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See detailEffects of Hyperchloremia on Blood Oxygen Binding in Healthy Calves
Cambier, Carole ULg; Detry, B.; Beerens, Dominique ULg et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1998), 85(4), 1267-1272

Three different levels of hyperchloremia were induced in healthy Friesian calves to study the effects of chloride on blood oxygen transport. By infusion, the calves received either 5 ml/kg of 0.9% NaCl ... [more ▼]

Three different levels of hyperchloremia were induced in healthy Friesian calves to study the effects of chloride on blood oxygen transport. By infusion, the calves received either 5 ml/kg of 0.9% NaCl (low-level hyperchloremia; group A), 5 ml/kg of 7.5% NaCl (moderate hyperchloremia; group B), or 7.5 ml/kg of 7.5% NaCl (high-level hyperchloremia; group C). Blood was sampled from the jugular vein and the brachial artery. Chloride concentration, hemoglobin content, arterial and venous pH, PCO2, and PO2 were determined. At each time point (0, 15, 30, 60, and 120 min), the whole blood oxygen equilibrium curve (OEC) was measured under standard conditions. In groups B and C, hyperchloremia was accompanied by a sustained rightward shift of the OEC, as indicated by the significant increase in the standard PO2 at 50% hemoglobin saturation. Infusion of hypertonic saline also induced relative acidosis. The arterial and venous OEC were calculated, with body temperature, pH, and PCO2 values in arterial and venous blood taken into account. The degree of blood desaturation between the arterial and the venous compartments [O2 exchange fraction (OEF%)] and the amount of oxygen released at tissue level by 100 ml of bovine blood (OEF vol%) were calculated from the arterial and venous OEC combined with the PO2 and hemoglobin concentration. The chloride-induced rightward shift of the OEC was reinforced by the relative acidosis, but the altered PO2 values combined with the lower hemoglobin concentration explained the absence of any significant difference in OEF (% and vol%). We conclude that infusion of hypertonic saline induces hyperchloremia and acidemia, which can explain the OEC rightward shift observed in arterial and peripheral venous blood. [less ▲]

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See detailChronic exposure to ozone causes tolerance to airway hyperresponsiveness in guinea pigs: lack of SOD role.
Vargas, M. H.; Romero, L.; Sommer, B. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1998), 84(5), 1749-1755

Tolerance to respiratory effects of O3 has been demonstrated for anatomic and functional changes, but information about tolerance to O3-induced airway hyperresponsiveness (AHR) is scarce. In guinea pigs ... [more ▼]

Tolerance to respiratory effects of O3 has been demonstrated for anatomic and functional changes, but information about tolerance to O3-induced airway hyperresponsiveness (AHR) is scarce. In guinea pigs exposed to air or O3 (0.3 parts/million, 4 h/day, for 1, 3, 6, 12, 24, or 48 days, studied 16-18 h later), pulmonary insufflation pressure changes induced by intravenous substance P (SP, 0.032-3.2 micro ug/kg) were measured, then the animals were subjected to bronchoalveolar lavage (BAL). Bronchial rings with or without phosphoramidon were also evaluated 3 h after air or a single O3 exposure. O3 caused in vivo AHR (increased sensitivity) to SP after 1, 3, 6, 12, and 24 days of exposure compared with control. However, after 48 days of exposure, O3 no longer caused AHR. Total cell, macrophage, neutrophil, and eosinophil counts in BAL were increased in most O3-exposed groups. When data from all animals were pooled, we found a highly significant correlation between degree of airway responsiveness and total cells (r = 0.55), macrophages (r = 0.54), neutrophils (r = 0.47), and eosinophils (r = 0.53), suggesting that airway inflammation is involved in development of AHR to SP. Superoxide dismutase (SOD) levels in BAL fluids were increased (P < 0.05) after 1, 3, 6, and 12 days of O3 exposure and returned to basal levels after 24 and 48 days of exposure. O3 failed to induce hyperresponsiveness to SP in bronchial rings, and phosphoramidon increased responses to SP in air- and O3-exposed groups, suggesting that neutral endopeptidase inactivation was not involved in O3-induced AHR to SP in vivo. We conclude that chronic exposure to 0. 3 ppm O3, a concentration found in highly polluted cities, resulted in tolerance to AHR to SP in guinea pigs by an SOD-independent mechanism. [less ▲]

