Airflow Oscillation Research Articles

1506 細気管支モデル内の振動気流計測(2)(OS15-2 生体流体解析とその応用,OS15 生体流体解析とその応用,オーガナイズドセッション)

1506 細気管支モデル内の振動気流計測(2)(OS15-2 生体流体解析とその応用,OS15 生体流体解析とその応用,オーガナイズドセッション)

Dynamic measurements of the elastic constants of glass wool

The sound wave in the air between the fibers of glass wool exerts an oscillatory viscous drag on the fibers and excites a mechanical wave in the fiber skeleton. Accurate calculations of sound attenuation in glass wool must take the mechanical wave in the fiber skeleton into account, and this requires knowledge of the dynamic elastic constants of the fiber skeleton. The mechanical properties of glass wool are highly anisotropic. Previously only one of the elastic constants has been measured dynamically, but here all the elastic constants are reported. The measurement method is well known. But a new mechanical design, which reduces mechanical resonance, is described. The measurements were carried out in atmospheric air at normal pressure, and this causes an oscillatory airflow in the sample. To obtain the elastic constants, the influence of the airflow was subtracted from the data by a new formula. The elastic constants were measured in the frequency range 20–160Hz for glass wool of mass density 30kg∕m3. The elastic constant C11 depended on the frequency; at 20Hz it was 1.5+0.01iMPa, and at 160Hz it was 2.6+0.06iMPa. The constant C33=12+0.6ikPa did not depend on frequency. The shear constant C44=40+2ikPa was constant. The two constants C12,C13 were zero.

Investigation of non-uniform airflow signal oscillation during high frequency chest compression

BackgroundHigh frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC.MethodsThe computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations.Results and discussionWe could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system.ConclusionWe found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

LES解析結果を用いたADPIによる居住域温熱環境評価 : 可動式ノズル吹出口の大空間への適用に関する研究(第1報)

Nozzles or slotted supply air outlets are used for air conditioning in large spaces because its throw is long and these outlet types cause the least noise. One of the disadvantages of fixed nozzles, however, is that in the case of air conditioning, the current of cold air is directed straight at the occupied zone, often causing a cold, uncomfortable draft. Since air jets tend not to spread very much, there also occur stagnant volumes in locations not reached by the jets, which can result in unsatisfactory air quality. The number of air outlets must be increased to eliminate this problem. In order to maintain a uniform temperature and airflow throughout the occupied zone, air conditioning system designers generally select the number of outlets either using existing design guidelines or values accepted in the industry through experiment or practical experience. We propose herein movable nozzles, which include the following benefits: (1) A reduction in the number of necessary air conditioning outlets due to improved jet terminal velocities and diffusivities in the horizontal occupied zone; (2) reduction in stagnant portions and elimination of dirty air "pockets" in the occupied zone; (3) uniform temperatures and airflow distribution throughout the horizontal occupied zone; and (4) improvement in perceived comfort and coolness due to time-dependent fluctuations in airflow generated by airflow oscillation and other factors. In this study, the environment resulting from regular design and that resulting from movable-nozzle design were compared using LES (Large Eddy Simulation). ADPI (Air Diffusion Performance Index), an indicator of the conditions in the occupied zone during air conditioning, was calculated, and confirmed the effectiveness of air conditioning using movable nozzle outlets.

Airflow synchronous with oscillatory acceleration reflects involuntary respiratory muscle activity

To explore mechanisms causing involuntary airflow synchronous with oscillatory axial whole body acceleration (oscillatory axial acceleration, OAA) such as that during locomotion, we monitored airflow, acceleration, and electromyograms (EMGs) of the rib cage and abdominal muscles in standing subjects undergoing OAA at 3, 6, and 9 Hz at accelerations of 0.1-0.95 g. Subjects relaxed or performed static respiratory maneuvers at constant lung volume with glottis open. Oscillatory airflows (0.01-3.01 s(-1)) synchronous with OAA were not consistent with expectations for a passive respiratory system, and were larger during active respiratory efforts than during relaxation. Peak inspiratory airflow usually preceded peak upward acceleration by 90-180 degrees. In 80% of runs with respiratory muscles voluntarily activated or relaxed, EMGs showed activity synchronous with OAA. Changes in periodic muscle activity coincided with changes in oscillatory airflow. We conclude that periodic muscle activity, probably a reflex response to body wall deformation during OAA, strongly influences the involuntary airflow synchronous with OAA.

