Ventilatory CO2 drive in the tortoise Testudo horsfieldi

1980 ◽  
Vol 87 (1) ◽  
pp. 229-236
Author(s):  
G. Benchetrit ◽  
P. Dejours
Keyword(s):  
Tidal Volume ◽  
Air Flow ◽  
Respiratory Frequency ◽  
Vagus Nerves ◽  
Peripheral Chemoreceptors ◽  
Before And After ◽  
Flow Inhalation ◽  
Bilateral Vagotomy

1. Ventilation was recorded by pneumotachography, before and after bilateral vagotomy, in conscious tortoises (Testudo horsfieldi) (breathing 0, 2, 3 or 4% CO2 in air or oxygen). 2. Each breath consists of expiratory and inspiratory phases and an apneic plateau (absence of air flow). Inhalation of hypercapnic mixtures led to increased ventilatory flow, augmentation of tidal volume, and an increase in respiratory frequency through the shortening of the apneic plateau. 3. Intact tortoises breathing hypercapnic-hyperoxic mixtures hyperventilated less than with hypercapnic-normoxic mixtures. 4. In bivagotomized animals, the respiratory frequency decreased, the expiratory and inspiratory durations lengthened, and the apneic plateau was prolonged. The tidal volume was increased, but ventilation, nevertheless, decreased slightly. 5. Bivagotomized animals breathing hypercapnic-normoxic or hypercapnic-hyperoxic mixtures hyperventilated, but less than intact animals under the same conditions. 6. It is concluded that in tortoises there are: (1) peripheral chemoreceptors which are innervated by branches of the vagus nerves, and are sensitive to CO2; and (2) an extrathoracic, probably central, ventilatory CO2 drive.

Hypoxic respiratory responses attenuated by ablation of the cerebellum or fastigial nuclei

1995 ◽  
Vol 79 (4) ◽  
pp. 1181-1189 ◽  
Author(s):  
F. Xu ◽  
J. Owen ◽  
D. T. Frazier
Keyword(s):  
Tidal Volume ◽  
Minute Ventilation ◽  
Sodium Cyanide ◽  
Respiratory Frequency ◽  
Peripheral Chemoreceptors ◽  
Before And After ◽  
Progressive Hypoxia ◽  
End Tidal ◽  
Diaphragm Activity ◽  
Respiratory Responses

The general contribution of the cerebellum to hypoxic respiratory responses and the special role of the fastigial nucleus (FN) in the hypoxic respiratory reflex mediated via peripheral chemoreceptors were investigated in anesthetized and spontaneously breathing cats. Seven cats were exposed to isocapnic progressive hypoxia before and after cerebellectomy by decreasing the fractional concentration of end-tidal O2 (FETO2) from 15 +/- 0.3% to 7% while maintaining the pressure of end-tidal CO2 at a constant level of approximately 30 mmHg. Five additional cats inhaled five breaths of pure N2 (transient hypoxia) and received sodium cyanide (50 micrograms iv) before and after thermal lesions of the bilateral FN. The results showed that cerebellectomy or FN lesions failed to alter the respiratory variables (minute ventilation, tidal volume, respiratory frequency, and the peak of integrated diaphragm activity) during eupneic breathing. However, cerebellectomy significantly attenuated minute ventilation (FETO2 < or = 13%) and the peak of integrated diaphragm activity (FETO2 < or = 10%) compared with control. During progressive hypoxia, changes in respiratory frequency were noted earlier (FETO2 < or = 13%) than changes in tidal volume (FETO2 < or = 10%). Similarly, bilateral lesions of the FN resulted in a profound reduction in these respiratory responses to transient hypoxia and sodium cyanide. We conclude that the cerebellum can facilitate the respiratory response to hypoxia and that the FN is an important region in the modulation of the hypoxic respiratory responses, presumably via its effects on inputs from peripheral chemoreceptors.

