Increased oxygen consumption associated with breathing activity in fetal lambs

Rurak, D. W.; Gruber, Nancy

doi:10.1152/jappl.1983.54.3.701

Cited by 51 publications

(32 citation statements)

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“…Although we did not measure right ven- 936 tricular output in this study, it is likely to have been increased during accentuated FBM. This is indicated by an increase in fetal heart rate (by 12.8 Ϯ 4.2 bpm) in combination with añ 5% increase in left pulmonary arterial pressure (23) and has been observed previously during accentuated FBM (21,22). This finding is consistent with previous studies that demonstrated that vigorous FBM impose a significant oxygen demand in the fetus (21) and are commonly associated with increased fetal body movements (24).…”

Section: Discussionsupporting

confidence: 90%

“…This is indicated by an increase in fetal heart rate (by 12.8 Ϯ 4.2 bpm) in combination with añ 5% increase in left pulmonary arterial pressure (23) and has been observed previously during accentuated FBM (21,22). This finding is consistent with previous studies that demonstrated that vigorous FBM impose a significant oxygen demand in the fetus (21) and are commonly associated with increased fetal body movements (24). Indeed, during vigorous FBM, fetal oxygen consumption can increase by 30% (21), and blood flow to the main respiratory muscles (diaphragm and intercostals) increases (22).…”

Section: Discussionsupporting

confidence: 71%

“…As the incidence of nonaccentuated FBM greatly exceeds that of accentuated FBM, it is likely that the effect of accentuated FBM on PBF was masked in the analysis by prolonged periods of low amplitude FBM (Ͻ3 mm Hg). However, we divided the epochs of FBM into accentuated and nonaccentuated periods of FBM, as defined by us and others (15,21,22), and recorded FBM for 6 h/d for 7 d, which allowed a rigorous analysis of the impact of FBM on PBF and PVR. Furthermore, as PBF increases with gestational age and can vary considerably between fetuses and within individual fetuses over a 24-h period, a comparison of PBF during episodes of FBM with the preceding apneic period is a sensitive method for assessing the specific effects of FBM on PBF.…”

Section: Discussionmentioning

confidence: 99%

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Influence of Fetal Breathing Movements on Pulmonary Hemodynamics in Fetal Sheep

et al. 2004

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During fetal development, pulmonary vascular resistance (PVR) is high, and, as a result, blood flow through the fetal lungs is low. Although PVR markedly decreases at the time of birth, the factors that regulate pulmonary blood flow (PBF) and PVR before and immediately after birth are not clear. Our aim was to examine the relationship between episodes of fetal breathing movements (FBM) and pulmonary hemodynamics during late gestation to further understand the relationship among lung luminal volume, phasic changes in intrapulmonary pressure, and PVR before birth. In chronically catheterized fetal sheep (120 -128 d gestation; n ϭ 5; term~147 d), PBF and PVR were measured during periods of FBM and apnea. Episodes of FBM were divided into periods of accentuated (amplitude of Ͼ3.5 mm Hg change in tracheal pressure) and nonaccentuated periods of FBM. During accentuated episodes of FBM, mean PBF was increased to 159.5 Ϯ 23.4% (p Ͻ 0.0025) of the preceding apneic period and was associated with a 19.1 Ϯ 5.2% reduction in PVR. In addition, during accentuated episodes of FBM, the retrograde flow of blood through the left pulmonary artery was reduced to 90.1 Ϯ 1.0% of the preceding apneic period, which most likely contributed to the increase in mean PBF at this time. Although a change in PBF and PVR could not be detected during nonaccentuated FBM, compared with the preceding apneic period, PBF was linearly and positively correlated with the amplitude (change in pressure) of FBM. We conclude that PVR is decreased and PBF is increased during accentuated episodes of FBM, possibly as a result of phasic reductions in intrapulmonary pressures. At birth, blood flow through the lungs markedly increases as a result of a large reduction in pulmonary vascular resistance (PVR). Although this process plays a vital role in the transition from intra-to extrauterine life, the precise mechanisms involved are still not clear. In particular, it is not clear why PVR is high in the fetus, relative to the newborn. During fetal life, the majority (88%) of right ventricular output bypasses the lungs and is shunted into the systemic circulation via the ductus arteriosus (1). In the late-gestation fetus, the relatively high PVR has been attributed to the low PO 2 of blood perfusing the lungs (2,3), to the balance between vasoconstrictor and vasodilator activity (4 -7), and to the high level of resting lung expansion in the fetus (8).Previous studies have investigated the relationship between lung luminal volume and PVR in the fetus and have shown that PVR is directly proportional to the changes in lung volume, causing pulmonary blood flow (PBF) to cease at total lung capacity (9). Conversely, a reduction in lung liquid volume, to a volume that is equivalent to the end-expiratory lung volume in the air-filled lung after birth, caused a 3-to 4-fold increase in PBF and a substantial decrease in PVR (8). Together, these studies indicate that the degree of lung expansion and the associated change in intraluminal pressure may be important physiologic dete...

