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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 ...
McLoughlin P - - 1994
1. It has been reported that, during incremental exercise testing, the patterns of change in ventilation (VE) and arterial K+ (Ka+) are similar, suggesting that changing Ka+ may lead to the phenomenon of the ventilatory threshold through its action on the peripheral chemoreceptors. 2. Expiratory ventilation, oxygen consumption, CO2 production ...
Berkenbosch A - - 1994
BACKGROUND: It has been reported that physostigmine antagonizes morphine-induced respiratory depression, but it is not known whether this is due to a central chemoreceptor effect, an effect on the peripheral chemoreflex loop, or both. We therefore assessed the effect of morphine and physostigmine on the normoxic hypercapnic ventilatory response mediated ...
Seelagy M M - - 1994
We studied the effect of respiratory reflexes on maximal inspiratory flow (VImax) and its mechanical determinants, pharyngeal critical pressure (Pcrit) and nasal resistance, in an isolated feline upper airway preparation. Chemoreceptor reflexes were evaluated by varying inspired oxygen and end-tidal CO2 concentrations. At each gas concentration, we found that changes ...
Alexander C M - - 1994
BACKGROUND: Although diphenhydramine is frequently used to treat pruritus and nausea in patients who have received neuraxial opioids, there are no data regarding its effect on ventilatory control. We conducted the current study to evaluate the effects of diphenhydramine on hypercapnic and hypoxic ventilatory control in healthy volunteers. METHODS: First, ...
Wolsink J G - - 1994
In 12 piglets aged 0-1.5 days we assessed the relative contribution of the peripheral and central chemoreceptors in mediating the ventilatory response to CO2 at three levels of arterial O2 tension using the dynamic end-tidal forcing technique. With this technique the ventilatory response is separated into a peripheral and a ...
Breen P H - - 1994
The sidestream capnogram is delayed behind real time by transport delay (TD; time to aspirate gas through the sampling tubing) and by the dynamic response (DR) of the measurement cuvette. In six capnometers, we measured TD and DR by plunging the end of the sample tubing into a flask containing ...
Eldridge F L - - 1994
Many hypotheses have been advanced to explain the hyperpnea of exercise and its close relations to the level of metabolic work, expressed as oxygen uptake (VO2) and carbon dioxide production (VCO2). Evidence is presented that a neural central command mechanism from the hypothalamus is important in the driving of both ...
Fratacci M D - - 1994
The effects of digoxin on diaphragmatic contraction were studied in 12 sheep, within 6 days after a right thoracotomy, during the period of intense diaphragmatic inhibition. Diaphragmatic function was assessed by implanting sonomicrometry crystals and electromyographic (EMG) electrodes in both the costal and crural diaphragmatic regions. Awake sheep were studied ...
Whipp B J - - 1994
Estimates of the proportional contribution of the peripheral chemoreceptors (i.e., the carotid bodies) to human ventilatory control during moderate exercise (i.e., below the lactate threshold, theta L) suggest that they: (a) exert no discernible influence on the initial (usually rapid) phase I component; (b) provide significant modulation of the slower, ...
Forster H V - - 1994
Our objective was to gain insight into the role of the carotid chemoreceptors (CC) in the exercise hyperpnea. Humans and ponies were studied at rest and during submaximal exercise breathing room air. In healthy humans, alveolar ventilation (VA) was tightly matched to CO2 production (CO2) resulting in PaCO2 deviating during ...
Holmes J M - - 1994
Fourteen nonstrabismic volunteers were monocularly patched for 2 and 24 hours in separate experiments. Horizontal and vertical phorias were measured at 6 m and 30 cm, at 30-second intervals, for at least 30 minutes, following removal of the patch. After 24 hours of monocular occlusion, the initial change from baseline ...
Kowalchuk J M - - 1994
The interaction between systems regulating acid-base balance (i.e., CO2, strong ions, week acids) was studied in six subjects for 10 min after 30 s of maximal isokinetic cycling during control conditions (CON) and after 3 days of chronic acetazolamide (ChACZ) administration (500 mg/8 h po) to inhibit carbonic anhydrase (CA). ...
Schleifer L M - - 1994
The present study was designed to assess the utility of end-tidal PCO2 (peak concentration of carbon dioxide in a single breath of exhaled air) as an index of psychophysiological activity during performance of a computer-based task and during relaxation. Eleven data-entry operators were monitored continuously for three consecutive, 6 hour ...
Zhang Y Y - - 1994
A method to estimate the CO2 derived from buffering lactic acid by HCO3- during constant work rate exercise is described. It utilizes the simultaneous continuous measurement of O2 uptake (VO2) and CO2 output (VCO2), and the muscle respiratory quotient (RQm). The CO2 generated from aerobic metabolism of the contracting skeletal ...
