Ventilatory interaction between hypoxia and [H+] at chemoreceptors of man

1975 ◽  
Vol 39 (2) ◽  
pp. 292-296 ◽  
Author(s):  
R. A. Gabel ◽  
R. B. Weiskopf
Keyword(s):  
Experimental Design ◽  
High Altitude ◽  
Sea Level ◽  
Acute Hypoxia ◽  
Simulated Altitude ◽  
Peripheral Chemoreceptor ◽  
Peripheral Chemoreceptors ◽  
Central Chemoreceptors ◽  
Progressive Hypoxia ◽  
The Mean

By measuring ventilation during isocapnic progressive hypoxia, peripheral chemoreceptor sensitivity to acute hypoxia (deltaV40) was measured in five normal young men under four sets of conditions: 1) at sea level at the subject's resting PCO2, 2) at sea level with PCO2 5 Torr above resting PCO2, 3) after 24 h at a simulated altitude of 4,267 m (PB = 447 Torr) at the subject's resting PCO2 measured during acute hyperoxia, and 4) after 24 h at high altitude, with PCO2 elevated to the subject's sea-level resting PCO2. With this experimental design, we were able to systematically vary the PCO2 and [H+] at the peripheral and central chemoreceptors of man. When mean pHa was decreased from 7.424 to 7.377 without significant change in PACO2, the mean deltaV40 increased from 18.0 to 55.9 1/min. Conversely, when mean PACO2 was altered between 33.8 and 41.6 Torr with pHa held relatively constant, the mean deltaV40 did not change. This suggests that it is the H+ and not CO2 which interacts with hypoxia in stimulating the ventilation of man. An additional finding was that the intrinsic sensitivity of the peripheral chemoreceptors to acute hypoxia did not change during 24 h of acclimatization to high altitude.

Effect of peripheral chemoreceptor denervation on acclimatization of goats during hypoxia

1981 ◽  
Vol 50 (2) ◽  
pp. 392-398 ◽  
Author(s):  
H. V. Forster ◽  
G. E. Bisgard ◽  
J. P. Klein
Keyword(s):  
Sea Level ◽  
Chronic Hypoxia ◽  
Alveolar Ventilation ◽  
Simulated Altitude ◽  
Peripheral Chemoreceptor ◽  
Peripheral Chemoreceptors ◽  
Carotid Chemoreceptors ◽  
Co2 Output

The purpose of this study was to determine the effect of peripheral chemoreceptor denervation on ventilatory acclimatization of goats during chronic hypoxia. After 1 h of stimulated altitude (PB 450 Torr), arterial O2 tension (PaO2) in seven normal goats averaged 42 Torr, and arterial CO2 tension (PaCO2) was 1.3 Torr below control (P less than 0.001). In these goats nearly 66% of the increase in alveolar ventilation (VA) associated with acclimatization occurred between 1.5 and 4 h of hypoxia. Acclimatization was complete by the 3rd day of hypoxia, and it caused 1) a 23% increase in VA/CO2 output (P less than 0.001); 2) a 5-Torr increase in PaO2 (P less than 0.001); and 3) a 6.5-Torr decrease in PaCO2 (P less than 0.001). Denervation of the carotid chemoreceptors in seven goats caused hypoventilation during eupnea at sea level (PaCO2 change from control +7 Torr, P less than 0.001). Denervation also attenuated but did not eliminate peripheral chemoreceptor responsiveness. No additional changes were observed following attempted denervation of the aortic chemoreceptors. After 1 h of simulated altitude (PB 530 Torr), PaO2 in the denervated goats averaged 46 Torr, and PaCO2 was increased 1.1 Torr above control (P less than 0.001). In these goats VA did not change significantly during the subsequent 3 days of hypoxia. Accordingly, we conclude that the peripheral chemoreceptors are essential for ventilatory acclimatization of goats during chronic hypoxia.