A108 PIV Measurements of Oscillatory air flow in a micro-channel

Pulsatory or oseillatory gas flows in micro-channel are obsorved in some engineering devices and biological cases. One of the typicral cases is the oscillatory air flow in bronchiole of human lung. The mechanism of gas transfer and diffusion in it has nut been clarified in detail. As the first approach of the subject. oscillatory flows in straight and T-shalred micro-channels have been measured by PIV at different phase of the oscillation in order to eslablish the fundamental technique of PIV measurements on oscillatory air flow in a micro-channel and the techniques of tracer particle suspension. illumination. image capturing and so on have been investigated in this report

스트레인 게이지 변위추정 센서를 사용한 유동공진 가진기 설계

Heat dissipation technology using the flow resonant phenomenon is a kind of a new concept in the heat transfer area. A vibration exciter is needed to enhance air flow mixing which has the natural shedding frequency of thermal system. A mechanical vibrating device for the air flow oscillation is introduced, which is driven by a moving coil actuator with a displacement estimator using strain gage. An analytical dynamic model for this mechanical vibration exciter is presented and its validity is checked by the comparison with experimental data. Values of some unknown system parameters in the analytic model are estimated through the system identification approach. Based on this mathematical model, the vibration exciter using strain displacement estimator is developed. During the experimental verification phase, it turns out the high modal resonant characteristics of a vibrating plate are a major barrier against obtaining a high bandwidth vibration exciter.

Biotransport in the human respiratory system

The human respiratory system is an 'open' organ, which is designed to exchange oxygen and carbon dioxide between the circulating blood and the external environment. This gas exchange is successfully accomplished via a set of transport phenomena comprised of oscillatory air flow, heat and water vapor exchange, mucus transport and air-blood gas exchange all of which take place in a complex geometry that undergoes large changes. These transport phenomena occur simultaneously to supply the body's need for oxygen in different physiological conditions and/or environments, while defending it from external hazards. The need for better comprehension of the mechanisms involved in pulmonary diseases and for advanced techniques for both diagnosis and intervention stimulated numerous studies of the different biotransport processes that take place in the human respiratory system.

Effects of sputum oscillations and rhDNase in vitro: a combined approach to treat cystic fibrosis lung disease.

Mucolytic treatment with rhDNase is part of the current therapy for cystic fibrosis (CF) lung disease. The Flutter valve, a device for enhancing airway mucus clearance, has recently been approved for use in CF patients. Exhalation through the Flutter valve leads to oscillations of expiratory airflow, improving mucus viscoelasticity and stimulating clearance. The goal of our in vitro study was to evaluate the individual and combined effects of Flutter valve oscillations and rhDNase treatment on the viscoelastic (rheological) properties of CF sputum. Sputum specimens were collected from 19 CF patients and subjected to the following protocols: 1) baseline sample with no treatment applied; 2) application of oscillations generated by airflow through the Flutter valve; 3) incubation at 37 degrees C for 30 min with 10% vol/wt rhDNase (Pulmozyme) to achieve a final concentration of 2.5 microg/mL (approximately 100 nM); 4) combination of Flutter valve oscillations and 10% vol/wt normal saline (0.9% NaCl); 5) combination of Flutter valve oscillations and 10% vol/wt rhDNase at 2.5 microg/mL final concentration. For each protocol, the mucus rigidity index (log G* at 1 rad/s) was measured at baseline and at 30 min. Values are presented as mean+/-SEM. The cough clearability index (CCI) was computed from measurements of mucus viscoelasticity, based on relationships established in model studies. Flutter valve treatment alone did not result in a significant reduction in the rigidity of CF sputum (2.24+/-0.13 vs. 2.11+/-0.13, P=0.19), nor did rhDNase (2.5 microg/mL) alone, although we have previously shown (Pediatr. Pulmonol. 1995; 20:78) that both of these treatments reduce sputum spinnability, which is more sensitive to molecular weight reduction. In comparison to individual treatments, combined treatment with Flutter valve oscillations and rhDNase significantly reduced the mucus rigidity to 1.85+/-0.19 from 2.24+/-0.13 (P< 0.001), consequently increasing the predicted clearability of the sputum (from 1.09+/-0.26 to 1.83+/-0.48, P=0.012). These in vitro results suggest that a combination of biochemical treatment (e.g., DNase) and mechanical oscillation may have a better therapeutic potential for mucus clearance in CF lung disease.