Sonomicrometric regional diaphragmatic shortening in awake sheep after thoracic surgery

1989 ◽  
Vol 67 (6) ◽  
pp. 2357-2368 ◽  
Author(s):  
A. Torres ◽  
W. R. Kimball ◽  
J. Qvist ◽  
K. Stanek ◽  
R. M. Kacmarek ◽  
...  
Keyword(s):  
Thoracic Surgery ◽  
Tidal Volume ◽  
Minute Ventilation ◽  
Respiratory Frequency ◽  
Quiet Breathing ◽  
Transdiaphragmatic Pressure ◽  
Right Thoracotomy ◽  
Before And After ◽  
End Tidal ◽  
End Tidal Co2

Through a right thoracotomy in seven sheep we chronically implanted sonomicrometry crystals and electromyographic electrodes in the costal and crural diaphragmatic regions. Awake sheep were studied during recovery for 4-6 wk, both during quiet breathing (QB) and during CO2 rebreathing. Tidal volume, respiratory frequency, and esophageal and gastric pressures were studied before and after surgery. Normalized resting length (LFRC) was significantly decreased for the costal segment on postoperative day 1 compared with postoperative day 28. Fractional costal shortening both during QB and at 10% end-tidal CO2 (ETCO2) increased significantly from postoperative days 1 to 28, whereas crural shortening did not change during QB but progressively increased at 10% ETCO2. Maximal costal shortening during electrophrenic stimulation was constant at 40% LFRC during recovery, although maximal crural shortening increased from 23 to 32% LFRC. Minute ventilation, tidal volume, and transdiaphragmatic pressure at 10% ETCO2 increased progressively after thoracotomy until postoperative day 28. Our results suggest there is profound diaphragmatic inhibition after thoracotomy and crystal implantation in sheep that requires at least 3-4 wk for stable recovery.

Breathing pattern of anesthetized humans during pancuronium-induced partial paralysis

1988 ◽  
Vol 64 (1) ◽  
pp. 78-83 ◽  
Author(s):  
T. Nishino ◽  
N. Yokokawa ◽  
K. Hiraga ◽  
Y. Honda ◽  
T. Mizuguchi
Keyword(s):  
Tidal Volume ◽  
Respiratory Muscles ◽  
Respiratory Frequency ◽  
Breathing Patterns ◽  
Inspiratory Time ◽  
Muscle Paralysis ◽  
Airway Occlusion ◽  
Enflurane Anesthesia ◽  
Before And After ◽  
The Face

We investigated the breathing patterns of 17 subjects anesthetized with enflurane before and after partial muscle paralysis produced by pancuronium bromide. In the face of significant muscle weakness produced by pancuronium, breathing patterns are characterized by decreases in both tidal volume and respiratory frequency. The decreased tidal volume corresponded to the decrease in occlusion pressure, indicating that the decreased tidal volume results solely from a decreased contractile force of the respiratory muscles. The decreased respiratory frequency was due to prolongation of both inspiratory and expiratory time without changing the ratio of the inspiratory time to the total breath time. Withdrawal of phasic vagal influence by airway occlusion before partial muscle paralysis revealed that an active Breuer-Hering inflation reflex was operative in only 8 of all 17 subjects. Since the contribution of the Breuer-Hering inflation reflex alone does not seem to account for the consistent decrease in respiratory frequency, some other mechanisms modulating respiratory frequency might be involved in the characteristic breathing patterns during partial muscle paralysis under enflurane anesthesia.

