Search

The particle deposition in human upper airway and lung airways were intensively studied. Most of the investigations considered the flow as steady, and the flow was either laminar or turbulent. However, the actually respiratory flow is strongly dependant on time, and the unsteadiness would affect the particle deposition significantly. In this study, we compared the respiratory flow and particle deposition in CT-scanned human upper airway with both steady and unsteady model in laminar regime. The result indicates that the unsteady effect has significant influence on flow and particle deposition in human upper airways.

A common way of obtaining information about a physiological system is to measure one or more signals from the system, consider their temporal evolution in the form of numerical time series, and obtain quantitative indexes through the application of time series analysis techniques. While historical approaches to time series analysis were addressed to the study of single signals, recent advances have made it possible to study collectively the behavior of several signals measured simultaneously from the considered system. In fact, multivariate (MV) time series analysis is nowadays extensively used to characterize interdependencies among multiple signals collected from dynamical physiological systems. Applications of this approach are ubiquitous, for instance, in neurophysiology and cardiovascular physiology (see, e.g., (Pereda et al., 2005) and (Porta et al., 2009) and references therein). In neurophysiology, the time series to be analyzed are obtained, for example, sampling electroencephalographic (EEG) or magnetoencephalographic (MEG) signals which measure the temporal dynamics of the electro-magnetic fields of the brain as reflected at different locations of the scalp. In cardiovascular physiology, the time series are commonly constructed measuring at each cardiac beat cardiovascular and cardiorespiratory variables such as the heart period, the systolic/diastolic arterial pressure, and the respiratory flow. It is well recognized that the application of MV analysis to these physiological time series may provide unique information about the coupling mechanisms underlying brain dynamics and cardiovascular control, and may also lead to the definition of quantitative indexes useful in medical settings to assess the degree of mechanism impairment in pathological conditions. MV time series analysis is not only important to detect coupling, i.e., the presence or absence of interactions, between the considered time series, but also to identify driver-response relationships between them. This problem is a special case of the general question of assessing causality, or cause-effect relations, between (sub)systems, processes or phenomena. The assessment of coupling and causality in MV processes is often performed by linear time series analysis approaches, i.e. approaches in which a linear model is supposed to underlie the generation of temporal dynamics and interactions of the considered signals (Kay, 1988; Gourevitch et al., 2006). While non-linear methods are continuously under development

Snoring is a breathing noise caused by coupled oscillation of the walls of the airway as the air passes through. It occurs in at least 20% of the general population. Snoring is recognized as a cardinal symptom of sleep apnea. The snorers, compared with non-snorers, generate more negative inspiration pressure, prolonged inspiration time, and limitation of respiratory flow. Therefore, it may cause impaired daytime performance, sleepiness and nocturnal awakenings, which may increase traffic accidents. In this study, a pillow with contact microphones was developed to detect snoring sounds and restrain snoring by inflation of air bladder located inside the pillow. Experiment was performed to adjust the threshold value in order to separate the snoring sounds from the environment sounds. Then, clinical evaluation was performed at the sleep center to verify the effectiveness of the pillow. A volunteer was participated for two nights. Regular foam pillow and developed pillows were used for the first and second nights, respectively. Snoring times were reduced 49.8%, the average snoring episodes in minutes were increased 0.2 minutes (12 seconds), and longest snoring episodes were reduced down to 43.8% with the use of developed pillow. It means that the volunteer underwent much less snoring with the use of the developed pillow. The further study would be continued for more wide clinical studies with various inflation/deflation conditions of air bladder.

Statistical analysis, power spectral density, and Lempel Ziv complexity, are used in a multi-parameter approach to analyze four temporal series obtained from the Electrocardiographic and Respiratory Flow signals of 126 patients on weaning trials. In which, 88 patients belong to successful group (SG), and 38 patients belong to failure group (FG), i.e. failed to maintain spontaneous breathing during trial. It was found that mean values of cardiac inter-beat and breath durations give higher values for SG than for FG; Kurtosis coefficient of the spectrum of the rapid shallow breathing index is higher for FG; also Lempel Ziv complexity mean values associated with the respiratory flow signal are bigger for FG. Patients were then classified with a pattern recognition neural network, obtaining 80% of correct classifications (81.6% for FG and 79.5% for SG).

In the present study we modeled the time dependent velocity profile of human upper airway during pranayama. The human upper airway is the passage that allows the interchange of gases between the lungs and the ambient air. During the process of inspiration, the upper airway plays an important role in warming, humidifying and cleaning the air. The objective of this paper is to investigate the influence of pressure waveform and velocity profiles in human lungs bifurcation. An attempt is made to formulate an unsteady two dimensional bifurcation of human lungs airway in the upper respiratory system. Flow of air (oxygen) in the lung is considered as Newtonian fluid. The cylindrical coordinate system has been taken for analytical formulation. A qualitative analysis of numerical results has finally been performed together with their discussion at length in order to validate the applicability of the present mathematical model.