Performance Prediction of Contrarotating Wells Turbines for Wave Energy Converter Design

Wave energy can be captured and converted to a vertical pistonlike oscillatory motion by semiinsertion of a chamber with a submerged opening into the ocean. The roof of the chamber will open onto a ducted Wells air turbine, which will be driven by the oscillatory airflow developed by the forcing action of the surface of the Oscillating Water Column (OWC) inside the chamber. The design of such an OWC conversion plant is considered with particular reference to the air turbine stage and its synthesis into the system. Consequently, a semiempirical method for predicting the performance of the contrarotating Wells turbine configuration is presented, notably, detailing aerofoil performance into the stall region. The predicted turbine performance is subsequently utilized to facilitate the design of a 310 kW plant, including efficient accommodation of the pneumatic power levels for maximal aerodynamic conversion.

Computational model of oscillatory airflow in a bronchial bifurcation

Airflow distribution in the bronchial tree is an important factor that controls gas mixing in the lungs, especially, in diseased lungs or during high frequency ventilation. A nonlinear analog model has been developed to investigate the dependency of airflow distribution in asymmetric bronchial bifurcations on structural and physiological parameters. The system parameters (electrical analogs) are time-dependent and were extracted from laboratory studies of airway models and physiological measurements. The model was used to study flow distribution in peripheral pathways of normal and pathological airways during different modes of quiet breathing as well as high frequency ventilation. Model simulations revealed that (i) increasing of ventilation frequency or stroke volume increases the time and percentage of pendelluft in each cycle, (ii) diameter asymmetry between parallel pathways is more dominant than length asymmetry and enhances the degree of asynchronous ventilation to peripheral pathways, and (iii) asymmetry in the compliance of peripheral airways and lung parenchyma greatly increases the degree of asynchronous ventilation.

Evidence of a critical period of airway instability during central apneas in preterm infants.

The timing and magnitude of airway narrowing in central apneas is unknown. We have developed a method of apnea classification that relies on the transmission of cardiac airflow oscillation to indicate airway patency. Using a theoretical model, we showed that the amplitude of the cardiac airflow oscillation is proportional to airway diameter for small lumens. While in the majority of central apneas the amplitude of the cardiac airflow oscillation remains nearly constant, in a subset of events the waveform decreases with time, suggesting airway narrowing. We hypothesized that this is not a random occurrence but reflects a critical period of airway instability during central apnea. To test this hypothesis we studied 41 preterm infants. Of 4,456 central apneas, 585 had a decrease in the amplitude of the cardiac oscillation. The amplitude of the cardiac airflow oscillation during an apnea was recorded to provide a dynamic measure of changes in airway diameter with time. To allow for comparisons between patients the amplitude of each cardiac airflow oscillation was expressed as a proportion of the maximum amplitude observed in each infant. We then compared the amplitude at multiple successive 0.5 s intervals with the amplitude of the cardiac airflow oscillation observed at the apnea outset using ANOVA. We found a significant decrease in cardiac airflow oscillation after only 1 s irrespective of the apnea duration (3 to 16 s). We conclude that airway narrowing during central apnea is not a random occurrence but appears shortly after the onset of the apnea. We speculate that the phenomenon is secondary to passive airway relaxation.

