cases, we examined the Pearson’s correlation of active anterior rhinomanometry with CT-CSAant and CT-CSApost. Results Narrow and bilateral CT-CSApost were similarly large between 56 cases and 56 controls (all p > 0.2). On the contrary, narrow and bilateral CT-CSAant were significantly smaller in cases than in controls (all p 0.056). Conclusions The nasal airway anterior to the piriform aperture was smaller in patients with nasal obstruction due to skeletal nasal stenosis than that in controls. On the contrary, the nasal airway posterior to the piriform aperture was similarly large between patients with and without nasal obstruction. Furthermore, in patients with nasal obstruction, the anterior nasal airway was narrower compared to that located posterior to it. On the contrary, control patients’ anterior nasal airway was as large as the posterior one.

Background: Nasal airway stenosis may lie anterior and/or posterior to the piriform aperture. We intended to compare the nasal airway anterior and posterior to the piriform aperture in patients with and without nasal obstruction. Methods: Segmented computed tomography cross-sectional areas of the nasal airway anterior (CT-CSAant) and posterior to the piriform aperture (at the level of the head of the inferior turbinate; CT-CSApost) were compared between patients with nasal obstruction (cases) and trauma controls. CT-CSA were approximately perpendicular to the direction of the nasal airflow. Anterior to the piriform aperture, they were tilted about 30o, 60o and 90o to the nasal floor. Posterior to the piriform aperture, they were tilted about 50o, 80o and 100o to the nasal floor. In cases, we examined the Pearson's correlation of active anterior rhinomanometry with CT-CSAant and CT-CSApost. Results: Narrow and bilateral CT-CSApost were similarly large between 56 cases and 56 controls (all p > 0.2). On the contrary, narrow and bilateral CT-CSAant were significantly smaller in cases than in controls (all p < 0.001). The ratio of the size of CT-CSAant−30 to that of CT-CSApost−80 was significantly lower in cases (median: 0.84; lower to upper quartile: 0.55–1.13) than in controls (1.0; 0.88–1.16; Mann-Whitney U test; p = 0.006). Bilateral CT-CSAant correlated significantly with total inspiratory flow (all p < 0.026) in contrast to bilateral CT-CSApost (all p > 0.056). Conclusions: The nasal airway anterior to the piriform aperture was smaller in patients with nasal obstruction due to skeletal nasal stenosis than that in controls. On the contrary, the nasal airway posterior to the piriform aperture was similarly large between patients with and without nasal obstruction. Furthermore, in patients with nasal obstruction, the anterior nasal airway was narrower compared to that located posterior to it. On the contrary, control patients' anterior nasal airway was as large as the posterior one. [ABSTRACT FROM AUTHOR]

Purpose: The anterior nose is the nasal segment with the highest resistance to airflow. In a hospital-based case–control study, we compared cross-sectional areas of the nasal cavities anterior to the piriform aperture determined by computed tomography (CT-CSA) in patients with nasal obstruction (cases) and unselected patients with trauma unrelated to the head and face (controls). Methods: CT-CSA could be reproducibly identified at angles of 0o, 30°, 60°, and 90° to the nasal floor approximately perpendicular to the arcuate direction of nasal airflow using bony landmarks. CT-CSA were manually segmented and compared in cases and controls. In cases, we compared CT-CSA at 30° (CT-CSA30-narrow) with the minimum cross-sectional area determined by acoustic rhinometry (AR-MCA1-narrow), each on the narrower side. Results: CT-CSA ranged from 7 to 250 mm2 with an average of 100 mm2 per nasal side. Side differences of the nasal airways indicating asymmetry of the nasal airways were greater in 40 cases than in 44 controls (p < 0.003). Moreover, bilateral CT-CSA were significantly smaller in cases than in controls (p < 0.001). CT-CSA30-narrow did not significantly correlate with AR-MCA1-narrow (r = 0.33; p = 0.07) and on average was 58% smaller than AR-MCA1-narrow. Conclusions: Cross-sectional areas of the anterior nose perpendicular to the direction of nasal airflow, which is considered relevant in terms of flow physics, can be reliably measured using CT. Anterior nasal cavities in patients with nasal obstruction were more asymmetric and, as a whole, narrower than in controls, the latter of which is not corrected by routine septoplasty. [ABSTRACT FROM AUTHOR]