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See detailDoes an Acute COPD Crisis Modify the Cardiorespiratory and Ventilatory Adjustments to Exercise in Horses?
Art, Tatiana ULg; Duvivier, Dominique Hannia; Votion, Dominique ULg et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1998), 84(3), 845-52

The present study was conducted to understand better the mechanisms leading to the decrease in exercise capacity observed in horses suffering from chronic obstructive pulmonary disease (COPD). Five COPD ... [more ▼]

The present study was conducted to understand better the mechanisms leading to the decrease in exercise capacity observed in horses suffering from chronic obstructive pulmonary disease (COPD). Five COPD horses were submitted to a standardized submaximal treadmill exercise test while they were in clinical remission or in acute crisis. Respiratory airflow, O2 and CO2 fractions in the respired gas, pleural pressure changes and heart rate were recorded, and arterial and mixed venous blood were analyzed for gas tensions, hemoglobin, and plasma lactate concentrations. O2 consumption, CO2 production, expired minute ventilation, tidal volume, alveolar ventilation, cardiac output, total pulmonary resistance, and mechanical work of breathing were calculated. The results showed that, when submaximally exercised, COPD horses in crisis were significantly more hypoxemic and hypercapnic and that their total pulmonary resistance and mechanical work of breathing were significantly higher and their expired minute ventilation significantly lower than when they were in remission. However, their O2 consumption remained unchanged, which was probably due to the occurrence of compensatory mechanisms, i.e., higher heart rate, cardiac output, and hemoglobin concentration. Last, their net anaerobic metabolism seemed to be more important. [less ▲]

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See detailInfluence of Age and Breed on the Binding of Oxygen to Red Blood Cells of Bovine Calves
Gustin, Pascal ULg; Detry, B.; Robert, Alain ULg et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1997), 82(3), 784-90

The influence of somatic growth and genetic selection on the whole blood oxygen equilibrium curve (OEC) was measured under standard conditions in double-muscled and dairy calves during their first 3 mo of ... [more ▼]

The influence of somatic growth and genetic selection on the whole blood oxygen equilibrium curve (OEC) was measured under standard conditions in double-muscled and dairy calves during their first 3 mo of life. Crossbreed animals were also investigated. Hemoglobin, 2,3-diphosphoglycerate (DPG), Cl, and Pi concentrations were also measured. The percentage of fetal hemoglobin (HbF) was determined. The influence of exogenous Cl, Pi, and pH on the OEC was also assessed. The PO2 at 50% hemoglobin saturation (P50) increased during somatic growth, probably because of the increase in DPG recorded in double-muscled neonates and to the progressive disappearance of HbF in both breeds. The oxygen exchange fraction (OEF%) was used to assess the combined influence of the OEC shift and OEC shape changes on blood oxygen desaturation under standard conditions, when the PO2 decreases within a physiological range. The OEF% showed an increase during the first month, then a stabilization. The effects of Cl, Pi, and pH in Friesian calves were similar as in adult cattle. Double-muscled neonates had a lower P50, OEF% values, and DPG concentrations and higher hemoglobin and Cl concentrations than Friesian neonates. The Pi concentration and the percentage of HbF were similar in both breeds. The pH and the Cl concentration had significantly less effect on the OEC in double-muscled than in Friesian calves. Crossbreed animals exhibited intermediate parameter values, between those recorded for double-muscled and Friesian calves. All differences between breeds progressively disappeared during the first month. These data show that blood function changes markedly in calves during the first month of life and that genetic selection can alter blood function. [less ▲]

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See detailMultiple-Breath Washout and Washin Experiments in Steers
Rollin, Frédéric ULg; Desmecht, Daniel ULg; Verbanck, S. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1996), 81(2), 957-63

