Ovine physiological responses to elevated ambient carbon dioxide

Hoover, W.H.; Young, P. J.; Sawyer, Margaret; Apgar, W. P.

doi:10.1152/jappl.1970.29.1.32

Cited by 6 publications

(4 citation statements)

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“…The decreased RR is somewhat contradictory to previous results demonstrating that hypercapnia increased MV via simultaneous elevations in V T and RR in humans, cats, and rats ( Eckenhoff and Helrich, 1958 ; Read, 1967 ; Clark and von Euler, 1972 ; Peever and Stephenson, 1997 ; Seifert and Mortola, 2002 ). However, previous reports in rabbits (as well as in cats, dogs, and sheep) demonstrated that respiratory frequency can also decrease with CO 2 concentration rising in the inspired air ( Hoover et al, 1970 ; Jennings and Macklin, 1972 ; Romo-Salas et al, 1978 ; Maskrey and Nicol, 1980 ; Szlyk and Jennings, 1987 ). In these reports, the respiratory frequency is described to shift towards an optimal value that results in maximum CO 2 elimination, depending on the CO 2 concentration and the initial frequency.…”

Section: Discussionmentioning

confidence: 92%

Sevoflurane and Hypercapnia Blunt the Physiological Variability of Spontaneous Breathing: A Comparative Interventional Study

et al. 2022

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Background: Although spontaneous breathing is known to exhibit substantial physiological fluctuation that contributes to alveolar recruitment, changes in the variability of the respiratory pattern following inhalation of carbon dioxide (CO2) and volatile anesthetics have not been characterized. Therefore, we aimed at comparing the indices of breathing variability under wakefulness, sleep, hypercapnia and sedative and anesthetic concentrations of sevoflurane.Methods: Spontaneous breathing pattern was recorded on two consecutive days in six rabbits using open whole-body plethysmography under wakefulness and spontaneous sleep and following inhalation of 5% CO2, 2% sevoflurane (0.5 MAC) and 4% (1 MAC) sevoflurane. Tidal volume (VT), respiratory rate (RR), minute ventilation (MV), inspiratory time (TI) and mean inspiratory flow (VT/TI) were calculated from the pressure fluctuations in the plethysmograph. Means and coefficients of variation were calculated for each measured variable. Autoregressive model fitting was applied to estimate the relative contributions of random, correlated, and oscillatory behavior to the total variance.Results: Physiological sleep decreased MV by lowering RR without affecting VT. Hypercapnia increased MV by elevating VT. Sedative and anesthetic concentrations of sevoflurane increased VT but decreased MV due to a decrease in RR. Compared to the awake stage, CO2 had no effect on VT/TI while sevoflurane depressed significantly the mean inspiratory flow. Compared to wakefulness, the variability in VT, RR, MV, TI and VT/TI were not affected by sleep but were all significantly decreased by CO2 and sevoflurane. The variance of TI originating from correlated behavior was significantly decreased by both concentrations of sevoflurane compared to the awake and asleep conditions.Conclusions: The variability of spontaneous breathing during physiological sleep and sevoflurane-induced anesthesia differed fundamentally, with the volatile agent diminishing markedly the fluctuations in respiratory volume, inspiratory airflow and breathing frequency. These findings may suggest the increased risk of lung derecruitment during procedures under sevoflurane in which spontaneous breathing is maintained.

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Section: Discussionmentioning

confidence: 92%

Sevoflurane and Hypercapnia Blunt the Physiological Variability of Spontaneous Breathing: A Comparative Interventional Study

et al. 2022

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“…Dogs breathing 4 % C02 at a T. of 40 TC showed a 25 % reduction in frequency compared to when breathing air (Albers et al 1975). In sheep exposed to a range of inhaled C02 ofup to 16 %, frequency increased from an initial f value of 30 (Hoover et al 1970), while in panting sheep the f value was decreased when C02 was inhaled (Fawcett, 1971). Thus the frequency response to CO2 in the dog and the sheep may be similar in pattern to that seen in the rabbit.…”

