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Results 401 - 450 of 816
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Swenson E R - - 1993
The effects of acetazolamide (ACTZ) on ventilatory control are thought to be mediated by metabolic acidosis. However, carbonic anhydrase (CA) inhibition within brain and chemoreceptors and tissue respiratory acidosis may also be important. We compared the acute effects of ACTZ (tissue respiratory acidosis and tissue CA inhibition without metabolic acidosis) ...
Sargent T T - - 1992
The original transmethylation hypothesis of schizophrenia has evolved with time and experiment to the present concept that a defect in the methyl-carbon metabolic pathway may be causative in this illness. Various researchers have proposed that specific steps in the methyl-carbon pathway may be defective, and have presented evidence to support ...
Saunders K B - - 1992
The partial pressure of carbon dioxide in arterial blood is an important operator in the control of breathing, by actions on peripheral and central chemoreceptors. In experiments on man we must often assume that lung alveolar PCO2 equals arterial PCO2 and obtain estimates of the former derived from measurements in ...
Burnier P - - 1992
The metabolic and respiratory effects of intravenous 0.5 M sodium acetate (at a rate of 2.5 mmol/min during 120 min) were studied in nine normal human subjects. O2 consumption (VO2) and CO2 production (VCO2) were measured continuously by open-circuit indirect calorimetry. VO2 increased from 251 +/- 9 to 281 +/- ...
Linton R A - - 1992
It is known that during exercise there is an increase in plasma epinephrine. The purpose of the present investigation was to determine whether stimulation of carotid chemoreceptors by epinephrine is a direct effect or secondary to epinephrine-induced increases in arterial plasma [K+] and whole body CO2 production (VCO2). Chemoreceptor discharge ...
Slater R M - - 1992
STUDY OBJECTIVE: To investigate whether hyperventilation significantly altered oxygen consumption in anesthetized and paralyzed patients undergoing surgery. DESIGN: Open crossover trial with 1 hour of hyperventilation preceded and followed by 1 hour of normoventilation. SETTING: University medical center. PATIENTS: Eight patients (five men and three women) undergoing lengthy orthopedic surgery ...
MacFarlane D J - - 1992
1. Four human subjects exercised in hypoxia (end-tidal partial pressure of O2 (P(ET),O2) ca 55 Torr; heart rate ca 100-130 beats min-1), and the contribution to the respiratory drive of the peripheral and central chemoreflex pathways have been separated on the basis of the latencies and the time courses of ...
Espanol M T - - 1992
Metabolic tolerance of low intracellular pH (pH(i)) was studied in well-oxygenated, perfused, neonatal, rat cerebrocortical brain slices (350 microns thick) by inducing severe hypercapnia. In each of 17 separate experiments 80 brain slices (approximately 3.2 g wet weight) were suspended in an NMR tube, perfused with artificial CSF (ACSF), and ...
Benevenga N J - - 1992
Fifteen newborn pigs (1.5 kg) were used to estimate CO2 "production" over a 5-h experiment. In each piglet, the average expired air CO2 irreversible loss rate measured over 15-min intervals was compared with an estimate of CO2 "produced" by a continuous infusion of NaH14CO3 into either the aortic artery (seven ...
Wolsink J G - - 1992
1. The ventilatory response to square-wave challenges in end-tidal partial pressure of CO2 (PCO2) was investigated at three levels of arterial PO2 (Pa,O2) in nineteen anaesthetized 2- to 11-day-old piglets. 2. The ventilatory responses, measured on a breath-to-breath basis, were separated into a peripheral and a central component using a ...
Lands L C - - 1992
Cardiac output (Q) determination using the equilibrium CO2-rebreathe indirect Fick technique (Equil) to estimate mixed venous PCO2 (Pv-CO2) has been validated during steady state (SS) exercise in subjects with lung disease. A modification of the exponential method using a low concentration of CO2 with an exponential rise in PEt-CO2 (Ex) ...
Manner T - - 1992
A series of investigations suggest a specific role for BCAA in the regulation of respiration. In vitro incubation studies have shown that BCAAs improve the recovery of muscle force after fatigue. Further investigations revealed that leucine plays a key role in this action and acts in a manner not dependent ...