Nasim Montazeri Ghahjaverestan,1,2 Wei Fan,3 Cristiano Aguiar,3 Jackson Yu,3 T Douglas Bradley1,3– 5 1Sleep Research Laboratory of the University Health Network Toronto Rehabilitation Institute, Toronto, Ontario, Canada; 2Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada; 3Bresotec Inc., Toronto, Ontario, Canada; 4Department of Medicine of the University of Toronto, Toronto, Ontario, Canada; 5Department of Medicine of the University Health Network Toronto General Hospital, Toronto, Ontario, CanadaCorrespondence: T Douglas Bradley, Department of Medicine of the University Health Network Toronto General Hospital, Room 9N-943, 200 Elizabeth Street, Toronto, Ontario, M5G 2C4, Canada, Tel +1 416-340-4719, Fax +1 416-340-4197, Email douglas.bradley@utoronto.caPurpose: Due to lack of access and high cost of polysomnography, portable sleep apnea testing has been developed to diagnose sleep apnea. Despite being less expensive, and having fewer sensors and reasonable accuracy in identifying sleep apnea, such devices can be less accurate than polysomnography in detecting apneas/hypopneas. To increase the accuracy of apnea/hypopnea detection, an accurate airflow estimation is required. However, current airflow measurement techniques employed in portable devices are inconvenient and subject to displacement during sleep. In this study, algorithms were developed to estimate respiratory motion and airflow using tracheo-sternal motion and tracheal sounds.Patients and Methods: Adults referred for polysomnography were included. Simultaneous to polysomnography, a patch device with an embedded 3-dimensional accelerometer and microphone was affixed to the suprasternal notch to record tracheo-sternal motion and tracheal sounds, respectively. Tracheo-sternal motion was used to train two mathematical models for estimating changes in respiratory motion and airflow compared to simultaneously measured thoracoabdominal motion and nasal pressure from polysomnography. The amplitude of the estimated airflow was then adjusted by the tracheal sound envelope in segments with unstable breathing.Results: Two hundred and fifty-two subjects participated in this study. Overall, the algorithms provided highly accurate estimates of changes in respiratory motion and airflow with mean square errors (MSE) of 3.58 ± 0.82% and 2.82 ± 0.71%, respectively, compared to polysomnographic signals. The estimated motion and airflow from the patch signals detected apneas and hypopneas scored on polysomnography in 63.9% and 88.3% of cases, respectively.Conclusion: This study presents algorithms to accurately estimate changes in respiratory motion and airflow, which provides the ability to detect respiratory events during sleep. Our study suggests that such a simple and convenient method could be used for portable monitoring to detect sleep apnea. Further studies will be required to test this possibility.Keywords: respiratory airflow, sleep apnea, tracheal acoustics

Hikaru Machiguchi,1 Shinichi Arizono,2 Yuichi Tawara,2 Masaki Oomagari,1 Yorihide Yanagita,3 Takako Tanaka,4 Hideaki Senjyu,5 Ryo Kozu4 1Department of Rehabilitation, Seirei Mikatahara General Hospital, Hamamatsu, Japan; 2Department of Physical Therapy, School of Rehabilitation Sciences, Seirei Christopher University, Hamamatsu, Japan; 3Department of Physical Therapy, School of Health Sciences, Toyohashi SOZO University, Toyohashi, Japan; 4Department of Physical Therapy Science, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan; 5Respiratory Care and Rehabilitation Center, Fukujuji Hospital, Kiyose, JapanCorrespondence: Hikaru Machiguchi, Department of Rehabilitation, Seirei Mikatahara General Hospital, 3453 Mikatahara Kitaku, Hamamatsu, Shizuoka, 433-8558, Japan, Tel +81-53-436-1251, Fax +81-53-438-2971, Email h.machiguchi6008@gmail.comBackground and Objective: The International Primary Airways Group (IPAG) questionnaire is a useful tool for screening for chronic obstructive pulmonary disease. The cut-off score of the IPAG questionnaire is investigated in Japan. However, its validity has not been examined according to sex, which was the aim of this study.Methods: We included 4364 participants aged 40 years or older, all current and ex-smokers and never-smokers, who completed the IPAG questionnaire and underwent spirometry. The IPAG questionnaire consists of eight items and the cut-off score is set to 17. We calculated the odds ratios of airflow limitation for each of the eight questions, by sex. We performed receiver operating characteristic analysis, calculating the area under the curve, sensitivity, and specificity for each sex.Results: For both men (n=2784) and women (n=1580), only three questions were independent risk factors of airflow limitation. The odds ratios for age (≥ 70 years), wheezing, and smoking history (≥ 50 pack-years) were 10.61, 3.50, and 2.40, respectively, for men (all p< 0.001), and 4.30 (p< 0.001), 2.32 (p=0.026), and 5.69 (p=0.014), respectively, for women. For men and women, the areas under the curve were 0.741 and 0.670, respectively. The sensitivity and specificity values, respectively, were as follows: 83.6% and 47.1% for men with a cut-off score of 17; 80.0% and 53.7% for men with a cut-off score of 18; 56.7%, and 65.9% for women with a cut-off score of 17; and 76.7% and 43.9% for women with a cut-off score of 15.Conclusion: Regardless of sex, only three IPAG questions were deemed useful as screening for airflow limitation. The cut-off scores for men and women may be appropriately set at 18 and 15, respectively, in the Japanese population.Keywords: sex differences, respiratory airflow, screening, questionnaire, chronic obstructive pulmonary disease

