We studied chest wall mechanics at functional residual capacity (FRC) and near total lung capacity (TLC) in 14 supine anesthetized and vagotomized dogs. During breathing near TLC compared with FRC, tidal volume decreased (674 +/- 542 vs. 68 +/- 83 ml; P less than 0.025). Both inspiratory changes in gastric ...

The American Thoracic Society recommends that the largest FEV1 be reported from a set of forced expiratory vital capacity maneuvers performed with maximal expiratory effort. However, increased expiratory effort can decrease the FEV1. When we evaluated the peak expiratory flow rate (PEFR) in 5 normal subjects, measured from flow-volume curves, ...

To determine the antiarrhythmic efficacy of beta-blockers (beta-B) and verapamil (V) in exercise-induced ventricular tachycardia (Ex-VT), nine patients with reproducible Ex-VT (in two consecutive exercise tests) were studied by means of electrophysiologic study (EPS) in basal conditions and serial exercise testing after beta-B (metoprolol 25 mg tid to 100 mg ...

Previous experimental evidence has shown that in healthy humans inspiratory airflow waveform can be optimized according to minimum rate of work criteria when the respiratory energetic requirements become a substantial fraction of the general metabolism (i.e., during exercise hyperpnea and maximum voluntary ventilation). In patients with chronic airway obstruction (CAO) ...

During progressive exercise ventilation (VI) initially increases through increases in both tidal volume (VT) and respiratory frequency (f) but at high levels of exercise further increases in VI are almost completely due to increases in f and a VT plateau is seen. We wished to determine whether the presence of ...

Lung volumes in sex-, age-, height-, and weight-matched Black subjects are 10-15% lower than those in Caucasians. To determine whether this decreased lung volume affected the ventilatory adaptation to exercise, minute ventilation (VE), its components, frequency (f) and tidal volume (VT), and breathing pattern were observed during incremental cycle-ergometer exercise. ...

We describe an apparatus for altering the mechanical load against which the respiratory muscles operate in humans. A closed system incorporates a rolling seal spirometer. The spirometer piston shaft is coupled to a fast-responding linear actuator that develops force in proportion to desired command signals. The command signal may be ...

Thirteen dogs in whom at least one morphologically distinct sustained ventricular tachycardia (VT) could be reproducibly initiated by programmed cardiac stimulation 18 +/- 3 days following experimental myocardial infarction were placed on total cardiopulmonary bypass for detailed study of the endocardial and epicardial activation during VT under hemodynamically stable conditions. ...

The objective of this study was to determine the stability of the function describing subjects' magnitude estimates of added inspiratory resistive loads following short-term exposure (STE) to a high but nonfatiguing, inspiratory load. Four inspiratory resistive loads (8.9-35.7 cmH2O X l-1 X s) were presented twice each in random order. ...

First-breath ventilatory responses to graded elastic and resistive loads were obtained from 15 people with Duchenne muscular dystrophy (DMD), 5 people with facioscapulohumeral MD (FSH), 3 people with Becker MD, and 3 people with limb-girdle MD. For each load tidal volumes from different individuals ranged from relatively small to comparatively ...

The intrinsic relationship between ventilation (VE) and carbon dioxide output (VCO2) is described by the modified alveolar ventilation equation VE = VCO2 k/PaCO2(1-VD/VT) where PaCO2 is the partial pressure of CO2 in the arterial blood and VD/VT is the dead space fraction of the tidal volume. Previous investigators have reported ...

Activity of genioglossus muscle (GG) was recorded in anesthetized rabbits at control and under SO2 block of slowly adapting stretch receptors in thoracic airways (T) or in bronchi alone (B). At control peak activity occurred at 10% of inspiratory time, followed by a slight and a marked decrease. T and, ...

In five healthy subjects, we studied the effects of controlled mechanical unloading of the respiratory system on ventilatory control during moderate exercise, utilizing a modified positive-pressure ventilator (IEEE Trans. Biomed. Eng. BME-33: 361-365, 1986). We were especially interested in whether isocapnia was maintained when a portion of the normal ventilatory ...

We examined the effect of inspiratory resistive loaded breathing (IRL) on the electromyographic (EMG) activity of the costal and crural diaphragm in nine anesthetized spontaneously breathing piglets (age 10-23 days, weight 2.8-4.4 kg). Bipolar wire electrodes were inserted into the anterior paratendinous costal diaphragm and the midportion of the crural ...