Patient-specific or subject-specific biofluid dynamics modelling has been an active area of research over the last 10 years. This is one of the advancing areas of research in computer-assisted biomechanics and it has started making an impact in terms of clinical use. However, the progress has been slow and the day-to-day use of modelling as a clinical tool is a long way away. This presentation investigates the genuine reasons for the slow progress and it also addresses how progress could be accelerated.

The pectoral muscles in birds comprise up to a third of the body weight and provide the principal drive to the wing. Their attachment to the sternum suggests that they could compress the thorax and assist ventilation during flight. Most, but not all, birds have an integer ratio relationship between wingbeat and breathing frequency, but no measurements of the respiratory flow associated with the act of wingbeat are available. We recorded respiratory flow and wing timing in three starlings that flew at 22 knots (11 m·s −1 ) for up to 5 min in a wind tunnel. Triggering on wingbeat, we ensemble averaged flow records for many wingbeats in each flight. Because wingbeats occured throughout the respiratory cycle, breathing flow tended to average to zero, and a small flow event related to wingbeat emerged. The volume change associated with wingbeat ranged from 3 to 11% of tidal volume, and this is probably an overestimate. We conclude that wingbeat and breathing in starlings are essentially mechanically independent, despite the direct attachment of the locomotor muscles to the thorax.

Respiratory drives folow various afferent pathways to the respiratory centres; nevertheless, steady-state breathing patterns described in terms of tidal volumes and phase durations are largely independent of the nature of the respiratory stimulus. Flow has now been recorded during steady states from six subjects in rest and hyperpnoea induced by exercise, and hypercapnia in euoxia and in hypoxia (asphyxia). Flow patterns from different stimuli were compared isopnoeically. Quantitative methods allowed the patterns to be described in terms of several variables. The consistent small differences in isopnoeic flow patterns were: In asphyzia, the initial inspiratory acceleration was greater than in hypercapnia, and the peak flow was reached earlier. In exercise the peak flow occured later in inspiration, and the expiratory flow was maintained high until nearer the end of the phase than with the chemical drives so that the flow pattern was less angular in shape. Stimulus-dependent effects, obvious during transient changes, are greatly attenuated rather than absent in steady states.

Background Although inspiratory assist of spontaneous breathing in intubated patients is common, expiratory assist functions have rarely been reported. Effective expiratory support (ES) could be used to compensate for endotracheal tube (ETT) resistance during spontaneous breathing. In this study, we examined the performance of a new system designed to provide both inspiratory support (IS) and ES during spontaneous breathing with the goal of reducing the effective resistance of the ETT. Methods The ES system consisted of a ventilator demand valve and a computer-controlled piston cylinder, which aspirated gas from the respiratory circuit during the expiratory phase. The movement of the piston was synchronized with spontaneous breathing. We compared the pressures at the tip of the ETT and in the breathing circuit during spontaneous breathing through an ETT of internal diameter (ID) 5 mm with that of an ETT with ID 8 mm in nine healthy adult male volunteers. The ventilatory mode was set to maintain a continuous airway pressure of 0 cm H(2)O. Three ventilator settings (no support, IS only, and IS plus ES) were compared using ID 5 mm ETT. Results We monitored pressure in the breathing circuit (P(aw)), ETT tip pressure (P(tip)), and respiratory flow. The P(tip) of the ID 5 mm ETT showed a large negative deflection during inspiration and a positive deflection during expiration without support. IS alone did not improve the respiratory pattern through the small ETT. However, IS plus ES resulted in negative P(aw) during expiration in addition to positive deflection of P(aw) during inspiration, making the pressure characteristics of P(tip) similar to those of ID 8 mm ETT. Moreover, IS plus ES produced a respiratory pattern through the ID 5 mm ETT that was similar to that through the ID 8 mm ETT. Conclusions In this study of healthy volunteers, IS plus ES compensated for the airway resistance imposed by a ID 5.0 mm ETT to create pressure changes at the tip of the ETT similar to those of an ID 8.0 mm ETT.

In breathing model study, most research focus on the characteristic of breathing system. Less study concentrate on the breath power. In order to get the sponeous breath model, respiratory muscle pressure must be taken into consideration. In this paper, the respiratory muscle pressure of autonomous respiration is used as source power and the simplest linear model is used in the model construction. Simulink is utilized as the tool, respiratory flow is obtained, which validated the model.

