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Results 401 - 450 of 823
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Lerman B B - - 1995
BACKGROUND: The most common form of idiopathic ventricular tachycardia (VT) is repetitive monomorphic VT (RMVT), which is characterized by frequent ventricular ectopy and salvos of nonsustained VT with intervening sinus rhythm. Unlike most other forms of idiopathic VT, this tachycardia typically occurs at rest and is nonsustained. The mechanism of ...
Pokorski M - - 1995
The question was investigated of whether thoracic feedback could play a role in shaping the tidal and frequency components of the breathing pattern. The changes in the breathing pattern of tetraplegic subjects were examined and compared with those of normal subjects during hypoxic and hypercapnic rebreathing tests, using data from ...
Simon P M - - 1995
To evaluate the role of phrenic and sternocleidomastoid afferents as alternate sources of inhibitory feedback during mechanical ventilation, we studied five C2-C3 quadriplegics with sensory denervation of the rib cage and diaphragm, six C1-C2 quadriplegics with additional loss of sensory feedback from the neck muscles, and seven normal subjects. We ...
Watanabe S - - 1995
We designed this study to determine whether orally administered L- and DL-carnitine can improve exercise tolerance in a group of patients with exercise intolerance. Nineteen patients with cardiac disease were randomly divided into 2 groups, an L-carnitine treatment group (n = 9) and a DL-carnitine treatment group (n = 10). ...
Neary J P - - 1995
This study compared breathing frequency (fB) during a ventilation threshold (VT) test with fB during a simulated 40 km time trial (40TT) to assess whether fB can be used to monitor exercise intensity. Twenty-six male cyclists (mean +/- SD VO2max = 4.42 +/- 0274 l.min-1) performed an incremental VT ergometer ...
Ferguson G T - - 1995
The effects of oxygenation and hypercapnia on diaphragmatic function and central drives were assessed during the development of respiratory failure in anesthetized unbound spontaneously breathing rabbits. Oxygenation significantly altered endurance times, whereas hypercapnia had no effect. Isolated high-frequency contractile fatigue of the diaphragm was found in hyperoxic animals; all other ...
Rafferty G F - - 1995
Combinations of 17 normal awake humans breathed mildly hyperoxic and hypercapnic gas mixtures via a pneumotachograph into an open circuit. Respiratory pattern was measured for each breath in real time by computer. Use of computer-controlled auditory feedback at a constant end-tidal PCO2 (PETCO2) allowed prolonged changes of 1) inspiratory time ...
Frappell P B - - 1995
Oxygen consumption (VO2) and a number of components of the breathing pattern were measured in 14 species of non-fossorial marsupials ranging in mass from 0.008 to 30 kg. All the exponents of the allometric relationships for VO2, ventilation (VE) and breathing pattern scaled as previously determined for eutherians. However, compared ...
Janssens S - - 1995
The effect of theophylline on diaphragmatic blood flow (Qdi) and oxygen consumption (VO2di) was studied in eight lightly anesthetized dogs during quiet breathing and inspiratory resistive loading. Qdi was determined with the radioactive microsphere tracer technique, and VO2di was calculated as the product of Qdi and the diaphragmatic arterio-venous oxygen ...
Goodman N W - - 1995
In the records of breathing from five of 32 patients in two previous studies, the distribution of expiratory times appeared bimodal. Records of breathing from another 40 patients anaesthetized for up to 1 h with propofol infusions were examined; there was clear evidence of bimodality in the distribution of expiratory ...
Cooper C B - - 1995
Chronic pulmonary diseases are common in the community and their pathophysiology is complex. The principal symptoms are dyspnea and limited exercise capacity. Some, but not all, patients have true ventilatory limitation where the maximal exercise ventilation (VEmax) equals the measured maximal ventilatory volume (MVV). Those with obstructive disease have impeded ...
Fontana G A - - 1995
We investigated the effects of prostaglandin synthesis blockade on the changes in breathing pattern, mean blood pressure (MBP), and heart rate (HR) elicited by 3 min of static handgrip at 30% of the maximum voluntary contraction in 12 healthy volunteers. Before each handgrip trial, subjects were treated with intravenous administration ...
