Search Results
Results 301 - 350 of 817
< 2 3 4 5 6 7 8 9 10 11 12 >
DeHaan J D - - 1996
Victims of fires are sometimes discovered to have less-than-lethal levels of carbon monoxide (CO) in the blood and no significant antemortem fire damage. Such occurrences are often linked to flash fires involving volatile hydrocarbon fuels. In this study, the dynamics of hydrocarbon fuel fires are examined, and the results of ...
Mortola J P - - 1996
Conscious newborns of 12 species from 4 mammalian orders, ranging in body mass (M) from 1 g (mouse) to 5 kg (deer), were studied during air and during 5% CO2 breathing. The interspecies relationship between oxygen consumption (VO2) and M was the same in air and hypercapnia, in both cases ...
McConnell A k - - 1996
We examined the exercise hyperpnoea during hypocapnia which, by necessity, was brought about by voluntary hyperventilation (VHV). At cessation of VHV, ventilation (VE) decays gradually exhibiting a phenomenon known as the afterdischarge (AD; Eldridge, Med. Sci. Sports Exerc. 26:319--327, 1994). A new technique was employed to overcome the potentially contaminating ...
Reybrouck T - - 1996
In pediatric exercise testing, conventional measures of aerobic exercise function such as maximal O2 uptake or the ventilatory anaerobic threshold (VAT) use only one value for the assessment of exercise capacity. We studied a more comprehensive approach to evaluate aerobic exercise function by analyzing the steepness of the slope of ...
Wang C Y - - 1996
We studied the influences of lung vagal afferents on the delayed ventilatory response to inhaled wood smoke in 35 Sprague-Dawley rats. Wood smoke (approximately 6 ml) was inhaled via tracheostomy when animals breathed spontaneously. Immediately after inhalation, wood smoke evoked a slowing of respiration or an augmented inspiration, followed by ...
Chang L P - - 1996
This study tested three possible mechanisms that could explain the prolonged breath-holds (BH) previously observed in humans during submersion in 35 degrees C (thermoneutral) water, including a reduced metabolism, a decreased CO2 sensitivity, and an increased CO2 storage capacity. During immersed BH (n = 13), maximal BH time was prolonged ...
Neuberger T J - - 1996
BACKGROUND: During prolonged laparoscopic operations with carbon dioxide (CO2) pneumoperitoneum (PP), hypercapnia with significant acidosis has been reported to occur in some patients with pulmonary dysfunction. An alternate inert insufflation gas like helium (He) could avoid this problem. METHODS: This prospective, IRB-approved study compared the cardiopulmonary response in 20 patients ...
Banzett R B - - 1996
Hypercapnia evokes an uncomfortable sensation, termed 'air hunger'. We examined the relationship between PETCO2 and ratings of air hunger intensity under three conditions in 16 subjects: 1) mechanical ventilation with hyperoxic gas mixtures at fixed frequency and tidal volume (twice resting ventilation), 2) the same mechanical ventilation, but with hypoxic ...
Hoffman W E - - 1995
These studies were conducted in neurosurgical patients to determine brain tissue nonbicarbonate buffering of pH changes during hypercapnia. Following a craniotomy, a sensor which continuously measures oxygen pressure, carbon dioxide pressure, pH and temperature was inserted into cortex tissue of nine subjects. Bicarbonate concentration was calculated from the Henderson-Hasselbach equation. ...
Kerem D - - 1995
We evaluated CO2 retention in 24 Navy construction divers breathing air at 1 atm abs (101.3 kPa) and 40% O2 (40/60) nitrox at 4 atm abs (Po2 of 162.1 kPa) inside a pressure chamber. The divers sat immersed to the sternal notch and exercised against pneumatically loaded pedals at a ...
Linton R A - - 1995
1. The rate of change sensitivity of some carotid chemoreceptors to within-breath changes in PaCO2 would suggest that the half-life of adaptation of these receptors to a step increase is shorter than the 5-10 s previously reported. 2. In six anesthetized cats, step increases in PaCO2 (10 in each cat) ...
St Croix C M - - 1995
Arterial PCO2 (PaCO2), determined directly in the radial artery, was compared with indirect estimates of PCO2 in six elderly men (mean age 73.8 yr). Estimates of PaCO2 included arterialized venous PCO2 (PavCO2); end-tidal PCO2; mean alveolar PCO2, calculated by using a reconstruction of the alveolar oscillation in PCO2 and accounting ...