Geiser D R - - 1992
End-tidal carbon dioxide tension (PetCO2) and arterial carbon dioxide tension (PaCO2) were determined and compared in isoflurane-anesthetized spontaneously breathing equine neonates. End-tidal carbon dioxide and PaCO2 values increased with respect to time. Difference between values of PetCO2 and PaCO2 increased over time. End-tidal carbon dioxide tension was useful to predict ...
Glomb W B - - 1992
Siblings of sudden infant death syndrome (SIDS) victims have been shown to have abnormal ventilatory patterns and altered responses to respiratory stimuli during infancy. To evaluate whether these abnormalities persist, we studied ventilatory responses in 20 older SIDS siblings (9.8 +/- 0.9 (mean +/- SEM) years of age) and 20 ...
Forslid A - - 1992
The aim of the study was to evaluate from the ethical point of view the importance of transient muscular jerks commonly exhibited by swine at an early stage of pre-slaughter CO2-anaesthesia. The influence of 5 min restraint upon plasma concentrations of adrenaline (A) and noradrenaline (NA) was studied in swine ...
Tan P L - - 1992
Twelve ASA physical status I-II patients undergoing pelvic laparoscopy for infertility were enrolled in a study to quantify the effects of CO2 insufflation and the Trendelenburg position on CO2 elimination and pulmonary gas exchange, and to determine the minute ventilation required to maintain normocapnia during CO2 insufflation. Measurements of O2 ...
Henson L C - - 1992
We investigated whether dopamine, an inhibitory neuromodulator in the carotid body, would alter the ventilatory response typically associated with metabolic (lactic) acidosis during exercise. Six subjects performed incremental cycle ergometer exercise to exhaustion during infusions of dopamine (3 micrograms.kg-1.min-1) or saline. Ventilation and pulmonary gas exchange were computed breath-by-breath; arterialized ...
Poon C S - - 1992
We examined the effects of different modes of airway CO2 load on the ventilation-CO2 output (VE-VCO2) relationship during mild to moderate exercise. Four young and three older male subjects underwent incremental steady-state treadmill exercise while breathing a mixture of CO2 in O2 (CO2 loading) or 100% O2 with and without ...
McConnell A K - - 1992
Elderly adults are assumed to have an exaggerated ventilatory response to exercise. This study sought to examine this assumption by comparing the steady-state ventilatory and gas exchange responses of a group of elderly and younger humans. Steady-state ventilatory responses to moderate cycle ergometer exercise were measured in 14 elderly (71.0 ...
Harris A - - 1992
Previous reports suggest that isometric exercise (2-min handgrip at 50% maximal voluntary contraction [MVC]) substantially lowers intraocular pressure (IOP). The authors questioned whether the mechanism for lowered IOP in exercise is secondary to hyperventilation. Accordingly, in this study 11 subjects, with elevated IOP (greater than or equal to 18 mm ...
Sponsel W E - - 1992
Retinal leukocyte velocity and density were estimated using blue-field entoptic imaging techniques in a controlled double-masked study to determine the relative effects of oxygen and carbon dioxide on perimacular hemodynamics in single eyes of ten normal human subjects. Mild hypoxia (inspiration of 16% O2) did not significantly alter leukocyte velocity ...
Teppema L J - - 1992
In normoxemic cats, acetazolamide (ACTZ) has been shown to cause a large rise in ventilation (VE) but a decrease in peripheral chemoreceptor activity. The relative contribution of the peripheral chemoreceptors to ventilation is higher during hypoxemia than during normoxemia. Therefore, what are the effects of ACTZ during steady-state hypoxemia? The ...
Pandit J J - - 1992
Five subjects underwent each of three protocols for 43 min: (A) at rest; end-tidal PCO2 was held constant at 2-5 Torr above resting values; (B) during 70 Watt bicycle exercise; PETCO2 was uncontrolled; (C) during 70 Watt exercise; PETCO2 was held 2-5 Torr above exercising values. During all protocols, end-tidal ...
Symreng T - - 1992
Ventilatory and metabolic changes were measured in seven patients undergoing high efficiency hemodialysis using a cuprophane dialyzer and bicarbonate-containing dialysate. At an HCO3 concentration of 35 mEq/liter and a mean in vivo urea clearance of 3.6 ml/kg/min, hypoxemia was not detected during dialysis (PaO2 was 14.00 and 13.60 kPa before ...
Sum Ping S T - - 1992
The sensitivity and reliability of the FEF end-tidal CO2 detector were investigated for its suitability in the assessment of correct placement of an endotracheal tube. Sensitivity was determined by having eight blinded volunteers observe the color change in the FEF detector with the administration of different volumes and varying CO2 ...