Watanabe S - - 1995
We assessed the changes in arterial potassium concentration during exercise and recovery in relation to exercise tolerance in patients with impaired exercise tolerance. Sixteen patients with cardiac disease were subjected to a cardiopulmonary exercise test on a cycle ergometer. Arterial potassium and lactate concentrations were measured every minute during and ...
Lafortuna C L - - 1995
A simple and inexpensive new extensometer for measuring changes in chest wall circumference during human respiratory movements is presented. The instrument detects the delay between ultrasound emission and reception at opposite ends of two rubber tubes encircling the rib cage and abdomen. Assuming a two degree of freedom model of ...
Aldrich T K - - 1995
BACKGROUND: Maximal inspiratory pressure (MIP) is often relied upon as an index of inspiratory muscle strength, and reproducibility of MIP taken to indicate maximal effort. This study was designed to determine whether reproducibility is a valid indicator of maximal effort. METHODS: Ten normal subjects were studied, all of whom were ...
Kolarzyk E - - 1995
The contribution of the central and peripheral nervous system to the regulation of breathing in acute carbon monoxide poisoning was evaluated through the analysis of respiratory pattern parameters, mainly the values of tidal volume to the inspiratory flow (VT/T(in)--driving component), and the relation of inspiratory time to the total cycle ...
Wassermann K - - 1995
AIM: The aim of this study was (1) to assess the value of common lung function variables in the follow-up of patients with obstructive lesions of the larynx and trachea and (2) to study the respiratory response to progressive upper airway stenosis at rest and during exercise. METHODS: Lung function ...
Grucza R - - 1994
Influence of work rate (30 and 30 rpm) on exercise hyperpnoea, respiratory entrainment and cardiovascular system was studied in 9 healthy men performing rhythmic-static exercise (RSE). Respiratory frequency (f), tidal volume (VT), minute ventilation (VE), heart rate (HR), stroke volume (SV), and cardiac output (Q) were continuously measured. RSE was ...
Lewis D A - - 1994
To evaluate the accuracy of noninvasive estimates of VD/VT in clinical exercise testing, we compared measurements of standard VD/VT with estimates based either on end-tidal CO2 (VD/VTET) or a published estimate of arterial PCO2 (VD/VTest) at peak exercise in 68 patients. Using regression analysis, we identified highly significant differences (p ...
Caretti D M - - 1994
This study was designed to determine the reliability of measurements of respiratory volumes obtained with a respiratory inductive plethysmograph (RIP) during exercise. Tidal volumes (VT) from the RIP were compared with simultaneous flowmeter volumes in 8 healthy subjects at 5 incremental work rates of 60, 90, 120, 150, and 180 ...
Yokoyama H - - 1994
Although exertional dyspnea is an important symptom limiting daily lives in patients with chronic heart failure, there is no objective assessment of this symptom. To characterize the exertional dyspnea, ventilatory responses to exercise were studied in relation to exertional dyspnea. Gas exchange data were obtained during a maximal bicycle exercise ...
Ewald F W FW - - 1994
The inspiratory flow-volume (FV) curve can be used to identify patients with upper airway obstruction, air trapping, and restriction. Current computed pulmonary function testing equipment often mandates a forced expiratory maneuver (FEM) immediately prior to the forced inspiratory maneuver (standard method). We evaluated the inspiratory FV curve with and without ...
Tessler M J - - 1994
We measured the tidal volumes (VT) delivered by two anesthesia ventilators (the Narkomed 2B and the Ohmeda 7800) to a model lung at frequencies of 60 breaths/min and 99-100 breaths/min under two conditions of compliance and resistance designed to mimic mild and severe adult respiratory distress syndrome (ARDS) (mild ARDS ...
Xu F - - 1994
The cerebellar contribution to the ventilatory response to progressive hypercapnia was examined in 18 anesthetized tracheotomized spontaneously breathing cats. The absolute values for minute ventilation (VE), tidal volume (VT), respiratory frequency (f), inspiratory duty cycle (TI/TT), and mean inspiratory flow (VT/TI) were measured. Progressive hypercapnia [35-65 Torr end-tidal PCO2 (PETCO2)] ...
Tzelepis G E - - 1994
The inspiratory muscles (IM) can be trained by having a subject breathe through inspiratory resistive loads or by use of unloaded hyperpnea. These disparate training protocols are characterized by high inspiratory pressure (force) or high inspiratory flow (velocity), respectively. We tested the hypothesis that the posttraining improvements in IM pressure ...
