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1.
Experiments were done to determine if endogenous opiates cause the arousal response decrement that follows repeated exposure to hypoxemia during sleep in lambs. Five lambs were anesthetized and instrumented for sleep staging and measurement of arterial Hb oxygen saturation. No sooner than 3 d after surgery, measurements were made in quiet sleep and active sleep during control periods when the lambs were breathing 21% oxygen and during experimental periods when the lambs were breathing 5% oxygen. The experimental period was terminated during each epoch by changing the inspired gas mixture back to 21% oxygen, once the lamb aroused from sleep. After each lamb had been exposed to 5% oxygen during 100 consecutive epochs of sleep, naloxone--an opiate antagonist--was given i.v. in a dose of 3 mg/kg as a bolus. The animals continued to be exposed to 5% oxygen during six more epochs of sleep after the administration of naloxone. Arousal occurred from both sleep states during rapidly developing hypoxemia but was delayed in active sleep compared to quiet sleep. The arterial Hb oxygen saturation at arousal was significantly lower, and the time to arousal was significantly longer with repeated exposure to hypoxemia during both quiet sleep and active sleep. Naloxone did not alter this arousal response decrement to hypoxemia. Thus, our data provide evidence that endogenous opiates do not play a major role in causing the arousal response decrement that follows repeated exposure to hypoxemia during sleep in lambs.  相似文献   

2.
Factors modulating the fetal aldosterone response to hypoxemia were studied in three groups of chronically catheterized fetal lambs between 131 and 143 days of gestation (term, 145 days). One group (control group) received an infusion of 5% dextrose in water; the second group (captopril-treated group) was given captopril, an inhibitor of angiotensin-converting enzyme; the third group (captopril plus dexamethasone-treated group) received dexamethasone in addition to captopril. In all groups of fetuses, hypoxemia was associated with a significant increase in plasma K+ concentration (+0.7 +/- 0.1 meq/liter). In control fetuses, changes in plasma aldosterone concentration during hypoxemia correlated closely with changes in plasma K+ concentration r = 0.79; P less than 0.001) and with changes in plasma angiotensin II concentration (r = 0.77; P less than 0.001). In the captopril-treated fetuses, the rise in plasma aldosterone concentration during hypoxemia correlated closely with plasma K+ (r = 0.79; P less than 0.001) but not with plasma angiotensin II values (r = 0.17). No significant correlation was found between percent changes in maternal aldosterone and percent changes in fetal aldosterone during hypoxemia and following recovery (r = 0.36; P greater than 0.1) in captopril-treated fetuses. Administration of dexamethasone to fetuses receiving captopril completely inhibited the rise in plasma aldosterone associated with hypoxemia. Taken together, the present results suggest that the rise in plasma aldosterone during hypoxemia is not related to the level of activity of the renin-angiotensin system but depends probably on the increased secretion of adrenocorticotrophin by the fetus.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
Arousal from sleep during rapidly developing hypoxemia in lambs   总被引:3,自引:0,他引:3  
Arousal is an important protective response that may prevent severe hypoxemia and death during sleep. However, very little is known about arousal from sleep in response to respiratory stimuli in newborns. Experiments were therefore done to investigate the arousal response from sleep to rapidly developing hypoxemia in eight lambs. Each lamb was anesthetized and instrumented for recordings of electrocorticogram, electrooculogram, nuchal and diaphragm electromyograms, and measurements of arterial hemoglobin oxygen saturation. A tracheotomy was done and a tracheostomy tube placed in the trachea so that the fraction of inspired oxygen could be changed quickly. No sooner than 3 days after surgery, measurements were made in quiet sleep and active sleep (AS) during 30-s control periods when the animals were breathing 21% oxygen and during experimental periods of hypoxemia when the animals were breathing either 10, 5, or 0% oxygen in nitrogen. During quiet sleep, arousal occurred at similar arterial hemoglobin oxygen saturations (81 +/- 6% on 10% O2, 80 +/- 5% on 5% O2 and 83 +/- 5% on 0% O2) suggesting that arousal was independent of the rate of change of arterial oxygen. However, during AS arousal occurred at different arterial hemoglobin oxygen saturations (76 +/- 6% on 10% O2, 55 +/- 11% on 5% O2, and 44 +/- 17% on 0% O2) suggesting that arousal was dependent on the rate of change of arterial oxygen. During some epochs of AS, electrocortical signs of cerebral hypoxia and primary apnea occurred before arousal. These data provide evidence that arousal from quiet sleep in response to hypoxemia occurs once an arousal threshold has been reached.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
Newborn humans may develop myocardial dysfunction in conjunction with severe birth asphyxia. Subendocardial or papillary muscle ischemia appears to be the basis for the myocardial dysfunction, yet patent coronary arteries have been demonstrated in the nonsurvivors. The asphyxiated newborns also have experienced hypoxemia, which has been suggested as the cause of myocardial ischemia. This study was designed to determine the relationship between reduced aortic blood oxygen content and blood flow as well as oxygen delivery within different regions of the heart. Three days after surgery, we measured blood flow and oxygen delivery to the free walls and papillary muscles of the right and left ventricles, the ventricular septum, and the atria in 10 lambs, during 20-min periods in 8-10% and 5-6% environmental oxygen concentrations. In each region of myocardium, blood flow increased linearly as the aortic blood oxygen content decreased. The slopes of the regression lines were similar for each region of ventricular myocardium. Atrial myocardial blood flow also increased as a linear function of the reductions in aortic blood oxygen content, but at a slower rate than in the ventricular regions. Hypoxemia was associated with increased oxygen delivery in each region of myocardium, but the two variables were not related in a linear or quadratic fashion. The results demonstrate that isolated hypoxemia is associated with increased blood flow and oxygen delivery in the free walls and papillary muscles of the right and left ventricles, the ventricular septum, and the atria.  相似文献   