Multiple-breath N2 washouts (WO) and washins (WI) were performed during regular tidal breathing in 11 unsedated healthy steers approaching pulmonary functional maturity (mean body weight = 271 kg). They ... [more ▼]

Multiple-breath N2 washouts (WO) and washins (WI) were performed during regular tidal breathing in 11 unsedated healthy steers approaching pulmonary functional maturity (mean body weight = 271 kg). They inspired 20% O2 in 80% Ar during the WO and air during the WI. For each steer, we computed two indexes of ventilation inhomogeneity from the N2 WO curves: 1) the curvilinearity of the logarithm of end-tidal N2 concentrations as a function of cumulative expired volume reflected in the ratio of two slopes fitted between 100 and 50% and between 50 and 10%, respectively, of end-tidal N2 concentration of the first breath of the WO; and 2) the N2 phase III slope divided by the mean expired concentration (Sn) of each breath also plotted as a function of cumulative expired volume. Equivalent computation of both parameters was done on WI and WO curves, and similar results were obtained. The mean slope ratio was 0.812 +/- 0.119 (SD) for all the steers, which is consistent with topographic gravity-dependent specific ventilation distribution inhomogeneity. Sn was independent of the breath number both for WO and WI (mean Sn = 0.130 +/- 0.057 liters-1), suggesting that emptying between unequally ventilated units, is synchronous. This behavior resembles that observed in rats postmortem (S. Verbanck, E.R. Weibel, and M. Paiva. J. Appl Physiol. 71: 847-854, 1991) but contrasts with experiments in humans, in whom convection-dependent ventilation inhomogeneities generate a marked increase in Sn throughout the entire WO (A. B. H. Crawford, M. Makowska, M. Paiva, and L. A. Engel. J. Appl. Physiol. 59: 838-846, 1985). This is surprising because one would expect gravity-dependent sequential emptying in animals of this size. [less ▲]

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See detailChanges in breath 13CO2/12CO2 during exercise of different intensities.
Gautier, J. F.; Pirnay, Freddy ULg; Lacroix, M. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1996), 81(3), 1096-102

The measurement of breath 13CO2/12CO2 is commonly used during exercise to evaluate the oxidation rate of exogenous carbohydrates enriched in 13C. The aim of this study was to investigate whether exercise ... [more ▼]

The measurement of breath 13CO2/12CO2 is commonly used during exercise to evaluate the oxidation rate of exogenous carbohydrates enriched in 13C. The aim of this study was to investigate whether exercise itself affects the 13C/12C ratio in expired air CO2 in relation to exercise intensity. The relative abundance of 13C and 12C in expired air CO2 was determined by isotoperatio mass spectrometry and expressed as delta 13C (in %o) by using Craig's formula and calibrated standards. Five healthy young men exercised on a treadmill after an overnight fast during > or = 105 min on four occasions and in a randomized order. Work rates were performed at approximately 30, 45, 60, and 75% of their maximal O2 uptake (VO2max). Delta 13C in expired air CO2 and respiratory exchange ratio (RER) were determined every 15 or 30 min during exercise. At 30 and 45% VO2max, a slight and not statistically significant increase in delta 13C was observed at 30 min. In contrast, at 60 75% VO2max, the rise was statistically significant and averaged 0.83 and 0.99%o, respectively. Average delta 13C (between 0 and 105 min) progressively increased with the intensity of exercise. Individual values of delta 13C and RER were positively correlated (r = 0.653, P = 0.002) as were values of delta 13C and endogenous carbohydrates utilized (r = 0.752, P < 0.001). Factitious or "pseudooxidation" of a 13C-enriched exogenous glucose load (indeed noningested) was calculated from the changes in expired air delta 13C. Over the whole period of exercise it was not statistically significant at 30 and 40% VO2max. However, over the first 60 min of exercise, such pseudooxidation of exogenous glucose was significant at 30 and 45% VO2max. In conclusion, by modifying the mix of endogenous substrates oxidized, exercise at 60% VO2max and above significantly increases the 13C/12C ratio in expired air CO2. At these intensities, this could lead to overestimation of the oxidation of 13C-labeled substrates given orally. At lower intensities of exercise, such overestimation is much smaller an affects mainly the values recorded during the initial part of the exercise bout. [less ▲]