Ventilatory control in peripheral chemoreceptor-denervated ponies during chronic hypoxemia

1976 ◽  
Vol 41 (6) ◽  
pp. 878-885 ◽  
Author(s):  
H. V. Forster ◽  
G. E. Bisgard ◽  
B. Rasmussen ◽  
J. A. Orr ◽  
D. D. Buss ◽  
...  
Keyword(s):  
Sea Level ◽  
Hypobaric Hypoxia ◽  
Acute Hypoxia ◽  
Inhibitory Influence ◽  
Ventilatory Control ◽  
Peripheral Chemoreceptor ◽  
Peripheral Chemoreceptors ◽  
Chronic Hypoxemia ◽  
Insight Into

The present study was designed to provide further insight into the role of the carotid and aortic chemoreceptors in ventilatory (VE) acclimatization during sojourn at altitude. Measurements were made: 1) on 10 ponies near sea level(SL, 740 Torr) under normal conditions, 2) on 6 of these at SL following chemoreceptor denervation (CD), and 3) subsequently on all 10 during 4 days of hypobaric hypoxia (PaO2 = 40–47 Torr). CD resulteo in hypoventilation at SL (deltaPaCO2 = d8 Torr, P less than 0.05), and it prevented hyperventilation normally observed with injection of NaCN and acute exposure to hypoxia (less than 1 h). In contrast, hyperventilation was evidentin normal ponies during acute hypoxia (deltaPaCO2 = -6.7 Torr). Ventilationincreased in both groups between the 2nd and 8th h of hypoxia (deltaPaCO2 from 1 h = -4 Torr, P less than 0.05). This change, a common characteristic of acclimatization, persisted throughout 4 days of hypoxia in the normal ponies. However, in the CD ponies this change was evident consistently only through the 12th h and after the 44 h hyperventilation was no longer evident.We conclude that the peripheral chemoreceptors are essential in ponies for normal VE acclimatization to this degree of hypoxemia. Two additional findingsin CD ponies suggest the presence of a CNS inhibitory influence on theVEcontrol center during chronic hypoxemia. First, acute hyperoxygenation on the 4th day of hypoxemia induced hyperventilation (deltaPaCO2 = -5 Torr, P less than 0.05). Second, again on the 4th day and during hyperoxygenation, VE responsiveness to CO2 and doxapram HCl was greater than at sea level.

Cerebrospinal fluid in man native to high altitude

1964 ◽  
Vol 19 (2) ◽  
pp. 319-321 ◽  
Author(s):  
J. W. Severinghaus ◽  
A. Carceleń B.
Keyword(s):  
Cerebrospinal Fluid ◽  
High Altitude ◽  
Sea Level ◽  
Regulation Of Respiration ◽  
Acid Base ◽  
Peripheral Chemoreceptor ◽  
Arterial Blood ◽  
Blood Ph ◽  
The Difference

CSF pH was shown in a prior report to remain essentially constant during 8 days of acclimatization to 3,800 m. In order to further evaluate the possible role of CSF acid-base equilibria in the regulation of respiration, 20 Peruvian Andean natives were studied at altitudes of 3,720–4,820 m. In ten subjects at 3,720 m, means were: CSF pH 7.327, Pco2 43, HCO3- 21.5, Na+ 136, K+ 2.6, Cl- 124, lactate 30 mg/100 ml. Arterial blood: pH 7.43, Pco2 32.5, HCO3- 21.3, Na+ 136, K+ 4.2, Cl- 107, hematocrit 49, SaOO2 89.6. In six subjects at 4,545 m and four at 4,820 m CSF values were not significantly different; mean arterial Pco2 was 32.6 and 32.3, respectively. The only significant variations with altitude were the expected lowering of PaOO2 to 47 and 43.5 mm Hg, and of SaOO2 to 84.2 and 80.7, and increase of hematocrit to 67% and 75%, respectively. The natives differed from recently acclimatized sea-level residents in showing less ventilation (higher Pco2) in response to the existing hypoxia, and less alkaline arterial blood. The difference appears to relate to peripheral chemoreceptor response to hypoxia rather than central medullary chemoreceptor. respiratory regulation at high altitude; chronic acclimatization to altitude; peripheral chemoreceptor response to hypoxia; CSF and medullary respiratory chemoreceptors Submitted on June 12, 1963

scholarly journals Central and peripheral chemoreceptors evoke distinct responses in simultaneously recorded neurons of the raphé-pontomedullary respiratory network