Calculation of the dynamic air flow resistivity of fiber materials

The acoustic attenuation of acoustic fiber materials is mainly determined by the dynamic resistivity to an oscillating air flow. The dynamic resistance is calculated for a model with geometry close to the geometry of real fiber material. The model consists of parallel cylinders placed randomly. Two cases are treated: flow perpendicular to the cylinder axes, and flow parallel to the axes. In each case two new approximate procedures were used. In the first procedure, one solves the equation of flow in a Voronoi cell around the fiber, and averages over the distribution of the Voronoi cells. The second procedure is an extension to oscillating air flow of the Brinkman self-consistent procedure for dc flow. The procedures are valid for volume concentration of cylinders less than 0.1. The calculations show that for the density of fibers of interest for acoustic fiber materials the simple self-consistent procedure gives the same results as the more complicated procedure based on average over Voronoi cells. Graphs of the dynamic resistivity versus frequency are given for fiber densities and diameters typical for acoustic fiber materials.

Use of a magnified cardiac airflow oscillation to classify neonatal apnea.

Currently the classification of neonatal apnea relies upon an inference of airway closure based upon the presence of breathing efforts against such an obstruction. In this study we evaluate a new method of classification which utilizes the presence or absence of cardiac airflow oscillation to detect airway closure. Specifically, this evaluation consisted of an examination of the transmission characteristics of an artificially produced airflow oscillation through discrete airway narrowing in a model system; a confirmation that voluntary upper airway occlusion in adult volunteers uniformly induces complete loss of the oscillation; and a comparison of the cardiac oscillation method with the traditional method of apnea classification in a cohort of 4,309 apneas in 32 infants. We determined that the amplitude of the oscillation is negatively correlated with resistance (r = 0.97) and positively with the radius (r = 0.98) of narrowing in a model system, and that voluntary airway obstruction in adult subjects uniformly results in loss of transmitted cardiac oscillations. Moreover, although there was similarity in the frequency distribution of central, obstructive, and mixed apneas in our infants, there were statistically significantly greater obstructive events detected by the cardiac oscillation method. In addition, the cardiac oscillation method had the additional advantage of providing information regarding the timing of airway obstruction during apnea.

Role of syringeal muscles in controlling the phonology of bird song.

1. The contribution of syringeal muscles to controlling the phonology of song was studied by recording bilateral airflow, subsyringeal air sac pressure, electromyograms (EMGs) of six syringeal muscles, and vocal output in spontaneously singing brown thrashers (Toxostoma rufum). 2. EMG activity in musculus syringealis ventralis (vS), the largest syringeal muscle, increases exponentially with the fundamental frequency of the ipsilaterally generated sound and closely parallels frequency modulation. 3. The EMG activity of other syringeal muscles is also positively correlated with sound frequency, but the amplitude of their EMGs changes only a small amount compared with variation in the amplitude of their EMGs correlated with changing syringeal resistance. The elevated activity in all syringeal muscles during high-frequency sounds may reflect an increased need for structural stability during the strong contractions of the largest syringeal muscle (vS). 4. Several syringeal mechanisms are used to generate amplitude modulation (AM). The most common of these involves modulating the rate of syringeal airflow, through activity by adductor (m. syringealis dorsalis and m. tracheobronchialis dorsalis) and abductor (m. tracheobronchialis ventralis) muscles, which change syringeal resistance, switch sound production from one side of the syrinx to the other, or produce rapid oscillatory flow changes. Variation in the phase relationship between AM and EMG bursts during oscillatory airflow suggests complex biomechanical interaction between antagonistic muscles. 5. AM can also arise from acoustic interactions of two independently generated sounds (beat notes) including cross talk signals between the two syringeal halves. In this latter mechanism, sound generated on one side radiates slightly out of phase with the source from the contralateral side, resulting in lateralized AM generation.