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See detailChloride and Inorganic Phosphate Modulate Binding of Oxygen to Bovine Red Blood Cells
Gustin, Pascal ULg; Detry, Benoît; Cao, M. L. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1994), 77(1), 202-208

The influence of Pi and Cl on the equilibrium of oxygen binding to bovine red blood cells was assessed by plotting the whole blood oxygen dissociation curve measured under standard conditions with and ... [more ▼]

The influence of Pi and Cl on the equilibrium of oxygen binding to bovine red blood cells was assessed by plotting the whole blood oxygen dissociation curve measured under standard conditions with and without added KCl and K2HPO4. Both salts shifted the oxygen dissociation curve to the right. This effect was more marked at the highest saturation levels. At a given saturation level, the anion-induced shift was linearly related to the concentration of salt added to the blood. Cl had a greater effect than Pi. The relationship between changes in Po2 at 50% hemoglobin saturation (in Torr) and concentrations of ions added (in mmol/l) was equal to 0.0515[Cl] + 0.0302[Pi] (r2 = 0.94; P < 0.001). These changes were not due to the hyperosmolality induced by salt addition, since sucrose added in place of salts was without effect on the measured parameters. The oxygen exchange fraction expressed as percentage of saturation, i.e., the difference in hemoglobin saturation when Po2 decreases from 130 to 40 Torr, was linearly correlated to added anion concentration (in mmol/l) (= 0.102[Cl] + 0.059[Pi] (r2 = 0.95; P < 0.001)). No significant interaction between the anions was observed; their effects were purely additive. This original mechanism of controlling the oxygen affinity of bovine blood may have clinical relevance: Cl and Pi could be used to increase oxygen transport efficiency in hypoxic animals [less ▲]

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See detailDo canine scalene and sternomastoid muscles play a role in breathing?
De Troyer, A.; Cappello, M.; Brichant, Jean-François ULg

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1994), 76(1), 242-52

To assess the respiratory function of the scalene and sternomastoid muscles in the dog, we studied the effect of graded increases in inspiratory airflow resistance and single-breath airway occlusion on ... [more ▼]

To assess the respiratory function of the scalene and sternomastoid muscles in the dog, we studied the effect of graded increases in inspiratory airflow resistance and single-breath airway occlusion on the electrical activity of these muscles in 18 supine anesthetized spontaneously breathing animals. The sternomastoids never showed any activity, and the scalenes showed some inspiratory activity during occlusion in only two animals. The adoption of the prone position and bilateral cervical vagotomy did not affect this pattern. Hypercapnia also did not elicit any sternomastoid activity and induced scalene inspiratory activity during occlusion in only four of nine animals. On microscopic examination, however, both muscles were found to contain large numbers of spindles, suggesting that they have the capacity to respond to stretch. In addition, with increases in inspiratory resistance, both the sternum and ribs were displaced in the caudal direction. As a result, the scalenes demonstrated a gradual inspiratory lengthening and the normal inspiratory lengthening of the sternomastoids was accentuated. Additional studies in three unanesthetized animals showed consistent activity in the scalene and sternomastoid muscles during movements of the trunk and neck but no activity during breathing, including occluded breathing. These observations thus indicate that the alpha-motoneurons of the scalene and sternomastoid muscles in the dog have very small central respiratory drive potentials with respect to their critical firing threshold. In this animal, these muscles do not have a significant respiratory function. [less ▲]

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See detailFructose utilization during exercise in men: rapid conversion of ingested fructose to circulating glucose.
Jandrain, Bernard ULg; Pallikarakis, N.; Normand, S. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1993), 74(5), 2146-54

The aim of the present study was to compare the metabolic fate of repeated doses of fructose or glucose ingested every 30 min during long-duration moderate-intensity exercise in men. Healthy volunteers ... [more ▼]