The inhalation of micron-sized aerosols into the lung's acinar region may be recognized as a possible health risk or a therapeutic tool. In an effort to develop a deeper understanding of the mechanisms responsible for acinar deposition, we have numerically simulated the transport of nondiffusing fine inhaled particles (1 mum and 3 microm in diameter) in two acinar models of varying complexity: (i) a simple alveolated duct and (ii) a space-filling asymmetrical acinar branching tree following the description of lung structure by Fung (1988, "A Model of the Lung Structure and Its Validation," J. Appl. Physiol., 64, pp. 2132-2141). Detailed particle trajectories and deposition efficiencies, as well as acinar flow structures, were investigated under different orientations of gravity, for tidal breathing motion in an average human adult. Trajectories and deposition efficiencies inside the alveolated duct are strongly related to gravity orientation. While the motion of larger particles (3 microm) is relatively insensitive to convective flows compared with the role of gravitational sedimentation, finer 1 microm aerosols may exhibit, in contrast, complex kinematics influenced by the coupling between (i) flow reversal due to oscillatory breathing, (ii) local alveolar flow structure, and (iii) streamline crossing due to gravity. These combined mechanisms may lead to twisting and undulating trajectories in the alveolus over multiple breathing cycles. The extension of our study to a space-filling acinar tree was well suited to investigate the influence of bulk kinematic interaction on aerosol transport between ductal and alveolar flows. We found the existence of intricate trajectories of fine 1 microm aerosols spanning over the entire acinar airway network, which cannot be captured by simple alveolar models. In contrast, heavier 3 microm aerosols yield trajectories characteristic of gravitational sedimentation, analogous to those observed in the simple alveolated duct. For both particle sizes, however, particle inhalation yields highly nonuniform deposition. While larger particles deposit within a single inhalation phase, finer 1 microm particles exhibit much longer residence times spanning multiple breathing cycles. With the ongoing development of more realistic models of the pulmonary acinus, we aim to capture some of the complex mechanisms leading to deposition of inhaled aerosols. Such models may lead to a better understanding toward the optimization of pulmonary drug delivery to target specific regions of the lung.

In breathing model study, most research focus on the characteristic of breathing system. Less study concentrates on the breath power. In order to get the spontaneous breath model, respiratory muscle pressure must be taken into consideration. In this paper, the respiratory muscle pressure of autonomous respiration is used as source power and the simplest linear model is used in the model construction. Control Design and Simulation module in LabVIEW is utilized as the tool, respiratory flow is obtained, which validated the model.

We measured purring in unrestrained intact pumas, cheetahs and domestic cats. Domestic cats, Felis silvestris f. catus, purr at a frequency of 26·3 ±; 1·95 (S.D.) Hz. The frequency at mid-expiration exceeds that at mid-inspiration by 2·4 ± 1·3 Hz. Purring frequency for individuals does not change with age. Purring can occur simultaneously with other vocalization. Two-channel acoustic measurements confirm that the primary mechanism for sound and vibration production is a centrally driven laryngeal modulation of respiratory flow. The diaphragm and other muscles appear to be unnecessary for purring other than to drive respiration.

Capnography waveforms and capnometry are useful perioperative monitoring tools. The paramagnetic oxygen analyzers incorporated in many clinical monitoring systems estimate oxygen concentration in the breathing circuit during various phases of ventilation. The oxygen concentration is plotted as a real-time waveform and displayed as an oxygraph. However, the clinical utility of oxygraphy is under evaluated. We are reporting four different clinical scenarios in neurosurgical patients, wherein the information yielded by oxygraphy were either not available on the capnograph or were revealed in a more promising way on the oxygraph than on the capnograph. A real-time oxygraphy waveform has four phases similar to a capnograph, although displayed in a reverse manner. Oxygraphy was useful in our patient to determine the adequacy of preoxygenation. Airway complications and unwanted neuromuscular recovery can be detected earlier by oxygraphy compared to capnography. The oxygraphy peak-to-baseline scale difference can be compressed to as low as to 6% of oxygen concentration. When the peak-to-baseline scale difference is 6 mmHg, the oxygraph becomes sensitive to even minute changes in respiratory flow characteristics. Oxygraphy may have a potential role in clinical monitoring.