Respiratory responses in reversible diaphragm paralysis

1981 ◽  
Vol 51 (5) ◽  
pp. 1150-1156 ◽  
Author(s):  
M. L. Nochomovitz ◽  
M. Goldman ◽  
J. Mitra ◽  
N. S. Cherniack
Keyword(s):  
Electrical Activity ◽  
Tidal Volume ◽  
Phrenic Nerve ◽  
Respiratory Activity ◽  
Vagus Nerves ◽  
Inspiratory Time ◽  
Transdiaphragmatic Pressure ◽  
Co2 Partial Pressure ◽  
Diaphragm Paralysis ◽  
Before And After

The effects of diaphragm paralysis on respiratory activity were assessed in 13 anesthetized, spontaneously breathing dogs studied in the supine position. Transient diaphragmatic paralysis was induced by bilateral phrenic nerve cooling. Respiratory activity was assessed from measurements of ventilation and from the moving time averages of electrical activity recorded from the intercostal muscles and the central end of the fifth cervical root of the phrenic nerve. The degree of diaphragm paralysis was evaluated from changes in transdiaphragmatic pressure and reflected in rib cage and abdominal displacements. Animals were studied both before and after vagotomy breathing O2, 3.5% CO2 in O2, or 7% CO2 in O2. In dogs with intact vagi, both peak and rate of rise of phrenic and inspiratory intercostal electrical activity increased progressively as transdiaphragmatic pressure fell. Tidal volume decreased and breathing frequency increased as a result of a shortening in expiratory time. Inspiratory time and ventilation were unchanged by diaphragm paralysis. These findings were the same whether O2 or CO2 in O2 was breathed. After vagotomy, no significant change in phrenic or inspiratory intercostal activity occurred with diaphragm paralysis in spite of increased arterial CO2 partial pressure. Ventilation and tidal volume decreased significantly, and respiratory timing was unchanged. These results suggest that mechanisms mediated by the vagus nerves account for the compensatory increase in respiratory electrical activity during transient diaphragm paralysis. That inspiratory time is unchanged by diaphragm paralysis whereas the rate or rise of phrenic nerve activity increases suggest that reflexes other than the Hering-Breuer reflex contribute to the increased respiratory response.

Role of the carotid bodies in chemosensory ventilatory responses in the anesthetized mouse

2004 ◽  
Vol 97 (4) ◽  
pp. 1401-1407 ◽  
Author(s):  
Masahiko Izumizaki ◽  
Mieczyslaw Pokorski ◽  
Ikuo Homma
Keyword(s):  
Tidal Volume ◽  
Carotid Body ◽  
Minute Ventilation ◽  
Respiratory Frequency ◽  
Whole Body ◽  
Sudden Increase ◽  
Ventilatory Responses ◽  
Carotid Bodies ◽  
Before And After ◽  
Carotid Body Denervation

We examined the effects of carotid body denervation on ventilatory responses to normoxia (21% O2 in N2 for 240 s), hypoxic hypoxia (10 and 15% O2 in N2 for 90 and 120 s, respectively), and hyperoxic hypercapnia (5% CO2 in O2 for 240 s) in the spontaneously breathing urethane-anesthetized mouse. Respiratory measurements were made with a whole body, single-chamber plethysmograph before and after cutting both carotid sinus nerves. Baseline measurements in air showed that carotid body denervation was accompanied by lower minute ventilation with a reduction in respiratory frequency. On the basis of measurements with an open-circuit system, no significant differences in O2 consumption or CO2 production before and after chemodenervation were found. During both levels of hypoxia, animals with intact sinus nerves had increased respiratory frequency, tidal volume, and minute ventilation; however, after chemodenervation, animals experienced a drop in respiratory frequency and ventilatory depression. Tidal volume responses during 15% hypoxia were similar before and after carotid body denervation; during 10% hypoxia in chemodenervated animals, there was a sudden increase in tidal volume with an increase in the rate of inspiration, suggesting that gasping occurred. During hyperoxic hypercapnia, ventilatory responses were lower with a smaller tidal volume after chemodenervation than before. We conclude that the carotid bodies are essential for maintaining ventilation during eupnea, hypoxia, and hypercapnia in the anesthetized mouse.

