A critical value for O2 transport in the rat

Adams, R. P.; Dieleman, Levinus A.; Cain, S. M.

doi:10.1152/jappl.1982.53.3.660

Cited by 70 publications

(24 citation statements)

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“…Certainly, it was demonstrated in dog skeletal muscle that, even though pop was usually constant over a wide range of blood flows, it was dependent on flow in preparations in which vasodilator responses to local metabolic influences were absent (Duran & Renkin, 1974). Moreover, our results are consistent with others obtained in anaesthetized rats which showed that during systemic hypoxia, whole body Vo,, which would be expected to strongly reflect Vo, of skeletal muscle, did not become dependent on total 0, delivery (cardiac output x Ca, , , , ) until Ca,O, was below -13 ml (1 00 mI)-' (Adams et al 1982). This is below the level reached in the present study during 8 YO 0, (Fig.…”

Section: Acute ~~~~~~A In N Ratssupporting

confidence: 91%

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

Marshall¹,

Davies²

1999

Experimental Physiology

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SUMMARYThe aims of the present study were to evaluate how acute systemic hypoxia affects 0, delivery to skeletal muscle and muscle 0, consumption (voJ of the rat and to establish how these relationships are altered by chronic systemic hypoxia. Thus, the effects of breathing different concentrations of 0, (air, 12 % and 8 % 0,) upon oxygen delivery and vo, were studied in hindlimb muscles of control, normoxic (N) rats and of rats that had been made chronically hypoxic in a chamber at 12 % 0, for 3-4 weeks (CH) rats. Under anaesthesia, arterial blood pressure, femoral blood flow (FBF), arterial 0, content (Ca,02) and venous 0, content in the efflux from hiindlimb were measured. In N rats, changing the inspirate from air to 12 YO and 8 % 0, for 5 min each, reduced C,,,? from 20 f 0.3 ml (100 ml)-' in air to 13 f 1.0 ml (100 ml)-' in 8 % 0,. FBF did not change significantly (1.7 f 0.1 ml m i d in air) so that 0, delivery to hindlimb muscles fell from 0.28 f 0.07 to 0.16 f 0.02 ml min-' in 8 % 0,. Nevertheless, the-??, of hindlimb muscles was well maintained: 0.06 & 0.02 ml min-' in air and 0.08 k 0.02 ml min in 8 % 0,. In CH rats breathing 12 % 0,, Ca,02 (23 f 1.0 ml (100 ml)-') was comparable to that of N rats breathing air, due to an increase in haematocrit, as were FBF (1.6 f 0.2 ml m i d ) and 0, delivery (0.39 f 0.05 ml min-').However, vo2 was 2.5-fold greater in CH rats (0.16 f 0.03 ml min-'). As in N rats, FBF was well maintained at 1.7 f 0.2 and 1.6 f 0.2 ml min-' in 8 % 0, and air, respectively. Further, 3 was also well maintained, at 0.17 f 0.02 and 0.12 f 0.02 ml min-' in 8 % 0, and air, respectively.These results suggest that, contrary to previous reports, muscle vo2 of the rat is independent of 0, delivery over a wide range of 0, delivery values. They also sugges: that muscle Vo, #of CH rats is similarly independent of 0, delivery. The novel finding that muscle Voz has a greater absolute value in CH rats can, we propose, be explained by an increase in voz of the vasculature rather than of the skeletal muscle fibres and reflects increased biosynthetic activity of the vessel walls and/or vascular remodelling. 0 2 .

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Section: Acute ~~~~~~A In N Ratssupporting

confidence: 91%

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

Marshall¹,

Davies²

1999

Experimental Physiology

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“…The critical oxygen delivery, below which VO 2 becomes supply dependent, has not been reported in rabbits. In multiple species, however, the onset of supply dependence is associated with reductions of mixed venous saturations to the range of 30 -50% (1,8,36,60), well below the lowest venous saturation of 64% observed in the current study. The paired differences in Sv O 2 between the two groups (high rate, low PEEP vs. low rate, high PEEP), therefore, support the cardiac output data measured by pulse contour analysis.…”

Section: Discussioncontrasting

confidence: 65%

Maintenance of end-expiratory recruitment with increased respiratory rate after saline-lavage lung injury