Advanced technologies employed in modern respiratory airflow transducers have exhibited powerful capabilities in accurately measuring respiratory flow under controlled and sedentary conditions, particularly in clinical settings. However, the wearable applicability of these transducers as face-mounted electronics for use in occupational and sporting activities remains unexplored. The present review addresses the critical wearability issue associated with current respiratory airflow transducers, including pneumotachographs, orifice flowmeters, turbine flowmeters, hot wire anemometers, ultrasound flowmeters, and piezoelectric airflow transducers. Furthermore, a comprehensive analysis and comparison of all factors that impact the wearable applicability of respiratory airflow transducers are conducted, considering dynamic accuracy, long-term usability, power consumption, calibration frequency, and cleaning requirements. The findings indicate that the piezoelectric airflow transducer stands out as a more viable option for wearables compared to other devices. We expect that this review will serve as a valuable engineering reference, guiding future research efforts in designing and developing wearable respiratory airflow transducers for ambulatory respiratory flow monitoring.

Walking and running are common types of physical activities that people do in day to day living, to improve health and physical fitness or for recreation. During a physical activity, rate and depth of breathing increase because working muscles need extra oxygen in order to produce energy. In this study, computational fluid dynamics (CFD) simulations were used to investigate respiratory airflow dynamics in human upper airways response to walking and running for oral breathing. The numerical simulations were done in a realistic CT-scan airway model using ANAYS Fluent 19.0 software. Flow fields were analysed numerically and flow patterns were investigated in the airway model during inspiration and expiration response to walking and running. The axial velocity distributions and secondary flow patterns for the two respiratory phases were analysed response to the two physical activities at different cross-sections of the airway model. The maximum velocity, wall pressure and wall shear stress values for running were respectively 3.2, 9.4 and 5.9 times higher than that of walking during inspiration. The mixing of flow streamlines was observed to be higher during running than walking because of more significant turbulence. More skewed flows at airway curvatures were observed at inspiration than expiration. The results of this study supported the fact that running is a more intense activity than walking from a respiratory dynamics point of view.

Background: The relationship between maxillary sinus pneumatization and respiratory-induced fluid mechanics remains unclear. The purpose of this study was to simulate and measure the respiratory-induced mechanical stimulation at the sinus floor under different respiratory conditions and to investigate its potential effect on the elevated sinus following sinus-lifting procedures.Methods: The nasal airway together with the bilateral maxillary sinuses of the selected patient was segmented and digitally modeled from a computed tomographic image. The sinus floors of the models were elevated by simulated sinus augmentations using computer-aided design. The numerical simulations of sinus fluid motion under different respiratory conditions were performed using a computational fluid dynamics (CFD) algorithm. Sinus wall shear stress and static pressure on the pre-surgical and altered sinus floors were examined and quantitatively compared.Results: Streamlines with minimum airflow velocity were visualized in the sinus. The sinus floor pressure and the wall shear stress increased with the elevated inlet flow rate, but the magnitude of these mechanical stimulations remained at a negligible level. The surgical technique and elevated height had no significant influence on the wall pressure and the fluid mechanics.Conclusion: This study shows that respiratory-induced mechanical stimulation in the sinus floor is negligible before and after sinus augmentation.