Paterson D J - - 1992
The drive to breathe in exercise is thought to result from a combination of neural and humoral factors, but the exact nature of the controlling signals is controversial. This review examines evidence suggesting that potassium could be a signal that drives ventilation (VE) in exercise. Potassium is lost from working ...
Barstow T J - - 1992
We previously described bicarbonate exchange dynamics in humans at rest and during exercise using a three-compartment model. In the present study we tested the effect of certain assumptions of this model on the prediction of the change in exchangeable bicarbonate with the increased metabolic rate of exercise. We compared this ...
Puri G D - - 1992
We have studied 14 female patients undergoing elective laparoscopy under general anaesthesia with peritoneal insufflation of carbon dioxide in order to examine changes in physiological deadspace (VDphys), arterial to end-tidal carbon dioxide partial pressure difference (PaCO2-PE' CO2) and PaCO2. VCO2 increased after insufflation of carbon dioxide with a mean (SD) ...
Mercier J - - 1992
The aim of this study was to determine during moderate exercise whether response to the CO2 rebreathing test was dependent on differences in breathing pattern components among individuals recorded before the test and whether differences in tidal volume response and/or breathing frequency response to CO2 during the test could influence ...
Kiwull-Schöne H - - 1992
The Haldane effect (HE), i.e. the difference in plasma pH of oxygenated and deoxygenated blood, was investigated in rabbits over a wide range of respiratory (PCO2 2.7 to 8.0 kPa) and metabolic (BE +5 to -15 mM) acid-base conditions and compared to cats, dogs and humans. Even under standard conditions ...
Hannhart B - - 1992
The respiratory effects of analgesia with nalbuphine were studied in 9 patients after thoracotomy. The pain score was measured by a visual analogue scale. Ventilatory pattern and occlusion pressure (P0.1) were studied during spontaneous breathing and during CO2 rebreathing, before and 0.5, 1, 2.5, 3.5 and 6 h after a ...
Douse M A - - 1992
Reptiles increase ventilation during hypercapnia at a constant temperature. In this study, the contributions of vagal vs non-vagal receptors to CO2 ventilatory responses were investigated in 16 sedated Alligator mississippiensis (25 mg/kg pentobarbital; 3 days prior to data collection). Four animals served as controls to assess the effects of time ...
Rau G H - - 1992
The delta 13C of suspended particulate organic matter (SPOM) in surface waters increased from -22.9 to -18.1% during April 25-May 31, 1989 at the JGOFS North Atlantic Bloom Experiment Site (NABE Site; 47 degrees N, 20 degrees W). During the same period, nearly parallel increases in sinking POM delta 13C ...
Metges C C - - 1992
Utilization of three milk diets including cream, casein or whey, each naturally labelled with 13C (1 mmol 13C excess) from C4 sources, by six young male calves of the Deutsche Fleckvieh breed was investigated in a Latin-square split-plot design. Each milk diet was examined under resting conditions and during a ...
Fitzgerald S D - - 1992
Patients with cardiopulmonary insufficiency undergoing laparoscopic surgery with carbon dioxide (CO2) pneumoperitoneum may retain CO2 resulting in clinically significant respiratory acidosis. A canine model of pulmonary emphysema induced by papain inhalation was utilized to evaluate the respiratory effects of both CO2 and helium pneumoperitoneum. Prior to papain inhalation and 5 ...
Oku Y - - 1992
The dynamic influences of end-tidal CO2 and exercise on ventilation are compared when CO2 and exercise are imposed separately and when they are imposed simultaneously. Five human subjects are studied. The subjects performed three trials: random work rate forcing, random CO2 inhalation and their simultaneous loading. The work rate was ...
Hirakoba K - - 1992
We attempted to determine the change in total excess volume of CO2 output (CO2 excess) due to bicarbonate buffering of lactic acid produced in exercise due to endurance training for approximately 2 months and to assess the relationship between the changes of CO2 excess and distance-running performance. Six male endurance ...
Modarreszadeh M - - 1992
It has often been assumed that under normoxia, closed-loop ventilatory responses to transient CO2 stimulation (i.e., lasting for 1-3 breaths) are less likely to be mediated by the slow-responding central (medullary) chemoreflex. This assumption, however, has not been quantitatively examined in humans. We hypothesized that in the closed-loop respiratory chemical ...
