Bolus Contaminant Dispersion in Oscillating Flow in Curved Tubes

1998 ◽  
Vol 120 (2) ◽  
pp. 238-244 ◽  
Author(s):  
D. M. Eckmann
Keyword(s):  
Tidal Volume ◽  
Pulmonary Ventilation ◽  
Effective Diffusion ◽  
Effective Diffusivity ◽  
Radius Of Curvature ◽  
Dimensionless Frequency ◽  
Gas Dispersion ◽  
Artificial Pulmonary Ventilation ◽  
Argon Concentration ◽  
Helical Tubes

The investigation of longitudinal dispersion of tracer substances in unsteady flows has biomechanical application in the study of heat and mass transport within the bronchial airways during normal, abnormal, and artificial pulmonary ventilation. To model the effects of airway curvature on intrapulmonary gas transport, we have measured local gas dispersion in axially uniform helical tubes of slight pitch during volume-cycled oscillatory flow. Following a small argon bolus injection into the flow field, the time-averaged effective diffusion coefficient 〈Deff/Dmol〉 for axial transport of the contaminant was evaluated from the time-dependent local argon concentration measured with a mass spectrometer. The value of 〈Deff/Dmol〉 is extracted from the curve of concentration versus time by two techniques yielding identical results. Experiments were conducted in two helical coiled tubes (δ = 0.031, λ = 0.022 or δ = 0.085, λ = 0.060) over a range of 2 < α < 15, 3 < A < 15, where δ is the ratio of tube radius to radius of curvature, λ is the ratio of pitch height to radius of curvature, α is the Womersley parameter or dimensionless frequency, and A is the stroke amplitude or dimensionless tidal volume. Experimental results show that, when compared to transport in straight tubes, the effective diffusivity markedly increases in the presence of axial curvature. Results also compare favorably to mathematical predictions of bolus dispersion in a curved tube over the ranges of frequency and tidal volume studied.

scholarly journals Drying kinetics of crushed mass of ‘jambu’: Effective diffusivity and activation energy

2018 ◽  
Vol 22 (7) ◽  
pp. 499-505 ◽  
Author(s):  
Francileni P. Gomes ◽  
Resende Osvaldo ◽  
Elisabete P. Sousa ◽  
Daneil E. C. de Oliveira ◽  
Francisco R. de Araújo Neto
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Agricultural Research ◽  
Effective Diffusion ◽  
Effective Diffusivity ◽  
Information Criterion ◽  
Drying Kinetics ◽  
Coefficient Of Determination ◽  
Chi Square ◽  
Chi Square Test

ABSTRACT The aim of this paper was to analyze the drying kinetics, test the Akaike information criterion (AIC) and Schwarz’s Bayesian information criterion (BIC) in the selection of models, determine the effective diffusivity and activation energy of the crushed mass of ‘jambu’ leaves for different conditions of temperature and layer thicknesses. The experiment was carried out at the Food Laboratory of the Brazilian Agricultural Research Corporation (Embrapa) in Macapá-AP. Drying was carried out in air circulation oven with speed of 1.0 m s-1 at various temperatures (60, 70 and 80 ºC) and layer thicknesses (0.005 and 0.010 m). The experimental data were fitted to 11 mathematical models. Coefficient of determination (R2), mean relative error (P), mean estimated error (SE), Chi-square test (χ2), AIC and BIC were the selection criteria for the models. For the effective diffusivity, the Fick’s diffusion model was used considering the flat plate geometry. It was found that Midilli and Logarithmic models showed the best fit to the experimental data of drying kinetics. Effective diffusion coefficient increases with increment in the thickness of the material and with the temperature elevation. Activation energy of the material was of 16.61 kJ mol-1 for the thickness of 0.005 m, and 16.97 kJ mol-1 for the thickness of 0.010 m. AIC and BIC can be additionally included to select models of drying.

