Lung-Air-Sac Anatomy and Respiratory Pressures in the Bird

1972 ◽  
Vol 57 (2) ◽  
pp. 543-550
Author(s):  
JOHN H. BRACKENBURY
Keyword(s):  
Steady State ◽  
Tidal Volume ◽  
Pressure Wave ◽  
Airway Resistance ◽  
Equilibrium Distribution ◽  
Wave Form ◽  
Pressure Waves ◽  
Air Sacs ◽  
Maximum Value ◽  
Respiratory Phase

1. Regardless of its tidal volume an individual air sac shows a respiratory pressure-wave which is similar to that of every other sac. These is a process of pressure equilibration within the lung-air-sac system involving very short-lived streams of air between air sacs, whose significance becomes larger as pressure accelerations become bigger; and when a steady state has been achieved in any respiratory phase the pressure wave becomes normalized in all parts of the system. 2. Small pressure differentials between sacs are part of the equilibrium distribution of pressure within the lung-air-sac system. They result from differences in the resistance path through the lung to each sac, and differences in their respective tidal volumes. Their wave-form closely resembles that of the parent pressure waves and has a maximum value of one-tenth their value. 3. In general, the bronchial pathways to the posterior sacs have greater resistances to air flow than those to the anterior sacs. 4. During vocalization pressures in the coelom and air sacs exceed normal respiratory pressures by about 40 times. Airway resistance vastly increases as the syringeal membranes begin to vibrate.

Effects of Weakly Compressibility on Propagating Properties of Water Hammer in a Long Pipe

2013 ◽  
Vol 444-445 ◽  
pp. 490-497
Author(s):  
Kun Xiong Zhou ◽  
Li Xiang Zhang
Keyword(s):  
Pressure Wave ◽  
Pipe Wall ◽  
High Water ◽  
Water Hammer ◽  
Wave Form ◽  
Pressure Waves ◽  
Water Head ◽  
The Waves ◽  
Theoretical Analyses

This paper is concerned with propagating features of pressure waves induced by water hammer in a long liquid-conveyed pipe subjected to hyper high water head. Effects of dynamically weak compressibility of the water in pipe and pipe wall elasticity on the propagating physics were investigated by comparing in-site measurements and theoretical analyses. The pressure wave form and propagating speed were significantly effected due to weak compressibility of the water and the interactions of the waves. The wave performs a strong unsteadiness while it propagates along the pipe. This study tries to explain an event with consideration of both the dynamically weak compressibility of the water in pipe and the closing features of the valves controlled actively.

Dependence of central airway resistance on frequency and tidal volume: a model study

1986 ◽  
Vol 61 (1) ◽  
pp. 113-126 ◽  
Author(s):  
D. Isabey ◽  
H. K. Chang ◽  
C. Delpuech ◽  
A. Harf ◽  
C. Hatzfeld
Keyword(s):  
Steady State ◽  
Pressure Drop ◽  
Tidal Volume ◽  
Strouhal Number ◽  
Airway Resistance ◽  
Peak Flow ◽  
Flow Reversal ◽  
Peak Flows ◽  
Wide Range ◽  
40 Hz