Infant monitoring is a common procedure in clinical practice in neonatal critical care units. A number of vital functions are monitored, such as heart beat, breathing, blood flow, etc. Specifically, preterm and/or low-birth-weight infants often present respiratory problems that require monitoring. These may range from insufficient ventilation to apnoea. One of the most common events that may affect the respiratory flow is crying, a physiological action made by the infant to communicate and draw attention, but, for a preterm infant, this action requires great effort, which may cause distress and even may have an adverse impact on blood oxygenation. Acoustic analysis of newborn infant cry is thus of importance, since it is related to other basic neuro-physiological parameters. Being easy to perform, cheap and completely non-invasive, it can be successfully applied in many circumstances. The newborn infant cry is characterised by very high fundamental frequency ( F 0 ) and resonance frequency (RFs) values, with abrupt changes and voiced/unvoiced features of very short duration in a single utterance. To deal with such signals, a new user-friendly software tool has been developed, that allows robust tracking of main acoustic parameters on very short and time-varying signal frames. The software developed provides the user with a high-resolution picture of the cry signal characteristics.

In the present document, the design and the construction of a low cost digital spirometer is presented like a basic tool for evaluate of the respiratory capacity. A Spirometer is the ideal instrument to measure the mechanics ventilatoria in respiratory studies that allow the analysis, determination and monitoring of diverse human respiratory diseases like asthma, pulmonary embolism, respiratory bronchitis and others deficiencies. The spirometer developed is an instrument portable, of easy handling and computerized that fulfills with the American norms given by the American Thorax Society (ATS) and the requirements of the Mexican population. By means of digital electronics and a pneumotachometer, the virtual instrument acquires and the respiratory flow using a NI USB interface. The volume-time and flow-volume graphs are displayed means a virtual instrument developed in Labview. The spirometrics test includes parameters of the mechanics ventilatoria like the FEV1 (Forced Expiratory Volume in the first second), FVC (Forced Vital Capacity), and MEF (Maximum Expiratory Flow).

The degree of accuracy of anterior rhinomanometry and the plethysmographic method in determining nasal resistance was examined in a mechanical model. The plethysmographic method allows a precise estimation of nasal resistance. It was found that the absolute variation of the plethysmographically measured values is not greater than 5%. Anterior rhinomanometry as described by Bachmann (2) allows a valid estimation of the pressure-flow relation. Here, too, inaccuracy remains within a range of 5% if the values are recorded with an X-Y-plotter. With the system developed by EVG, a microprocessor-controlled analysis is also possible. The flow rate is measured at pressure rates of 75, 150, and 300 Pa. Inconstancies in respiratory flow cause deviations from the correct pressure-flow graph. Should these deviations accidentally coincide with the predefined points of evaluation these erroneously achieved results will be assumed to be representative for the whole graph. This analytical fault has meanwhile been corrected by interpolating the points at the predefined pressure rates. Due to the differences in analytic techniques the methods of determining nasal resistance are not comparable in practice. The authors therefore recommend that, in addition to the usual results of analysis, average value of nasal resistance be determined for each measuring procedure. Today, this can be done without any problem by using microprocessors.

1. Resonant frequency of the chest-lung system in six tracheotomized, spontaneously breathing dogs was determined by analyzing the shape of the respiratory flow curve. 2. The resonant frequency was calculated from the periodic deviations from a sinusoidal flow pattern observed in the inspiratory phase of the breathing cycle. 3. Mean (+/- S.D.) resonant frequency was 6.1 +/- 0.9 Hz which was very close to the panting frequency (5.7 Hz) of the same dogs. 4. Resonant frequencies of the respiratory system in various species are compared.

This subchronic inhalation study compared the effects of nose-only exposure in hamsters to the smoke from the University of Kentucky 1R4F reference cigarette, which burns tobacco, and a test cigarette, which only heats tobacco. Thirty-four Syrian golden hamsters per sex per group were exposed to either reference or test smoke at 0, 120, 350, or 640 pg wet total particulate matter (WTPM)/l of air, 1 h/day, 5 days/wk. Of these 34 hamsters, 9 hamsters/sex/group were evaluated for respiratory flow, blood carboxyhemoglobin, and plasma nicotine and coining during the first 12 wk of exposure and then killed. Another 75 of the 34 hamsters/sex/group were killed and evaluated after 13 wk of exposure (Basic Study); the remaining 10 hamsters/sex/group were held without smoke exposure for an additional 6 wk (Recovery Croup). Clinical appearance, mortality body and selected organ weights, and gross and histologic changes were examined in hamsters killed after 13 wk of exposure and 6 wk after cessation of exposu...

While lung sounds intensity is significantly different during inspiratory and expiratory phases, such difference is not audible between the two respiratory phases when listening to tracheal breath sounds. In this study we investigated whether any difference exists between the average power and log-variance of the band-pass filtered tracheal breath sound between the respiratory phases. We used data from 9 healthy subjects without any pulmonary diseases at 4 different flow rates (low, medium, high and very high) and compared the two features at six different frequency ranges from 70 to 1200Hz. The most pronounced differences between the two respiratory phases were found in the 300-450Hz and 800-1000Hz for the average power and log-variance, respectively.