Syring

Otto²,

Spivack³

et al. 2007

Journal of Applied Physiology

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Cyclical recruitment of atelectasis with each breath is thought to contribute to ventilator-associated lung injury. Extrinsic positive end-expiratory pressure (PEEPe) can maintain alveolar recruitment at end exhalation, but PEEPe depresses cardiac output and increases overdistension. Short exhalation times can also maintain end-expiratory recruitment, but if the mechanism of this recruitment is generation of intrinsic PEEP (PEEPi), there would be little advantage compared with PEEPe. In seven New Zealand White rabbits, we compared recruitment from increased respiratory rate (RR) to recruitment from increased PEEPe after saline lavage. Rabbits were ventilated in pressure control mode with a fraction of inspired O(2) (Fi(O(2))) of 1.0, inspiratory-to-expiratory ratio of 2:1, and plateau pressure of 28 cmH(2)O, and either 1) high RR (24) and low PEEPe (3.5) or 2) low RR (7) and high PEEPe (14). We assessed cyclical lung recruitment with a fast arterial Po(2) probe, and we assessed average recruitment with blood gas data. We measured PEEPi, cardiac output, and mixed venous saturation at each ventilator setting. Recruitment achieved by increased RR and short exhalation time was nearly equivalent to recruitment achieved by increased PEEPe. The short exhalation time at increased RR, however, did not generate PEEPi. Cardiac output was increased on average 13% in the high RR group compared with the high PEEPe group (P < 0.001), and mixed venous saturation was consistently greater in the high RR group (P < 0.001). Prevention of end-expiratory derecruitment without increased end-expiratory pressure suggests that another mechanism, distinct from intrinsic PEEP, plays a role in the dynamic behavior of atelectasis.

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“…Under most physiologic conditions in which SOT is independently reduced, oxygen consumption initially remains unchanged and then is decreased by further, more severe limitations in oxygen transport (26)(27)(28). With the decline in oxygen transport and consumption there is metabolic evidence of tissue hypoxia, reflected by an increase in arterial blood lactate concentration (27)(28)(29).…”

Section: Discussionmentioning

confidence: 99%

Ouabain Effects on Oxygen Physiology in Anemic Lambs

et al. 1987

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ABSTRACT. We studied the effects of anemia and ouabain administration on cardiac function, oxygen physiology, and blood catecholamine levels in nine newborn lambs. We measured oxygen consumption continuously, along with traditional hemodynamic variables. Oxygen transport was calculated. Following baseline measurements, lambs were made anemic (mean hematocrit = 12%) by isovolemic exchange transfusion with Plasmanate, and measurements were repeated. Thereafter ouabain was administered as a 75 pg/kg bolus, followed by 30 min of infusion at a rate of 0.05 pg/kg/min. Measurements were repeated at the conclusion of infusion. Anemia was associated with a heart rate related rise in left ventricular rate of pressure rise, a rise in oxygen consumption, an increase in cardiac output, a decrease in systemic vascular resistance, and a rise in fractional oxygen extraction (oxygen consumption/transport). Following ouabain administration, cardiac output, oxygen consumption, and stroke work fell, but left ventricular rate of pressure rise and the extraction ratio did not change. Serum levels of epinephrine and norepinephrine rose with sustained anemia and ouabain infusion. In this setting, ouabain effects are manifested primarily by alterations in oxygen transport and metabolism rather than by changes in traditional assessments of left ventricular contractile function. (Pediatr Res 21: 447-452, 1987) Abbreviations LV, left ventricle dP/dt, rate of pressure rise PEP, preejection period ET, ejection time VOz, oxygen consumption A-V. arterial-venous SOT, systemic oxygen transport SVR, systemic vascular resistance Cardiac glycosides are used commonly to treat circulatory congestion in infants and children with congenital cardiac defects (1-3). Traditionally, the weight-related doses of digoxin used in immature subjects are higher than those used in adults (4, 5), although the reasons for that practice remain unclear (6-10). Moreover, because the high resting level of myocardial muscle function early in life may not be affected adversely by structural cardiac defects (1 1-14), some have questioned the appropriateness of inotropic therapy for this patient group. Nevertheless, clinical impression and a few selected studies suggest that young subjects with structural cardiac defects benefit from cardiac glycoside therapy (15)(16)(17), although the precise mechanism of the effect has not been established (18)(19)(20).Despite the presence of vigorous myocardial muscle function with many congenital cardiac defects, the congested circulatory state can perturb oxygen transport to the tissues (15, 21). It is possible that in this setting cardiac glycosides may exert their predominant influence on the peripheral supply and demand for oxygen through their effect on the energy requiring sodiumpotassium ATPase pump enzyme system. In the present study we created circulatory conditions characterized by normal to increased myocardial function, yet compromised systemic oxygen transport by inducing anemia in conscious newborn lambs. It was our purp...

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A critical value for O2 transport in the rat

Cited by 70 publications

References 0 publications

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

The effects of acute and chronic systemic hypoxia on muscle oxygen supply and oxygen consumption in the rat

Maintenance of end-expiratory recruitment with increased respiratory rate after saline-lavage lung injury

Ouabain Effects on Oxygen Physiology in Anemic Lambs

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