The resistance of a hollow cast of human central airways was measured during true sinusoidal airflow oscillations over a wide range of frequencies (0.5–40 Hz) and for various flow amplitudes up to 8 l/s. Pressure and flow were measured in the trachea with high-performance transducers, digitized and averaged over 100 cycles. Data were studied at two points in the flow cycle: at peak inspiratory and expiratory flows and in the two neighborhoods around zero flow where airway resistance (Rv approximately equal to o) was taken as the average slope of the pressure-flow (P-V) curve in each zone. When data obtained near peak flow were plotted in terms of dimensionless pressure drop vs. peak Reynolds number (Rem) and compared with steady-state data, we found no difference up to 2 Hz as previously reported (Isabey and Chang, J. Appl. Physiol. 51: 1338–1348, 1981), a slight decay in pressure drop between 4 and 8 Hz, a frequency-dependent increase in peak flow resistance at high frequencies (10–40 Hz) governed by the Strouhal number alpha 2/Rem beyond alpha 2/Rem = 0.5. On the other hand RV approximately equal to o was found to increase relative to steady state as local acceleration increases, e.g., as peak flow increases at a fixed frequency; this differs from the classical linear theory of oscillatory flow in a long straight tube. To explain these results, we had to use, as in our previous study, an alternative expression for the Strouhal number, i.e., epsilon = L X A X (dV/dt)/V2 (where L and A are the length and cross-sectional area of the trachea and V is a constant flow range over which resistance around flow reversal was computed), which accurately reflects the ratio of local acceleration [d(V/A)/dt)] to convective acceleration [(V/A)2/L] in developing branching flow. Finally, to delineate the regions of dominance of each of the dimensionless parameters, we compiled frequency-tidal volume diagrams for peak flows as well as for reversal. Epsilon, which is negligible near peak flows, appeared to govern the oscillatory P-V relationship near flow reversal in a transitional region of the diagram located between regions of steadiness, or moderate unsteadiness, and a region of dominant unsteadiness governed by alpha.

Effects of spontaneous swallows on breathing in awake goats

2002 ◽  
Vol 92 (5) ◽  
pp. 1923-1935 ◽  
Author(s):  
Thom R. Feroah ◽  
H. V. Forster ◽  
Carla G. Fuentes ◽  
Ivan M. Lang ◽  
David Beste ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Tidal Volume ◽  
Onset Time ◽  
Phase Response ◽  
Response Analysis ◽  
Dependent Effect ◽  
Pharyngeal Muscle ◽  
Awake State ◽  
Respiratory Phase

The effects of spontaneous swallows on breathing before, during, and after solitary swallows were investigated in 13 awake goats. Inspiratory (Ti) and expiratory (Te) time and respiratory output were determined from inspiratory airflow [tidal volume (Vt)] and peak diaphragmatic activity (Diapeak). The onset time for 1,128 swallows was determined from pharyngeal muscle electrical activity. During inspiration, the later the swallowing onset, the greater increase in Ti and Vt, whereas there was no significant effect on Te and Diapeak. Swallows in early expiration increased the preceding Ti and reduced Te, whereas later in expiration swallows increased Te. After expiratory swallows, Ti and Vt were reduced whereas minimal changes in Diapeak were observed. Phase response analysis revealed a within-breath, phase-dependent effect of swallowing on breathing, resulting in a resetting of the respiratory oscillator. However, the shift in timing in the breaths after a swallow was not parallel, further demonstrating a respiratory phase-dependent effect on breathing. We conclude that, in the awake state, within- and multiple-breath effects on respiratory timing and output are induced and/or required in the coordination of breathing and swallowing.

Transient Analysis on Helium Coolant Tube Break Accident of Dual-Functional Lithium Lead Test Blanket Module

2016 ◽  
Author(s):  
Qian Sun ◽  
Tianji Peng ◽  
Zhiwei Zhou ◽  
Zhibin Chen ◽  
Jieqiong Jiang
Keyword(s):  
Pressure Wave ◽  
Transient Analysis ◽  
Structural Integrity ◽  
Maximum Pressure ◽  
Pressure Waves ◽  
Operating Pressure ◽  
Pressure Shock ◽  
Dual Functional ◽  
Short Time ◽  
Helium Coolant

Dual-functional Lithium Lead Test Blanket Module (DFLL-TBM) was proposed by China for testing in the International Thermonuclear Experimental Reactor (ITER).When an in-TBM helium coolant tube breaks, high pressure helium will discharge into the Pb-Li breeding zones. The pressure shock in the TBM will threaten the structural integrity and safety of ITER. Simulation and analysis on helium coolant tube break accident of DFLL-TBM was performed, and two cases with different break sizes were considered. Computational results indicate that intense pressure waves spread quickly from the break to the surrounding structures and the variation of pressure in the TBM breeding box is drastic especially when the pressure wave propagation encounters large resistance such as at the bending corner of the flow channel, the inlet and outlet of Pb-Li, etc. The maximum pressure in the TBM breeding box which is even higher than the operating pressure of helium also occurs in these zones. Although the pressure shock lasts for a very short time, its effect on the structural integrity of DFLL-TBM needs to be paid attention to.