Estimation of pulmonary ventilation with nitrogen and helium, using the mass spectrometer

1959 ◽  
Vol 14 (4) ◽  
pp. 499-506 ◽  
Author(s):  
K. Tokuyasu ◽  
A. Coblentz ◽  
H. R. Bierman
Keyword(s):  
Tidal Volume ◽  
Mass Spectrometer ◽  
Functional Residual Capacity ◽  
Pulmonary Ventilation ◽  
Normal Subjects ◽  
Alveolar Ventilation ◽  
Pulmonary Lesions ◽  
Normal Subject ◽  
Residual Capacity ◽  
Uneven Ventilation

Estimation of pulmonary ventilation was attempted by measuring the elimination of nitrogen and helium with the mass spectrometer. Exhalatory concentrations of nitrogen and helium were continuously recorded in each of 12 normal subjects and 10 patients with pulmonary enphysema or space-occupying pulmonary lesions. Uniform values for both slow and rapid uneven ventilation were found in all normal subjects but always less than in emphysematous states. Ratios of effective tidal volume (Vt) and alveolar ventilation volume (f·Vt) to functional residual capacity P = Vt/Vr and Q = f·Vt/Vr were one half or less than those in the normal subject. Smaller values of uneven ventilation were found for helium than nitrogen. Data computed by the theory of 'periodic' ventilation gave greater values for uneven ventilation (Q) and more accurately represented the physiologic conditions than derived by ‘continuous’ ventilation. Submitted on August 7, 1958

scholarly journals Hypoxia-induced vagal withdrawal is independent of the hypoxic ventilatory response in men

2019 ◽  
Vol 126 (1) ◽  
pp. 124-131 ◽  
Author(s):  
Christoph Siebenmann ◽  
Camilla K. Ryrsø ◽  
Laura Oberholzer ◽  
James P. Fisher ◽  
Linda M. Hilsted ◽  
...  
Keyword(s):  
Heart Rate ◽  
Tidal Volume ◽  
Respiratory Rate ◽  
Spontaneous Breathing ◽  
Animal Studies ◽  
Pulmonary Ventilation ◽  
Vagal Activity ◽  
Adrenergic Blockade ◽  
Controlled Breathing ◽  
Vagal Withdrawal

Hypoxia increases heart rate (HR) in humans by sympathetic activation and vagal withdrawal. However, in anaesthetized dogs hypoxia increases vagal activity and reduces HR if pulmonary ventilation does not increase and we evaluated whether that observation applies to awake humans. Ten healthy males were exposed to 15 min of normoxia and hypoxia (10.5% O2), while respiratory rate and tidal volume were volitionally controlled at values identified during spontaneous breathing in hypoxia. End-tidal CO2 tension was clamped at 40 mmHg by CO2 supplementation. β-Adrenergic blockade by intravenous propranolol isolated vagal regulation of HR. During spontaneous breathing, hypoxia increased ventilation by 3.2 ± 2.1 l/min ( P = 0.0033) and HR by 8.9 ± 5.5 beats/min ( P < 0.001). During controlled breathing, respiratory rate (16.3 ± 3.2 vs. 16.4 ± 3.3 breaths/min) and tidal volume (1.05 ± 0.27 vs. 1.06 ± 0.24 l) were similar for normoxia and hypoxia, whereas the HR increase in hypoxia persisted without (8.6 ± 10.2 beats/min) and with (6.6 ± 5.6 beats/min) propranolol. Neither controlled breathing ( P = 0.80), propranolol ( P = 0.64), nor their combination ( P = 0.89) affected the HR increase in hypoxia. Arterial pressure was unaffected ( P = 0.48) by hypoxia across conditions. The hypoxia-induced increase in HR during controlled breathing and β-adrenergic blockade indicates that hypoxia reduces vagal activity in humans even when ventilation does not increase. Vagal withdrawal in hypoxia seems to be governed by the arterial chemoreflex rather than a pulmonary inflation reflex in humans. NEW & NOTEWORTHY Hypoxia accelerates the heart rate of humans by increasing sympathetic activity and reducing vagal activity. Animal studies have indicated that hypoxia-induced vagal withdrawal is governed by a pulmonary inflation reflex that is activated by the increased pulmonary ventilation in hypoxia. The present findings, however, indicate that humans experience vagal withdrawal in hypoxia even if ventilation does not increase, indicating that vagal withdrawal is governed by the arterial chemoreflex rather than a pulmonary inflation reflex.