McKenzie D K - - 1994
BACKGROUND: Clinical tests of diaphragmatic strength are limited by the wide normal variation in maximal pressure which result, in part, from changes in diaphragmatic length. During relaxation at different lung volumes diaphragmatic length (LDI) can be estimated from the length of the zone of apposition (LZapp) and the transverse diameter ...
Zimmerman M I - - 1994
The physiologic dead space/tidal volume ratio (VD/VT) at rest and during exercise is a sensitive measurement of gas exchange that reflects matching of ventilation to perfusion, but requires an invasive measurement for its calculation. Determining VD/VT noninvasively uses estimations of arterial PCO2 based on the end-tidal PCO2. To further standardize ...
Ceugniet F - - 1994
It is often admitted that heat exchange in the airways is a major cause of exercise-induced asthma. Because a decrease in the inspiratory time/expiratory time ratio (TI/TE) decreases these exchanges, we postulated that it might decrease bronchoconstriction as well. Twenty-four asthmatic children, divided into three groups, underwent two exercise provocation ...
Barrett J - - 1994
Tilting from supine to upright purportedly enhances both segmental and pulmonary proprioceptive feedback, whereas an expiratory threshold load (ETL) preferentially enhances pulmonary feedback. To test this we studied 13 adults when supine and 60 degrees and 90 degrees head up. We measured tidal volume, inspiratory duration (TI), and expiratory duration ...
Shih J F - - 1994
To further assess the clinical significance of asbestos-induced pleural fibrosis, we performed cardiopulmonary exercise testing in 90 subjects who were exposed to asbestos. Of the 82 subjects without an abnormal resperate exercise, 35 had normal pleura, 33 had circumscribed pleural plaques, and 14 had diffuse pleural thickening. Interstitial fibrosis (International ...
Cordain L - - 1994
In order to evaluate a mechanism which may be responsible for the often observed acute increase in residual lung volume (RV) following exercise, 12 non-smoking males (20-30 yrs) performed two bouts of exercise on separate days; one to maximal heart rate (HRmax) and one to 85% of HRmax for 20 ...
Manning H L - - 1994
We examined the relationship between tidal volume (VT) perception and level of CO2. Ten normal subjects were connected to a volume-cycled ventilator set in control mode, and VT and respiratory rate were adjusted until subjects were comfortable. At 2 levels of CO2 which differed by 6-8 mmHg, subjects rated ten ...
Kobayashi Y - - 1994
Sustained VT in two patients was terminated by intravenous administration of dipyridamole, an adenosine transport inhibitor. VT was induced by rapid atrial or ventricular pacing, isoproterenol, or dibutyryl cyclic AMP infusion, or exercise. VT also was aborted by adenosine triphosphate or acetylcholine injection, or by vagal stimulation. VT was terminated ...
Wilson T A - - 1994
The gravitational force on the rib cage has been found to be an expiratory force of approximately 8 cmH2O. The gravitational force on the abdomen is an inspiratory force of the same magnitude. Because the compliance of the rib cage is greater than the compliance of the abdomen, it follows ...
Forster H V - - 1994
We determined the effect of pulmonary vagal (hilar nerve) denervation (HND) and diaphragm deafferentation (DD) on inspiratory load compensation. We studied awake intact (I; n = 10), DD (n = 5), HND (n = 4), and DD+HND (n = 7) ponies at rest and during mild (1.8 mph, 5% grade) ...
Beck K C - - 1994
To demonstrate physiologic changes associated with asthma symptoms that many patients with asthma develop during exercise, we used sustained constant-load and interval exercise protocols with subjects breathing dry room temperature air. In constant-load exercise, subjects pedaled a stationary bicycle at 50% of their maximal power capacity for 36 min. In ...
Dwyer G B - - 1994
Metabolic control, as assessed by glycosylated hemoglobin (HbA1c), has been reported to have a relationship to various submaximal exercise responses. However, due to the narrow range of HbA1c and the limited exercise data from previous studies on individuals with diabetes, little support for the above statement exists in the literature. ...
