Transient effect of sudden mild hypoxia on respiration

1961 ◽  
Vol 16 (1) ◽  
pp. 11-14 ◽  
Author(s):  
Thomas F. Hornbein ◽  
Albert Roos ◽  
Zora J. Griffo
Keyword(s):  
Steady State ◽  
Sea Level ◽  
Carotid Body ◽  
Ventilatory Response ◽  
Transient Increase ◽  
Transient Responses ◽  
Transient Effect ◽  
The Difference ◽  
Mild Hypoxia

Recent studies of carotid body chemoreceptor activity in cats show that the activity of these organs increases markedly over a range of alveolar pO2 considerably higher than the alveolar pO2 of 50–60 mm Hg known to produce an increase in ventilation in the steady state. In an attempt to explain this discrepancy between chemoreceptor activity and ventilation, the transient ventilatory response to two breaths of a low O2 mixture was observed and correlated with the alveolar pO2 during this brief hypoxic stimulus. A transient increase in ventilation could be detected at an alveolar pO2 of 93 mm Hg, that is, considerably higher than the highest pO2 known to increase ventilation during the steady state. These findings are interpreted as evidence of an increased chemoreceptor drive when alveolar O2 tension is lowered only slightly below that existing at sea level. Possible reasons for the difference between the steady state and transient responses are discussed. Submitted on June 6, 1960

Increased propensity for apnea via dopamine-induced carotid body inhibition in sleeping dogs

2005 ◽  
Vol 98 (5) ◽  
pp. 1732-1739 ◽  
Author(s):  
Bruno J. Chenuel ◽  
Curtis A. Smith ◽  
Kathleen S. Henderson ◽  
Jerome A. Dempsey
Keyword(s):  
Steady State ◽  
Carotid Body ◽  
Pressure Support Ventilation ◽  
Pressure Support ◽  
Ventilatory Response ◽  
Rapid Eye Movement Sleep ◽  
The Difference ◽  
End Tidal ◽  
Carotid Body Chemoreceptors

We determined the effects of specific carotid body chemoreceptor inhibition on the propensity for apnea during sleep. We reduced the responsiveness of the carotid body chemoreceptors using intravenous dopamine infusions during non-rapid eye movement sleep in six dogs. Then we quantified the difference in end-tidal Pco2 (PetCO2) between eupnea and the apneic threshold, the “CO2 reserve,” by gradually reducing PetCO2 transiently with pressure support ventilation at progressively increased tidal volume until apnea occurred. Dopamine infusions decreased steady-state eupneic ventilation by 15 ± 6%, causing a mean CO2 retention of 3.9 ± 1.9 mmHg and a brief period of ventilatory instability. The apneic threshold PetCO2 rose 5.1 ± 1.9 Torr; thus the CO2 reserve was narrowed from −3.9 ± 0.62 Torr in control to −2.7 ± 0.78 Torr with dopamine. This decrease in the CO2 reserve with dopamine resulted solely from the 20.5 ± 11.3% increase in plant gain; the slope of the ventilatory response to CO2 below eupnea was unchanged from normal. We conclude that specific carotid chemoreceptor inhibition with dopamine increases the propensity for apnea during sleep by narrowing the CO2 reserve below eupnea. This narrowing is due solely to an increase in plant gain as the slope of the ventilatory response to CO2 below eupnea was unchanged from normal control. These findings have implications for the role of chemoreceptor inhibition/stimulation in the genesis of apnea and breathing periodicity during sleep.

Effect of mild hypoxia on ventilation during exercise

1962 ◽  
Vol 17 (2) ◽  
pp. 239-242 ◽  
Author(s):  
Thomas F. Hornbein ◽  
Albert Roos
Keyword(s):  
Steady State ◽  
Ventilatory Response ◽  
Human Subjects ◽  
Sympathetic Innervation ◽  
Mild Degree ◽  
Flow Through ◽  
Neural Discharge ◽  
Response To Exercise ◽  
Mild Hypoxia ◽  
Rest And Exercise

Hypoxia of mild degree (PaOO2 above 60 mm Hg) produces little or no ventilatory response in resting man during the steady state. To evaluate the possibility that the effectiveness of a hypoxic chemoreceptor drive might be enhanced by exercise, the ventilatory response to mild hypoxia was measured in two human subjects during rest and exercise. Though no significant increase in ventilation occurred at rest above a PaOO2 of 60 mm Hg, a decrease in PaOO2from 100 to 94 mm Hg produced a statistically significant increase in steady state ventilation during moderate exercise. In addition, temporary block of the sympathetic innervation to the carotid and aortic bodies in one subject resulted in a diminution of work hyperpnea. This suggests that increased sympathetic tone during exercise, by reducing blood flow through the chemoreceptors, might result in increased neural discharge and hence increased ventilation even though arterial POO2 is the same as at rest. Thus, activity of the chemoreceptors as modified by sympathetic control of their blood supply may be an important determinant of the ventilatory response to exercise. Since work hyperpnea is enhanced by even mild hypoxia, this ventilatory response may be sufficient to initiate respiratory acclimatization to altitudes so low that resting ventilation on acute exposure is unaffected. Submitted on July 31, 1961