Patients who need an x-ray while under anesthesia are at risk because clinicians turn off the anesthesia ventilator for an x-ray and may forget to turn it back on afterwards. This problem occurred in a case study reported by the Anesthesia Patient Safety Foundation in 2004. We demonstrate a system in which automatic synchronization of the x-ray exposure with ventilation eliminates the need to turn off the ventilator to obtain an x-ray. This is accomplished by triggering the x-ray (simulated with a web camera) with the respiratory flow signal.

For any respiratory sound analysis or assessment, respiratory flow must also be measured simultaneously with the sounds. However, due to difficulties and/or inaccuracy of the most flow measurement techniques, several researchers have attempted to estimate flow from respiratory sounds. However, all of the proposed methods heavily depend on the availability of different rates of flow for calibration of the model, which makes their use limited by a large degree. In this paper, a robust and novel method for estimating flow using entropy of the band pass filtered tracheal sounds is proposed. The proposed method is independent of the flow rate chosen for calibration; it requires only one breath for calibration and can estimate any flow rate even out of the range of calibration flow. The method was tested on data of 10 healthy subjects at three different flow rates above 15 ml/s/kg. The estimation error was found to be 7.3 plusmn 2.0% and 7.4 plusmn 3.2% for inspiration and expiration phases, respectively

Brachycephalic obstructive airway syndrome (BOAS) is an important health and welfare problem in several popular dog breeds. Whole-body barometric plethysmography (WBBP) is a non-invasive method that allows safe and repeated quantitative measurements of respiratory cycles on unsedated dogs. Here respiratory flow traces in French bulldogs from the pet population were characterised using WBBP, and a computational application was developed to recognise affected animals. Eighty-nine French bulldogs and twenty non-brachycephalic controls underwent WBBP testing. A respiratory functional grading system was used on each dog based on respiratory signs (i.e. respiratory noise, effort, etc.) before and after exercise. For development of an objective BOAS classifier, functional Grades 0 and I were considered to have insignificant clinical signs (termed here BOAS-) and Grades II and III to have significant signs (termed here BOAS+). A comparison between owner-perception of BOAS and functional grading revealed that 60 % of owners failed to recognise BOAS in dogs that graded BOAS+ in this study.WBBP flow traces were found to be significantly different between non-brachycephalic controls and Grade 0 French bulldogs; BOAS- and BOAS+ French bulldogs. A classifier was developed using quadratic discriminant analysis of the respiratory parameters to distinguish BOAS- and BOAS + French bulldogs, and a BOAS Index was calculated for each dog. A cut-off value of the BOAS Index was selected based on a receiver operating characteristic (ROC) curve. Sensitivity, specificity, positive predictive value, and negative predictive value of the classifier on the training group (n=69) were 0.97, 0.93, 0.95, and 0.97, respectively. The classifier was validated using a test group of French bulldogs (n=20) with an accuracy of 0.95. WBBP offers objective screening for the diagnosis of BOAS in French Bulldogs. The technique may be applied to other brachycephalic breeds affected by BOAS, and possibly to other respiratory disease in dogs.

Background Maximum pressures developed by the respiratory muscles can indicate the health of the respiratory system, help to determine maximum respiratory flow rates, and contribute to respiratory power development. Past measurements of maximum pressures have been found to be inadequate for inclusion in some exercise models involving respiration. Methods Maximum inspiratory and expiratory airway pressures were measured over a range of lung volumes in 29 female and 19 male adults. A commercial bell spirometry system was programmed to occlude airflow at nine target lung volumes ranging from 10% to 90% of vital capacity. Results In women, maximum expiratory pressure increased with volume from 39 to 61 cmH2O and maximum inspiratory pressure decreased with volume from 66 to 28 cmH2O. In men, maximum expiratory pressure increased with volume from 63 to 97 cmH2O and maximum inspiratory pressure decreased with volume from 97 to 39 cmH2O. Equations describing pressures for both sexes are: Pe/Pmax = 0.1426 Ln( %VC) + 0.3402 R2 = 0.95 Pi/Pmax = 0.234 Ln(100 - %VC) - 0.0828 R2 = 0.96 Conclusion These results were found to be consistent with values and trends obtained by other authors. Regression equations may be suitable for respiratory mechanics models.