Response of Laryngeal Airway Resistance to Chemoreceptor Stimulation: Effect of Pulmonary Afferent Denervation

1982 ◽  
Vol 90 (6) ◽  
pp. 723-727
Author(s):  
Thomas V. McCaffrey
Keyword(s):  
Airway Resistance ◽  
Afferent Input ◽  
Respiratory Neurons ◽  
Vagus Nerves ◽  
Before And After ◽  
Bilateral Vagotomy ◽  
Recurrent Laryngeal Nerves ◽  
Laryngeal Resistance ◽  
Stimulation Of ◽  
Laryngeal Airway

The response of laryngeal airway resistance to chemoreceptor stimulation was measured before and after vagotomy in ten anesthetized dogs. With the vagus nerves intact, stimulation of chemoreceptors produced a decrease in both inspiratory and expiratory laryngeal resistance. After bilateral vagotomy below the origin of the recurrent laryngeal nerves, stimulation of chemoreceptors produced a smaller decrease in inspiratory laryngeal resistance and an increase in expiratory laryngeal resistance. We concluded that pulmonary afferent input to the respiratory neurons maintains a low airway resistance during chemoreceptor stimulation.

Effects of Bilateral Vagotomy on Renal Function in the Rat

1971 ◽  
Vol 49 (5) ◽  
pp. 420-426 ◽  
Author(s):  
Paul F. Mercer
Keyword(s):  
Blood Pressure ◽  
Renal Function ◽  
Carotid Arteries ◽  
Control Group ◽  
Vagus Nerves ◽  
Renal Nerve ◽  
Arterial Blood ◽  
Before And After ◽  
Bilateral Vagotomy ◽  
Common Carotid Arteries

Renal function was studied in rats before and after section of the vagus nerves at the level of the common carotid arteries. In the control group of rats, sodium output and volume rate of urine flow increased following vagal section but glomerular filtration rate did not change. This response was not altered in other rats by desoxycorticosterone acetate, vasopressin, or renal nerve section. This response was similar to that seen in rats in which both common carotid arteries had been occluded. The natriuresis following bilateral vagotomy did not occur in rats in which the blood pressure was prevented from rising by means of aortic constriction. It is concluded that a natriuresis does occur following bilateral vagotomy. This natriuresis may be a result of the effect of arterial blood pressure following the vagotomy.

Vagal control of respiratory pattern during hyperpnea in domestic fowl

1984 ◽  
Vol 56 (6) ◽  
pp. 1650-1654 ◽  
Author(s):  
M. Gleeson ◽  
J. H. Brackenbury
Keyword(s):  
Body Temperature ◽  
Tidal Volume ◽  
Domestic Fowl ◽  
Ventilatory Response ◽  
Normal Animal ◽  
Minute Volume ◽  
Respiratory Frequency ◽  
Respiratory Pattern ◽  
Varied Pattern ◽  
Before And After

Minute volume, tidal volume, and respiratory frequency were measured during hyperpnea induced by exercise, increased body temperature, and CO2 inhalation. Ventilatory characteristics were compared before and after the vagus nerve had been blocked. In normal birds exercise produced increases in both tidal volume and respiratory frequency; hyperthermia produced a typical thermal polypnea consisting of greatly increased respiratory frequency and reduced tidal volume; CO2 inhalation produced increases in tidal volume and respiratory frequency when the birds were euthermic but a slowing of respiratory rate when the birds were hyperthermic. After vagal block these pronounced differences in the pattern of ventilatory response to the various respiratory stimuli were abolished. Instead there was a uniform ventilatory response to all three stimuli consisting mainly of increases in tidal volume combined with small increases in respiratory frequency. It is concluded that in the normal animal control of the varied pattern of ventilatory response to different respiratory stimuli is dependent on vagal fiber activity.

