The mammalian breathing mechanism

McCutcheon, F. H.

doi:10.1002/jcp.1030370307

Cited by 18 publications

(11 citation statements)

References 17 publications

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“…Our results have shown higher respiratory rates in normal rats than those recorded by Guyton (1947) and McCutcheon (1951) using various spirometrie and respirographic techniques. Tliis could be due to increased excitement in our animals during recording but, from observation of normal rats in cages, respiratory rates higher than those recorded rcspirographically are readily counted.…”

Section: Discussionsupporting

confidence: 58%

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Factors Affecting the Intrapleural Pressure and Pulmonary Ventilation in Rats

Davis

Morris

1953

Aust J Exp Biol Med

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Investigations of the lymphatic absorption of material from the serous cavities have indicated that the rate of this absorption is influenced by the rate and force of the respiratory movements, particularly those of the diaphragm (ef. Florey, 1927; Ili^'gins, Beaver and Lemon, 1930; Cooray, 1949;Courtice and Simmonds, 1949; Conrtice and Steinbeck, 1950). The pressure changes occurring within the pleural cavity as a result of changes in respiratory movement probably play au important part in the processes underlying absorption hy the lymphatics. The protein moleeules or partieles injected have first to pass through a serous membrane, then the membranous wall of the Ijnnphatie capillary and finally must be propelled along the main lymph trunks passing througli the mediastinum to enter the veins at the base of the neek.Before investigating further some of the factors, in particular diaphragmatic movement, which might affect lymphatic absorption from the pleural and peritoneal cavities, it was decided to analyse the changes which these factors produce in the respiratory pattern, pulmonary ventilation and intrapleural pressure. METHODS.Albino rats of the Wistar atraiu wore U3cd. Tlic liigh respiratory rate and small tidal air changes of tKe unanaosthetized rat nL-coasitateii a sysU-m of recording capable of catiniatinK accurately rapid volume changes of small degree. Ordinary spiroinetrip techniqiie.s involving the U8G of valves are not satisfactory at high respiratory rates and systems with a large dead space and high resistance arc unsatisfactory for ventilation studies in small laboratory animals.The method employed for determining the pulmonary ventilation and respiratory rate was a modification of that used by Guyton (1947). The system used is shown diagraniatically in Fig. 1 and the actual arrangement of the various eomponents of the apparatus is shown in Fig. 2. The principle of the method involves the recording and calibration of the pressure changes that oceur when the animal breathes iu a closed air system. With each inspiration a small amount of air equal to the animal's tidal volume is removed from the system reducing » This work was carried out with the aid of a grant from the

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Section: Discussionsupporting

confidence: 58%

“…This seemed a more effective method of restraint than the glycerine coated tubes which McCutcheon (1951) used. The animals appeared quiet and reasonably content after an initial period of excitement had passed.…”

Section: Methodsmentioning

confidence: 99%

Factors Affecting the Intrapleural Pressure and Pulmonary Ventilation in Rats

Davis

Morris

1953

Aust J Exp Biol Med

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“…We are not aware of any study to date that has specifically examined the effect of metabolic rate per se on the incidence of augmented breaths. However, it is known that larger mammals are known to express less frequent augmented breaths compared with small mammals (46,47). Indeed, one of the benefits of using rats to study mechanisms involved in the generation of augmented breaths is that they express them relatively frequently, several times per hour in normal conditions.…”

Section: Discussionmentioning

confidence: 98%

“…Augmented breaths have been documented and studied across a diverse spectrum of species (46,47), and their ubiquitous presence alludes to the physiological importance of their function in the animal. Augmented breaths function to prevent atelectisis, which otherwise results in collapsed and hypoventilated regions of the lung (58).…”

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confidence: 99%

Hypocapnia increases the prevalence of hypoxia-induced augmented breaths

Bell

Ferguson

Kehoe

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Augmented breaths promote respiratory instability and have been implicated in triggering periods of sleep-disordered breathing. Since respiratory instability is well known to be exacerbated by hypocapnia, we asked whether one of the destabilizing effects of hypocapnia might be related to an increased prevalence of augmented breaths. With this question in mind, we first sought to determine whether hypoxia-induced augmented breaths are more prevalent when hypocapnia is also present. To do this, we studied the breath-by-breath ventilatory responses of a group of freely behaving adult rats in a variety of different respiratory background conditions. We found that the prevalence of augmented breaths was dramatically increased during hypocapnic-hypoxia compared with room air conditions. When hypocapnia was prevented during exposure to hypoxia by adding 5% CO2 to the inspired air, the rate of occurrence of augmented breaths was no greater than that observed in room air. The addition of CO2 alone to room air had no effect on the prevalence of augmented breaths. We conclude that in spontaneously breathing rats, hypoxia promotes the generation of augmented breaths, but only in poikilocapnic conditions, where hypocapnia develops. Our results, therefore, reveal a means by which CO2 exerts a stabilizing influence on breathing, which may be of particular relevance during sleep in conditions commonly associated with respiratory instability.