5.
Insufficient cerebral O(2) supply leads to brain cell damage and loss of brain cell function. The relationship between the severity of hypoxemic brain cell damage and the loss of electrocortical brain activity (ECBA), as measure of brain cell function, is not yet fully elucidated in near-term newborns. We hypothesized that there is a strong relationship between cerebral purine and pyrimidine metabolism, as measures of brain cell damage, and brain cell function during hypoxemia. Nine near-term lambs (term, 147 d) were delivered at 131 (range, 120-141) d of gestation. After a stabilization period, prolonged hypoxemia (fraction of inspired oxygen, 0.10; duration, 2.5 h) was induced. Mean values of carotid artery blood flow, as a measure of cerebral blood flow, and ECBA were calculated over the last 3 min of hypoxemia. At the end of the hypoxemic period, cerebral arterial and venous blood gases were determined and CSF was obtained. CSF from 11 normoxemic siblings was used for baseline values. HPLC was used to determine purine and pyrimidine metabolites in CSF, as measures of brain cell damage. Concentrations of purine and pyrimidine metabolites were significantly higher in hypoxemic lambs than in their siblings, whereas ECBA was lower in hypoxemic lambs. Significant negative linear relationships were found between purine and pyrimidine metabolite concentrations and, respectively, cerebral O(2) supply, cerebral O(2) consumption, and ECBA. We conclude that brain cell function is related to concentrations of purine and pyrimidine metabolites in the CSF. Reduction of ECBA indeed reflects the measure of brain damage due to hypoxemia in near-term newborn lambs.  相似文献   

6.
BACKGROUND: Sufficient O2 supply to the brain is necessary for adequate cerebral energy metabolism, function and growth. OBJECTIVES: To elucidate the relation between changes in cerebral arterial O2 content and cerebral O2 supply and changes in the oxygenation state of cerebral hemoglobin, and to determine whether concentration changes in oxyhemoglobin (DeltacO2Hb), deoxyhemoglobin (DeltacHHb), and cerebral arterial oxygenation (DeltacHbD; the difference between DeltacO2Hb and DeltacHHb), and cerebral blood volume (DeltaCBV) can be used to assess the decline in brain cell function during hypoxemia in lambs born near term. METHODS: 17 preterm lambs were delivered at a mean gestational age of 133 days. Decreases in cerebral arterial oxygen content were induced by a stepwise reduction in inspired oxygen concentration. Mean values of all continuous variables were calculated over the last 180 s of each hypoxemic level. Cerebral arterial blood gases were analyzed at the end of each level to calculate cerebral arterial O2 content and cerebral O2 supply. RESULTS: Changes in cerebral arterial O2 content and cerebral O2 supply were positively linearly related with DeltacO2Hb and DeltacHbD, and negatively with DeltacHHb and the concentration changes in total hemoglobin. Electrocortical brain activity remained stable until the cO2Hb and cHbD decreased to >3.0 +/- 0.9 and >8.1 +/- 1.9 (mean +/- SD) micromol/100 g, respectively, and cHHb and CBV increased to >4.3 +/- 1.7 and 1.37 +/- 0.48 ml/100 g, respectively, as compared to baseline. CONCLUSIONS: Changes in cerebral arterial O2 content and cerebral O2 supply are adequately reflected by changes in the oxygenation state of cerebral hemoglobin. Concentration changes in DeltacO2Hb, DeltacHHb, DeltacHbD and DeltaCBV can be used to assess the decline in brain cell function during hypoxemia in lambs born near term.  相似文献   