The aim of the present study was to compare the metabolic fate of repeated doses of fructose or glucose ingested every 30 min during long-duration moderate-intensity exercise in men. Healthy volunteers exercised for 3 h on a treadmill at 45% of their maximal oxygen consumption rate. "Naturally labeled" [13C]glucose or [13C]fructose was given orally at 25-g doses every 30 min (total feeding: 150 g; n = 6 in each group). Substrate utilization was evaluated by indirect calorimetry, and exogenous sugar oxidation was measured by isotope ratio mass spectrometry on expired CO2. Results were corrected for baseline drift in 13C/12C ratio in expired air due to exercise alone. Fructose conversion to plasma glucose was measured combining gas chromatography and isotope ratio mass spectrometry. Most of the ingested glucose was oxidized: 81 +/- 4 vs. 57 +/- 2 g/3 h for fructose (2P < 0.005). Exogenous glucose covered 20.8 +/- 1.4% of the total energy need (+/- 6.7 MJ) compared with 14.0 +/- 0.6% for fructose (2P < 0.005). The contribution of total carbohydrates was significantly higher and that of lipids significantly lower with glucose than with fructose. The blood glucose response was similar in both protocols. From 90 to 180 min, 55-60% of circulating glucose was derived from ingested fructose. In conclusion, when ingested repeatedly during moderate-intensity prolonged exercise, fructose is metabolically less available than glucose, despite a high rate of conversion to circulating glucose. [less ▲]

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See detailEndogenous substrate oxidation during exercise and variations in breath 13CO2/12CO2.
Gautier, J. F.; Pirnay, Freddy ULg; Jandrain, Bernard ULg et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1993), 74(1), 133-8

This study attempted to induce a major shift in the utilization of endogenous substrates during exercise in men by the use of a potent inhibitor of adipose tissue lipolysis, Acipimox, and to see to what ... [more ▼]

This study attempted to induce a major shift in the utilization of endogenous substrates during exercise in men by the use of a potent inhibitor of adipose tissue lipolysis, Acipimox, and to see to what extent this affects the 13C/12C ratio in expired air CO2. Six healthy volunteers exercised for 3 h on a treadmill at approximately 45% of their maximum O2 uptake, 75 min after having ingested either a placebo or 250 mg Acipimox. The rise in plasma free fatty acids and glycerol was almost totally prevented by Acipimox, and no significant rise in the utilization of lipids, evaluated by indirect calorimetry, was observed. Total carbohydrate oxidation averaged 128 +/- 17 (placebo) and 182 +/- 21 g/3 h (Acipimox). Conversely, total lipid oxidation was 84 +/- 5 (placebo) and 57 +/- 6 g/3 h (Acipimox; P < 0.01). Under placebo, changes in expired air CO2 delta 13C were minimal, with only a 0.49/1000 significant rise at 30 min. In contrast, under Acipimox, the rise in expired air CO2 delta 13C averaged 1/1000 and was significant throughout the 3-h exercise bout; in these conditions calculation of a "pseudooxidation" of an exogenous sugar naturally or artificially enriched in 13C, but not ingested, would have given an erroneous value of 19.8 +/- 2.6 g/3 h. Thus under conditions of extreme changes in endogenous substrate utilization, an appropriate control experiment is mandatory when studying exogenous substrate oxidation by 13C-labeled substrates and isotope-ratio mass spectrometry measurements on expired air CO2. [less ▲]

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See detailRespiratory response to abdominal and rib cage muscle paralysis in dogs.
Brichant, Jean-François ULg; Gorini, Massimo; De Troyer, André

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1993), 74(5), 2309-17

To assess the respiratory response to abdominal and rib cage muscle paralysis, we measured tidal volume, esophageal and gastric pressures, arterial blood gases, and the electromyogram (EMG) of the ... [more ▼]