Intra-airway gas mixing during high-frequency ventilation

1984 ◽  
Vol 56 (2) ◽  
pp. 343-354 ◽  
Author(s):  
J. Solway ◽  
N. Gavriely ◽  
R. D. Kamm ◽  
J. M. Drazen ◽  
R. H. Ingram ◽  
...  
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
Effective Diffusivity ◽  
High Frequency Ventilation ◽  
Breath Hold ◽  
Transport Parameter ◽  
Gas Mixing ◽  
High Frequency Oscillations ◽  
Co2 Output ◽  
Bias Flow

We examined the intra-airway gas transport mediated by high-frequency oscillations (HFO) in 10 nonintubated healthy volunteers using a method based on comparisons of single-breath N2-washout curves obtained after various durations of breath hold or high-frequency oscillations. With a mathematical analysis based on Fick's law of diffusion we computed the local transport parameter, effective diffusivity, during oscillations of frequency 2–24 Hz and tidal volume 10–120 ml and during breath hold alone. Local effective diffusivity increased with both oscillatory frequency and tidal volume at all levels in the tracheobronchial tree; the enhancing effect of tidal volume on local effective diffusivity was more pronounced than that of frequency so that effective diffusivity was greater with larger tidal volume at fixed frequency-tidal volume product (f . VT). The greatest enhancement of gas mixing within the lung during HFO (over breath hold) was seen in the central airways. In previous studies examining CO2 removal rate during HFO (J. Clin. Invest. 68: 1475, 1981), we found that CO2 output was also greater with larger tidal volume at fixed f . VT, and we attributed this to an end constraint imposed by a fresh gas bias flow. Results of the current study, performed without a bias flow, indicate that bias flow end constraint does not solely account for the observed dependence of CO2 output on frequency and tidal volume.

scholarly journals Nudegimų gydymas pasireiškus bakteriemijai

2005 ◽  
Vol 3 (1) ◽  
pp. 0-0
Author(s):  
Kristina Vostrugina ◽  
Daiva Gudavičienė ◽  
Rytis Rimdeika
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Therapy ◽  
Plastic Surgery ◽  
Pulmonary Ventilation ◽  
Age Factors ◽  
Multiple Organ ◽  
Parenteral Feeding ◽  
Burned Area ◽  
Hospital Department ◽  
Artificial Pulmonary Ventilation

Kristina Vostrugina, Daiva Gudavičienė, Rytis RimdeikaKauno medicinos universiteto klinikųPlastinės chirurgijos ir nudegimų skyrius,Eivenių g. 2, LT-50009 KaunasEl paštas: [email protected] Tikslas Ištirti 1999–2003 m. Kauno medicinos universiteto klinikų Plastinės chirurgijos ir nudegimų skyriaus ligonių, kuriems patvirtinta bakteriemija, gydymo aspektus. Ligoniai ir metodai Atlikta retrospektyvi 82 nudegusių ligonių, kuriems patvirtinta bakteriemija, ligos istorijų analizė. Vertintas pacientų amžius, nudegimą sukėlę veiksniai, nudegimo plotas, kvėpavimo takų nudegimas. Analizuota, kokiam skaičiui pacientų reikėjo kateterizuoti centrines venas, prireikė dirbtinės plaučių ventiliacijos, enterinio ar parenterinio maitinimo, kokių radosi komplikacijų, kokie mikroorganizmai išaugo žaizdų pasėliuose ir toks jų sutapimas su kraujo pasėlių duomenimis, nagrinėti antibiotikų terapijos aspektai. Rezultatai Pacientų, kuriems patvirtinta bakteriemija, vidutinis amžius buvo 50 metų, standartinis nuokrypis – 16. Vyravo nudegimai liepsna (82%) ir skysčiais (8,5%). Vidutinis nudegusio kūno paviršiaus plotas buvo 29%, standartinis nuokrypis – 19. Centrines venas reikėjo kateterizuoti 78% pacientų. Dirbtinės plaučių ventiliacijos prireikė 13% pacientų. Enterinis maitinimas skirtas 48% pacientų, parenteriniu būdu maitinta 90% ligonių. Pneumonija nustatyta 29% pacientų, kardiovaskulinis nepakankamumas – 15%, dauginis organų funkcijos nepakankamumas – 13%, inkstų funkcijos nepakankamumas – 7% ligonių. Visais atvejais sutapo žaizdos ir kraujo pasėlių duomenys, kai iš kraujo išaugo Pseudomonas aeruginosa, 87% – kai išaugo meticilinui atsparus Staphylococcus aureus ir 74% – kai išaugo meticilinui jautrus S. aureus. Antibiotikais gydyta 80 ligonių, dažniausiai penicilinu, gentamicinu ir vankomicinu. Išvados Bakteriemija dažnai nustatoma didelius plotus nudegusiems ligoniams, kuriems tenka kateterizuoti centrines venas, skirti parenterinį maitinimą. Dažniausiai iš kraujo mėginių išauga tie mikroorganizmai, kurie auga žaizdų pasėliuose. Reikšminiai žodžiai: nudegimai, bakteriemija, antibiotikų terapija Treatment of burned patients with diagnosed bacteremia Kristina Vostrugina, Daiva Gudavičienė, Rytis RimdeikaKaunas University of Medicine Hospital,Department of Plastic Surgery and Burns,Eivenių str. 2, LT-50009 Kaunas, LithuaniaE-mail: [email protected] Objective The aim of the study was to investigate the aspects of treatment of burned patients with confirmed bacteremia treated at Kaunas University of Medicine Hospital Department of Plastic Surgery and Burns during 1999–2003. Patients and methods A retrospective analysis of case histories of 82 burned patients with confirmed bacteremia was performed. The evaluated factors included the patients’ age, factors that caused the burns, the burned area, and burns of the airways. We also analyzed how many patients required catheterization of the central veins, artificial pulmonary ventilation, enteral or parenteral feeding, and complications, as well as what microorganisms grew in wound crops, how many cases corresponded to the blood crop findings, and the aspects of antibiotic therapy. Results Mean age of patients with confirmed bacteremia was 50 years, standard deviation (SD) – 16. Flame burns (82%) and scalds (8.5%) predominated. Mean burned body surface area was 29%, SD – 19. 78% of patients required catheterization of central veins, and 13% – artificial pulmonary ventilation. 48% of patients were fed enterally, and 90% – parenterally. 29% of patients had pneumonia, 15% – cardiovascular insufficiency, 13% – multiple organ failure, and 7% – renal failure. The coincidence of the findings of wound and blood crops was 100% in cases of Pseudomonas aueruginosa growth, 87% – in cases of methicillin-resistant Staphylococcus aureus growth, and 74% – in cases of methicillin-sensitive Staphylococcus aureus growth. 80 patients received antibiotics, mostly penicillin, gentamicin, and vancomycin. Conclusions Bacteremia was very common among extensively burned patients requiring catheterization of the central veins and parenteral feeding. In most cases, microorganisms that grew in wound crops also grew in blood samples. Key words: burns, bacteremia, antibiotic therapy