7.
The purpose of this investigation was to determine the role of increased beta-adrenergic activity in regulating the increase in myocardial oxygen consumption that occurs during hypoxemia in unanesthetized newborn lambs. Through a left thoracotomy, fluid-filled catheters were placed in the ascending aorta, coronary sinus and left atrium, a pressure transducer was introduced into the left ventricle, and pacing wires were sutured onto the left atrium. The lambs were studied 3 d later by making intermittent measurements of aortic and coronary sinus blood oxygen saturations and Hb concentrations, left ventricular myocardial blood flow, cardiac output, heart rate, left atrial and aortic blood pressures, the maximal first derivative of left ventricular pressure, aortic and coronary sinus blood oxygen contents, the arteriovenous difference of oxygen across the left ventricular myocardium, myocardial oxygen consumption, and external cardiac work (aortic mean blood pressure times cardiac output). In nine lambs with an intact beta-adrenergic nervous system (group 1), the above measurements were made during a control period and during hypoxemia (FiO2 = 0.08-0.10) with spontaneous tachycardia. In another group of 12 lambs (group 2), the measurements were made during a control period, after beta-blockade (1.5 mg/kg intravenous propranolol) with pacing at the control heart rate, during hypoxemia with pacing at the control heart rate, and during hypoxemia with pacing-induced tachycardia. In the group 2 lambs, beta-blockade completely inhibited the increase in heart rate, maximal first derivative of left ventricular pressure, cardiac output and cardiac work that occurred during hypoxemia in the group 1 lambs that had an intact beta-adrenergic nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

8.
Experiments were done on 12 lambs to determine if repeated exposure to hypoxemia influences the interaction between oxygen and carbon dioxide in causing arousal response from sleep. Each lamb was anesthetized and instrumented for sleep staging and measurements of arterial Hb oxygen saturation. No sooner than 3 days after surgery, measurements were made in quiet and active sleep during control periods when the lambs were breathing 21% oxygen and during experimental periods when the lambs were breathing either 5% O2-0% CO2, 5% O2-5% CO2 or 5% O2-10% CO2. Each experimental period was terminated during each epoch by changing the inspired gas mixture back to 21% oxygen once the animal aroused from sleep. The lambs were divided into two groups. One group (n = 7) was studied without prior exposure to hypoxemia and the other group (n = 5) was studied after exposure to 5% oxygen during approximately 100 epochs of sleep until they aroused. In lambs not previously exposed to hypoxemia, there was evidence for a slight interaction between oxygen and carbon dioxide in initiating arousal but only from quiet sleep. Repeated exposure to hypoxemia resulted in an arousal response decrement to hypoxemia. In lambs previously exposed to hypoxemia, there was evidence for an interaction between oxygen and carbon dioxide in initiating arousal from both quiet and active sleep (i.e. the time to arousal decreased and the saturation at arousal increased as increasing amounts of carbon dioxide were added to the hypoxic gas mixture).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