Teppema L - - 1995
1. The effect of inhibition of erythrocyte carbonic anhydrase on the ventilatory response to CO2 was studied by administering benzolamide (70 mg kg-1, i.v.), an inhibitor which does not cross the blood-brain barrier, to carotid body denervated cats which were anaesthetized with chloralose-urethane. 2. In the same animals the effect ...
Furilla R A - - 1995
Many investigators have reported finding intrapulmonary chemoreceptors (IPCs) in several species of birds and reptiles; however, the role of IPCs in ventilatory control in birds has not been identified. This study was undertaken to assess the role of intrapulmonary CO2 dynamics on the control of breathing. Ducks were unidirectionally ventilated, ...
Forster H V - - 1995
The mechanisms mediating the exercise hyperpnea remain controversial; there is no unequivocal evidence that any of numerous proposed mechanisms mediates the hyperpnea. However, a great deal has been learned including the potential role of changes in PCO2, [H+], strong ion differences (SID), weak acids, or any other acid-base component. The ...
Madsen P - - 1995
Near-infrared spectrophotometry-determined cerebral (ScO2) and muscle oxygen saturations (SmO2) were followed in 15 volunteers during passive 50 degrees head-up-tilt-induced central hypovolaemia, and in nine volunteers during ventilatory manoeuvres affecting arterial carbon dioxide tension. During head-up tilt, mean arterial pressure [MAP, 88 (77-118) to 97 (80-136) mmHg, median and range] and ...
Walker J K - - 1995
Intravenous infusion of arginine vasopressin (AVP) depresses the slope of the ventilatory response to CO2 during acute hypercapnia. We therefore tested the hypothesis that AVP V1-receptor blockade would increase the slope of the ventilatory response to CO2. After a 20-min control period, an AVP V1-receptor antagonist (d(CH2)5[Tyr(Me)2]AVP) was injected into ...
Lawler J M - - 1995
Increases in blood flow and CO2 return to the heart and lungs at the onset of exercise have been proposed to initiate reflexive feedback which increases ventilation (VE), via mechanoreceptors in the heart and/or intrapulmonary CO2 flow receptors. Both lower body negative pressure (-40 mm Hg) release (LBNP-release) and acute ...
Greenberg H E - - 1995
Acute resistive loading of the airway has been shown to activate the endogenous opioid system, with subsequent depression of ventilation. The present investigation was designed to assess the effect of chronic airway loading on ventilation and CO2 sensitivity, and to determine whether the endogenous opioid system contributes to long-term modulation ...
Harms C A - - 1995
Is inadequate hyperventilation a cause of the exercise-induced hypoxemia observed in some athletes during intense exercise? If so, is this related to low chemoresponsiveness? To test the hypothesis that exercise-induced hypoxemia, inadequate hyperventilation, and chemoresponsiveness are related, 36 nonsmoking healthy men were divided into hypoxemic (Hyp; n = 13) or ...
Kimoto H - - 1995
The changes of cerebral blood oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), and total hemoglobin (tHb) induced by acetazolamide and CO2 loading on near-infrared spectroscopy (NIRS) were recorded. In anesthetized 2-week-old rabbits, acetazolamide (10 mg/kg i.v.) increased HbO2 and tHb, concomitant with an increase in tissue PCO2, and decreased HbR only at 5 ...
Waldau T - - 1995
Although several short communications have appeared describing attempts to record the concentrations of carbon dioxide (cCO2) from the unintubated airway by a catheter placed in the nose, so far only few reports have documented the reliability of the method. To evaluate the reliability of CO2 measurements by a catheter in ...
Pianosi P - - 1995
The Dejours hyperoxic test has been used to quantitate peripheral chemoreceptor contribution to the hyperpnea of exercise. The strength of this drive, measured by the percent reduction in ventilation, varies among individuals and is lacking in chemodenervated humans, who also fail to manifest a hyperventilatory response in heavy exercise. We ...
Pan L G - - 1995
In three previously reported studies, we had documented that the normal exercise hyperventilation in ponies is accentuated by carotid body denervation (CBD), not affected by hilar nerve pulmonary vagal denervation (HND), and mildly attenuated by spinal cord ablation of the dorsal lateral columns at L2 (SA). In the present study, ...