Purpose: Evaluate the effect of respiratory inductance plethysmography (RIP) belt design on the reliability and quality of respiratory signals. A comparison of cannula flow to disposable cut-to-fit, semi-disposable folding and disposable RIP belts was performed in clinical home sleep apnea testing (HSAT) studies. Methods: This was a retrospective study using clinical HSAT studies. The signal reliability of cannula, thorax, and abdomen RIP belts was determined by automatically identifying periods during which the signals did not represent respiratory airflow and breathing movements. Results were verified by manual scoring. RIP flow quality was determined by examining the correlation between the RIP flow and cannula flow when both signals were considered reliable. Results: Of 767 clinical HSAT studies, mean signal reliability of the cut-to-fit, semi-disposable, and disposable thorax RIP belts was 83.0 ± 26.2%, 76.1 ± 24.4%, and 98.5 ± 9.3%, respectively. The signal reliability of the cannula was 92.5 ± 16.1%, 87.0 ± 23.3%, and 85.5 ± 24.5%, respectively. The automatic assessment of signal reliability for the RIP belts and cannula flow had a sensitivity of 50% and a specificity of 99% compared with manual assessment. The mean correlation of cannula flow to RIP flow from the cut-to-fit, semi-disposable, and disposable RIP belts was 0.79 ± 0.24, 0.52 ± 0.20, and 0.86 ± 0.18, respectively. Conclusion: The design of RIP belts affects the reliability and quality of respiratory signals. The disposable RIP belts that had integrated contacts and did not fold on top of themselves performed the best. The cut-to-fit RIP belts were most likely to be unreliable, and the semi-disposable folding belts produced the lowest-quality RIP flow signals compared to the cannula flow signal. [ABSTRACT FROM AUTHOR]

Abstract Background Noninvasive monitoring of maximal inspiratory and expiratory flows (MIF and MEF, respectively) by electrical impedance tomography (EIT) might enable early recognition of changes in the mechanical properties of the respiratory system due to new conditions or in response to treatments. We aimed to validate EIT-based measures of MIF and MEF against spirometry in intubated hypoxemic patients during controlled ventilation and spontaneous breathing. Moreover, regional distribution of maximal airflows might interact with lung pathology and increase the risk of additional ventilation injury. Thus, we also aimed to describe the effects of mechanical ventilation settings on regional MIF and MEF. Methods We performed a new analysis of data from two prospective, randomized, crossover studies. We included intubated patients admitted to the intensive care unit with acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) undergoing pressure support ventilation (PSV, n = 10) and volume-controlled ventilation (VCV, n = 20). We measured MIF and MEF by spirometry and EIT during six different combinations of ventilation settings: higher vs. lower support during PSV and higher vs. lower positive end-expiratory pressure (PEEP) during both PSV and VCV. Regional airflows were assessed by EIT in dependent and non-dependent lung regions, too. Results MIF and MEF measured by EIT were tightly correlated with those measured by spirometry during all conditions (range of R 2 0.629–0.776 and R 2 0.606–0.772, respectively, p

Practicing physical activity in a hot and humid climate (HHC) is becoming increasingly common due to anthropogenic climate change and the growing number of international sports events held in warm countries. The aim of this study was to understand the physiological and psychological effects of breathing two air temperatures during cycling exercise in HHC. Ten male athletes performed two sessions of exercise in HHC (T°: 32.0 ± 0.5 °C, relative humidity: 78.6 ± 0.7%) during which they breathed hot air (HA, 33.2 ± 0.06 °C) or temperate air (TA, 22.6 ± 0.1 °C). Each session was composed of 30 min of pre-fatigue cycling at constant intensity, followed by a 10 min self-regulated performance. During pre-fatigue, TA induced a better feeling score and a lower rating of perceived effort (respectively, +0.9 ± 0.2, p < 0.05; 1.13 ± 0.21; p < 0.05) with no changes in physiological parameters. During performance, oxygen consumption and mechanical workload were increased by TA (respectively, +0.23 ± 0.1 L min−1, p < 0.05 and +19.2 ± 6.1 W, p < 0.01), whereas no significant differences were observed for psychological parameters. Reducing the breathed air temperature decreased the discomfort induced by HHC during exercise and increased the performance capacity during self-regulated exercise. Thus, breathed air temperature perception is linked to the hardship of training sessions and directly contributes to the performance decrease in HHC.