9.
We studied the effects of beta-adrenergic receptor blockade on general circulatory and metabolic responses to moderate (FIO2 = 0.09) acute hypoxemia in newborn (protocol 1) and 3-wk-old (protocol 2) lambs, and on regional blood flow distribution in newborn lambs (protocol 1). Via a left thoracotomy we placed an electromagnetic flow transducer around the ascending aorta and inserted various vascular catheters. After 2 days of recovery, the lambs were studied. In protocol 1, we measured cardiovascular variables and regional blood flow distribution during control conditions, after 45 min of acute hypoxemia, and after 0.5 mg/kg of propranolol during acute hypoxemia. In protocol 2, we measured cardiovascular variables during control conditions and after 45 min of acute hypoxemia with and without propranolol pretreatment. In both groups, propranolol limited the increase in cardiac output and heart rate caused by hypoxemia, and thus decreased oxygen delivery. However, propranolol also decreased oxygen consumption so that pulmonary arterial pO2 was either higher (protocol 1) or the same (protocol 2) as during acute hypoxemia alone. Neither metabolic acidosis nor hypothermia ensued. In protocol 1, propranolol decreased renal, carcass, and most importantly, myocardial blood flows. However, myocardial O2 consumption also fell, coronary sinus pO2 increased, and blood was redistributed toward the subendocardium, suggesting that myocardial perfusion improved. Thus, beta-adrenergic receptor blockade during acute moderate hypoxemia may have a beneficial effect by reducing total body and myocardial oxygen demand in excess of the reduction in oxygen delivery.  相似文献   

10.
Experiments were done to investigate the effects of increased inspired oxygen on the arousal response from sleep to upper airway obstruction in 10 newborn lambs. Each lamb was anesthetized and instrumented for recordings of electrocorticograms, electrooculogram, nuchal and diaphragm electromyograms, and measurements of systemic arterial blood pressure and oxygen saturation (fiberoptic catheter oximeter). A tracheotomy was performed and a fenestrated tracheostomy tube was placed in the trachea. A 5F balloon tipped catheter was inserted into the tube so that airflow could be obstructed by inflating the balloon. No sooner than 3 days after surgery, measurements were made during a control period and during an experimental period of upper airway obstruction; the inspired oxygen fraction was alternated hourly between 0.21 and 0.60. A total of 57 epochs of quiet sleep and 58 epochs of active sleep was obtained in eight lambs. Arousal was significantly delayed (p less than 0.005) during active sleep (21 +/- 6 s; mean +/- 1 SD) compared to quiet sleep (7 +/- 2 s) in room air. Increased inspired oxygen significantly delayed arousal (p less than 0.05) during active sleep (47 +/- 25 s), but had little effect on arousal in quiet sleep (10 +/- 4 s). These results provide evidence that arousal from active sleep following upper airway obstruction in lambs is primarily initiated by a decrease in arterial oxygen. However, arousal from quiet sleep following upper airway obstruction in lambs appears to be initiated by other stimuli.  相似文献   

11.
A study was made to determine whether adenosine is involved in the regulation of breathing and whether the respiratory response to injections of adenosine and its analogue L-PIA (phenylisopropyl adenosine) is modified by moderate hypoxemia or by heat stress. Unanesthetized lambs with chronically implanted catheters were used for the investigation. Intravenous injections of adenosine caused an increase in the rate of breathing lasting for 5-30 s, except during heat stress, when the rate of breathing decreased. Injection of L-PIA also increased the rate of breathing, but the effects lasted longer than after injection of adenosine. During heat stress the response to injection of L-PIA varied. Both the arterial blood pressure and heart rate decreased transiently after intravenous injection of adenosine or L-PIA, while the central venous pressure increased. Adenosine might thus be part of a positive feedback system that stimulates breathing under normal environmental conditions with or without moderate hypoxemia. The respiratory responses to injection of adenosine during heat stress are different, which might indicate that under this condition the effects of adenosine on breathing are modified by its influence on temperature control.  相似文献   

12.
13.
Growth failure is a major complication of chronic hypoxemia, as seen in infants and children with cyanotic congenital heart disease. To determine whether chronic hypoxemia during infancy affects the gastrointestinal tract, we examined small intestinal growth and digestive enzyme activities in chronically hypoxemic newborn lambs and in age-matched controls. Chronic hypoxemia was produced by placing an inflatable occluder around the main pulmonary artery and performing a balloon atrial septostomy. Aortic oxygen saturation was reduced to 60-74% for 2 wk, after which the small intestine was removed for analysis. During chronic hypoxemia, somatic growth rate was decreased to 60% of control (hypoxemic, 135 +/- 20 versus control, 216 +/- 26 g/d, p less than 0.02). No differences in caloric intake were found (hypoxemic, 129 +/- 4 versus control, 128 +/- 4 kcal/kg/d). Chronic hypoxemia did not alter small intestinal growth, as measured by jejuno-ileal weight, jejuno-ileal length, mucosal weight, or mucosal protein or DNA contents. However, sp act of lactase, the principal disaccharidase of the infant lamb intestine, were significantly decreased (hypoxemic, 0.08 +/- 0.01 versus control, 0.146 +/- 0.03 units of enzyme activity/mg DNA, p less than 0.05), as were the total small intestinal contents of lactase (hypoxemic, 61.7 +/- 7.0 versus control, 120.6 +/- 21.7 units of enzyme activity, p less than 0.01). There also were decreases in specific and total activities of other digestive enzymes such as maltase, amino-oligopeptidase, and alkaline phosphatase in hypoxemic intestine that did not achieve statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