Protection of the human respiratory system from exposure to nanoparticles is becoming an emerging issue in occupational hygiene. The potential adverse health effects associated with particles of approximately 1-100 nm are probably greater than submicron or micron-sized particles. The performance of two models of N95 half-facepiece-filtering respirators against nano-sized particles was evaluated at two inhalation flow rates, 30 and 85 l min(-1), following a manikin-based protocol. The aerosol concentration was measured outside and inside the facepiece using the Wide-Range Particle Spectrometer. Sodium chloride particles, conventionally used to certify N-series respirators under NIOSH 42 CFR 84 regulations, were utilized as the challenge aerosol. The targeted particle sizes ranged from 10 to 600 nm, although the standard certification tests are performed with particles of approximately 300 nm, which is assumed to be the most penetrating size. The results indicate that the nanoparticle penetration through a face-sealed N95 respirator may be in excess of the 5% threshold, particularly at high respiratory flow rates. Thus, N95 respirators may not always provide the expected respiratory protection for workers. The highest penetration values representing the poorest respirator protection conditions were observed in the particle diameter range of approximately 30-70 nm. Based on the theoretical simulation, we have concluded that for respirators utilizing mechanical filters, the peak penetration indeed occurs at the particle diameter of approximately 300 nm; however, for pre-charged fiber filters, which are commonly used for N95 respirators, the peak shifts toward nano-sizes. This study has confirmed that the neutralization of particles is a crucial element in evaluating the efficiency of a respirator. The variability of the respirator's performance was determined for both models and both flow rates. The analysis revealed that the coefficient of variation of the penetration ranged from 0.10 to 0.54 for particles of 20-100 nm in diameter. The fraction of N95 respirators for which the performance test at 85 l min(-1) demonstrated excessive (>5%) penetration of nanoparticles was as high as 9/10. The test results obtained in a relatively small (0.096 m(3)) test chamber and in a large (24.3 m(3)) walk-in chamber were found essentially the same, thus, suggesting that laboratory-based evaluations have a good potential to adequately represent the respirator field performance.

The possible mechanism of wheeze generation in tracheostenosis was identified by measuring inspiratory and expiratory flow in a “morphological and distensible” realistic tracheostenosis model. The shape of the model was based on CT (Computed Tomography) images of a patient that had tracheostenosis. A trachea consists of tracheal cartilage rings and smooth muscle. Spatial variation of wall distensibility was achieved in the model by varying the wall thickness based on the elastic modulus measured in pig airways. The spatial variation influenced the flow in the airway and the turbulence production rate decreased faster at smooth muscles. Using the model, we investigated the mechanism of wheeze generation by focusing on the turbulence intensity. The turbulence intensity in expiratory flow was about twice that in inspiratory flow, and larger vortices existed in post-stenosis in expiratory flow, and thus might contribute to wheeze generation.

In order to advance our understanding of the relation between respiration and deglutition, simultaneous videofluoroscopy and respirodeglutometry was performed. Fifteen normal, healthy, young adults (20–29 years of age) were connected to a respirodeglutometer and positioned for simultaneous videofluoroscopic assessment in the lateral plane. Subjects performed three swallows each of a 5-ml and a 10-ml bolus of liquid barium and a 5-ml bolus of paste barium, for a total of nine swallows per subject. Location of the bolus head as identified with videofluoroscopy was associated with eight respirodeglutometric variables. In addition, temporal relations for seven respirodeglutometric variables were calculated as a function of bolus volume and viscosity. Significant temporal differences were found for five of the variables by volume. No significant temporal differences were noted by viscosity. Expiration occurred before 79% and after 96% of the swallows. The number of inspirations preceding a swallow suggested a possible effect resulting from the need to hold a bolus in the mouth before receiving instructions to swallow during videofluoroscopic assessment. This effect may be important during patient evaluation. For a significant number of swallows, respiratory flow ceased before the velum was fully elevated.

Summary The effects of training on ventilation and blood gases during exercise were investigated in 6 clinically normal, detrained Thoroughbred horses. They underwent a 16 week training programme similar to the type frequently used for Thoroughbred racehorses in Great Britain. Standardised treadmill exercise tests (2 min canter at 8 and 10 m/s [C8 and C10] and 2 min gallop at 12 m/s [G12], on a level surface) were performed prior to and after 16 weeks of training. Respiratory flow rates were measured using ultrasound flow transducers. Blood samples were drawn from a transverse facial artery and the right atrium. Minute ventilation, respiratory frequency and tidal volume were not significantly altered by training. Peak inspiratory flow rate was lower following training at 8 and 10 m/s, but not at 12 m/s. Arterial oxygen tension was decreased during trot and canter following training. Blood lactate concentration post G12 decreased following training (10.5 ± 2.2 mmol/l vs. 7.7 ± 2.2 mmol/l; P