OVERT AND SILENT OBSTRUCTIVE APNEAS DO NOT DIFFER IN VENTILATORY PARAMETERS IN THE MINUTE PRECEDING THE APNEA. † 2010

Airway obstruction can be defined by the complete absence of a transmitted cardiac airflow oscillation in the flow tracing during an apnea. It may be further classified as overt or silent depending on the presence or absence of breathing efforts against the obstruction. Many patients manifest both types of obstructive apnea during an apnea study. We hypothesized that the presence or absence of a breathing effort response to obstruction is reflected in differences in oxygenation and/or ventilation in the minute prior to the apnea. To test this, we examined 3056 apneas of ≥ 3 s duration in 24 infants [birth weight 2100±190 g (mean±SE), study weight 2765±220 g, gestational age 33±1 wk, postnatal age 35±5 d] studied on 27 occasions, yielding 51 overt and 45 silent obstructive apneas. Although there was a significant difference in apnea duration between overt and silent types (13.0±1.25 vs 7.2±0.55s, p < 0.005), we detected no differences in oxygen saturation (97±0.7 vs 91±4.8), minute ventilation (0.249±0.011 vs 0.240±0.017 L·min-1·kg-1), respiratory rate (35±2 vs 37±2 breaths per minute), tidal volume (7.3±0.4 vs 6.6±0.4 ml·kg-1) and PACO2 (38±4 vs 35±1 Torr) in the minute preceding the apneas. These findings suggest that 1). The presence or absence of breathing efforts which defines overt and silent obstructive apnea respectively, is not attributable to differences in either oxygenation or ventilation in the minute prior to the apnea; and 2). the observed difference in apnea length between silent and overt obstructions, and the fact that no apneas have ever contained elements of both obstruction types, supports the idea that overt and silent obstructions have different underlying pathophysiologic mechanisms. Supported by the Canadian Lung Association, & Children's Hospital of Winnipeg Research Foundation.

EVIDENCE OF A CRITICAL PERIOD OF AIRWAY INSTABILITY DURING CENTRAL APNEAS IN PRETERM INFANTS. • 2314

We have developed a method of apnea classification which relies on the transmission of cardiac airflow oscillation to indicate airway patency. Using a theoretical model we have previously shown that the amplitude of the cardiac airflow oscillation is proportional to airway diameter for small lumens. While in the majority of central apneas, the amplitude of the cardiac airflow oscillation remains constant, there is a subset of events where the waveform decreases with time. We hypothesized that this is not a random occurrence but reflects a critical period of airway instability during a central apnea. To test this we examined 212/1257 central apneas in 12 infants [birth weight 1625±240 g (mean±SE), study weight 2065±270 g, gestational age 30±1 wk, postnatal age 35±9 d] referred to our laboratory. The amplitude of the cardiac airflow oscillation produced by each individual heart beat during an apnea was measured and tabulated to provide a dynamic measure of changes in airway diameter with time. To allow for comparisons between patients the amplitude of each cardiac airflow oscillation was expressed as a proportion of the maximum amplitude observed in each infant. We then compared the amplitude at multiple successive 0.5 second intervals with the amplitude of the cardiac airflow oscillation observed at the apnea outset using an ANOVA. We found a significant decrease in cardiac airflow oscillation after only one second (initial=0.609±0.215, vs. 0.5s=0.611±0.213, p=0.53; vs. 1s=0.589±0.235, p≤0.01; vs. 2s=0.471±0.301, p≤0.001) irrespective of the apnea duration (3 to 16 s). We conclude that airway narrowing during central apnea is not a random occurrence but occur shortly after the onset of the apnea. We speculate that the phenomenon is secondary to passive airway relaxation. Supported by Canadian Lung Association and Children's Hospital of Winnipeg Research Foundation.