Section: Discussionmentioning

confidence: 99%

“…While it is agreed that tidal volume (VT) always increases with inhalation of CO2, reports vary as to the frequency response obtained. In some reports, respiratory frequency (f) remains unchanged (Bentley, Herreid & Schmidt-Neilsen, 1967;Hales & Findlay, 1968;Greco, Fordyce, Gonzalez, Reischl & Grodins, 1978); in others there is an increase in frequency (Chapin, 1954;Schaefer, 1958;Hoover, Young, Sawyer & Apgar, 1970; Darden, 1972;Lai, Tsuya & Hildebrandt, 1978). Under certain circumstances, it is possible to obtain a fall in frequency when C02 is inhaled, (Jennings & Macklin, 1972;.…”

Section: Introductionmentioning

confidence: 99%

The respiratory frequency response to carbon dioxide inhalation in conscious rabbits

Maskrey

Nicol

1980

The Journal of Physiology

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SUMMARY1. The respiratory responses to C02 inhalation were measured in New Zealand White rabbits. Prior to testing, the rabbits either received drinking water ad libitum (C), or were subjected to 72 hr water deprivation (WD). The rabbits were tested in a climatic chamber at either 20 0, (C20, WD20) or 30 0C (C30, WD30).2. C02 exposure caused increases in both tidal volume (VT) and minute volume (VE). The direction and magnitude of changes in respiratory frequency (f), however, were dependent upon treatment.3. Linear regressions were drawn for f vs. % C02 in inhaled gas. Treatment C20 showed zero slope, treatment C30 a large negative slope, and treatments WD20 and WD30 a significant positive slope.4. The slopes ofthe regression lines obtained from plottingf vs. % C02 were plotted against their intercepts for each rabbit under each treatment condition. This yielded a highly significant linear regression from which it could be concluded that the frequency response to C02 exposure is dependent upon the initial frequency when the rabbits are breathing air.5. It is suggested that frequency is shifted during hypercapnia towards an optimal value which is dependent upon the existing % C02 in the inspired gas.6. Comparison of the results obtained for the rabbit with results reported for the conscious dog and sheep suggest that a similar relationship may hold for these species.

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“…For instance, rhesus monkeys have been acclimated to 0.06 bar CO 2 to no ill effect 24 . Sheep exhibited some minor discomfort at 0.08 bar, but it was tolerable until 0.12 bar 25,26 , with death not occurring until 0.16 bar 25,26 . It is worth noting that an acclimatization threshold was only achieved in the sheep experiment, but not with the rhesus monkeys.…”

Section: Co 2 and N 2 Limits For Complex Life Habitable Zonementioning

confidence: 99%

A Complex Life Habitable Zone Based On Lipid Solubility Theory

Ramirez

2020

Sci Rep

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To find potentially habitable exoplanets, space missions employ the habitable zone (HZ), which is the region around a star (or multiple stars) where standing bodies of water could exist on the surface of a rocky planet. Follow-up atmospheric characterization could yield biosignatures signifying life. Although most iterations of the HZ are agnostic regarding the nature of such life, a recent study argues that a complex life HZ would be considerably smaller than that used in classical definitions. Here, I use an advanced energy balance model to show that such an HZ would be considerably wider than originally predicted given revised CO 2 limits and (for the first time) N 2 respiration limits for complex life. The width of this complex life HZ (CLHZ) increases by ~35% from ~0.95-1.2 AU to 0.95-1.31 AU in our solar system. Similar extensions are shown for stars with stellar effective temperatures between 2,600-9,000 K. I define this CLHZ using lipid solubility theory, diving data, and results from animal laboratory experiments. I also discuss implications for biosignatures and technosignatures. Finally, I discuss the applicability of the CLHZ and other HZ variants to the search for both simple and complex life.

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Ovine physiological responses to elevated ambient carbon dioxide

Cited by 6 publications

References 0 publications

Sevoflurane and Hypercapnia Blunt the Physiological Variability of Spontaneous Breathing: A Comparative Interventional Study

Sevoflurane and Hypercapnia Blunt the Physiological Variability of Spontaneous Breathing: A Comparative Interventional Study

The respiratory frequency response to carbon dioxide inhalation in conscious rabbits

A Complex Life Habitable Zone Based On Lipid Solubility Theory

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