Previous studies have described a neurogenic-induced ventilatory tachypneic response during exercise. The present paper compares the breathing pattern of control and myopathic human subjects submitted to exercise. Peripheral neurogenic stimuli (PNS) at the same level of oxygen consumption should be enhanced in myopathic subjects as a consequence of muscular mass ...

Breathing pattern was studied in six subjects in normoxia (FIO2 = 0.21) and hypoxia (FIO2 = 0.12) at rest and during incremental work-rate exercise. Ventilation (V) as well as mean inspiratory flow (VT/TI) increased with exercise intensity and were augmented in the hypoxic environment, whereas the ratio between inspiratory (TI) ...

Standardization of bronchial challenge (BC) in order to improve repeatability of both non-specific and specific challenges is desirable. In the tidal volume breathing BC (tBC), the patient inhales bronchoconstrictor during the entire inspiratory phase of the tidal volume breathing. We determined 2 min ventilation (VE) at each histamine concentration during ...

Low level exercise is frequently used to assess cardiac and pulmonary function. This study examines the differences in both metabolic and respiratory patterns between the sitting and supine position. Six normal male subjects were studied in both positions during four levels of exercise (12.5, 25, 37.5 and 50 W). Oxygen ...

This study was designed to determine whether inspiratory resistive training could improve the exercise performance of patients with severe chronic airflow limitation who had already received optimum conventional therapy with bronchodilators and physiotherapy. Eighteen patients were studied. Ten patients were trained with an inspiratory resistance device for six weeks and ...

The authors compared the respiratory effects of an intravenous infusion of ketamine (1 mg X kg-1) with droperidol (0.1 mg X kg-1), or placebo on three different occasions in a double-blind, randomized fashion in eight healthy volunteers. Breathing pattern, thoraco-abdominal motion, end-expiratory positions of the rib cage and abdomen, arterial ...

To examine the effect of changing tidal volume (VT) on ventilation distribution, we studied multiple breath nitrogen washouts in 4 normal subjects breathing with a VT of 0.6, 1.0 or 1.5 L. We used a recently developed technique of analysis (Crawford et al., 1985) that distinguishes inhomogeneity of gas concentrations ...

In four normal subjects and 51 patients with chronic bronchitis-emphysema, bronchial asthma and pulmonary fibrosis, the VD/VT ratio was measured by a helium washout technique (wVD/VT) and by the conventional Bohr's method using the arterial CO2 tension (VD/VT). In 16 patients the wVD/VT ratio was compared with that calculated from ...

Ventilation and breathing pattern were recorded in a group of seven anesthetized cats during rewarming from 24 to 38 degrees C of esophageal temperature. It was found that at 24 degrees C, ventilation was very much depressed accounting for an alveolar hypoventilation resulting in hypoxia and hypercapnia. During rewarming, ventilation ...

The effects of acute bronchoconstriction, produced by inhalation of Ascaris suum antigen, on both the amplitude and timing of phrenic nerve activity were studied in anesthetized dogs. Blood gas tensions and inspiratory air flow were maintained constant. Bronchoconstriction resulted in a significant increase in the magnitude and rate of rise ...

This report describes a 6-step process for prescribing resistive inspiratory exercise using the PFLEX device, which is an inexpensive and effective method of enhancing the performance of the vital muscles of respiration. Until further clinical validation of minimal threshold guidelines for prescribing PEPs is achieved, the clinical judgment of the ...

The major differential diagnosis for VT is supraventricular tachycardia with a wide QRS complex due to aberrant conduction. Although VT may be slightly irregular, gross irregularities, such as those typically seen in atrial fibrillation, are uncommon during VT; such marked irregularities suggest atrial fibrillation. The QRS configuration is helpful in ...

A female patient had recurrent sustained ventricular tachycardia (VT) as a late sequela after complete repair of tetralogy of Fallot, and the clinically documented VT could be induced and terminated in a reproducible manner by programmed stimulation. VT was accompanied by fragmented electrical activities when the electrode was positioned at ...

Few studies have examined the response of individuals with restrictive lung disease (RLD) to respirator wear. Such information should be of theoretical and practical interest when the need to determine fitness to wear respirators is considered. Seventeen females performed progressive submaximal treadmill exercise. Twelve control subjects with total lung capacity ...

