On the barometric method for measurements of ventilation, and its use in small animals

1998 ◽  
Vol 76 (10-11) ◽  
pp. 937-944 ◽  
Author(s):  
Jacopo P Mortola ◽  
Peter B Frappell
Keyword(s):  
Tidal Volume ◽  
Historical Development ◽  
Total Pressure ◽  
Pulmonary Ventilation ◽  
Chamber Pressure ◽  
Small Animals ◽  
Potential Sources ◽  
Common Technique ◽  
Animal Chamber

The barometric method is a common technique for measurements of pulmonary ventilation in unrestrained animals. It basically consists of recording the changes in chamber pressure generated during breathing. In fact, as the air inspired is warmed and humidified from the ambient to the pulmonary values, the total pressure in the animal chamber increases; the opposite occurs in expiration. The present commentary is an introduction to this method, briefly reviewing its historical development, the conceptual pitfalls, and potential sources of errors during practical applications.Key words: barometric technique, plethysmography, pulmonary ventilation, respiratory techniques, tidal volume.

An automatic, closed-circuit oxygen consumption apparatus for small animals

1975 ◽  
Vol 39 (5) ◽  
pp. 849-850 ◽  
Author(s):  
M. J. Stock
Keyword(s):  
Oxygen Consumption ◽  
Continuous Measurement ◽  
Differential Pressure ◽  
Closed Circuit ◽  
Chamber Pressure ◽  
Small Animals ◽  
Experimental Conditions ◽  
Rate Of Oxygen Consumption ◽  
Rats And Mice ◽  
Animal Chamber

An apparatus suitable for the continuous measurement of oxygen consumption of rats and mice is described. The system uses a motorized syringe dispenser to deliver fixed volumes of oxygen to a closed animal chamber. The dispenser is controlled by a micro-differential pressure switch to maintain chamber pressure slightly above ambient. The rate of oxygen consumption is determined by timing the interval between successive operations of the dispenser. The system has proved suitable for a range of experimental conditions and treatments.

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.

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.

Respiratory Response of Anesthetized Dogs to Progressive Anemic Hypoxia

1957 ◽  
Vol 190 (2) ◽  
pp. 361-364 ◽  
Author(s):  
Wayland E. Hull
Keyword(s):  
Tidal Volume ◽  
Pulmonary Ventilation ◽  
Breathing Rate ◽  
Blood Oxygen ◽  
Respiratory Response ◽  
High Concentration ◽  
Disturbing Factor ◽  
Oxygen Capacity ◽  
Anesthetized Dogs ◽  
And Control

Breath-to-breath analyses of air-flow responses of lightly anesthetized dogs to progressive anemic hypoxia by hemodilution or by breathing dilute carbon monoxide in air reveal only moderate changes in pulmonary ventilation. However, tidal volume undergoes progressive diminution, the alveolar ventilation remaining normal or slightly above normal by the concurrent increase in breathing rate. Despite the increase in breathing rate, hypoventilation and respiratory failure ensue when but 20–30% of the blood oxygen capacity is present. Administration of oxygen of high concentration to severely hypoxic dogs increases tidal volume, usually slowing the rate. The experimental method described lends itself to the study of factors which regulate and control pulmonary ventilation in the absence of chemoreceptor activity and when diminished blood oxygen capacity is the primary disturbing factor.

Locomotion in men has no appreciable mechanical effect on breathing

1992 ◽  
Vol 72 (5) ◽  
pp. 1922-1926 ◽  
Author(s):  
R. B. Banzett ◽  
J. Mead ◽  
M. B. Reid ◽  
G. P. Topulos
Keyword(s):  
Tidal Volume ◽  
Pulmonary Ventilation ◽  
Respiratory Muscles ◽  
Mechanical Effect ◽  
Respiratory Volume

It has been suggested that the act of taking a stride produces substantial respiratory volume displacement and that this assists the respiratory muscles during locomotion. We measured the flow at the mouth associated with stride in walking and running humans and found it to be 1–2% of respiratory tidal volume, which is too small to make an appreciable contribution to pulmonary ventilation.