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“…The present work shows for the first time that catecholaminergic inputs to PVN contribute to respiratory responses to chemoreflex activation. Augmented breaths increase in frequency during hypoxia (6,39) and are thought to limit atelectasis and the resulting hypoventilated regions of the lung (41). Therefore, occasional augmented breaths are important for effective lung function.…”

Section: R725mentioning

confidence: 99%

Catecholaminergic neurons projecting to the paraventricular nucleus of the hypothalamus are essential for cardiorespiratory adjustments to hypoxia

King

Ruyle

Kline

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

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King TL, Ruyle BC, Kline DD, Heesch CM, Hasser EM. Catecholaminergic neurons projecting to the paraventricular nucleus of the hypothalamus are essential for cardiorespiratory adjustments to hypoxia. Am J Physiol Regul Integr Comp Physiol 309: R721-R731, 2015. First published July 8, 2015 doi:10.1152/ajpregu.00540.2014.-Brainstem catecholamine neurons modulate sensory information and participate in control of cardiorespiratory function. These neurons have multiple projections, including to the paraventricular nucleus (PVN), which contributes to cardiorespiratory and neuroendocrine responses to hypoxia. We have shown that PVN-projecting catecholaminergic neurons are activated by hypoxia, but the function of these neurons is not known. To test the hypothesis that PVN-projecting catecholamine neurons participate in responses to respiratory challenges, we injected IgG saporin (control; n ϭ 6) or anti-dopamine ␤-hydroxylase saporin (DSAP; n ϭ 6) into the PVN to retrogradely lesion catecholamine neurons projecting to the PVN. After 2 wk, respiratory measurements (plethysmography) were made in awake rats during normoxia, increasing intensities of hypoxia (12, 10, and 8% O 2) and hypercapnia (5% CO 2-95% O2). DSAP decreased the number of tyrosine hydroxylase-immunoreactive terminals in PVN and cells counted in ventrolateral medulla (VLM; Ϫ37%) and nucleus tractus solitarii (nTS; Ϫ36%). DSAP produced a small but significant decrease in respiratory rate at baseline (during normoxia) and at all intensities of hypoxia. Tidal volume and minute ventilation (V E) index also were impaired at higher hypoxic intensities (10-8% O 2; e.g., VE at 8% O2: IgG ϭ 181 Ϯ 22, DSAP ϭ 91 Ϯ 4 arbitrary units). Depressed ventilation in DSAP rats was associated with significantly lower arterial O 2 saturation at all hypoxic intensities. PVN DSAP also reduced ventilatory responses to 5% CO 2 (VE: IgG ϭ 176 Ϯ 21 and DSAP ϭ 84 Ϯ 5 arbitrary units). Data indicate that catecholamine neurons projecting to the PVN are important for peripheral and central chemoreflex respiratory responses and for maintenance of arterial oxygen levels during hypoxic stimuli.chemoreflex; blood pressure; ventilation; anti-dopamine ␤-hydroxylase saporin; brainstem PERIPHERAL CHEMOREFLEX ACTIVATION by systemic hypoxia produces highly integrated respiratory, autonomic, behavioral, and endocrine responses (15,17). Together these responses are critical for homeostasis, serving to restore and maintain tissue oxygenation. The central nervous system pathways involved in responses to acute hypoxia are complex. Peripheral chemoreceptor afferent nerves from the carotid bodies project onto neurons located in the nucleus tractus solitarii (nTS) (40, 51), where chemoreceptor afferent input is modulated and integrated. The nTS sends projections to the rostral ventrolateral medulla (RVLM) (28,30), and this projection is considered the primary pathway mediating cardiorespiratory chemoreflex responses.The hypothalamic paraventricular nucleus (PVN) is also important in the integrated respo...

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The mammalian breathing mechanism

Cited by 18 publications

References 17 publications

Factors Affecting the Intrapleural Pressure and Pulmonary Ventilation in Rats

Factors Affecting the Intrapleural Pressure and Pulmonary Ventilation in Rats

Hypocapnia increases the prevalence of hypoxia-induced augmented breaths

Catecholaminergic neurons projecting to the paraventricular nucleus of the hypothalamus are essential for cardiorespiratory adjustments to hypoxia

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