To assess the respiratory response to abdominal and rib cage muscle paralysis, we measured tidal volume, esophageal and gastric pressures, arterial blood gases, and the electromyogram (EMG) of the diaphragm during progressive epidural anesthesia (lidocaine 2%) in 35 supine anesthetized dogs. The EMG activity of the diaphragm was measured with fine-wire electrodes; the abdominal cavity was thus left intact. Paralysis of the abdominal muscles alone did not produce any alterations. In contrast, when all rib cage muscles were also paralyzed, there were substantial increases in the peak height and the rate of rise of diaphragmatic EMG activity that were associated with a decrease in tidal volume and an increase in arterial PCO2 (PaCO2); swings in transdiaphragmatic pressure, however, were unchanged. The increased diaphragmatic activation due to rib cage muscle paralysis persisted after bilateral cervical vagotomy and was well explained by the increased PaCO2. These observations indicate that in the dog 1) the rib cage muscles contribute significantly to tidal volume, and their paralysis causes, through the increased hypercapnic drive, a compensatory increase in diaphragmatic activation; and 2) the rib cage inspiratory muscles enhance the diaphragm's ability to generate pressure during breathing. [less ▲]

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See detailChest wall motion during epidural anesthesia in dogs.
Warner, David O; Brichant, Jean-François ULg; Ritman, Erik L et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1991), 70(2), 539-47

To determine the relative contribution of rib cage and abdominal muscles to expiratory muscle activity during quiet breathing, we used lumbar epidural anesthesia in six pentobarbital sodium-anesthetized ... [more ▼]

To determine the relative contribution of rib cage and abdominal muscles to expiratory muscle activity during quiet breathing, we used lumbar epidural anesthesia in six pentobarbital sodium-anesthetized dogs lying supine to paralyze the abdominal muscles while leaving rib cage muscle motor function substantially intact. A high-speed X-ray scanner (Dynamic Spatial Reconstructor) provided three-dimensional images of the thorax. The contribution of expiratory muscle activity to tidal breathing was assessed by a comparison of chest wall configuration during relaxed apnea with that at end expiration. We found that expiratory muscle activity was responsible for approximately half of the changes in thoracic volume during inspiration. Paralysis of the abdominal muscles had little effect on the pattern of breathing, including the contribution of expiratory muscle activity to tidal breathing, in most dogs. We conclude that, although there is consistent phasic expiratory electrical activity in both the rib cage and the abdominal muscles of pentobarbital-anesthetized dogs lying supine, the muscles of the rib cage are mechanically the most important expiratory muscles during quiet breathing. [less ▲]

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See detailEffect of osmolality on availability of glucose ingested during prolonged exercise in humans.
Jandrain, Bernard ULg; Pirnay, Freddy ULg; Lacroix, M. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1989), 67(1), 76-82

The aim of this study was to investigate whether the osmolality of a glucose solution, ingested at the beginning of a prolonged exercise bout, affects exogenous glucose disposal. We investigated the ... [more ▼]

The aim of this study was to investigate whether the osmolality of a glucose solution, ingested at the beginning of a prolonged exercise bout, affects exogenous glucose disposal. We investigated the hormonal and metabolic response to a 50-g glucose load dissolved in either 200 (protocol A), 400 (protocol B), or 600 (protocol C) ml of water and given orally 15 min after adaptation to exercise in five healthy male volunteers. Naturally labeled [13C]glucose was used to follow the conversion of the ingested glucose to expired-air CO2. Total carbohydrate oxidation (indirect calorimetry) was similar in the three protocols (A, 237 +/- 20; B, 258 +/- 17; C, 276 +/- 20 g/4 h), as was lipid oxidation (A, 128 +/- 4; B, 132 +/- 15; C, 124 +/- 12 g/4 h). Exogenous glucose oxidation rates were similar under the three experimental conditions, and the total amount of exogenous glucose utilized was slightly, but not significantly, increased with the more diluted solution (A, 42.6 +/- 4.4; B, 43.4 +/- 4.1; C, 48.7 +/- 7.2 g/4 h). The blood glucose response was similar in the three protocols. Thus, within the range investigated, the osmolality of the glucose solution ingested had no significant influence either on its oxidation (which was 86-98% of the load ingested) or on the utilization of endogenous carbohydrate, lipid, or protein stores. [less ▲]

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See detailHalothane decreases both tissue and airway resistances in excised canine lungs.
Vettermann, Jörg; Warner, David O; Brichant, Jean-François ULg et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1989), 66(6), 2698-703

