Increased Breathing Rate Research Articles

The pattern and influential factors of aquatic pharyngeal movements of Trionyx sinensis

1. 1. The pharyngeal movements of Trionyx sinensis during submersion where recorded with physiological instruments. 2. 2. Anoxia or hypercapnia caused a marked increase in breathing rate of tested turtles during voluntary diving, and in anoxia there was a significant increase in the frequency of aquatic pharyngeal movements while hypercapnia had a slight or no effect on the frequency of these movements. 3. 3. During voluntary diving when turtles could easily extend their heads out of water to breathe air, the frequency of rhythmic pharyngeal movements was lower; but during forced submersion, the frequency was higher and the movements were continuous. 4. 4. The frequency increased more rapidly and greatly when turtles were in forced submersion than when they dived freely and could easily surface to breathe in N 2. 5. 5. The frequency of pharyngeal movements of T. sinensis during diving in an aquarium with water depth of 30 or 45 cm was markedly higher than that at a water depth of 15 cm. Disturbing stimuli also influenced the aquatic rhythmic pharyngeal movements of T. sinensis.

Respiratory and cardiovascular effects of inhaled and intravenous bradykinin, PGE2, and PGF2 alpha in dogs.

Prostaglandins (PGs) and bradykinin act as potent respiratory irritants in both normal and asthmatic subjects, but their sites of action are unknown. We compared the cardiorespiratory effects of bradykinin, PGE2, and PGF2 alpha nebulized into the isolated "in situ" larynx, inhaled into the tracheobronchial tree, and injected intravenously in anesthetized spontaneously breathing dogs. Laryngeal administration only resulted in a brief burst of rapid shallow breaths produced by bradykinin (1,000 micrograms/ml) in one of five dogs. Tracheobronchial administration of bradykinin (1,000 micrograms/ml) increased breathing rate and tidal volume (VT) in four of seven dogs without changing cardiovascular parameters, whereas PGE2 (500 micrograms/ml) caused similar effects in two of six dogs. Lower concentrations of both agents were essentially without effect. PGF2 alpha (50-500 micrograms/ml) inhaled into the lower airway increased breathing rate, reduced VT, and caused a concentration-dependent bronchoconstriction that was significantly reduced by atropine. Inhaled PGF2 alpha only slightly increased arterial blood pressure (5.8 +/- 2.8%) and heart rate (12.0 +/- 6.4%). Intravenous PGF2 alpha (5 micrograms/kg) increased upper and lower airway resistances, which were accompanied by a decrease in breathing rate and VT, hypertension, and bradycardia. Bradykinin (1 micrograms/kg) and PGE2 (1 and 3 micrograms/kg) produced apnea followed by rapid shallow breathing, bradycardia, and hypotension. These results indicate that the tracheobronchial tree is considerably more responsive to aerosolized bradykinin, PGE2, and PGF2 alpha than the laryngeal region. Moreover, the stronger effects produced by intravascular administration suggest a greater accessibility of rapidly adapting stretch receptors and C-fiber endings from the vascular bed than from the airway lumen.

The effect of CO 2- and O 2-gas mixtures on laser Doppler measured cochlear and skin blood flow in guinea pigs

The effects of carbogen (5% CO 2:95% O 2) 10% CO 2-in-air and 100% O 2 on cochlear blood flow (CBF), skin blood flow (SBP), blood pressure (BP) and arterial blood gases were investigated in the anesthetized, respired or self-respiring guinea pig. In respired animals, CBF and SBF were increased with carbogen and 10% CO 2-in-air and decreased with O 2. BP was elevated with each gas. In freely breathing animals, only 10% CO 2-in-air caused a small increase in CBF; both carbogen and O 2 caused CBF to decrease. SPF changes were similar in form, but larger than those seen in respirated subjects. No consistant change in BP was seen during breathing of these mixtures. Arterial PO 2 was increased by carbogen and 10% CO 2-in-air for both groups. PCO 2 increased for both CO 2 gas mixtures during forced respiration; but in free-breathing animals PCO 2 only increased for 10% CO 2-in-air (normal PCO 2 values were maintained with carbogen thorough increased breathing rate). The observed changes in CBF were consistant with a balance between a combined vasoconstrictive effect of PO 2 and vasodilation effect of PCO 2 on cochlear vessels. Analysis of cochlear vascular conductivity (CBF/BP) indicated that vasodilation was significant only with 10% CO 2-in-air in respirated animals. In all other conditions the increased CBF apparently reflects the increase profusion pressure associated with respiration of each gas. For clinical purposes, while carbogen does not appear to directly cause vasodilation of cochlear vessels it does lead to an increased oxygenation of the cochlea blood and would appear to avoid the cochlear vasoconstriction caused by 100% O 2.