Hopman M T - - 1994
Since arm exercise affects the respiratory muscles the CO2 rebreathing method for determining cardiac output (Q) has to be evaluated during arm exercise. The purpose of this study was (1) to compare three different methods of determining arterial CO2 tension (PaCO2) during arm exercise, (2) to verify the linearity of ...
Koskolou M D - - 1994
In order to determine the level of hypoxemia which is sufficient to impair maximal performance, seven well-trained male cyclists [maximum oxygen consumption (VO2max) > or = 5 l.min-1 or 60 ml.kg-1.min-1] performed a 5-min performance cycle test to exhaustion at maximal intensity as controlled by the subject, under three experimental ...
Stäubli M - - 1994
Voluntary hyperventilation for 20 min causes haemoconcentration and an increase of white blood cell and thrombocyte numbers. In this study, we investigated whether these changes depend on the changes of blood gases or on the muscle work of breathing. A group of 12 healthy medical students breathed 36 l.min-1 of ...
Rai L - - 1994
Reports of energy expenditure and ventilatory responses to yogic seated posture of Siddhasana are lacking in literature. Various cardio-ventilatory responses were studied in states of the horizontal supine, chair-sitting and Siddhasana. It was observed that sitting in Siddhasana posture was characterised by greater minute ventilation, larger tidal volume, higher oxygen ...
Trillò G - - 1994
End-tidal carbon dioxide concentration in the expired air (ETCO2) is measured with different technologies. ETCO2 allows the global evaluation of three main body functions: metabolism, circulation and ventilation. If two of these parameters are held constant, changes in ETCO2 reflect a variation of the third. Thus, ETCO2 is now widely ...
McCutcheon K - - 1994
We report our experience in developing a two-day training course for the Nd:YAG (Neodymium: Yttrium-Aluminium-Garnet) laser and describe the curriculum. This project arose from an attempt to modify an existing course on the CO2 laser for a newly-acquired Nd:YAG laser in such a way as to adequately demonstrate the properties ...
Arnold J H - - 1993
OBJECTIVES: To evaluate the bias and precision of a simple, bedside method of quantification of minute CO2 production (study 1) and then apply the technique to measure physiologic deadspace in a group of neonates undergoing extracorporeal membrane oxygenation (ECMO) (study 2). DESIGN: A prospective, clinical study comparing a simple method ...
Kotby M N - - 1993
The effect of the increased flow rate (delta U) in response to the Accent Method exercises on fundamental frequency (FO) and sound pressure level (SPL) was studied in three subjects (professionally trained, trained, and untrained in this method). In all the subjects, the rhythmic accentuated exercises produced a variable degree ...
Gautier H - - 1993
We investigated in conscious rats the characteristics and modes of action of CO2 on thermoregulation and ventilatory control during cold stress. In a group of 10 rats studied intact and after carotid body denervation, measurements of metabolic rate (VO2), ventilation (V), shivering, and colonic temperature (Tc) were made at controlled ...
Persson M G - - 1993
The concentrations of endogenous nitric oxide (NO) and CO2 were measured in exhaled air from healthy humans. During a single exhalation, NO concentrations peaked when the CO2 level reached its plateau. However, whereas CO2 levels remained at a plateau throughout the exhalation, NO concentrations declined after having peaked. After breathholding ...
Loeppky J A - - 1993
Empirical relationships are demonstrated for whole blood base excess (BE) and CO2 content (CCO2), both calculated from in vivo measurements of PCO2, pH, hemoglobin concentration and O2 saturation. Comparisons are provided by measurements from three separate studies: (1) supine exercise (arterial and mixed venous samples); (2) chronic obstructive disease patients ...
Martin P A - - 1993
1. To test the hypothesis that repeated associations of exercise and increased respiratory dead space elicit mechanisms that augment future ventilatory responses to exercise alone, experiments were conducted on normal adult goats familiarized with experimental procedures. 2. Measurements of ventilation, arterial blood gases and CO2 production were made at rest, ...
Bennett F M - - 1993
A nonlinear mathematical model of the CO2 control system was used to examine a number of issues concerning the regulation of PaCO2 during rest and exercise. To gain insight to the regulatory properties of the respiratory system, the open loop gain (GL) and closed loop sensitivities SI = delta PaCO2/delta ...
Poon C S - - 1993
An adaptive neural network model that exhibits the optimality and homeostasis characteristics of the respiratory control system is described. Based upon the Hopfield network structure and a postulated Hebb-like respiratory synapse with correlational short-term potentiation, the model is capable of mimicking the normal ventilatory responses to exercise and CO2 inputs ...