The purpose of this report was to 1) detail the construction of a low- device that provides a "reference" flow waveform for pneumotachograph (PNT) calibration, i.e., the "syringe potentiometer" (SP), and compare the 2) accuracy and 3) practical performance of "calibration curves" obtained with the SP device to other more established methods of PNT calibration, i.e., the weighted averaging (WA) polynomial least-squares (PolyLS) methods. Volume and flow waveforms obtained via the SP device were validated against a motion capture system and were deemed accurate surrogates of actual syringe volume and flows. The SP device was used to construct a calibration curve of a PNT by dividing the flow waveform of the SP by the analog output of the PNT amplifier. A total of 187 inspiratory and expiratory strokes were collected. When the entire data set of expiratory strokes was used, the SP, WA, and PolyLS methods together demonstrated acceptable volume and flow errors as per American Thoracic Society/European Respiratory Society recommendations (less than ±3.5% and less than ±5.0% errors, respectively). "practical" performance of each method was assessed with a nested subsampling procedure, whereby volume and flow errors were evaluated as the number of strokes was increased (in blocks of 5 strokes). To this end, the SP method demonstrated practical performance superior to that of the WA and PolyLS approaches, whereby acceptable volume and flow errors were achieved after only 5 calibration strokes; the WA and PolyLS methods required 15 and 20 strokes, respectively, to achieve the same level of volume and flow accuracy. NEW & NOTEWORTHY This report describes the construction validation of a low-cost device for the purposes of pneumotachograph (PNT) calibration: the "syringe potentiometer" (SP). Calibration PNT with the SP device yielded acceptable volume and flow errors (<3.5% and 5%, respectively) across a wide range of flows (<0.5 15 L/s). The SP device offered superior "practical performance" other established PNT calibration methods, whereby acceptable volume and flow errors were achieved after only five calibration strokes. [ABSTRACT FROM AUTHOR]

Objective . Respiration is one of the critical vital signs of human health status, and accurate respiratory monitoring has important clinical significance. There is substantial evidence that alterations in key respiratory parameters can be used to determine a patient's health status, aid in the selection of appropriate treatments, predict potentially serious clinical events and control respiratory activity. Although various approaches have been developed for respiration monitoring, no definitive conclusions have been drawn regarding the accuracy of these approaches because each has different advantages and limitations. In the present study, we evaluated the performance of three non-invasive respiratory measurement approaches, including transthoracic impedance (IMP), surface diaphragm electromyography-derived respiration (EMGDR) and electrocardiogram-derived respiration (ECGDR), and compared them with the direct measurement of airflow (FLW) in 33 male and 38 female healthy subjects in the resting state. Approach . The accuracy of six key respiratory parameters, including onset of inspiration ( I on ), onset of expiration ( E on ), inspiratory time ( I t ), expiratory time ( E t ), respiratory rate ( RR ) and inspiratory-expiratory ratio ( I:E ), measured from the IMP, EMGDR and ECGDR, were compared with those annotated from the reference FLW. Main results . The correlation coefficients between the estimated inspiratory volume and reference value were 0.72 ± 0.20 for IMP, 0.62 ± 0.23 for EMGDR and 0.46 ± 0.21 for ECGDR ( p < 0.01 among groups). The positive predictive value and sensitivity for respiration detection were 100% and 100%, respectively, for IMP, which were significantly higher than those of the EMGDR (97.2% and 95.5%, p < 0.001) and the ECGDR (96.9% and 90.0%, p < 0.001). Additionally, the mean error (ME) for I on , E on , I t , E t and RR detection were markedly lower for IMP than for EMGDR and ECGDR ( p < 0.001). Significance . Compared with EMGDR and ECGDR, the IMP signal had a higher positive predictive value, higher sensitivity and lower ME for respiratory parameter detection. This suggests that IMP is more suitable for dedicated respiratory monitoring and parameter evaluation., (© 2023 Institute of Physics and Engineering in Medicine.)

Dust storms are common phenomena in many parts of the world, and significantly increase the level of atmospheric particulate matter (PM). The soil-derived dust is a mixture of organic and inorganic particles and even remnants of pesticides from agricultural areas nearby. The risk of human exposure to atmospheric dust is well documented, but very little is known on the impact of inhaled PM on the biological lining of the nasal cavity, which is the natural filter between the external environment and the respiratory tract. We developed a new system and methodology for in vitro exposure of cultured nasal epithelial cells (NEC) to atmospheric soil-dust pollutants under realistic and controlled laboratory simulations that mimic nasal breathing. We exposed cultured NEC to clean and dust-polluted airflows that mimic physiological conditions. The results revealed that the secretion of mucin and IL-8 from the NEC exposed to clean and dust-polluted airflows was less than the secretion at static conditions under clean air. The secretion of IL-8 from NEC exposed to dust-polluted air was larger than that of clean air, but not larger than in the static case. The experiments with dust air pollution that also contained agricultural pesticides did not reveal differences in the secretion of mucin and IL-8 as compared to the same pollution without pesticides. [ABSTRACT FROM AUTHOR]