Release of Tumor Necrosis Factor in Guinea Pigs upon Acute Inhalation of Cotton Dust

In guinea pigs, inhalation of cotton dust results in an acute pulmonary response with symptoms of increased breathing rate, cough, bronchoconstriction, and periods of apnea. These symptoms resemble those noted in individuals upon exposure to cotton and other organic dusts. A major contaminant of cotton dust is bacterial endotoxin. Because endotoxin, or lipopolysaccharide, is recognized to be a potent stimulator of tumor necrosis factor (TNF), it was postulated that TNF might be released in the lung following cotton dust exposure and associated with the pulmonary inflammatory response. Groups of guinea pigs were exposed to an atmosphere of 33 mg/m3 cotton dust for up to 6 h. At 3, 6, 7.5, and 24 h, lungs were isolated and lavaged to assess cell populations and production of TNF. Neutrophil infiltration was apparent by 3 h as was a marked increase in TNF in bronchial alveolar lavage fluid. Alveolar macrophages (AM) isolated at 3 h showed enhanced release of TNF upon in vitro culture when compared with those isolated at the other time points. AM were found to be primed to release TNF upon ex vivo stimulation with lipopolysaccharide. The greatest effect was noted with AM isolated 1.5 h after the 6-h cotton dust exposure. These results demonstrate the ability of cotton dust to cause release of TNF in the lung and suggest a role for TNF in the inflammatory response to cotton dust.

Characteristics of weekly pulmonary hypersensitivity responses elicited in the guinea pig by inhalation of ovalbumin aerosols

We have reported the development of a guinea pig animal model for pulmonary hypersensitivity to inhaled chemicals in which respirations of animals are monitored continuously for 24 hr permitting detection of immediate- (IAR) and late-onset (LAR) airway reactions. Additionally implanted temperature transmitters allow determination of accompanying febrile responses. The current study investigated the relationship between severity of IAR and occurrence of LAR in individual animals. To quantify severity, a grading system was devised which took into account time to response, increase in breathing rate, and occurrence of airway constriction (ACR). Guinea pigs were sensitized by ip injection with 1 mg ovalbumin (OA). On Day 14, inhalation challenge with 12 mg/m 3 OA resulted in severe IAR in all animals. No LAR were detected. Subsequent weekly inhalation challenges with OA resulted in less severe IARs and occasionally in absence of response. Febrile reactions were not detected. On one occasion a LAR was observed. It occurred in the animal demonstrating the most severe IARs and having the highest titer of specific homocytotropic antibody. These results are consistent with the mechanism of IAR involving release of spasmogenic mediators from mast cells as a result of antigen crosslinking of surface antibody. The mechanism of the LAR is addressed in the accompanying paper in which LARs are more consistently produced in OA-sensitized guinea pigs.

Yawning: No effect of 3–5% CO 2, 100% O 2, and exercise

Using human college-age subjects, the present study tested the commonly cited but previously untested hypothesis that yawning is facilitated by higher than normal levels of CO2 or lower than normal levels of O2 in the blood by comparing the effect on yawning of breathing 100% O2 and gas mixtures with higher than normal levels of CO2 (3 or 5%) with compressed air, the control condition. If yawning is a response to heightened blood CO2, the CO2 mixtures should increase yawning rate and/or duration. If low blood O2 produced yawning, breathing 100% O2 should inhibit yawning. The CO2/O2 hypothesis was rejected because breathing neither pure O2 nor gases high in CO2 had a significant effect on yawning although both increased breathing rate. A second study found that exercise sufficient to double breathing rate had no effect on yawning. The two studies suggest that yawning does not serve a primary respiratory function and that yawning and breathing are triggered by different internal states and are controlled by separate mechanisms.