Casaburi R - - 1995
1. The mechanisms underlying the exercise hyperpnoea have been difficult to define. Recently it has been suggested that exercise ventilation (VE) changes in proportion to changes in arterial potassium concentration ([K+]a). Similar VE and [K+]a time courses following work rate changes have been cited as supporting evidence. This study compared ...
Mullens B A - - 1995
Adult Culicoides variipennis sonorensis Wirth & Jones were collected using miniature suction traps during 12 nights in October and November at a southern California dairy. Traps were baited with carbon dioxide at a constant release rate of 300, 1,000, or 3,000 ml/min or with 1.3 kg of dry ice. The ...
Liu Z - - 1995
We undertook the present study with the following objectives: (1) to compare the difference between the end-tidal and the arterial carbondioxide concentration (P[ETa] CO2) gradients at rest and during exercise in normal subjects and patients with COPD; and (2) to analyze the factors contributing to this gradient. We studied seven ...
Gozal D - - 1995
In early phases of respiratory disease, patients are more likely to experience intermittent hypercapnia than a continuous increase in PCO2. The effect of intermittent arterial PCO2 elevation on subsequent breathing patterns is unclear. To examine this issue, a series of six ventilatory challenges (CH1-CH6), consisting of 2 min of breathing ...
Cohen I L - - 1995
OBJECTIVES: Respiratory quotient, the ratio of CO2 production to oxygen consumption (VO2), is principally affected by the fuel source used for aerobic metabolism. Since the respiratory quotient, VO2, and CO2 production cannot be directly measured easily, indirect calorimetry is commonly used to determine the value of these variables at the ...
Fernando S S - - 1995
We used single inspiratory capacity breaths of 5, 6 or 8% CO2 in air to obtain ventilatory responses in normal subjects, with ensemble averaging of repeated runs to define stimulus and response (Protocol 1). We also compared the effect of an inspiratory capacity (IC) breath of 8% CO2 with that ...
Sidney D A - - 1995
To investigate how breathing is controlled during CO2 stimulation, steady-state ventilatory responses to rebreathing through a tube (DS) and inspiring a fixed PCO2 (INH) were compared in healthy human subjects. Tests were performed in hyperoxia with (IRL) and without (NL) an inspiratory resistive load (15 cmH2O.l-1.s at 1 l/s). The ...
Pelletier N - - 1995
Thoroughbred horses (TB) have no ventilatory response to added CO2 during near-maximal exercise. To see whether that reflects mechanical limits to ventilation or the control of breathing, we examined the effects of varying inspired O2 fraction (0.16, 0.21, or 0.30) in five normal TB standing quietly and galloping at 10 ...
Sjögren D - - 1995
In order to evaluate the difference between poikilo-capnic (no CO2 added to inspired gas) and iso-capnic (CO2 added to keep end-tidal CO2 constant) hypoxic ventilatory responses (HVR) awake and during 0.6 MAC isoflurane anaesthesia, seven cardio-pulmonary healthy patients were investigated. Pneumotachography and capnography were used before and during hypoxia (end-tidal ...
Chang L P - - 1995
Hypercapnic ventilatory response was compared in 9 seated subjects during head-out immersion in 35 degrees C (thermoneutral) water and during non-immersion in 28 degrees C (thermoneutral) room air. Using Read's CO2-rebreathing technique, minute ventilation (VE) and end-tidal (ET) PCO2 were sampled continuously for 4-5 min with a spirometer and a ...
Pianosi P - - 1995
A single-breath CO2 test of peripheral chemosensitivity has recently been described, and elaborated based on model simulations. This study was designed to measure the peripheral CO2 chemoreflex at rest and during heavy exercise to see if carotid chemosensitivity to CO2 increased. Ten healthy, adult males performed an incremental exercise test ...
Miyamoto Y - - 1995
The aim of the present study was to explore the role of the carotid chemoreceptors in the regulation of breathing during incremental ramp exercise. We measured minute ventilation (VE), oxygen uptake (VO2), carbon dioxide output (VCO2), end-tidal PO2 and PCO2 (PETO2 and PETCO2), and heart rate (HR) during incremental exercise ...
Cerretelli P - - 1995
To gain an insight into the origin of the phase I ventilatory response to exercise (ph I) in humans, pulmonary ventilation (VE) and end-tidal partial pressures of oxygen and carbon dioxide (PETO2 and PETCO2, respectively) were measured breath-by-breath in six male subjects during constant-intensity exercise on the cycle ergometer at ...