Control of Breathing in Patients with Chronic Obstructive Lung Disease

1978 ◽  
Vol 54 (3) ◽  
pp. 295-304 ◽  
Author(s):  
J. Šorli ◽  
A. Grassino ◽  
G. Lorange ◽  
J. Milic-Emili
Keyword(s):  
Lung Disease ◽  
Tidal Volume ◽  
Obstructive Lung Disease ◽  
Pulmonary Ventilation ◽  
Chronic Obstructive Lung Disease ◽  
Control Of Breathing ◽  
Chronic Obstructive ◽  
Occlusion Pressure ◽  
Lower Tidal Volume ◽  
Mouth Occlusion Pressure

1. Using the mouth occlusion pressure technique, we have studied the control of breathing in seven hypercapnic and eight non-hypercapnic patients with chronic obstructive lung disease. 2. When breathing room air, pulmonary ventilation, mean inspiratory flow and P0·1 (mouth occlusion pressure developed 0·1 s after the onset of occluded inspiration at functional residual capacity) were not significantly different between the two groups of patients. Tidal volume, however, was significantly lower in the hypercapnic than in the non-hypercapnic patients, as a result of a significantly lower duration of inspiration. 3. The lower tidal volume in the hypercapnic patients leads to decreased alveolar ventilation, and appears to be the main cause of retention of carbon dioxide.

scholarly journals The Interrelationship Between Pulmonary Mechanics and the Spontaneous Breathing Pattern in the Tokay Lizard, Gekko Gecko

1984 ◽  
Vol 113 (1) ◽  
pp. 203-214 ◽  
Author(s):  
WILLIAM K. MILSOM
Keyword(s):  
Tidal Volume ◽  
Spontaneous Breathing ◽  
Breathing Pattern ◽  
Pulmonary Ventilation ◽  
Periodic Breathing ◽  
Breath Holding ◽  
Pulmonary Mechanics ◽  
Respiratory Drive ◽  
Breathing Patterns ◽  
Gekko Gecko

The normal breathing pattern of the Tokay gecko (Gekko gecko) consists of single breaths or bursts of a few breaths separated by periods of breath holding. Increases in pulmonary ventilation that accompany rises in body temperature are caused by increases in respiratory frequency due to shortening of the periods of breath holding. Tidal volume and breath duration remain relatively constant. Measurements of the mechanical work associated with spontaneous breathing yielded values that were similar to those calculated for breaths of the same size and duration based on work curves generated during pump ventilation of anaesthetized animals. In this species, the pattern of periodic breathing and the ventilatory responses to changes in respiratory drive correspond with predictions of optimal breathing patterns based on calculations of the mechanical cost of ventilation. Bilateral vagotomy drastically alters the breathing pattern producing an elevation in tidal volume, a slowing of breathing frequency, and a prolongation of the breath duration. These alterations greatly increase the mechanical cost of ventilation. These data suggest that periodic breathing in this species may represent an adaptive strategy which is under vagal afferent control and which serves to minimize the cost of breathing.

scholarly journals Numerical Study on Response Characteristics of Solid Rocket Pintle Motor

2019 ◽  
Author(s):  
Jeevan Sapkota ◽  
Yi Hua Xu ◽  
Hai Jun Sun
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
Total Pressure ◽  
Numerical Study ◽  
Rocket Motor ◽  
Chamber Pressure ◽  
Head Model ◽  
Solid Rocket Motor ◽  
Rapid Changes ◽  
Solid Rocket

Pintle technology is currently a versatile technology used in a solid rocket motor (SRM) to control the desired thrust by changing the nozzle throat area, while effectively controlling the chamber pressure at the same time. The sudden movement of the pintle can induce rapid changes in the flow field and the occurrence of pressure oscillations inside the combustion chamber. The analysis of such rapid changes is essential to design an efficient controllable pintle rocket motor for a better thrust regulation. Two-dimensional axisymmetric models with mesh generation and required boundary condition were designed to analyze the effects of three different pintle head shape models in SRM thrust regulation effect. Dynamic mesh method was used with specific velocity for moving plug/pintle in the numerical analysis of SRM thrust regulation. The effects of different pintle head models on the flow field, combustion chamber pressure, mass-flow rate, thrust and Mach number were investigated. According to the analysis of total pressure response time, the simulation data revealed that circular pintle head model responded faster among three different models. According to the thrust effect, parabolic pintle has the maximum value of thrust and the greatest total pressure recovery coefficient among all pintle head models.

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