Studies of the anesthetic effects on the airway often use pulmonary resistance (RL) as an index of airway caliber. To determine the effects of the volatile anesthetic, halothane, on tissue and airway ... [more ▼]

Studies of the anesthetic effects on the airway often use pulmonary resistance (RL) as an index of airway caliber. To determine the effects of the volatile anesthetic, halothane, on tissue and airway components of RL, we measured both components in excised canine lungs before and during halothane administration. Tissue resistance (Rti), airway resistance (Raw), and dynamic lung compliance (CL, dyn) were determined at constant tidal volume and at ventilatory frequencies ranging from 5 to 45 min-1 by an alveolar capsule technique. Halothane decreased RL at each breathing frequency by causing significant decreases in both Raw and Rti but did not change the relative contribution of Rti to RL at any frequency. Halothane increased CL,dyn at each breathing frequency, although there was little change in the static pressure-volume relationship. The administration of isoproterenol both airway and tissue components of RL; it may act by relaxing the contractile elements in the lung. Both components must be considered when the effects of volatile anesthetics on RL are interpreted. [less ▲]

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See detailInertance of the Respiratory System in Ponies
Art, Tatiana ULg; Lekeux, Pierre ULg; Gustin, Pascal ULg et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1989), 67(2), 534-540

The purpose of the present work was to measure the pulmonary inertance (IL) in ponies and to analyze its potential influence on the mechanics of breathing and on their aptitude to increase ventilation ... [more ▼]

The purpose of the present work was to measure the pulmonary inertance (IL) in ponies and to analyze its potential influence on the mechanics of breathing and on their aptitude to increase ventilation during exercise. Five healthy ponies 2.4-4 yr old [mean wt 255 +/- 15 (SE) kg] were used. On the one hand, inertance of the respiratory system (Irs) was computed from the value of the resonant frequency (fr) measured by the forced oscillation technique. On the other hand, respiratory airflow, tidal volume (VT), and transpulmonary pressure (PL) changes were recorded while the ponies were performing a light treadmill exercise, and IL was calculated as the ratio of the associated differences in inertial pressure (delta Pin) to volume acceleration (delta V). Respiratory airflow and VT were measured with a Fleisch pneumotachograph (no. 5) and PL with an intraesophageal balloon catheter. First, the protocol was carried out with the ponies breathing air and He-O2, second, while the ponies breathed through two additional tubes (100 cm long, 3 cm ID), then one, and finally none, fixed on the Fleisch pneumotachograph. Finally, the contribution of the extra- vs. the intrathoracic airways to IL was estimated by measuring the lateral midtracheal pressure recorded simultaneously with the aforementioned parameters. The values of Irs calculated with fr and of IL calculated on the basis of the delta Pin-delta V ratio were 29.8 +/- 0.4 and 19.8 +/- 1.0.10(-4) kPa.l-1.s-2, respectively. During He-O2 breathing IL decreased about three times; this result was similar to the predicted decrease based on gas density only.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailMeasurement of Total Respiratory Impedance in Calves by the Forced Oscillation Technique
Gustin, Pascal ULg; Dhem, A.R.; Lomba, Fernand et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1988), 64(5), 1786-1791

We have determined the resistance (Rrs) and the reactance (Xrs) of the total respiratory system in unsedated spontaneously breathing calves at various frequencies. A pseudorandom noise pressure wave was ... [more ▼]

We have determined the resistance (Rrs) and the reactance (Xrs) of the total respiratory system in unsedated spontaneously breathing calves at various frequencies. A pseudorandom noise pressure wave was produced at the nostrils of the animals by means of a loudspeaker adapted to the nose by a tightly fitting mask. A Fourier analysis of the pressure in the nostrils and flow signals yielded mean Rrs and Xrs, over 16 s, at frequencies of 2-26 Hz. A good correlation was found between values of pulmonary resistances measured by the isovolume method at the respiratory frequency of animals and values obtained at a frequency of 6 Hz by use of our technique. The linearity of the respiratory system, the reproducibility of the technique, and the effects of upper airways on results have been studied. In healthy calves, Rrs increases with frequency. Mean resonant frequency is 7.5 Hz. Bronchospasm was induced in six calves by administration of intravenous organophosphates. Rrs tended to decrease with increasing frequency. Resonant frequency exceeded 26 Hz. All parameters returned to initial values after administration of atropine. In healthy calves, atropine produces a decrease in Rrs, especially at low frequencies. Values of resonant frequency are not modified. [less ▲]