The authors present a new technique for studying airflow patterns and particle deposition in the nasopharynx. The nasal cavities and the nasopharynx from the head of a human cadaver were filled with siliconrubber and a "positive" model was then produced by moulding with plastic. An apparatus was constructed to provide calibrated flow of propandiol in both directions. Flow characteristics were visualized by introducing small particles in suspension or by injecting methylene blue with a needle. In addition, test aerosol was drawn in through the model to demonstrate dust deposition sites in the nasopharynx. In the future, this method will enable us to examine the nasopharyngeal airflow patterns and deposition sites of inhaled particles.

ResMed Autoset (AS) is a simplified diagnosis system for obstructive sleep apnoea/hypopnoea syndrome (OSAS) based on the respiratory flow/time relationship by pressure variation measured through simple nasal prongs. A multicentre prospective trial was used to compare AS and polysomnography (PSG) for diagnosing 95 patients, with suspected OSAS. Physicians gave a pretest probability of the patient having OSAS. The apnoea/hypopnoea index (AHI) was compared between the two methods of diagnosis for the whole population and for subgroups according to the pretest probability. Twenty-four patients had AHI < 15 events x h(-1) on PSG and 19 AHI 15-30, and 52 patients had AHI > or = 30. Correlation between AHI assessed by AS and PSG was r=0.87 for total sleep time (TST), p or = 15 events x h(-1) to diagnose OSAS, AS has a sensitivity of 92%, specificity of 79%, positive predictive value of 93% and negative predictive value of 76%. With a pretest probability > or = 80%, sensitivity and positive predictive value were 98 and 100% respectively. Of six false negative, four had a high pretest probability (> 80%) or Epworth score > or = 10. Using these parameters as a criterion for proceeding to PSG after a negative AS study would mean that two apnoeic patients (AHI 20 and 17 events x h(-1) by PSG) would escape detection. The Autoset is useful for the detection of obstructive sleep apnoea but with high pretest probability and a negative Autoset result polysomnography should be performed.

Average respiratory flow profiles during steady breathing have been of interest as an output of the respiratory controller. However, in the process of determining average flow profiles, distortions can occur that are caused by the great variability both between breaths and within breaths. The purpose of this study is to develop a method for determining typical flow profiles which minimises such distortions.

To investigate the influence of increased respiratory frequency on respiratory mechanics in the horse, measurements were made in two groups of seven tracheostomised horses before and after the administration of doxapram. The horses in group I had normal base line values for respiratory mechanics, whereas the horses in group II had significantly lower values of dynamic compliance (Cdyn), higher respiratory resistance (R), and a higher total change in pleural pressure (ΔP). The administration of 0·3 mg kg −1 doxapram intravenously resulted in a significant increase in respiratory frequency (f R ), R, ΔP, tidal volume (V T ), and peak to peak respiratory flow (V), and a decrease in Cdyn in both groups of horses. The group II horses had significantly greater increases in R and ΔP than the horses in group I.

Realizing an untethered, low-cost, and comfortably wearable respiratory rate sensor for long-term breathing monitoring application still remains a challenge. In this paper, a conductive-textile-based wearable respiratory rate sensing technique based on the capacitive sensing approach is proposed. The sensing unit consists of two conductive textile electrodes that can be easily fabricated, laminated, and integrated in garments. Respiration cycle is detected by measuring the capacitance of two electrodes placed on the inner anterior and posterior sides of a T-shirt at either the abdomen or chest position. A convenient wearable respiratory sensor setup with a capacitance-to-voltage converter has been devised. Respiratory rate as well as breathing mode can be accurately identified using the designed sensor. The sensor output provides significant information on respiratory flow. The effectiveness of the proposed system for different breathing patterns has been evaluated by experiments.

Computational bio-fluid mechanics, in the widest sense, is concerned with all aspects of biological flow, such as blood flow and respiratory flow. Tn this chapter, a general discussion of studies of blood flow by computational visualization emphasizing physiological relevance and pathological consequences is presented first. Further discussion follows on the extremely complex nature of blood flow, including its susceptibility to the geometrical configuration of blood vessels under unsteady conditions. A concise introduction of the basic governing equations, the methods of numerical computation, and the considerations of various computational conditions, particularly boundary conditions,.is also given. Modeling, which is the most important but the most time-consuming- part of computational studies, is also briefly discussed. Based on these fundamental discussions, two examples from both extremes of our multilevel computational bio-fluid mechanical studies are shown: realistic modeling and flow computation of the left ventricle, and the cellular-scale flow adjacent to cultured endothelial, cells.