Zwingelberg K M - - 1994
The Mapleson E breathing circuit used in anesthesia has no valves or CO2-absorbent canisters and thus entails low resistance to breathing and has low requirements for fresh gas flow (FGF). The authors investigated whether these advantages would make a circuit, modified for hyperbaric use, able to support ventilation during heavy ...
Leese G P - - 1994
In order to investigate the effects of muscular work and preceding exercise on the retention of exogenous labelled bicarbonate, we studied the effects of oral administration of [13C]bicarbonate (0.1 mg kg-1) in five subjects at rest before exercise and during and after 1 h of treadmill walking at 73% VO2max ...
Ley R - - 1994
Ten anxiety-disorder outpatients and 10 controls were monitored for heart rate and self reports of anxiety approximately 1 min before and 1 min after a single full-capacity inhalation of a gas consisting of either 65% CO2 + 35% O2 or compressed air. Under the CO2 + O2 condition, patients and ...
Midorikawa J - - 1994
It is known that the ventilatory response to carbon dioxide (CO2) is increased in asthmatics with airway obstruction. Increased vagal afferent activity as well as increased airway resistance have been postulated as the causative mechanisms. However, whether increased vagal afferent activity without bronchoconstriction increases the ventilatory response to CO2 has ...
O'Halloran K D - - 1994
The effects of upper airway (UA) cool air and CO2 on breathing and on laryngeal and supraglottic resistances were studied in anaesthetised rats breathing spontaneously through a tracheostomy. Warm, humidified air containing 0, 5 and 9-10% CO2 and cool, room-humidity air were delivered at constant flow to either the isolated ...
Tweddel A - - 1994
In patients with microvascular angina (MA), there is some evidence from studies of plethysmography, that there are widespread microvascular abnormalities. In addition to exertional chest pain, all these patients complain of breathlessness, with no evidence of airways obstruction or resting left ventricular dysfunction. Progressive exercise testing was performed in 12 ...
Nishino T - - 1994
Mechanical hyperventilation may produce hypocapnic apnoea below the carbon dioxide off-switch threshold whereas an increase in arterial PCO2 after post-hyperventilation apnoea causes reappearance of respiratory effort above the carbon dioxide on-switch threshold. To study the effects of surgical stimulation on these two thresholds, we have measured end-tidal PCO2 (PE'CO2) at ...
Webb C L - - 1994
Golden-mantled ground squirrels exhibited a strong hypoxic ventilatory response but a blunted hypercapnic ventilatory response and showed no interactive effects when both stimuli were presented together. They exhibited a resting hypoxic ventilatory drive which was eliminated by carotid body denervation. Carotid denervation also shifted the threshold of the hypoxic ventilatory ...
Raj M - - 1994
Spontaneous electroencephalograms (EEG) and somatosensory evoked potentials (SEPS) were recorded in turkeys while they were kept in an atmosphere of either 49 or 86 per cent carbon dioxide in air. The time to the loss of SEPS was not related to the concentration of carbon dioxide, but the time to ...
Erlichman J S - - 1994
We have studied the effects of carbonic anhydrase inhibition on the hypercapnic ventilatory response of the pulmonate snail, Helix aspersa, in an isolated brain-pneumostome preparation. We found that the cell permeant carbonic anhydrase inhibitor, acetazolamide (ACTZ), increased pneumostomal opening and ventilation during normocapnia (2-3% CO2) and decreased the rate of ...
Dempsey J A - - 1994
In this paper two types of evidence are presented which question the commonly presumed role of carotid chemoreceptor stimulation as the primary mediator of the hyperventilatory response to heavy exercise. First, carotid-body denervation in ponies increases their hyperventilatory response to heavy exercise. Second, the awake dog and the goat at ...
Ward S A - - 1994
The stability of arterial blood gas tensions and pH during steady-state moderate exercise has suggested an important humoral element of ventilatory control in humans. However, the involvement of central and peripheral chemoreflexes in this humoral control remains controversial. This reflects, in large part, technical and interpretational limitations inherent in currently ...
Jennings D B - - 1994
For optimal performance of exercising muscle, the charge state of proteins must be maintained; the pH environment of protein histidine imidazole groups must be coordinated with their pK. During exercise, increasing temperature and osmolality as well as changes in strong ions affect the pK of imidazole groups. Production of strong ...
< 2 3 4 5 6 7 8 9 10 11 12 >