The flow of water through the straits of Dover, related to wind and differences in sea level

1956 ◽  
Vol 248 (953) ◽  
pp. 517-551 ◽  
Keyword(s):  
Steady State ◽  
Sea Level ◽  
North Sea ◽  
Sea Water ◽  
Tidal Currents ◽  
English Channel ◽  
Mean Flow ◽  
North East ◽  
The North ◽  
The Difference

The difference in electric potential between the water on opposite sides of the English Channel, as recorded on a telephone cable running from St Margaret’s Bay to Sangatte, has been used to measure the mean flow of water through the Straits of Dover. The records were calibrated by means of the tidal currents, which were know from previous measurements. A p.d. of 1 V corresponds to a current of about 140 cm /s (2.75 knots), the exact calibration depending on the electrical conductivity o f the sea water and having a seasonal variation. Continuous records were obtained during the 15-month period from February 1953 to June 1954. For 4 months, from November 1953 to March 1954, similar records were also obtained on an other cable, crossing the southern North Sea from Aldeburgh to Domburg. Fluctuations due to the Earth currents associated with geomagnetic disturbances occurred from time to time, but did not usually cause any difficulty in in terpretin g the records. The residual flow, after eliminating the tidal currents, has been correlated with the local wind in the Straits and the difference in sea level between the eastern p a rt of the English Channel and the southern part of the North Sea, as determined from tide-gauge records. The tidal currents and elevations were eliminated, approximately, by taking means of 25 hourly readings centred at noon, for each day of the period covered by the observations. The greatest daily rates of flow recorded w ere 79 cm/s (T53 knots) towards the north-east on 1 November 1953 an d 77 cm /s (T49 knots) towards the south-w est on 3 January 1954. F or three periods of un usually strong flow, namely, 19 to 24 September 1953, 26 October to 8 November 1953, and 1 to 6 January 1954, a more detailed analysis was made, eliminating the tidal effects by a method previously used in the analysis of storm surges. The results show the existence of ‘current surges’, the peaks of which lag by up to 6 h behind the corresponding max im a in the wind stress or surface gradient producing them . An attempt has been made to relate the empirical results to the dynamics of flow through the Straits. On the assumption that the 25 h means can be regarded as referring to steady-state conditions, values o f 4-5 x 10<super>-3</super> for the w ind-stress coefficient y<super> 2</super> an d 3-8 x 10<super>-3</super> for the bottom friction coefficient k have been deduced. These rather high values may be due, in part, to the steady-state assumption not being justified. The general features of the current surges are consistent with the dynamical treatment.

Effects of altered CSF [H+] on ventilatory responses to exercise in the awake goat

1988 ◽  
Vol 65 (2) ◽  
pp. 921-927 ◽  
Author(s):  
C. A. Smith ◽  
L. C. Jameson ◽  
J. A. Dempsey
Keyword(s):  
Steady State ◽  
Carotid Body ◽  
Ventilatory Response ◽  
Fold Increase ◽  
Co2 Production ◽  
Acid Base ◽  
Ventilatory Responses ◽  
Exercise Hyperpnea ◽  
Acid Base Status ◽  
Response To Exercise

We investigated the effects of selective large changes in the acid-base environment of medullary chemoreceptors on the control of exercise hyperpnea in unanesthetized goats. Four intact and two carotid body-denervated goats underwent cisternal perfusion with mock cerebrospinal fluid (CSF) of markedly varying [HCO-3] (CSF [H+] = 21-95 neq/l; pH 7.68-7.02) until a new steady state of alveolar hypo- or hyperventilation was reached [arterial PCO2 (PaCO2) = 31-54 Torr]. Perfusion continued as the goats completed two levels of steady-state treadmill walking [2 to 4-fold increase in CO2 production (VCO2)]. With normal acid-base status in CSF, goats usually hyperventilated slightly from rest through exercise (-3 Torr PaCO2, rest to VCO2 = 1.1 l/min). Changing CSF perfusate [H+] changed the level of resting PaCO2 (+6 and -4 Torr), but with few exceptions, the regulation of PaCO2 during exercise (delta PaCO2/delta VCO2) remained similar regardless of the new ventilatory steady state imposed by changing CSF [H+]. Thus the gain (slope) of the ventilatory response to exercise (ratio of change in alveolar ventilation to change in VCO2) must have increased approximately 15% with decreased resting PaCO2 (acidic CSF) and decreased approximately 9% with increased resting PaCO2 (alkaline CSF). A similar effect of CSF [H+] on resting PaCO2 and on delta PaCO2/VCO2 during exercise also occurred in two carotid body-denervated goats. Our results show that alteration of the gain of the ventilatory response to exercise occurs on acute alterations in resting PaCO2 set point (via changing CSF [H+]) and that the primary stimuli to exercise hyperpnea can operate independently of central or peripheral chemoreception.