scholarly journals Effect of Reoxygenation on the Electrical Stability of the Rat Heart In Vivo: A Chronobiological Study

2013 ◽  
pp. S143-S149
Author(s):  
P. ŠVORC ◽  
A. MAROSSY ◽  
P. ŠVORC ◽  
M. BUŽGA
Keyword(s):  
Body Weight ◽  
Tidal Volume ◽  
Rat Heart ◽  
Ventricular Arrhythmias ◽  
Wistar Rats ◽  
Pulmonary Ventilation ◽  
Electrical Stability ◽  
Female Wistar Rats ◽  
Light:Dark Cycle

Reoxygenation following hypoxic episodes can increase the risk for the development of ventricular arrhythmias, which, in addition to circadian aspects of reoxygenation arrhythmias has not been studied extensively. The aim of the present study was to evaluate circadian changes in the electrical stability of the rat heart during reoxygenation following a hypoventilatory episode. The electrical stability of the heart, defined in the present study as the ventricular arrhythmia threshold (VAT), was measured at 3 h intervals at clock times 09:00, 12:00, 15:00, 18:00, 21:00, 24:00, 03:00, 06:00 and 09:00 during 20 min hypoventilation (20 breaths/min, tidal volume = 0.5 ml/100 g body weight [n=17]) and subsequent 20 min reoxygenation (50 breaths/min, tidal volume = 1 ml/100 g body weight [n=4]) intervals. The experiments were performed using pentobarbital-anesthetized (40 mg/kg intraperitoneally) female Wistar rats that first underwent a four-week adaptation to a 12 h light:12 h dark regimen. Detailed analysis showed that circadian VATs changed to biphasic rhythms at 10 min of hypoventilation. The VAT circadian rhythms were observed immediately following the commencement of reoxygenation, with the highest values measured between 12:00 and 15:00, and the lowest values between 24:00 and 03:00. These results suggest that myocardial vulnerability is dependent on the light:dark cycle and characteristics of pulmonary ventilation.

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