Effects of Combined Abdominal and Thoracic Airsac Occlusion on Respiration in Domestic Fowl

1990 ◽  
Vol 152 (1) ◽  
pp. 93-100 ◽  
Author(s):  
JOHN BRACKENBURY ◽  
JANE AMAKU
Keyword(s):  
Metabolic Rate ◽  
Tidal Volume ◽  
Dead Space ◽  
Domestic Fowl ◽  
Detrimental Effect ◽  
Minute Ventilation ◽  
Respiratory Pattern ◽  
Blood Gas ◽  
Control Value ◽  
Air Sacs

Ventilation and respiratory and blood gas tensions were monitored at rest and during running exercise, following bilateral occlusion of the cranial and caudal thoracic and the abdominal air sacs. This represents a removal of approximately 70% of the total air-sac capacity. At rest, the birds were strongly hypoxaemic/hypercapnaemic. Ventilation was maintained at its control value but respiratory frequency was significantly increased and tidal volume diminished. The birds were capable of sustained running at approximately three times the pre-exercise metabolic rate. Minute ventilation during exercise was the same as that of the controls, but breathing was faster and shallower. Exercise had no effect on blood gas tensions in either the control or the experimental birds. There was no evidence of a detrimental effect of air-sac occlusion on the effectiveness of inspiratory airflow valving in the lung: hypoxaemia appeared to be due to the altered respiratory pattern, which resulted in increased dead-space inhalation.

Kinetics of NO2 air space absorption in isolated rat lungs

1992 ◽  
Vol 73 (5) ◽  
pp. 1939-1945 ◽  
Author(s):  
E. M. Postlethwait ◽  
S. D. Langford ◽  
A. Bidani
Keyword(s):  
Steady State ◽  
Tidal Volume ◽  
Gas Phase ◽  
Initial Rate ◽  
Quasi Steady State ◽  
Closed Chamber ◽  
First Order ◽  
First Order Kinetics ◽  
Rat Lungs ◽  
Kinetics Of

We previously showed, during quasi-steady-state exposures, that the rate of inhaled NO2 uptake displays reaction-mediated characteristics (J. Appl. Physiol. 68: 594–603, 1990). In vitro kinetic studies of pulmonary epithelial lining fluid (ELF) demonstrated that NO2 interfacial transfer into ELF exhibits first-order kinetics with respect to NO2, attains [NO2]-dependent rate saturation, and is aqueous substrate dependent (J. Appl. Physiol. 71: 1502–1510, 1991). We have extended these observations by evaluating the kinetics of NO2 gas phase disappearance in isolated ventilating rat lungs. Transient exposures (2–3/lung at 25 degrees C) employed rebreathing (NO2-air) from a non-compliant continuously stirred closed chamber. We observed that 1) NO2 uptake rate is independent of exposure period, 2) NO2 gas phase disappearance exhibited first-order kinetics [initial rate (r*) saturation occurred when [NO2] > 11 ppm], 3) the mean effective rate constant (k*) for NO2 gas phase disappearance ([NO2] < or = 11 ppm, tidal volume = 2.3 ml, functional residual capacity = 4 ml, ventilation frequency = 50/min) was 83 +/- 5 ml/min, 4) with [NO2] < or = 11 ppm, k* and r* were proportional to tidal volume, and 5) NO2 fractional uptakes were constant across [NO2] (< or = 11 ppm) and tidal volumes but exceeded quasi-steady-state observations. Preliminary data indicate that this divergence may be related to the inspired PCO2. These results suggest that NO2 reactive uptake within rebreathing isolated lungs follows first-order kinetics and displays initial rate saturation, similar to isolated ELF.(ABSTRACT TRUNCATED AT 250 WORDS)