Transient responses to CO2 breathing of human subjects awake and asleep

1963 ◽  
Vol 18 (2) ◽  
pp. 289-294 ◽  
Author(s):  
F. J. D. Fuleihan ◽  
T. Nakada ◽  
J. T. Suero ◽  
E. S. Merrifield ◽  
R. E. Dutton ◽  
...  
Keyword(s):  
Steady State ◽  
Ventilatory Response ◽  
Human Subjects ◽  
Control Period ◽  
Sodium Pentobarbital ◽  
Transient Responses ◽  
Control Value ◽  
Oxygen Breathing ◽  
Significant Difference ◽  
End Tidal

Ventilation and end-tidal Pco2 were studied in six subjects awake and asleep (following the ingestion of 200–300 mg sodium pentobarbital) during oxygen breathing and the administration and withdrawal of 4% CO2 in oxygen. During the control period as well as steady-state CO2 breathing, ventilation was significantly lower in asleep than in awake subjects. There was no significant difference between sleep and wakefulness in end-tidal Pco2 or in the slope of the ventilatory response to 4% CO2. The transient responses of ventilation and end-tidal Pco2 of the group as a whole were similar in sleep and wakefulness. Ventilation changed more slowly than did end-tidal Pco2. End-tidal Pco2 overshot beyond the steady-state CO2 breathing value at the onset of CO2 breathing; and undershot below the control value during recovery. The magnitudes of both the overshoot and undershoot of end-tidal Pco2 were correlated significantly to the slope of the ventilatory response to 4% CO2, in the whole group awake and asleep. Submitted on October 4, 1962

Response time and sensitivity of the ventilatory response to CO2 in unanesthetized intact dogs: central vs. peripheral chemoreceptors

2006 ◽  
Vol 100 (1) ◽  
pp. 13-19 ◽  
Author(s):  
C. A. Smith ◽  
J. R. Rodman ◽  
B. J. A. Chenuel ◽  
K. S. Henderson ◽  
J. A. Dempsey
Keyword(s):  
Steady State ◽  
Carotid Body ◽  
Ventilatory Response ◽  
Periodic Breathing ◽  
Ventilatory Responses ◽  
Central Chemoreceptors ◽  
Carotid Bodies ◽  
Carotid Body Chemoreceptors ◽  
Relative Gains ◽  
Ventilatory Response To Co2

We assessed the speed of the ventilatory response to square-wave changes in alveolar Pco2 and the relative gains of the steady-state ventilatory response to CO2 of the central chemoreceptors vs. the carotid body chemoreceptors in intact, unanesthetized dogs. We used extracorporeal perfusion of the reversibly isolated carotid sinus to maintain normal tonic activity of the carotid body chemoreceptor while preventing it from sensing systemic changes in CO2, thereby allowing us to determine the response of the central chemoreceptors alone. We found the following. 1) The ventilatory response of the central chemoreceptors alone is 11.2 (SD = 3.6) s slower than when carotid bodies are allowed to sense CO2 changes. 2) On average, the central chemoreceptors contribute ∼63% of the gain to steady-state increases in CO2. There was wide dog-to-dog variability in the relative contributions of central vs. carotid body chemoreceptors; the central exceeded the carotid body gain in four of six dogs, but in two dogs carotid body gain exceeded central CO2 gain. If humans respond similarly to dogs, we propose that the slower response of the central chemoreceptors vs. the carotid chemoreceptors prevents the central chemoreceptors from contributing significantly to ventilatory responses to rapid, transient changes in arterial Pco2 such as those after periods of hypoventilation or hyperventilation (“ventilatory undershoots or overshoots”) observed during sleep-disordered breathing. However, the greater average responsiveness of the central chemoreceptors to brain hypercapnia in the steady-state suggests that these receptors may contribute significantly to ventilatory overshoots once unstable/periodic breathing is fully established.