14.
Administration of oxygen via a tube held close to the nose prevented hypoxemia during breastfeeding in 15 of 20 infants with bronchopneumonia.  相似文献   

15.
Experiments were done on five lambs to determine if carotid denervation influences the arousal and cardiopulmonary responses to upper airway obstruction during sleep. Each lamb was anesthetized and instrumented for recordings of electrocorticogram, electro-oculogram, nuchal and diaphragm electromyograms, and measurements of arterial blood pressure and arterial Hb oxygen saturation. A tracheotomy was done and a fenestrated tracheotomy tube placed in the trachea. During the study, a 5 F balloon-tipped catheter was inserted into the tracheotomy tube so that air flow could be obstructed by inflating the balloon. No sooner than 3 d after surgery, measurements were made in quiet sleep and active sleep during control periods when the animal was breathing room air and during experimental periods of upper airway obstruction. Carotid denervation significantly affected the arousal response to upper airway obstruction. Arousal occurred during 14 of 14 epochs in quiet sleep and during 12 of 13 epochs in active sleep before the arterial Hb oxygen saturation decreased to 30%. However, the time to arousal was increased and the arterial Hb oxygen saturation at arousal was decreased in carotid-denervated lambs compared with what we have previously observed in carotid-intact lambs. These data provide evidence that the carotid chemoreceptors and/or carotid baroreceptors play a major role in causing arousal from sleep during upper airway obstruction in lambs. Our results may have implications for sudden infant death syndrome, because it is possible that alterations in the arousal response to respiratory stimuli play a role in sudden infant death.  相似文献   

16.
We studied the comparative effects of HCl-induced metabolic acidemia (pH = 7.11 +/- 0.03, mean +/- SE) and hypoxemia (PO2 = 28 +/- 1 torr) on cardiac output and regional blood flows in newborn lambs 3 days after the surgical placement of catheters in the left atrium and aorta and pacing wires on the left atrium. Cardiac output decreased by 49 +/- 6% during metabolic acidemia in contrast to the 12 +/- 2% increase during hypoxemia. The adrenal glands and the diaphragm were the only organs that received increased blood flows during acidemia and hypoxemia. Cerebral and myocardial blood flows decreased during acidemia but increased during hypoxemia. Blood flows decreased to the carcass and gastrointestinal tract during acidemia but did not change significantly during hypoxemia. Renal and splenic blood flows decreased during both stresses, but the reductions were more severe during acidemia. The changes in regional blood flows were not a passive result of the respective changes in cardiac output. HCl-induced metabolic acidemia and hypoxemia each result in significant redistributions of available blood flows which are quantitatively and qualitatively different from each other.  相似文献   

17.
Experiments were done on five lambs to determine if repeated obstruction of the upper airway influences the arousal and cardiopulmonary response to upper airway obstruction. Each lamb was anesthetized and instrumented for recordings of electrocorticogram, electrooculogram, nuchal and diaphragm electromyograms, and measurements of arterial blood pressure and arterial hemoglobin oxygen saturation. A tracheostomy was done and a fenestrated tracheostomy tube placed in the trachea. The animals were studied after a 3-day recovery period. During a study, a 5F balloon-tipped catheter was inserted into the tracheostomy tube so that air flow could be obstructed by inflating the balloon. The balloon was inflated each time the animal went to sleep for approximately 100 consecutive epochs (17 to 30 h) and the time to arousal and the arterial hemoglobin oxygen saturation at arousal were recorded. Upper airway obstruction was terminated by deflating the balloon once the animal aroused from sleep. Arousal occurred from both sleep states during upper airway obstruction but was delayed in active sleep compared to quiet sleep. The time to arousal and the decrease in arterial hemoglobin oxygen saturation were significantly increased with repeated upper airway obstruction only during active sleep. Inasmuch as it is possible that alterations in the arousal response to respiratory stimuli play a role in sudden infant death, studies to investigate the mechanisms of the state-specific changes in the arousal response to upper airway obstruction are warranted.  相似文献   