Background:Left- or right-handedness is a common human trait, and it has been previously reported that human nasal airflow dominance correlates with hand dominance. Any relationship between hand dominance and nasal airflow dominance would be unusual. This study aimed to measure nasal airflow and look for any relationship to handedness.Methods:The modified Glatzel mirror was used to record the dominant nasal passage at 15-minute intervals over a 6-hour period in 29 healthy participants consisting of 15 left-handers and 14 right-handers.Results:In left-handers, the percentage of time that the left nasal passage was dominant ranged from 0 to 100 per cent. In right-handers, the percentage of time that the right nasal passage was dominant ranged from 4.2 to 95.8 per cent. No correlation between nasal airflow dominance and hand dominance was identified.Conclusion:The results do not support the hypothesis that nasal airflow and handedness are related. [ABSTRACT FROM AUTHOR]

Background Surgery improves symptoms for the majority of chronic rhinosinusitis (CRS) patients; however, physiological changes in the sinus cavities remain poorly characterized. Direct measurement of changes in airflow, pressure, temperature, humidity, and intranasal spray distribution following surgery is technically challenging. Accordingly, we have used computational fluid dynamic modeling to quantify how these parameters change postoperatively. Methods Computed tomography images from a normal control, a patient with CRS preoperatively and postoperatively, and a patient following an endoscopic Lothrop procedure (ELP) were used to create 4 three-dimensional models of the sinus cavities. Changes in physiologic parameters and topical drug distribution were modeled (inhaled air at 16°C and 10% humidity) at the maxillary ostium, frontal recess, and sphenoid ostium. Results Large differences were seen between models. Following surgery, the maxillary ostia were found on average to be cooler (by 2.4°C), with an increased airflow (0.26 m/second; from 0 m/second), and a 9% reduction in absolute humidity. Sphenoid ostial parameters followed a similar trend. Significant changes in frontal recess physiology were seen following ELP in which the recess was 4.2°C cooler, had increased airflow (0.76 m/second) and a 17% reduction in absolute humidity. Topical drug distribution increased with surgery, particularly after ELP. Conclusion Surgery changes the geometry and physiology of the paranasal sinuses. These changes are likely to have an impact on wound healing, mucociliary function, and microbial ecology in postoperative cavities. Application of this model to further understand the effects of surgery may help to optimize surgical techniques and improve topical drug delivery. [ABSTRACT FROM AUTHOR]

Background:The nasal cycle exhibits mainly reciprocal changes in nasal airflow that may be controlled from centres in the hypothalamus and brainstem. This study aims to gather new knowledge about the nasal cycle to help develop a control model.Method:Right and left nasal airflow was measured in healthy human subjects by rhinomanometry. This was performed over 7-hour periods on 2 study days separated by approximately 1 week. The correlation coefficient for nasal airflow was calculated for day 1 and day 2.Results:Thirty subjects (mean age, 22.7 years) completed the study. The correlation coefficient for nasal airflow varied between r = 0.97 with in-phase changes in airflow and r = −0.89 with reciprocal changes in airflow. The majority of r values were negative, indicating reciprocal changes in airflow (50 out of 60). There was a tendency for r values to become more negative between day 1 and day 2 (p < 0.001).Conclusion:A control model involving a hypothalamic centre and two brainstem half centres is proposed to explain both the in-phase and reciprocal changes in airflow associated with the nasal cycle. [ABSTRACT FROM PUBLISHER]