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See detailPartitioning of pulmonary resistance in calves
Gustin, Pascal ULg; Lomba, F.; Bakima, J. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1987), 62(5), 1826-1831

Nine right apical lobes of healthy Friesian calves and 10 right apical lobes of double-muscled calves of Belgian White and Blue (BWB) breed were suspended in an airtight box, inflated at a constant ... [more ▼]

Nine right apical lobes of healthy Friesian calves and 10 right apical lobes of double-muscled calves of Belgian White and Blue (BWB) breed were suspended in an airtight box, inflated at a constant transpulmonary pressure (Ptp), and subjected to quasi-sinusoidal pressure changes (amplitude: 0.5 kPa) at a frequency of 30 cycles/min. Lobar resistance (RL) was partitioned at six different lung volumes into three components: central airway resistance (Rc), small airway resistance (Rp), and tissue resistance (Rt). Pressure in small airways (2-3 mm ID) was measured with a retrograde catheter. Alveolar pressure was sampled in capsules glued onto the punctured pleural surface. RL was minimal at values of Ptp comprised between 0.5 and 0.7 kPa and increased at higher and lower values of Ptp. At a Ptp of 0.5 kPa, Rc, Rp, and Rt represented 30, 15, and 55% of RL, respectively, in Friesian calves and 25, 25, and 50% in BWB calves. Rp increased markedly at low lung volumes. Rt was responsible for the increase of RL at high Ptp. Rc tended to decrease at high Ptp. The significantly higher values of Rp in BWB calves (P less than 0.05) might explain the sensitivity of this breed to severe bronchopneumonia [less ▲]

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See detailEffects of high-frequency jet ventilation on arterial baroreflex regulation of heart rate.
Rouby, J. J.; Houissa, M.; Brichant, Jean-François ULg et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1987), 63(6), 2216-22

Fifteen anesthetized mechanically ventilated patients recovering from multiple trauma were studied to compare the effects of high-frequency jet ventilation (HFJV) and continuous positive-pressure ... [more ▼]

Fifteen anesthetized mechanically ventilated patients recovering from multiple trauma were studied to compare the effects of high-frequency jet ventilation (HFJV) and continuous positive-pressure ventilation (CPPV) on arterial baroreflex regulation of heart rate. Systolic arterial pressure and right atrial pressure were measured using indwelling catheters. Electrocardiogram (ECG) and mean airway pressure were continuously monitored. Lung volumes were measured using two linear differential transformers mounted on thoracic and abdominal belts. Baroreflex testing was performed by sequential intravenous bolus injections of phenylephrine (200 micrograms) and nitroglycerin (200 micrograms) to raise or lower systolic arterial pressure by 20-30 Torr. Baroreflex regulation of heart rate was expressed as the slope of the regression line between R-R interval of the ECG and systolic arterial pressure. In each mode of ventilation the ventilatory settings were chosen to control mean airway pressure and arterial PCO2 (PaCO2). In HFJV a tidal volume of 159 +/- 61 ml was administered at a frequency of 320 +/- 104 breaths/min, whereas in CPPV a tidal volume of 702 +/- 201 ml was administered at a frequency of 13 +/- 2 breaths/min. Control values of systolic arterial pressure, R-R interval, mean pulmonary volume above apneic functional residual capacity, end-expiratory pulmonary volume, right atrial pressure, mean airway pressure, PaCO2, pH, PaO2, and temperature before injection of phenylephrine or nitroglycerin were comparable in HFJV and CPPV. Baroreflex regulation of heart rate after nitroglycerin injection was significantly higher in HFJV (4.1 +/- 2.8 ms/Torr) than in CPPV (1.96 +/- 1.23 ms/Torr).(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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