Ventilatory response to CO2 and O2 near eupnea in awake dogs

1988 ◽  
Vol 65 (2) ◽  
pp. 788-796 ◽  
Author(s):  
W. W. Hwang ◽  
S. M. Yamashiro ◽  
D. Sedlock ◽  
F. S. Grodins
Keyword(s):  
Steady State ◽  
High Frequency ◽  
Ventilatory Response ◽  
Nonlinear Behavior ◽  
High Frequency Ventilation ◽  
Frequency Ventilation ◽  
Extracorporeal Circuits ◽  
The Subject ◽  
Ventilatory Response To Co2 ◽  
Mild Hypoxia

The problem faced in determining the ventilatory response to CO2 near eupnea has been the difficulty of unloading metabolically produced CO2 from the subject in the steady state. Previous methods using extracorporeal circuits to unload CO2 are technically difficult and provide a limited number of experimental states per experiment. Using the method of high-frequency ventilation to unload CO2, we were able to obtain a large number of determinations in the same subject under conditions of hypoxia, normoxia, and hyperoxia. Data collected in five awake dogs show that the ventilatory response to CO2 is linear down to apnea during normoxic conditions but exhibits nonlinear behavior dependent on the level of arterial O2 tension. During hyperoxic conditions, the response was concave curvilinear, with a statistically significant decrease in slope near apnea. In contrast, mild hypoxia led to a convex curvilinear response with an increased slope near apnea.

Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

1998 ◽  
Vol 29 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Peter Raben ◽  
Wilfred H. Theakstone
Keyword(s):  
Isotopic Composition ◽  
Sea Level ◽  
Oxygen Isotopes ◽  
Oxygen Isotopic Composition ◽  
Isotopic Ratios ◽  
Vertical Variations ◽  
Oxygen Isotopic ◽  
The Difference ◽  
Liquid Precipitation ◽  
Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

scholarly journals Effects of Genotypes and Treatment on Oxygenscan Parameters in Sickle Cell Disease

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 811
Author(s):  
Camille Boisson ◽  
Minke A. E. Rab ◽  
Elie Nader ◽  
Céline Renoux ◽  
Celeste Kanne ◽  
...  
Keyword(s):  
Steady State ◽  
Sickle Cell Disease ◽  
Blood Cell ◽  
Sickle Cell ◽  
Red Blood Cell ◽  
Cell Disease ◽  
Oxygen Gradient ◽  
Acute Complication ◽  
Adults And Children ◽  
The Difference

(1) Background: The aim of the present study was to compare oxygen gradient ektacytometry parameters between sickle cell patients of different genotypes (SS, SC, and S/β+) or under different treatments (hydroxyurea or chronic red blood cell exchange). (2) Methods: Oxygen gradient ektacytometry was performed in 167 adults and children at steady state. In addition, five SS patients had oxygenscan measurements at steady state and during an acute complication requiring hospitalization. (3) Results: Red blood cell (RBC) deformability upon deoxygenation (EImin) and in normoxia (EImax) was increased, and the susceptibility of RBC to sickle upon deoxygenation was decreased in SC patients when compared to untreated SS patients older than 5 years old. SS patients under chronic red blood cell exchange had higher EImin and EImax and lower susceptibility of RBC to sickle upon deoxygenation compared to untreated SS patients, SS patients younger than 5 years old, and hydroxyurea-treated SS and SC patients. The susceptibility of RBC to sickle upon deoxygenation was increased in the five SS patients during acute complication compared to steady state, although the difference between steady state and acute complication was variable from one patient to another. (4) Conclusions: The present study demonstrates that oxygen gradient ektacytometry parameters are affected by sickle cell disease (SCD) genotype and treatment.

Separation of carotid body chemoreceptor responses to O2 and CO2 by oligomycin and by antimycin A

1982 ◽  
Vol 242 (3) ◽  
pp. C200-C206 ◽  
Author(s):  
E. Mulligan ◽  
S. Lahiri
Keyword(s):  
Steady State ◽  
Carbonic Anhydrase ◽  
Partial Pressure ◽  
Carotid Body ◽  
Body Tissue ◽  
Antimycin A ◽  
Tissue Ph ◽  
Co2 Partial Pressure ◽  
O2 Partial Pressure ◽  
Metabolic Hypothesis

The cat carotid chemoreceptor O2 and CO2 responses can be separated by oligomycin and by antimycin A. Both of these agents greatly diminish or abolish the chemoreceptor O2 response but not the nicotine or CO2 responses. After either oligomycin or antimycin, the responses to increases and decreases in arterial CO2 partial pressure (PaCO2) consisted of increases and decreases in activity characterized respectively by exaggerated overshoots and undershoots. These were eliminated by the carbonic anhydrase inhibitor, acetazolamide, suggesting that they resulted from changes in carotid body tissue pH. The steady-state PaCO2 response remaining after oligomycin was no longer dependent on arterial O2 partial pressure (PaO2). All effects of antimycin were readily reversible in about 20 min. The separation of the responses to O2 and CO2 indicates that there may be at least partially separate pathways of chemoreception for these two stimuli. The similarity of the oligomycin and antimycin results supports the metabolic hypothesis of chemoreception.

Sign in / Sign up

Export Citation Format

Share Document