Lung damage after hemithoracic irradiation: Dependence on mouse strain

A comparative study was performed on CBA, C57Bl mice and their F1 hybrid cross (CBBF1) after right hemithorax irradiation using doses ranging from 15 to 35 Gy. A dose-dependent increase in breathing rate was observed, corresponding to the expression of radiation pneumonitis in the irradiated lung. The use of hemithoracic irradiation enabled this to be observed without any lethality. Results obtained from X-ray computerized tomography (CT), lung weight and histology complemented the breathing rate studies. CBA mice showed a peak response at 16 weeks followed by a decline in breathing rate coincident with a compensatory hypertrophy of the shielded left lung. The manifestation of radiation pneumonitis in C57Bl mice was considerably delayed, supporting previous findings on whole-thorax irradiated animals. The latent period in CBBF1 hybrid mice was intermediate between the parent strains.

Late Functional and Biochemical Changes in Mouse Lung after Irradiation: Differential Effects of WR-2721

The radioprotective effect of WR-2721 on late damage after whole thorax irradiation has been studied after split doses of radiation using the standard death and breathing rate assays at monthly intervals between 3 and 15 months after irradiation, as well as two biochemical measurements of injury at 15 months, hydroxyproline (HP), an indicator of tissue fibrosis, and DNA content, an indicator of tissue cellularity. A comparison of HP/lung and breaths per minute (BPM) in each dose group in the WR-2721 and non-WR-2721-treated mice 15 months after irradiation showed that the relationship between these two assays of late lung injury was not the same. There were large dose-related increases in breathing rate corresponding to relatively small changes in HP in the lungs of mice given radiation alone. In contrast, the mice given WR-2721 before irradiation showed large dose-related increases in HP/lung, but BPM remained relatively constant independent of dose. These data suggest then that changes in breathing rate and deaths later than 9 months after whole lung irradiation may not be due to collagen accumulation in the lung. WR-2721 did protect better against late lung functional changes (protection factors (PF) = 1.6) and late deaths (PF = 1.51) than against earlier changes in these same assays (PF = 1.4 and 1.28, respectively). Although the earlier-appearing injury after whole thoracic irradiation is most likely related to lung damage with deaths and increases in breathing rate resulting from pneumonitis, the cause of the late-appearing functional injury in the lung after radiation is not clear. Thus protection of late lung damage measured from either lethality or breathing rate is not related to the prevention of lung fibrosis.

Chronic ventilatory effects of diazepam and barbiturates in conscious cats

The chronic ventilatory effects of several hypnotics were investigated in six conscious cats recorded during control periods and during three consecutive days' administration of either diazepam (5 mg), pentobarbital (30 mg) or phenobarbital (60 mg). Ventilation was analyzed in terms of tidal volume (VT), breathing rate (BR) and minute ventilation (dotV = VT × BR). Minute ventilation was increased with diazepam owing to an increase in breathing rate in spite of a small decrease in tidal volume. With pentobarbital, minute ventilation was not changed because the decrease in breathing rate was compensated for by an increase in tidal volume. With phenobarbital, the results were more variable from one animal to another and on average, only tidal volume was increased. The animals were often excited following the administration of diazepam and sometimes drowsy with pentobarbital; with phenobarbital, behaviour varied among animals. Obviously, the present results cannot be extrapolated if different doses and perhaps different duration of drug administration are used. It is suggested that the ventilatory effects of the drugs cannot be explained only by a direct action on the brain stem respiratory network. Since the level of vigilance was altered by the various drugs, it is proposed that the ventilatory changes observed could be secondary to a supra-pontine action of the drugs which could modify both the level of alertness and respiratory activity.