Role of the carotid chemoreceptors in regulation of inspiratory onset

1982 ◽  
Vol 52 (4) ◽  
pp. 863-868 ◽  
Author(s):  
G. Bowes ◽  
S. M. Andrey ◽  
L. F. Kozar ◽  
E. A. Phillipson
Keyword(s):  
Tidal Volume ◽  
Eye Movement ◽  
Co2 Concentration ◽  
Direct Proportion ◽  
Vagus Nerves ◽  
Inspiratory Time ◽  
Cuffed Endotracheal Tube ◽  
Carotid Bodies ◽  
Before And After

We studied the effect of intermittent tidal breaths of CO2-enriched air (3–9% CO2) on the duration of expiratory time (TE) in five trained dogs, before and after (3 dogs) bilateral surgical denervation of the carotid bodies (CBD). During studies the dogs lay quietly, either awake or in nonrapid-eye-movement sleep, and breathed through a cuffed endotracheal tube inserted via a chronic tracheostomy. Studies were conducted during bilateral blockade of the cervical vagus nerves (VB), achieved by circulating cold alcohol through radiators placed around exteriorized vagal skin loops. Prior to CBD, single breaths of CO2 significantly shortened TE and thus advanced the onset of the subsequent inspiration. Further, the decrease in TE induced by the CO2 stimulus was in direct proportion to the inspired CO2 concentration. Thus 3% CO2 shortened TE by 1.82 +/- 0.93 (SD) s, and 9% CO2 by 3.44 +/- 1.53 s. Changes in TE occurred in the absence of associated changes in either tidal volume or inspiratory time. After CBD, test breaths of CO2 failed to shorten TE during VB. We conclude that the carotid bodies have the ability to mediate changes in the timing of inspiratory onset in response to a transient CO2 stimulus.

Respiratory modulation of the activity in postganglionic neurons supplying skeletal muscle and skin of the rat hindlimb

1993 ◽  
Vol 70 (3) ◽  
pp. 920-930 ◽  
Author(s):  
H. J. Habler ◽  
W. Janig ◽  
M. Krummel ◽  
O. A. Peters
Keyword(s):  
Skeletal Muscle ◽  
Tidal Volume ◽  
Phrenic Nerve ◽  
Sympathetic Activity ◽  
Artificial Ventilation ◽  
Sympathetic Outflow ◽  
Experimental Conditions ◽  
Before And After ◽  
Bilateral Vagotomy ◽  
Respiratory Modulation

1. The respiratory modulation of activity in postganglionic neurons of the lumbar sympathetic outflow to skeletal muscle and hairy skin of the hindlimb was studied in anesthetized rats, either breathing spontaneously or paralyzed and artificially ventilated, using single- and multifiber recordings. The activity of the neurons was analyzed with respect to the phrenic nerve discharges or with respect to the cycle of artificial ventilation under various experimental conditions. 2. In total, 19 single and 62 multiunit preparations supplying skeletal muscle and 42 single and 95 multiunit preparations supplying skin were analyzed. Qualitatively, both populations and single- and multiunit preparations exhibited similar patterns. The majority (187/218 preparations) exhibited a depression of activity during inspiration and a peak of activity during expiration that was mostly accentuated during early expiration. The remainder exhibited a peak of activity at the transition between expiration and inspiration (n = 15) or showed no respiratory modulation (n = 16). 3. Respiratory modulation in the postganglionic neurons was similar in animals breathing spontaneously and in those that were paralyzed and artificially ventilated. 4. Systemic hypercapnia and asphyxia in most cases enhanced both the peak of activity during early expiration and the depression of activity during inspiration. 5. No peripheral (reflex) component mediated by arterial baroreceptors was found in vagotomized animals that was related to the cycle of artificial ventilation using a tidal volume of 1-2 ml and a ventilation frequency of 70 +/- 7 (SD) strokes, min-1. However, a small ventilation-related rhythm of arterial baroreceptor activity recorded from the aortic nerve was found under these conditions. 6. Respiratory modulation of postganglionic activity was similar before and after bilateral vagotomy. 7. It is concluded that respiratory modulation of sympathetic activity in rats is less differentiated than in cats. The observed differences between neurons supplying different targets are only quantitative. Possible mechanisms involved in the generation of respiratory modulation are discussed.

Sign in / Sign up

Export Citation Format

Share Document