2009 ◽  
Vol 364 (1529) ◽  
pp. 2501-2516 ◽  
Author(s):  
Sarah C. Nuding ◽  
Lauren S. Segers ◽  
Roger Shannon ◽  
Russell O'Connor ◽  
Kendall F. Morris ◽  
...  
Keyword(s):  
Network Architecture ◽  
Motor Pattern ◽  
Specific Interaction ◽  
Raphe Nuclei ◽  
Short Time Scale ◽  
Peripheral Chemoreceptor ◽  
Peripheral Chemoreceptors ◽  
Central Chemoreceptors ◽  
Raphé Nuclei ◽  
Stimulation Of

The brainstem network for generating and modulating the respiratory motor pattern includes neurons of the medullary ventrolateral respiratory column (VRC), dorsolateral pons (PRG) and raphé nuclei. Midline raphé neurons are proposed to be elements of a distributed brainstem system of central chemoreceptors, as well as modulators of central chemoreceptors at other sites, including the retrotrapezoid nucleus. Stimulation of the raphé system or peripheral chemoreceptors can induce a long-term facilitation of phrenic nerve activity; central chemoreceptor stimulation does not. The network mechanisms through which each class of chemoreceptor differentially influences breathing are poorly understood. Microelectrode arrays were used to monitor sets of spike trains from 114 PRG, 198 VRC and 166 midline neurons in six decerebrate vagotomized cats; 356 were recorded during sequential stimulation of both receptor classes via brief CO 2 -saturated saline injections in vertebral (central) and carotid arteries (peripheral). Seventy neurons responded to both stimuli. More neurons were responsive only to peripheral challenges than those responsive only to central chemoreceptor stimulation (PRG, 20 : 4; VRC, 41 : 10; midline, 25 : 13). Of 16 474 pairs of neurons evaluated for short-time scale correlations, similar percentages of reference neurons in each brain region had correlation features indicative of a specific interaction with at least one target neuron: PRG (59.6%), VRC (51.0%) and raphé nuclei (45.8%). The results suggest a brainstem network architecture with connectivity that shapes the respiratory motor pattern via overlapping circuits that modulate central and peripheral chemoreceptor-mediated influences on breathing.

Pulmonary hypertension and pulmonary vascular reactivity in beagles at high altitude

1988 ◽  
Vol 65 (6) ◽  
pp. 2632-2640 ◽  
Author(s):  
R. F. Grover ◽  
R. L. Johnson ◽  
R. G. McCullough ◽  
R. E. McCullough ◽  
S. E. Hofmeister ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
High Altitude ◽  
Sea Level ◽  
Vascular Reactivity ◽  
Chronic Hypoxia ◽  
Acute Hypoxia ◽  
Prostaglandin Synthesis ◽  
Inhibition Of Prostaglandin Synthesis ◽  
Pulmonary Arterial ◽  
Low Altitude

It is unclear whether dogs develop pulmonary hypertension (PH) at high altitude. Beagles from sea level were exposed to an altitude of 3,100 m (PB 525 Torr) for 12-19 mo and compared with age-matched controls remaining at low altitude of 130 m (PB 750 Torr). In beagles taken to high altitude as adults, pulmonary arterial pressures (PAP) at 3,100 m were 21.6 +/- 2.6 vs. 13.2 +/- 1.2 Torr in controls. Likewise, in beagles taken to 3,100 m as puppies 2.5 mo old, PAP was 23.2 +/- 2.1 vs. 13.8 +/- 0.4 Torr in controls. This PH reflected a doubling of pulmonary vascular resistance and showed no progression with time at altitude. Pulmonary vascular reactivity to acute hypoxia was also enhanced at 3,100 m. Inhibition of prostaglandin synthesis did not attenuate the PH or the enhanced reactivity. Once established, the PH was only partially reversed by acute relief of chronic hypoxia, but reversal was virtually complete after return to low altitude. Hence, beagles do develop PH at 3,100 m of a severity comparable to that observed in humans at the same or even higher altitudes.