Exercise and air pollution

Abstract Will the air quality in Los Angeles be a matter of concern for athletes participating in the 1984 Olympics? This question and corollaries of it are being asked with increasing frequency as the time of the Olympics nears. This review identifies the major pollutants that have been shown to produce physiological changes which can and may effect athletic performance. Ozone is the major contaminant of Los Angles air which in recent times has received major research interest. Specifically, ozone has been documented as a potent airway irritant capable of initiating its effects at concentrations as low as 0.30 ppm. Recent evidence indicates that, when integrated with the sustained high ventilation volumes of the elite athlete, ozone's airway constrictive effect is manifest at concentrations of 0.20 ppm. The effect of ozone causes an increase in breathing rate and a decrease in tidal volume for a given workload along with substernal pain. At the current ambient levels it is unlikely that sulphur dioxide w...

Behavioral and autonomic thermoregulation in mice exposed to microwave radiation.

Preferred ambient temperature (Ta) and breathing rate were measured in free-moving mice exposed to 2,450-MHz microwaves. A waveguide-exposure system was imposed with a longitudinal temperature gradient that permitted mice to select their preferred Ta. Breathing rate was determined by analyzing the rhythmic shifts in microwave energy not absorbed by the animal. Without microwave exposure mice selected an average Ta of 31 degrees C. This preferred Ta did not change until the specific absorption rate (SAR) at 2,450 MHz exceeded approximately 7.0 W X kg-1. Mice maintained their breathing rate near baseline levels by selecting a cooler Ta during microwave exposure. In contrast, mice maintained at 31 degrees C underwent a sharp increase in breathing rate when SAR exceeded approximately 7.0 W X kg-1. Mice exposed to microwaves in a waveguide with a temperature gradient increased breathing rate 0.6 breaths/min per unit increase in SAR, whereas without the temperature gradient breathing rate increased by 9.6 breaths/min per unit increase in SAR. Data from this study support previous studies that have shown behavioral thermoregulation is more effective (or efficient) in minimizing a thermal load than autonomic thermoregulation.

Repair in Mouse Lung between Multiple Small Doses of X Rays

Multiple fraction experiments have been carried out to determine the response of mouse lung to repeated small doses of 240 kV X rays down to 150 rad/fraction using breathing rate and lethality to assess damage. Two experimental approaches were used to measure the effect of small doses in vivo: (1) multiple equal doses and (2) multiple priming doses followed by a large test dose. Analysis was performed using the multitarget two-component model and the linear quadratic model of cell survival. The amount of repair was calculated as a function of either dose per fraction (FR) or total dose (Frec). Both FR and Frec increased with decreasing dose per fraction but the change in FR was small. The advantage of Frec was that it varied more rapidly with dose per fraction than FR, so that possible differences between tissue repair capabilities are more visible on plots of repair as a function of dose per fraction. FR and Frec both decreased with the level of single-dose isoeffect injury; thus neither parameter is acceptable for comparing repair capability of different normal tissues with widely differing single-dose end point levels. Beta/alpha values were calculated and found to be a more acceptable index of repair capability than either FR or Frec because unlike those two parameters, beta/alpha varied little with level of damage. Beta/alpha values of 1.7 to 4.2 krad-1 were obtained for both lung death and increased breathing rate and are clearly intermediate between the lower beta/alpha ratios for acute reactions, i.e., skin and intestine, and the higher values for late reactions in kidney and spinal cord.

In-flight measures of stress reduction due to wearing expandable foam earplugs : Wichman, H., McIntyre, M., and Accomazzo, E.Aviation, Space and Environmental Medicine, Sep 1979, 50.9, 898–900

Ten low-time pilots (less than 150 h) who did not normally use earplugs flew three flights each in Cessna-152 training planes. The flight routines were all the same, lasting about 45 minutes. Each pilot flew one flight while adapting to earplugs, another flight with earplugs, and a third flight without earplugs. Pilot's breathing rate was the measure of autonomic arousal. A baseline rate was measured before each flight and in-flight scores were expressed as changes from baseline. Half the pilots flew their flights in the order, with-with-without earplugs and half flew in the order without-with-with. Results showed a mean increase in breathing rate above preflight baseline of 30% without earplugs and an increase of only 21% with earplugs (data taken from second flight with earplugs) for a significant savings of 9% (p less than 0.025, Wilcoxsen matched-pairs signed-ranks test, one tailed).