Numerical and experimental study of steady-state CO2 and inert gas washout

1988 ◽  
Vol 64 (3) ◽  
pp. 1022-1029 ◽  
Author(s):  
P. W. Scherer ◽  
S. Gobran ◽  
S. J. Aukburg ◽  
J. E. Baumgardner ◽  
R. Bartkowski ◽  
...  
Keyword(s):  
Steady State ◽  
Diffusion Equation ◽  
Tidal Volume ◽  
Sulfur Hexafluoride ◽  
Source Term ◽  
Gas Diffusion ◽  
Inert Gases ◽  
Phase Iii ◽  
Distributed Source ◽  
Single Path

The predictions of a single-path trumpet-bell numerical model of steady-state CO2 and infused He and sulfur hexafluoride (SF6) washout were compared with experimental measurements on healthy human volunteers. The mathematical model used was a numerical solution of the classic airway convention-diffusion equation with the addition of a distributed source term at the alveolar end. In the human studies, a static sampling technique was used to measure the exhaled concentrations and phase III slopes of CO2, He, and SF6 during the intravenous infusion of saline saturated with a mixture of the two inert gases. We found good agreement between the experimentally determined normalized slopes (phase III slope divided by mixed expired concentration) and the numerically determined normalized slopes in the model with no free parameters other than the physiological ones of upper airway dead space, tidal volume, breathing frequency, and breathing pattern (sinusoidal). We conclude 1) that the single-path (Weibel) trumpet-bell anatomic model used in conjunction with the airway convection-diffusion equation with a distributed source term is adequate to describe the steady-state lung washout of CO2 and infused He and SF6 in normal lungs and 2) that the interfacial area separating the tidal volume fron from the functional residual capacity gas, through which gas diffusion into the moving tidal volume occurs, exerts a major effect on the normalized slopes of phase III.

Effects of altering ventilation on steady-state diffusing capacity for carbon monoxide

1963 ◽  
Vol 18 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Kaye H. Kilburn ◽  
Harry A. Miller ◽  
John E. Burton ◽  
Ronald Rhodes
Keyword(s):  
Carbon Monoxide ◽  
Steady State ◽  
Tidal Volume ◽  
Lung Volume ◽  
Dead Space ◽  
Control Level ◽  
Alveolar Ventilation ◽  
Positive Pressure ◽  
Diffusing Capacity ◽  
Fixed Rate

Alterations in the steady-state diffusing capacity for carbon monoxide (Dco) by the method of Filley, MacIntosh, and Wright, produced by sequential changes in the pattern of breathing were studied in anesthetized, paralyzed, artificially ventilated dogs. The Dco of paralyzed, artificially ventilated control dogs did not differ significantly during 3 hr from values found in conscious and anesthetized controls. A fivefold increase in tidal volume without changing frequency of breathing raised alveolar ventilation and CO uptake 500% and Dco 186%. A high correlation between tidal volume and Dco was noted during reciprocal alterations of tidal volume and rate which maintained minute volume. The Dco appeared to fall when alveolar ventilation was tripled by increments of rate with a fixed-tidal volume, despite a 63% increase in CO uptake. Doubling end-expiratory lung volume by positive pressure breathing without altering tidal volume or rate did not affect Dco. The addition of 100 ml of external dead space with rate and tidal volume constant decreased Dco to 42% of control level, however, stepwise reduction of dead space from 100 ml to 0 in two dogs failed to change Dco. Added dead space equal to frac12 tidal volume (170 ml) reduced Dco to 25% of control in two dogs with a return to control with removal of dead space. Thus, in paralyzed artificially ventilated dogs, tidal volume appears to be the principal ventilatory determinant of steady-state Dco. Dco is minimally affected by increases in alveolar ventilation with a constant tidal volume effected by increasing the frequency of breathing. Prolonged ventilation, at fixed rate and volume, and increased dead space either did not effect, or they reduced Dco, perhaps by rendering less uniform the distribution of gas, and blood in the lungs. Although lung volume was doubled by positive-pressure breathing, pulmonary capillary blood volume was probably reduced to produce opposing effects on diffusing capacity and no net change. Submitted on March 14, 1962

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