Employing a bolus inhalation system, we noninvasively measured the fraction of inhaled ozone (O3) that is absorbed during a single breath (lambda) as a function of bolus penetration volume into the respiratory tract (Vp). During nasal breathing at a constant respiratory flow of 250 ml/s, lambda increased smoothly as Vp increased with 80% of the inhaled O3 absorbed in the upper airways and 90% absorbed at the distal end of the trachea. Oral breathing caused a distal shift of the lambda-Vp distribution to the extent that absorption in the upper airways was reduced to 50% and inhaled O3 was 90% absorbed only after a bolus reached the 13th bronchial generation. Therefore, an exercise-induced change from nasal to oral breathing can render the distal lung more susceptible to O3 damage because of an elevation in O3 dose. We also found that changing the peak inhaled bolus concentration over a 10-fold range of 0.4–4 ppm O3 did not affect the lambda-Vp distribution. This finding implies that the diffusion and chemical reaction dynamics that dictate O3 absorption are linear processes.

In our previous work, we developed a bolus inhalation apparatus and measured the longitudinal distribution of ozone (O3) uptake in intact human lungs at a quiet respiratory flow of 250 ml/min. The objective of the present study was to determine the effect of alternative respiratory flows between 150 and 1,000 ml/s. Uptake was expressed as the O3 absorbed during a single breath relative to the amount of O3 in the inhaled bolus (lambda). Measurements of lambda were correlated with the penetration volume of the bolus into the respiratory tract (Vp). Vp in the range of 20–70 ml was considered to indicate upper airways (UA), the Vp interval of 70–180 ml was identified as lower conducting airways (CA), and Vp > 180 ml was associated with the respiratory air spaces (RA). During quiet oral breathing at 250 ml/s, lambda increased smoothly as Vp increased, with 50% of the inhaled O3 absorbed in the UAs and the remainder absorbed within the CAs such that no O3 reached the RAs. The effect of increasing the respiratory flow was to shift the lambda-Vp distribution distally such that significantly less O3 was absorbed in the UAs and CAs and some O3 reached the RAs. For example, at 1,000 ml/s, only 10% of the inhaled O3 was absorbed in UAs and 65% was absorbed in the CAs such that 25% reached the RAs.(ABSTRACT TRUNCATED AT 250 WORDS)

The additional work attributable to breathing through five Mapleson A anaesthetic breathing systems (Magill, Lack, Parallel Lack, Humphrey ADE and Enclosed Magill) was studied using a lung model. With all five systems, the additional work was found to be a function of fresh gas flow, respiratory flow as well as system geometry. Within the range of fresh gas flow and respiratory flow studied, the additional work ranged between 80 mJ.l-1 and 182 mJ.l-1. Expiratory work was always greater than the inspiratory workload. Increasing fresh gas inflow into the system increases expiratory work, both resistive and elastic components. The Magill system posed the least work expenditure. The values for the additional work obtained with the lung model were of the same order of magnitude when measurements were taken in volunteers.

To the Editor: The manuscript by Drs. Sato and Robbins ([3][1]) presents a new method for determining average flow profiles. The resulting average flow profiles are compared with those obtained with our method ([2][2]). It is noteworthy that the method of flow profile analysis we used was first

A microprocessor-based data acquisition and diagnosis system has been developed to measure respiratory flow and partial pressure of oxygen in respiratory air simultaneously. Additional maneuvers which enhance the monitoring capabilities of the instrument are included. The system attributes comprise portability, expandability, ease of use and low cost.

This study investigates the effect of helium concentration in inspired gas on resistance to breathing during experimental upper airway obstruction. Obstruction was modeled by use of a series of four polyvinyl endotracheal tubes narrowed progressively in their midportions with C clamps. Percentage ratios of helium-oxygen gas mixtures were 0:100, 40:60, 60:40, and 80:20. Gas flow was provided by two methods: 1) nontidal flow from compressed gas tanks from which resistance was calculated from pressure and flow measurements, and 2) tidal respiratory flow from human volunteers from whom respiratory effort was evaluated by using airway pressure measurements integrated over 90-second trial periods. The results derived from both methods demonstrated that the effect of helium in reducing resistance and pressure in an obstructed airway is linear (p < .016) and inversely proportional to helium concentration. Reductions in resistance and pressure were larger for the tighter obstructions (p < .007). As helium was added to the gas mixture (from 0% to 80%), resistance and airway pressure measurements dropped 42% and 58%, respectively. The major conclusions are that 1) even low concentrations of helium may have therapeutic value and 2) helium is effective only for more severe obstructions.