Whole body plethysmography as a noninvasive assay of toxic lung injury in mice: Studies with the pulmonary alkylating agent and cytotoxin, 4-ipomeanol

The effect of 4-ipomeanol on the lungs of experimental animals often is measured by destructive assays, such as death, histology, or pulmonary alkylation. Breathing rate is a noninvasive assay routinely used to quantify the effects of radiation on the lungs of mice, which may be useful in assessing injury from other lung toxins. The effects of graded single doses of 4-ipomeanol on the breathing rate of mice were studied up to 3 weeks after treatment. Changes in breathing rate were observed up to 4 days after 4-ipomeanol treatment with nonlethal doses of the compound giving a clear, dose-dependent increase in breathing rate at 8 hr and 4 days after treatment. Time course and dose-response studies showed good agreement between changes in breathing rate and pulmonary alkylation after 4-ipomeanol treatment. Pretreatment of the mice with diethylmaleate (DEM) increased the pulmonary alkylation and toxicity of 4-ipomeanol. However, breathing rate was severely depressed by all doses of DEM that were examined. This decrease was not dose dependent within the range of doses studied. These studies indicate that breathing rate can be used to quantify the effects of nonlethal doses of 4-ipomeanol on the lungs of mice and does not require killing the animal. The technique may be similarly applicable to studies of other pulmonary toxins, but careful attention must be given to time and dose relationships and the possible effects of other drugs or pretreatments.

Regional blood flow changes in response to thermal stimulation of the brain and spinal cord in the Pekin duck

In conscious Pekin ducks, carotid and sciatic blood flows, respiratory rate, core and skin temperatures were measured during selective thermal stimulations of the spinal cord and rostral brain stem in thermoneutral (20 °C) and warm (32 °C) ambient conditions. At thermoneutral ambient temperature selective heating of the spinal cord by 2–3 °C (to 43–44 °C) increased the carotid blood flow by 138% and the sciatic blood flow by 46%. Increase in blood flows was correlated with increased breathing rate and beak and web skin temperatures. Selective cooling of the spinal cord at warm ambient temperatures and panting reduced the blood flow in both arteries and decreased the breathing rate. Heating or cooling of the brain stem showed generally very weak but otherwise similar responses as thermal stimulation of the spinal cord. In one duck out of six there was a marked effect on regional blood flow during brain stimulation. The results show that thermal stimulation of the spinal cord exerts a marked influence on regional blood flow important in thermoregulation, whereas the lower brain stem shows only a weak thermosensitivity, and stimulation caused only small cardiovascular changes of no major consequence in thermoregulation.

Breathing movements in fetal lambs and the effect of hypercapnia.

1. A breath-by-breath analysis was made of tracheal pressure records from fetal lambs in utero at 117--130 days gestation. 2. Episodes of rapid irregular breathing were accompanied by diaphragmatic e.m.g. activity and were characterized by a gradual increase in breathing rate initially and a terminal decline. Within each episode breathing was very irregular. 3. Inspiratory time increased with increasing expiratory time rapidly as the rate fell to about 80/min, and thereafter more slowly. 4. The principal effects of hypercapnia (a rise in fetal Pa, CO2 by approximately 11 mmHg) were to increase the depth of fetal breathing, by nearly twofold, and to make breathing much more regular. A change in rate was doubtful because of the skew distribution of normal breath intervals.