Yamashiro S M - - 1993
The optimization hypothesis of respiratory control during exercise is based on the minimization of a function reflecting both chemical and mechanical costs. Both additive and multiplicative controllers have been derived as optimal from similar cost functions. The purpose of the present study was to explore the uniqueness of such predictions. ...
Forster H V - - 1993
In humans, attenuating carotid chemoreceptor activity by hyperoxia does not alter arterial PCO2 (PaCO2) during submaximal exercise, yet a transient hypercapnia occurs in carotid chemoreceptor-resected (CBR) asthmatic subjects during submaximal exercise. We hypothesized that this difference was due to asthma and not CBR causing the abnormal response. Accordingly, we determined ...
Hamel N - - 1993
The failure of labeled CO2 to equilibrate between extracellular and intracellular CO2 compartments may influence the accuracy of substrate oxidation measurements during infusion of carbon-labeled tracers because it may generate errors in estimate of fixation of labeled CO2 derived from control experiments in which labeled bicarbonate is infused. In this ...
Shea S A - - 1993
1. In healthy humans during aerobic exercise ventilation increases and mean arterial PCO2 usually remains constant over a wide range of CO2 production. 2. Congenital central hypoventilation syndrome (CCHS) is associated with ineffective chemoreceptor regulation of breathing and severe hypoventilation during sleep (requiring mechanical ventilation) reflecting abnormalities in the brainstem ...
Reybrouck T - - 1993
OBJECTIVE: To assess the cardiorespiratory response to graded exercise in patients after the Senning operation for transposition of the great arteries. DESIGN: Cross sectional study. Exercise performance was assessed by determination of the ventilatory anaerobic threshold. This was defined as the exercise intensity at which the ventilatory equivalent for oxygen ...
Larsen P N - - 1993
A new tonometry system for continuous and synchronous measurement of tissue oxygen- and carbon dioxide tension is described and characterized in vitro. The tonometer system consists of an O2 and CO2 permeable silicone tube continuously flushed with isotonic saline by an injection pump. When the saline passes through the tonometer ...
Coggan A R - - 1993
Endurance training reduces the rate of CO2 release (i.e., VCO2) during submaximal exercise, which has been interpreted to indicate a reduction in carbohydrate oxidation. However, decreased ventilation, decreased buffering of lactate, and/or increased fixation of CO2 could also account for a lower VCO2 after training. We therefore used a primed ...
Sridhar M K - - 1993
BACKGROUND: Accurate and reliable measurement of gas exchange during exercise has traditionally involved arterial cannulation. Non-invasive devices to estimate arterial oxygen (O2) and carbon dioxide (CO2) tensions are now available. A method has been devised and evaluated for measuring gas exchange during exercise with a combined transcutaneous O2 and CO2 ...
Izumi Y - - 1993
The influence of sympathetic nervous activity on cerebral circulation and cerebrovascular CO2 reactivity was investigated by an alpha-adrenergic blockade with phenoxybenzamine (PBZ). Cerebral oxygen and carbon dioxide tension (BrPo2, BrPco2) and arterial blood pressure were continuously recorded before, during and after intracarotid infusion of 5 mg/kg of PBZ. The effects ...
Eriksson L I - - 1993
BACKGROUND: A previous study has demonstrated a decrease in the hypoxic ventilatory response in volunteers partially paralyzed with vecuronium. However, in this study, hypocapnia was allowed to occur. Because hypocapnia counteracts the ventilatory response to hypoxia during partial vecuronium-induced neuromuscular block and isocapnia, the hypoxic ventilatory response (HVR) was tested ...
Nielsen G D - - 1993
Respiratory rate (f), tidal volume (VT) and carbon dioxide production (VECO2) were measured in restrained, conscious CF-1 mice. Mean f +/- S.D. and mean VT +/- S.D. were 270 +/- 8 breaths/min. and 0.123 +/- 0.024 ml (STPD) for male, and 274 +/- 15 breaths/min. and 0.115 +/- 0.023 ml ...
Schreiner M S - - 1993
We investigated the effect of increasing doses of intravenously infused glass microspheres (mean diameter 125 microns) on gas exchange in anesthetized, heparinized, mechanically ventilated goats (VT = 16-18 ml/kg). Breath-by-breath CO2 expirograms were collected using a computerized system (Study A) during the infusion of a total of 15 g of ...
Ohtake P J - - 1993
The effects of intravenous infusions of physiologic doses of angiotensin II (AII) on expired ventilation (VE) and acid-base balance were determined in awake dogs. A control infusion of saline was followed by AII infusion, initially with mean arterial pressure (MAP) raised 15%, and then with MAP at control levels by ...
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