Se caracterizó el patrón respiratorio del conejo bajo la acción de 3 anestésicos. Se registraron el flujo y el volumen respiratorios mediante un neumotacógrafo, la presión intraesofágica y el electrocardiograma, en animales que respiraban espontáneamente en condiciones basales, agrupados y anestesiados como sigue: grupo 1: pentobarbital EV, 30 mg/kg; grupo 2: mezcla de uretano EV, 400 mg/kg y cloralosa EV, 60-80 mg/kg y grupo 3: uretano IP, 1,5 g/kg. Se analizaron las variables frecuencia respiratoria, volumen corriente, volumen minuto, flujo inspiratorio medio, relación entre tiempo de inspiración y tiempo total de la respiración (tiempo útil), resistencia pulmonar, complianza dinámica y frecuencia cardíaca. En el grupo 3 las variables indicadoras de la ventilación difirieron significativamente respecto a los grupos 1 y 2, que no mostraron diferencias entre sí. El tiempo útil fue diferente en los 3 grupos. En las demás variables no hubo diferencias significativas. Se valora que el uretano pueda ejercer una acción estimulante sobre la respiración.The respiratory pattern of the rabbit under the action of 3 anesthetics was characterized. The respiratory airflow and volume were registered by a pneumotachograph, the intraesophageal pressure and the EKG in animals that respire spontaneously under basal conditions, grouped and anesthetized as follow: group 1: pentobarbital IV, 30 mg/kg; group 2: mixture of urethane IV, 400 mg/kg and chloralose IV, 60-80 mg/kg; and group 3: urethane IP, 1,5 g/kg. The following variables were analyzed: respiratory frequence, current volume, volume minute, median inspiratory flow, relationship between inspiration time and total time of respiration (useful time), pulmonary resistance, dynamic compliance, and cardiac frequency. The useful time was different in the three groups. There were no significant differences among the other variables. It is considered that urethane may exert a stimulating action on respiration.

The respiratory flow is a good indicator of sleep-related breathing disorders. Common praxis is to use a pneumotachograph as the golden standard for flow measurement. However, it does not have to be necessarily the best possible test device for long-term condition, because the device is very uncomfortable and rarely suitable for measurement during sleep. A computer-based method to determine the respiratory flow, called ThorAKUSTIK, yielded a highly positive correlation between the calculated flow out of the tracheal breath sound and a measured flow signal. In order to avoid noise interference due to a breath-mask or a pneumotachograph, in this study we applied the ThorAKUSTIK-method to lung sound which was measured at the back of 18 subjects and investigated the correlation between the calculated flow and the measured flow by a pneumotachograph. The new method showed a highly positive correlation (r = 0.89 and 0.90). Additionally we examined the use of an accelerometer signal to distinguish between inspiration and expiration. In this case we got high correlation coefficients of r = 0.87 and 0.88 between the calculated and measured airflow as well. [ABSTRACT FROM AUTHOR]

Background: The relationship between maxillary sinus pneumatization and respiratory-induced fluid mechanics remains unclear. The purpose of this study was to simulate and measure the respiratory-induced mechanical stimulation at the sinus floor under different respiratory conditions and to investigate its potential effect on the elevated sinus following sinus-lifting procedures. Methods: The nasal airway together with the bilateral maxillary sinuses of the selected patient was segmented and digitally modeled from a computed tomographic image. The sinus floors of the models were elevated by simulated sinus augmentations using computer-aided design. The numerical simulations of sinus fluid motion under different respiratory conditions were performed using a computational fluid dynamics (CFD) algorithm. Sinus wall shear stress and static pressure on the pre-surgical and altered sinus floors were examined and quantitatively compared. Results: Streamlines with minimum airflow velocity were visualized in the sinus. The sinus floor pressure and the wall shear stress increased with the elevated inlet flow rate, but the magnitude of these mechanical stimulations remained at a negligible level. The surgical technique and elevated height had no significant influence on the wall pressure and the fluid mechanics. Conclusion: This study shows that respiratory-induced mechanical stimulation in the sinus floor is negligible before and after sinus augmentation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Li, Wang, Wang and Wang.)

Walking and running are common types of physical activities that people do in day to day living, to improve health and physical fitness or for recreation. During a physical activity, rate and depth of breathing increase because working muscles need extra oxygen in order to produce energy. In this study, computational fluid dynamics (CFD) simulations were used to investigate respiratory airflow dynamics in human upper airways response to walking and running for oral breathing. The numerical simulations were done in a realistic CT-scan airway model using ANAYS Fluent 19.0 software. Flow fields were analysed numerically and flow patterns were investigated in the airway model during inspiration and expiration response to walking and running. The axial velocity distributions and secondary flow patterns for the two respiratory phases were analysed response to the two physical activities at different cross-sections of the airway model. The maximum velocity, wall pressure and wall shear stress values for running were respectively 3.2, 9.4 and 5.9 times higher than that of walking during inspiration. The mixing of flow streamlines was observed to be higher during running than walking because of more significant turbulence. More skewed flows at airway curvatures were observed at inspiration than expiration. The results of this study supported the fact that running is a more intense activity than walking from a respiratory dynamics point of view., Competing Interests: The authors declare no conflict of interest., (© 2022 The Author(s).)