Kowalchuk J M - - 1992
To investigate the interactions between the systems that contribute to acid-base homeostasis after severe exercise, we studied the effects of carbonic anhydrase inhibition on exchange of strong ions and CO2 in six subjects after 30 s of maximal isokinetic cycling exercise. Each subject exercised on two randomly assigned occasions, a ...
Gutting S M - - 1991
We measured respiratory muscle electromyograms (EMG), inspiratory (I) and expiratory (E) airflow patterns and functional residual capacity (FRC) in six ponies at rest, during treadmill walking at 1.8 mph-5, 10, and 15% grades, and during 2, 4, and 6% CO2 inhalation. There were several similarities in the responses to exercise ...
Carroll J L - - 1991
In awake lambs we investigated the role of the peripheral chemoreceptors in producing dynamic ventilatory (VE) responses to CO2. The immediate VE response, within 15 s, to transient CO2 inhalation was studied in two groups: 1) five lambs before carotid denervation and 2) the same lambs after carotid denervation. The ...
Furilla R A - - 1991
Garter snakes increase ventilation in response to elevated venous PCO2 without a concomitant rise in arterial PCO2 (Furilla et al. Respir. Physiol. 83: 47-60, 1991). Elevating venous PCO2 will increase the PCO2 gradient between pulmonary arterial blood and intrapulmonary gas during inspiration, leading to a greater rate of rise of ...
Fadic R - - 1991
In pentobarbitone anesthetized cats, raising body temperature from 37 to 40 degrees C by external heat increased respiratory frequency, tidal volume, frequency of spontaneous gasps and mean inspiratory flow. It reduced end-tidal CO2 pressure, together with inspiratory and expiratory durations. After bilateral section of the carotid nerves, raising body temperature ...
Nattie E E - - 1991
Kainic acid (KA) injections into the retrotrapezoid nucleus (RTN) of anesthetized deafferented cats profoundly decreased phrenic activity (PA) and CO2 sensitivity (J. Appl. Physiol. 68: 1157-1166, 1990). In this study small electrolytic lesions of the RTN produced the same results, indicating that the KA destroyed cells. We then asked whether ...
Bidani A - - 1991
The importance of perfusate nonbicarbonate buffer capacity (beta nonHCO3) to intracapillary CO2-HCO3(-)-H+ reactions was assessed by theoretical analysis of CO2 exchange in saline-perfused pulmonary capillaries. Time courses for perfusate PCO2, [HCO3-], and [H+] were computed for capillaries containing different activities of luminal vascular carbonic anhydrase and different amounts of perfusate ...
Dunn W F - - 1991
Using the recruitment threshold technique, we measured the CO2 responsiveness of the unloaded respiratory pump in 14 mechanically ventilated patients prior to weaning. The CO2 recruitment threshold (CO2RT) was compared with the arterial CO2 tension during unassisted breathing (CO2SB) and with the PaCO2 during mechanical ventilation (CO2MV) at machine settings ...
Kasim Y A - - 1991
Many studies of Dengue Hemorrhagic Fever (DHF) have been done but only a few revealed the respiratory status. Respiratory problems arise because of plasma leakage through the damaged capillaries, causing lung edema and in turn result in hypoxemia. This later on will be compensated by a hyperventilation state. During a ...
Berkenbosch A - - 1991
We studied the peripheral ventilatory response dynamics to changes in end-tidal O2 tension (PETO2) in 13 cats anesthetized with alpha-chloralose-urethan. The arterial O2 tension in the medulla oblongata was kept constant using the technique of artificial perfusion of the brain stem. At constant end-tidal CO2 tension, 72 ventilatory on-responses due ...
Koike A - - 1991
The effect of low levels of carbon monoxide (CO) was studied during exercise in order to determine the work-rate dependent effect of CO breathing on exercise ventilation (VE). Ten normal subjects (aged 32.8 +/- 7.1 years) were studied during air breathing and air with added CO to bring carboxyhemoglobin (COHb) ...
Hachamovitch R - - 1991
BACKGROUND: The output of carbon dioxide (VCO2) is controlled by both hemodynamics and ventilation. To understand VCO2 in patients who have chronic heart failure (CHF), we studied 14 patients who had New York Heart Association functional class III failure by measurements of hemodynamics, ventilation, and arterial and venous blood gases ...
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