Alkaline shift in lumbar and intracranial CSF in man after 5 days at high altitude

1976 ◽  
Vol 41 (1) ◽  
pp. 93-97 ◽  
Author(s):  
R. B. Weiskopf ◽  
R. A. Gabel ◽  
V. Fencl
Keyword(s):  
Blood Flow ◽  
Cerebrospinal Fluid ◽  
High Altitude ◽  
Sea Level ◽  
Jugular Bulb ◽  
Alveolar Ventilation ◽  
Simulated Altitude ◽  
Healthy Male ◽  
Alkaline Shift ◽  
Breathing Room

In six healthy male volunteers at sea level (PB 747–759 Torr), we measured pH and PCO2 in cerebrospinal fluid (CSF), and in arterial and jugular bulb blood; from these data we estimated PCO2 (12) and pH for the intracranial portion of CSF. The measurements were repeated after 5 days in a hypobaric chamber (PB 447 Torr). Both lumbar and intracranial CSF were significantly more alkaline at simulated altitude than at sea level. Decrease in[HCO3-] IN lumbar CSF at altitude was similar to that in blood plasma. Bothat sea level and at high altitude, PCO2 measured in the lumbar CSF was higher than that estimated for the intracranial CSF. At altitude, hyperoxia, incomparison with breathing room air, resulted in an increase in intracranialPCO2, and a decrease in the estimated pH in intracranial CSF. With hyperoxia at altitude, alveolar ventilation was significantly higher than during sea-level hyperoxia or normoxia, confirming that a degree of acclimatization hadoccurred. Changes in cerebral arteriovenous differences in CO2, measuredinthree subjects, suggest that cerebral blood flow may have been elevated after 5 days at altitude.

scholarly journals Right Ventricular Response to Acute Hypoxia Exposure: A Systematic Review

2022 ◽  
Vol 12 ◽  
Author(s):  
Argen Mamazhakypov ◽  
Meerim Sartmyrzaeva ◽  
Nadira Kushubakova ◽  
Melis Duishobaev ◽  
Abdirashit Maripov ◽  
...  
Keyword(s):  
Systematic Review ◽  
High Altitude ◽  
Prospective Studies ◽  
Acute Hypoxia ◽  
Small Sample ◽  
Reproducible Research ◽  
Simulated Altitude ◽  
Hypoxia Exposure ◽  
Study Designs ◽  
Rv Function

Background: Acute hypoxia exposure is associated with an elevation of pulmonary artery pressure (PAP), resulting in an increased hemodynamic load on the right ventricle (RV). In addition, hypoxia may exert direct effects on the RV. However, the RV responses to such challenges are not fully characterized. The aim of this systematic review was to describe the effects of acute hypoxia on the RV in healthy lowland adults.Methods: We systematically reviewed PubMed and Web of Science and article references from 2005 until May 2021 for prospective studies evaluating echocardiographic RV function and morphology in healthy lowland adults at sea level and upon exposure to simulated altitude or high-altitude.Results: We included 37 studies in this systematic review, 12 of which used simulated altitude and 25 were conducted in high-altitude field conditions. Eligible studies reported at least one of the RV variables, which were all based on transthoracic echocardiography assessing RV systolic and diastolic function and RV morphology. The design of these studies significantly differed in terms of mode of ascent to high-altitude, altitude level, duration of high-altitude stay, and timing of measurements. In the majority of the studies, echocardiographic examinations were performed within the first 10 days of high-altitude induction. Studies also differed widely by selectively reporting only a part of multiple RV parameters. Despite consistent increase in PAP documented in all studies, reports on the changes of RV function and morphology greatly differed between studies.Conclusion: This systematic review revealed that the study reports on the effects of acute hypoxia on the RV are controversial and inconclusive. This may be the result of significantly different study designs, non-compliance with international guidelines on RV function assessment and limited statistical power due to small sample sizes. Moreover, the potential impact of other factors such as gender, age, ethnicity, physical activity, mode of ascent and environmental factors such as temperature and humidity on RV responses to hypoxia remained unexplored. Thus, this comprehensive overview will promote reproducible research with improved study designs and methods for the future large-scale prospective studies, which eventually may provide important insights into the RV response to acute hypoxia exposure.

Sign in / Sign up

Export Citation Format

Share Document