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

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Influence of Fetal Breathing Movements on Pulmonary Hemodynamics in Fetal Sheep

et al. 2004

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“…Small differences in arterial partial pressure of carbon dioxide have been observed between fetal behavioral states that have been either significant (4) or not significant (25). In addition, there is an effect of FBM on blood gas and pH such that as the amplitude and the duration of FBM increase, there is a fall in arterial oxygen pressure and pH with a rise in arterial partial pressure of carbon dioxide (26). In the present study, pH is lower during both spontaneous and carbachol-induced LV/REM behavioral state; however, these values are within the normal range (27).…”

Section: Discussioncontrasting

confidence: 54%

Cerebral Blood Flow during Spontaneous and Cholinergically Induced Behavioral States in the Sheep Fetus

et al. 2005

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The sleep-wake cycle has been studied extensively in both adult and fetal mammalian species with emphasis in different areas. Fetal studies have focused on characterization of behavioral states and responses to challenges such as hypoxia, and there have been relatively fewer studies that have investigated the control of fetal behavioral state. The objective of this study was to determine whether cerebral blood flow during cholinergically induced fetal behavioral states was similar to that during spontaneous fetal behavioral states in chronically catheterized near-term sheep fetuses. Injection of carbachol (1.25 g) into the cisterna magna increased the duration of the subsequent lowvoltage electrocortical epoch. Scopolamine infusion (0.3 mg) increased the duration of the subsequent high-voltage electrocortical activity epoch. Cerebral blood flow and oxygen delivery were higher during both spontaneous and carbachol-induced low-voltage/rapid eye movement behavioral state than during spontaneous and scopolamine-induced high-voltage/non-rapid eye movement behavioral state. Thus, pharmacologic manipulation of fetal behavioral state induced a state that resembled spontaneous fetal behavioral state both electrophysiologically and metabolically. This study shows that inducing extended periods of a desired fetal behavioral state is possible and that this method may be used to study their function. Cycles of behavioral state are present before birth in species in which significant brain development occurs in utero, including the rhesus monkey, guinea pig, and sheep. After 120 d gestation (term ϭ 145 Ϯ 3 d), the sheep fetus cycles between a low-voltage (LV)/rapid eye movement (REM) behavioral state-characterized by LV fast electrocortical activity, rapid eye movements, and nuchal muscle atonia-and a high-voltage (HV)/non-rapid eye movement (NREM) behavioral statecharacterized by HV slow electrocortical activity, no eye movements, and nuchal muscle tone (1) every 30 -40 min (2). Near term, after 135 d, the sheep fetus exhibits short periods of "wakefulness" as defined by LV fast electrocortical activity and nuchal muscle tone (3,4). In addition, cerebral metabolic rate (CMR) of oxygen and cerebral blood flow (CBF) are increased during LV/REM compared with HV/NREM behavioral state (5). These fetal behavioral states are electrophysiologically similar to the REM and NREM sleep states observed during adult sleep, and higher CBF has been measured during REM sleep compared with NREM sleep in all adult mammals studied (6 -8).Cholinergic drugs also alter REM and NREM sleep in adult species. Microinjection of carbachol into brainstem nuclei of the pontine reticular formation increases REM episodes in rats (9). Likewise, rats that are treated with s.c. infusion of scopolamine exhibit a decrease in sleep, with greater suppression of REM than NREM sleep (10). In the sheep fetus, a 90-min infusion of carbachol increases the incidence of LV/REM behavioral state (11,12), whereas scopolamine administration increases the incidence of HV/NREM...

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“…The fetal pig is also comparatively active in utero and has a higher incidence of breathing movements than the fetal lamb at a similar stage of gestation (Harding, Fowden & Silver, 1991;Fowden et al 1992). Since paralysis of the sheep fetus reduces 02 consumption by 20-30% (Rurak & Gruber, 1983), the increased activity of the respiratory and other muscles in the fetal pig is likely to contribute to its relatively high rates of glucose and oxygen utilization.…”

Section: Discussionmentioning

confidence: 99%

Glucose, lactate and oxygen metabolism in the fetal pig during late gestation

Fowden¹,

Forhead²,

Silver³

et al. 1997

Experimental Physiology

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SUMMARYUsing [U-_4C]glucose tracer, rates of umbilical uptake, utilization and production of glucose, and of CO2 production from glucose carbon, were measured in seven chronically catheterized fetal pigs, when the sow was in the fed state, between 100 and 113 days of gestation (term, 114 + 2 days). At the same time, rates of umbilical 02 and lactate uptake were determined in all seven fetuses by the Fick principle. The mean fetal rates of umbilical glucose uptake, glucose utilization and CO2 production from glucose carbon were 38.4 + 4.2, 41-3 + 5.2 and 126-9 + 12-6 #smol min-' (kg fetal body weight)-', respectively (n = 7). No glucose production was therefore detected in the fetuses. Production of CO2 from glucose carbon accounted for 37-3 + 3.4% (n =7) of the umbilical 02 uptake, which averaged 340 + 13 jumol min-kg-' (n = 7). There was also significant umbilical lactate uptake in the fetal piglets when the sow was in the fed state (32.6 + 10-4 #tsmol min-1 kg-', n = 7, P <0-05). No significant changes in fetal glucose, 0°or lactate metabolism were observed with increasing age towards term. The fetal rates of glucose metabolism and of umbilical uptake of 02 and lactate were not correlated with the fetal blood glucose level. Hence, glucose is used for both oxidative and tfOn-oxidative metabolism in utero and is an important, although not the sole, source of carbon for metabolic processes in the fetal pig during late gestation.

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Increased oxygen consumption associated with breathing activity in fetal lambs

Cited by 51 publications

References 0 publications

Influence of Fetal Breathing Movements on Pulmonary Hemodynamics in Fetal Sheep

Influence of Fetal Breathing Movements on Pulmonary Hemodynamics in Fetal Sheep

Cerebral Blood Flow during Spontaneous and Cholinergically Induced Behavioral States in the Sheep Fetus

Glucose, lactate and oxygen metabolism in the fetal pig during late gestation

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