Wanke T - - 1994
We investigated 8 patients undergoing continuous ambulatory peritoneal dialysis (CAPD) for diaphragmatic strength and the neuromechanical efficiency of the diaphragm while the abdomen was filled with dialysate and while it was empty. Maximum transdiaphragmatic pressure (Pdimax) served as parameter for diaphragmatic strength; diaphragmatic efficiency was assessed by simultaneously monitoring transdiaphragmatic ...
Lindstedt S L - - 1994
Symmorphosis predicts that animal design is optimized in such a way that structure 'statisfies but does not exceed' functional requirements. To provide one test of this hypothesis, we examined peak inspiratory flow and its relation to maximum oxygen uptake in humans. We measured maximal forced (peak) inspiratory flow (VImax) and ...
Foglio K - - 1994
Patients with multiple sclerosis (MS) show a poor exercise tolerance. A reduction in respiratory muscle strength has also been reported. The purpose of this study was to evaluate whether reduction in exercise tolerance was related to respiratory muscle dysfunction. Twenty four multiple sclerosis patients (mean +/- SD age: 48 +/- ...
Marciniuk D - - 1994
The role of central respiratory muscle fatigue in determining endurance time (ET) of steady-state ergometry, ventilation (VE), and breathing pattern during exhaustive submaximal exercise is not known. Six normal subjects exercised on a cycle ergometer to exhaustion at 72-82% of maximal power output on three occasions. During the second test, ...
Webb B - - 1994
Inspiratory mechanical loads elicit a reflex volume-timing response in human infants and experimental animals. In adult animals, this reflex has been shown to be mediated by vagal afferents. It was hypothesized that the volume-related regulation of inspiratory duration would also be vagally mediated in the newborn. Single-breath graded inspiratory loads ...
de Bruin P F - - 1993
To investigate how treatment can affect airway dynamics and respiratory muscle strength in Parkinson's disease (PD), we assessed maximum effort inspiratory and expiratory mouth pressures (MIP and MEP), oscillatory impedance, and maximum expiratory and inspiratory flow-volume curves (MEFV and MIFV) in 10 patients (8 male and 2 female; mean age ...
Lougheed M D - - 1993
The purpose of this study was to examine potential contributing factors to breathlessness during bronchoconstriction, in particular, to evaluate the role of lung hyperinflation. We also wished to elucidate qualitative aspects of the unpleasant sensory experience and to identify factors that contribute to intersubject variability in subjective and objective assessments ...
Greenberg H E - - 1993
Abnormal inspiratory load compensation may be one factor leading to development of obstructive sleep apnea (OSA). Alternatively, abnormalities in ventilatory load compensation may be a consequence of the manifestations of OSA. This investigation was designed to determine if impairment of awake inspiratory load compensation exists in OSA and to determine ...
Gill J S - - 1993
Inhomogeneity of ventricular repolarization reflected in prolongation of the QT interval of the surface electrocardiogram can predispose patients to ventricular arrhythmia. This study examines whether an abnormality of QT adaptation to changes in heart rate is likely to be of importance in the pathogenesis of ventricular tachycardia (VT) in patients ...
Fairbarn M S - - 1993
The circulating leukocyte (WBC) count increases with exercise, because WBCs enter the circulation from the marginated pool. The lung is a major source of the demarginating cells, but it is unclear whether this occurs because of increased ventilatory movements, increased cardiac output, or both. The present study examined the mechanical ...
Fontana G A - - 1993
We studied the time course of respiratory and cardiovascular responses by evaluating changes in the breathing pattern, mean blood pressure (MBP), and heart rate elicited by 3 min of static handgrip at 15, 25, and 30% of the maximum voluntary contraction (MVC) in 15 healthy volunteers. Muscle tension and integrated ...
Gill J S - - 1993
This study examines the efficacy of verapamil for the suppression of idiopathic ventricular tachycardia (VT) of left bundle branch block LBBB-like morphology. Forty-two patients (mean age 36.2 +/- 12.1 years; 20 men and 22 women) with VT and without any underlying cardiac abnormality on clinical examination and noninvasive investigation were ...
Sawyer E H - - 1993
This study documented the effect of inspiratory muscle conditioning in children with cystic fibrosis. Subjects, ages 7 to 14 years, were divided into two groups. The experimental group (n = 10) trained at a high pressure load (> or = 29 cm H2O) and the control group (n = 10) ...
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