Oxygen consumption and the arterial oxygen saturation in foetal and new‐born lambs

Acheson, George H.; Dawes, G. S.; Mott, Joan C.

doi:10.1113/jphysiol.1957.sp005735

Cited by 81 publications

(34 citation statements)

References 39 publications

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“…The results confirm the conclusion already reached elsewhere by different methods, that progressive hypoxaemia causes a progressive fall in 02 consumption in foetal lambs (Acheson et al 1957;Dawes & Mott, 1959). There are two differences in the results.…”

Section: Consumptionsupporting

confidence: 91%

Changes in O₂ distribution and consumption in foetal lambs with variations in umbilical blood flow

Dawes¹,

Mott²

1964

The Journal of Physiology

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Section: Consumptionsupporting

confidence: 91%

Changes in O₂ distribution and consumption in foetal lambs with variations in umbilical blood flow

Dawes¹,

Mott²

1964

The Journal of Physiology

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“…Other observations were made on animals anaesthetized with either Dial Liquid Compound (Ciba; diallylbarbituric acid 0-1 g, urethane 0-4 g/ml. ; dose 0-2-0-35 ml./kg intravenously) or pentobarbitone as described previously (Dawes, Mott & Widdicombe, 1954;Acheson et al 1957). Most lambs were born naturally.…”

Section: Methodsmentioning

confidence: 99%

The increase in oxygen consumption in the lamb after birth

Dawes¹,

Mott²

1959

The Journal of Physiology

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105

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The purpose of this paper is to describe experiments on the change in 02 consumption which takes place in lambs at birth. But before considering the evidence, it is necessary to be sure that the methods used for measuring foetal 02 consumption are reliable.In a previous paper (Acheson, Dawes & Mott, 1957) we concluded that in mature foetal lambs the rate of 02 consumption decreased when the umbilical arterial 02 saturation fell below 35 %. There was rather a wide scatter in successive estimations of 02 consumption (calculated by multiplying umbilical blood flow by the arteriovenous 02 difference) even in what we believed to be a steady state. Reconsideration of the available data, and particularly of Fig. 2 of the previous paper, suggested that the figure of 35 % might be an underestimate, and that 02 consumption might sometimes be reduced at an even higher umbilical arterial 02 saturation. It is obviously important to get as good a measure as possible of this figure.Among the possible causes of the variation in successive estimations of 02 consumption are the anaesthetic, the method of measuring umbilical blood flow and the method of causing partial anoxia. In previous experiments we had used pentobarbitone as the anaesthetic; this is not entirely satisfactory, because repeated intravenous injections are required at intervals of an hour or less, or a slow intravenous infusion is necessary to maintain anaesthesia, and adjustment of the rate of infusion is not always ideal. It seemed worth while to try chloralose as an anaesthetic in place of pentobarbitone. The rate of umbilical blood flow had been measured by a venous occlusion plethysmograph, using a modification of the system first described by Cooper & Greenfield (1949). Dynamic calibration in vitro had shown, in their hands as in ours, an error which varied from ± 5 % to ± 15 % (Cooper, Greenfield & Huggett, 1949). Successive estimations of umbilical blood flow at minute intervals in vivo also showed large variations with this instrument, even when the arterial blood pressure, heart rate and arterial 02 saturation were constant.

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“…Cross and his associates have also shown, by a type of direct calorimetry, that the heat production of the human infant is lower when breathing 15 % oxygen than when breathing air (Brodie, Cross & Lomer, 1956, 1957. Finally, Acheson et al (1957) showed a reduction in the oxygen consumption of foetal and new-born lambs when their arterial oxygen saturation fell below 35 %.…”

mentioning

confidence: 98%

The oxygen consumption of new‐born and adult mammals. Its dependence on the oxygen tension in the inspired air and on the environmental temperature

Hill¹

1959

The Journal of Physiology

219

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Infants during birth and shortly afterwards are particularly liable to suffer from hypoxia, and much research has been directed to elucidating the effects of oxygen lack in the new-born. Evidence that moderate hypoxia (15% oxygen) causes a significant reduction in oxygen consumption in human infants was first produced by Cross, Tizard & Trythall (1955; it was later reported that lambs (Acheson, Dawes & Mott, 1957), and puppies and kittens (Moore, 1956a, b), respond in a similar fashion. It thus appeared that the new-born respond differently from adults, since it was generally accepted that the oxygen consumption of an adult mammal does not fall until death due to hypoxia is imminent (in the region of 6 % oxygen). Then, in a review of the physiology of the new-born, McCance & Widdowson (1957) pointed out that adult small mammals behave in the same way as new-born animals, and not in the 'adult' manner. The situation was now confusing, since it was not clear whether it was size or maturity that determined the response to hypoxia. The present experiments were undertaken in order to make a direct comparison between new-born and adult animals of roughly the same size, and to obtain more information about the various types of response to hypoxia. A brief preliminary report of this work has been published (Hill, 1958). METHODSIn order to investigate the effect on metabolism of hypoxia, immaturity, body size and environmental temperature, an apparatus had to be devised which would measure the oxygen consumption of a single unanaesthetized small mammal, breathing gas of any chosen composition between 21 % and 5 % oxygen in nitrogen, at various environmental temperatures. Good time resolution was essential, so apparatus that would give a continuous direct record was desirable.Oxygen lies in the fact that any gas other than air must be supplied from a reservoir. Closedcircuit methods are more readily adapted to the problem in hand, since they permit much better time resolution, and easily lend themselves to graphic recording. In a closed circuit, if the C02 produced by the animal is absorbed, then the animal's oxygen consumption is indicated continuously by the amount of gas that must be added to keep the volume of the circuit constant. A closed-circuit apparatus was adopted; its essential features are: (1) The oxygen content of the circuit gas is readily and predictably varied, as required, by removing and replacing oxygen, i.e. by altering the total volume of the circuit. (2) Once the chosen oxygen level has been attained an automatic device is then used to feed oxygen into the circuit at exactly the same rate as the animal consumes it. The volume of the circuit is held constant, and thus the composition of the circuit gas is kept constant while oxygen consumption measurements are made. (3) The amount of oxygen allowed into the circuit during each minute or half minute is recorded on a kymograph, measuring the animal's rate of oxygen consumption, A02/At. (4) The need for a temperaturecontrolled room has been obviated by ...

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Oxygen consumption and the arterial oxygen saturation in foetal and new‐born lambs

Cited by 81 publications

References 39 publications

Changes in O₂ distribution and consumption in foetal lambs with variations in umbilical blood flow

Changes in O₂ distribution and consumption in foetal lambs with variations in umbilical blood flow

The increase in oxygen consumption in the lamb after birth

The oxygen consumption of new‐born and adult mammals. Its dependence on the oxygen tension in the inspired air and on the environmental temperature

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Oxygen consumption and the arterial oxygen saturation in foetal and new‐born lambs

Cited by 81 publications

References 39 publications

Changes in O2 distribution and consumption in foetal lambs with variations in umbilical blood flow

Changes in O2 distribution and consumption in foetal lambs with variations in umbilical blood flow

The increase in oxygen consumption in the lamb after birth

The oxygen consumption of new‐born and adult mammals. Its dependence on the oxygen tension in the inspired air and on the environmental temperature

Contact Info

Product

Resources

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Changes in O₂ distribution and consumption in foetal lambs with variations in umbilical blood flow

Changes in O₂ distribution and consumption in foetal lambs with variations in umbilical blood flow