Restoration of reflex ventilatory response to hypoxia after removal of carotid bodies in the cat

In mammals there are two sets of peripheral arterial chemoreceptors, the carotid bodies innervated by the sinus branch of the glossopharyngeal nerve and the aortic bodies innervated by the vagus nerves. The afferent impulse discharge from both receptors increases during hypoxia and there is a reflexly mediated increase in ventilation (hypoxic hyperventilation). In the present study we tested this response by exposing anesthetized cats to decreased inspired O 2 concentration before and up to 315 days after bilateral resection of the carotid bodies. Acutely after removing the carotid bodies, hypoxic hyperventilation was abolished. This observation supports the view that the reflex pathway from the aortic body receptors normally contributes minimally to hypoxic hyperventilation. Subsequently, there was a restoration of hypoxic hyperventilation. Restoration was significant 30–43 days after removing the carotid bodies, it reached 70% of the preoperative value at 93–111 days and was essentially complete in terminal experiments 260–315 days after carotid body resection. In terminal experiments, hypoxic hyperventilation was not affected by recutting the regenerated carotid sinus nerves but was abolished completely by bilateral transection of the cervical vagosympathetic trunks. The restored ventilatory response was due predominantly to an increase in rate of breathing while an increase in tidal volume was predominant before carotid body resection. Resting ventilation breathing room air was not consistently decreased after carotid body resection while expired CO 2 was elevated from day 20 to day 111 and at the preoperative level in terminal experiments. It is concluded that restoration of hypoxic hyperventilation in the cat after carotid body resection is mediated by the reflex pathway from aortic body chemoreceptors. The possible contribution of chemo-receptive regenerated carotid sinus nerve axons was excluded. It is suggested that restoration may be a consequence of the central reorganization of chemoreceptor afferent pathways consequent to interruption of the carotid body reflex pathway and that as a result the ‘gain’ of the aortic body ventilatory chemoreflex is enhanced.

Changes in Ventilatory Pattern Induced by Intravenous Anesthetic Agents in Human Subjects

The tidal volume-inspiratory duration relationship was studied during air breathing and rebreathing in conscious and anesthetized human subjects using three different intravenous agents. The results observed have been compared with similar experiments carried out in cats. Its has been shown that anesthesia provokes an increase in breathing rate associated with a decrease in tidal volume in human subjects; an opposite effect on breathing rate was observed in cats. Thus, the tidal volume-inspiratory duration relationship, although very similar in the conscious cat or human subject, is very different under anesthesia. The results were quite consistent in a given species whatever the nature of the drug used. It is suggested that modifications of the breathing rate by anesthesia, related to animal species, are caused by central effects of the drug. These effects are probably mediated by different actions on inputs to the inspiratory off-switch mechanisms in the two species.

Changes in ventilatory pattern induced by intravenous anesthetic agents in human subjects

The tidal volume-inspiratory duration relationship was studied during air breathing and rebreathing in conscious and anesthetized human subjects using three different intravenous agents. The results observed have been compared with similar experiments carried out in cats. Its has been shown that anesthesia provokes an increase in breathing rate associated with a decrease in tidal volume in human subjects; an opposite effect on breathing rate was observed in cats. Thus, the tidal volume-inspiratory duration relationship, although very similar in the conscious cat or human subject, is very different under anesthesia. The results were quite consistent in a given species whatever the nature of the drug used. It is suggested that modifications of the breathing rate by anesthesia, related to animal species, are caused by central effects of the drug. These effects are probably mediated by different actions on inputs to the inspiratory "off-switch" mechanisms in the two species.

Pulmonary reflexes and breathing pattern during sleep in the opossum

Paradoxical sleep (PS) in the opossum ( Didelphis virginiana) and other mammals is typically accompanied by irregular breathing, while even breathing is usually found during slow wave sleep (SWS). During PS certain brainstem reflexes are depressed, and it is possible that similar depression of pulmonary reflexes could contribute to the observed ventilatory uneveness. To test this possibility, we. assessed pulmonary reflexes in the opossum during SWS and during PS when breathing was irregular. Prolongation of expiratory duration with airway occlusion at end inspiration and prolongation of inspiratory duration with airway occlusion at end expiration are both associated with pulmonary reflexes activated by lung inflation. These responses were obtained during PS, and the results suggested that the reflex effects, could be as prominent during PS as during SWS. Pulmonary deflation, produced by raising pressure around the thorax, increased breathing rate during both PS and SWS and generally increased the regularity of respiration during PS. Results of this study do not support the idea that irregular breathing during PS is associated with maintained depression of pulmonary reflexes.