18.
To evaluate the effect of respiratory syncytial virus (RSV) infection on the response to laryngeal chemostimulation (LCS) with water, five lambs were inoculated with human RSV and three lambs were given control media at an age of 3-5 days. During RSV infection, LCS resulted in increased inhibition of minute ventilation and delayed recovery of regular breathing. Sleep further increased the response, and arousal was less likely to occur in active sleep. Two of the five infected lambs needed resuscitation after LCS when arousal was absent. Histological studies showed bronchiolitis and pneumonitis. Laryngeal tastebud morphology was unchanged at 8 days after inoculation. However, infected lambs had disrupted tastebuds 4-6 weeks after infection. Failure to arouse and to terminate reflex apnea may play a role in the pathogenesis of the sudden infant death syndrome associated with respiratory tract infection.  相似文献   

19.
In the vitreous humor from three hypoxemic and one control group of pigs, hypoxanthine, xanthine, and uric acid concentrations were measured. The purine concentrations were measured before the hypoxemia, at the time of death, and 24 h post-mortem. During hypoxemia with arterial O2 tension between 2.1 and 3.0 kPa [fractional inspired oxygen (FiO2) = 0.08], hypoxanthine concentrations increased from a mean basal value of 11.7 +/- 5.6 mumol/L to 16.3 +/- 2.4 mumol/L at the time of death (NS). Xanthine concentrations changed from a basal value of 0.3 +/- 0.1 mumol/L to 0.6 +/- 0.2 mumol/L (p less than 0.02), and uric acid changed from 3.4 +/- 1.1 mumol/L to 5.0 +/- 4.5 mumol/L (NS). During hypoxemia with arterial O2 tension between 3.0 and 4.0 kPa (FiO2 = 0.11), hypoxanthine increased in the vitreous humor from a mean basal value of 9.1 mumol/L to 20.3 mumol/L at the time of death (p less than 0.02). Xanthine concentrations increased from 0.3 mumol/L to 1.3 mumol/L (p less than 0.05), whereas there was no change in uric acid concentration (basal 5.0 +/- 0.8 mumol/L and final 4.5 +/- 1.0 mumol/L). During milder hypoxemia with arterial O2 tension between 4.3 and 5.6 kPa (FiO2 = 0.14), or in the control group (FiO2 = 0.21), neither of the metabolites changed significantly. The vitreous humor was not stable post-mortem, inasmuch as the mean concentration of hypoxanthine increased from 18.2 +/- 7.7 mumol/L to 121.6 +/- 57.4 mumol/L 24 h post-mortem (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

20.
We evaluated the adequacy of regional and transmural blood flow during exercise and rapid pacing after 1 wk of hypoxemia. Seven mature mongrel dogs were made hypoxemic (mean O2 saturation = 72.4%) by anastomosis of left pulmonary artery to left atrial appendage. Catheters were placed in the left atrium, right atrium, pulmonary artery, and aorta. Atrial and ventricular pacing wires were placed. An aortic flow probe was placed to measure cardiac output. Ten nonshunted dogs, similarly instrumented, served as controls. Recovery time was approximately 1 wk. Cardiac output, mean aortic pressure, and oxygen saturation were measured at rest, with ventricular pacing, atrial pacing, and with treadmill exercise. Ventricular and atrial pace and exercise were at a heart rate of 200. Right ventricular free wall, left ventricular free wall, and septal blood flow were measured with radionuclide-labeled microspheres. Cardiac output, left atrial blood pressure, and aortic blood pressure were similar between the two groups of dogs in all testing states. Myocardial blood flow was significantly higher in the right and left ventricular free wall in the hypoxemic animals during resting and exercise testing states. Myocardial oxygen delivery was similar between the two groups of animals. Pacing resulted in an increase in myocardial blood flow in the control animals but not the hypoxemic animals.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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