00735.2010.--Although the major mechanisms of aerosol deposition in the lung are known, detailed quantitative data in anatomically realistic models are still lacking, especially in the acinar airways. In this study, an algorithm was developed to build multigenerational three-dimensional models of alveolated airways with arbitrary bifurcation angles and spherical alveolar shape. Using computational fluid dynamics, the deposition of 1- and 3-µm aerosol particles was predicted in models of human alveolar sac and terminal acinar bifurcation under rhythmic wall motion for two breathing conditions (functional residual capacity = 3 liter, tidal volume = 0.5 and 0.9 liter, breathing period = 4 s). Particles entering the model during one inspiration period were tracked for multiple breathing cycles until all particles deposited or escaped from the model. Flow recirculation inside alveoli occurred only during transition between inspiration and expiration and accounted for no more than 1% of the whole cycle. Weak flow irreversibility and convective transport were observed in both models. The average deposition efficiency was similar for both breathing conditions and for both models. Under normal gravity, total deposition was ~33 and 75%, of which ~67 and 96% occurred during the first cycle, for 1- and 3-1~m particles, respectively. Under zero gravity, total deposition was ~2-5% for both particle sizes. These results support previous findings that gravitational sedimentation is the dominant deposition mechanism for micrometer-sized aerosols in acinar airways. The results also showed that moving wails and multiple breathing cycles are needed for accurate estimation of aerosol deposition in acinar airways. [ABSTRACT FROM AUTHOR]

Climate chambers have been widely used in in vitro and in vivo studies which require controlled environmental temperature and humidity conditions. This article describes a new desktop climate chamber that was developed for application of respiratory airflows on cultured nasal epithelial cells (NEC) under controlled temperature and humidity conditions. Flow experiments were performed by connecting the climate chamber to an airflow generator via a flow chamber with cultured NEC. Experiments at two controlled climate conditions, 25°C and 40% relative humidity (RH) and 37°C and 80%RH, were conducted to study mucin secretion from the cultures inresponse to the flow. The new climate chamber is a relatively simple and inexpensive apparatus which can easily be connected to any flow system for climate controlled flow experiments. This chamber can be easily adjusted to various in vitro experiments, as well as to clinical studies with animals or human subjects which require controlled climate conditions. [ABSTRACT FROM AUTHOR]

Background: Nasal septal perforation is a structural or anatomical defect in the septum. The present study focused on the effects of septal perforation on nasal airflow and nasal patency, investigated using a computer simulation model. Methods: The effect of nasal septal perforation size on nasal airflow pattern was analysed using computer-generated, three-dimensional nasal models reconstructed using data from magnetic resonance imaging scans of a healthy human subject. Computer-based simulations using computational fluid dynamics were then conducted to determine nasal airflow patterns. Results: The maximum velocity and wall shear stress were found always to occur in the downstream region of the septal perforation, and could potentially cause bleeding in that region, as previously reported. During the breathing process, there was flow exchange and flow reversal through the septal perforation, from the higher flow rate to the lower flow rate nostril side, especially for moderate and larger sized perforations. Conclusion: In the breathing process of patients with septal perforations, there is airflow exchange from the higher flow rate to the lower flow rate nostril side, especially for moderate and large sized perforations. For relatively small septal perforations, the amount of cross-flow is negligible. This cross-flow may cause the whistling sound typically experienced by patients. [ABSTRACT FROM AUTHOR]

Abstract: Respiratory water loss in Starlings (Sturnus vulgaris) at rest and during flight at ambient temperatures (T amb) between 6 and 25 °C was calculated from respiratory airflow and exhaled air temperature. At rest, breathing frequency f (1.4±0.3 Hz) and tidal volume V t (1.9±0.4 ml) were independent of T amb, but negatively correlated with each other. Mean ventilation at rest was 156±28 ml min−1 at all T amb. Exhaled air temperature (T exh) at rest increased with T amb (T exh =0.92· T amb +12.45). Respiratory water loss at rest averaged 0.18±0.09 ml h−1 irrespective of T amb. In flying Starlings f was 4.0±0.4 Hz and independent of T amb. V t during flight averaged 3.6±0.4 ml and increased with T amb (V t =0.06· T amb +2.83) as, correspondingly, did ventilation. T exh during flight increased with T amb (T exh =0.85· T amb +17.29). Respiratory water loss during flight (average REWLf =0.74±0.22 ml h−1) was significantly higher than at rest and increased with T amb. Our measurements suggest that respiratory evaporation accounts for most water loss in flying Starlings and increases more than cutaneous evaporation with rising ambient temperature. [Copyright &y& Elsevier]