COMPARISON OF THE PREVALENCE OF SILENT AND OVERT AIRWAY OBSTRUCTIONS DURING APNEA IN PRETERM AND TERM INFANTS. † 2011

We have previously described a system of infant apnea classification which relies on the presence or absence of a cardiac airflow oscillation during apnea to detect airway obstruction. Obstructive apneas are defined by absence of oscillations during the entire apnea. By noting a patient's respiratory efforts in response to obstruction one can further classify obstructive apneas as either overt or silent. Overt obstructions correspond to classically defined obstructive apnea where the patient makes respiratory efforts against the obstruction throughout the apnea. Although the prevalence of such overt obstruction in preterm and term infants is well known, data on silent obstructions are lacking. We therefore decided to examine the prevalence of these types of apneas in 17 preterm infants [BW 1590±150 g(means±SE), SW 2330±260 g, GA 30±0.7 wk, PNA 41±7 d] and 8 term infants [BW 3190±125 g, SW 3590±250 g, GA 40±0.3 wk, PNA 23±4 d] referred to our laboratory for investigation of apnea. A total of 2674 apneas ≥ 3 seconds (preterm 1357, term 1317) were analyzed yielding 68 overt and 108 silent obstructions. There were significantly more overt (60 vs 7, p < 0.001, Chi square) and silent(57 vs 31, p ≤ 0.01) obstructions in preterm infants when compared to term infants. While both apnea types were equally common in preterm infants (57 silent vs 60 overt), silent obstructions were four times more prevalent than overt obstructions in term infants (31 silent vs 7 overt). We conclude that preterm infants have a high prevalence of silent obstructions. We speculate that the lack of apparent deleterious effects with silent obstructions in term infants relates to i) the low prevalence of these events, andii) the greater maturity of the respiratory control system. Supported by Can. Lung Assoc. & Child. Hosp. Res. Found.

Characteristics of Loss at Rectifying Valve (Water-Valve) in a Wave Power Conversion System with Water-Valve Rectifer

This paper deals with a wave power generation system with water-valve rectifer. The water-valve rectifer converts oscillating air flow into steady air flow. The rectifier doesn't have a mechanical moving element, so the system is simple and maintenance free. However, because of the characteristic form of the rectifier, the loss in the rectifier is large and it is difficult to understand the characteristics of loss. In the paper, we indicate the characteristics by changing the cross-sectional area and the number of air pipes which affects the loss of water-valve rectifier.

Effects of combined treatment with rhDNase and airflow oscillations on spinnability of cystic fibrosis sputum in vitro.

Treatment with either rhDNase or high-frequency oscillation has been shown to be effective in improving the physical and transport properties of airway secretions in cystic fibrosis (CF). The objects of this in vitro study was to examine whether combined treatment with oscillation and rhDNase results in greater change of CF sputum spinnability than either treatment by itself. Aliquots of sputum (0.4 g) from eight CF patients were subjected to the following protocols for 15 minutes and then followed for a total of 30 minutes: 1) incubation with 0.04 ml DNase 50 micrograms rhDNase/normal saline (10% dilution) at 37 degrees C to achieve 5 micrograms DNase/g of sputum final concentration; 2) airflow oscillation at 27 Hz similar to the airflow magnitude produced by a commercial high-frequency chest compression (HFCC) device; 3) negative control with no treatment; 4) positive (dilution) control, incubating with 10% saline by volume; 5) combination of DNase and oscillation, and 6) combination of saline and oscillation. For each protocol, sputum spinnability (in mm, mean +/- SD) was measured by means of a filancemeter at baseline, 15, and 30 minutes. Treatment with DNase decreased spinnability significantly more than either saline or oscillation at 15 and 30 minutes (P < 0.02 and P < 0.04, respectively). Incubation with saline or oscillation of CF sputum for 15 and 30 minutes decreased spinnability significantly compared with control. The combination of DNase and oscillation decreased spinnability significantly more than treatment with DNase alone (3.74 +/- 0.45 vs. 6.54 +/- 0.73 at 15 minutes, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)