This study determined the effects of a 5-second inspiratory hold during ventilatory maneuvers on cardiopulmonary status before, during, and after endotracheal suctioning in an acute lung-injured model. Eight mongrel dogs were anesthetized, paralyzed, mechanically ventilated, and given intravenous oleic acid to produce pulmonary edema. Four protocols were tested in alternate ...

Bellemare and Grassino (J. Appl. Physiol. 53: 1196-1206, 1982) have reported that the diphragmatic time-tension index (TTdi) (i.e., the product of mean transdiaphragmatic pressure/maximum transdiaphragmatic pressure and the inspiratory duty cycle) can be used as a predictor of diaphragmatic fatigue in humans. However, the publications of these authors do not ...

We measured deadspace (VD) in ducks using CO2 expirograms (plots of expired PCO2 vs expired volume) obtained during artificial ventilation at different tidal volumes (VT) and respiratory system volumes (VRS). Conventional analysis of the expirograms for Bohr and Fowler VD indicated both were larger than anatomic VD. Most expirograms at ...

In anesthetized humans the nature of tidal volume (VT) compensation during elastic loading (as reflected in the difference between passive and effective respiratory elastances (Ers) and (E*rs), respectively) has not been fully elucidated. We assessed the relative contribution of various mechanisms contributing to VT compensation during linear elastic loading in ...

Lung function was studied by forced expiratory spirograms and measurement of peak expiratory flow in fourteen young male subjects of the age 20 to 30 years. Seven of the subjects were cotton spinners in small shops in Paharganj market with the duration of work from 1 to 3 years. The ...

Previous studies have led to the revival of the hypothesis that breathlessness is the perception of respiratory muscle effort and is present when the tension developed by muscles increases, when the muscles are weak, or when both conditions are present simultaneously. Using a category scale, the intensity of breathlessness was ...

The ability of acute, short-term, inspiratory flow-resistive loading to generate endogenous opioids was studied in 6 unanesthetized goats. Endogenous opioid generation was assessed by measurement of immunoreactive beta-endorphin levels in the cisternal cerebrospinal fluid (CSF) after high (80 cm H2O/L/s) and moderate (50 cm H2O/L/s) resistive loading. The results show ...

This study compared the respiratory responses to ventilatory loading in 8 normal subjects and 11 quadriplegic patients with low cervical spinal cord transection. Progressive hypercapnia was produced by rebreathing. Rebreathing trials were carried out with no added load and with inspiratory resistive loads of 5 and 16 cmH2O. l-1 X ...

Employment of mouthpiece and noseclips (MP + NC) has repeatedly been shown to increase tidal volume (VT), but its effect on respiratory frequency (f) and its subsets is controversial. The mechanisms accounting for this alteration in breathing pattern are poorly understood and may include stimulation of oral or nasal sensory ...

Maximal expiratory flow-volume maneuvers were performed by self-trained (FIT) and sedentary (UNFIT) asthmatic subjects. Both groups had similar pre-exercise pulmonary function limitations and attained the same exercising heart rate. The FIT group, however, exercised significantly longer than the UNFIT group. Although expiratory airflow increased in both groups during exercise, the ...

Diaphragmatic electromyogram (EMG) was obtained in eight 48-h-old unanesthetized monkeys while breathing air and then either of two different hypoxic gas mixtures (12 or 8% O2 in N2) for 5 min. Minute ventilation (VI) rose significantly above control levels by 1 min of hypoxemia while animals were breathing either of ...

The objective of this study was to determine the role of hilar nerve (lung vagal) afferents in the hyperpnea of exercise. Ten ponies were studied before and 2-4 wk and 3-12 mo after sectioning only the hilar branches of the vagus nerves (HND). After HND, lung volume feedback to the ...

To determine the predominant steady-state ventilatory responses to mild expiratory flow-resistive loads, we subjected 14 normal subjects to expiratory resistances of 0-10 cm H2O/L/sec (R0-R3). Breathing patterns and abdominal muscle activity (EMG) were recorded during quiet breathing, and when ventilation was augmented by dead space breathing (7 subjects) or treadmill ...

To study the changes in ventilation induced by inspiratory flow-resistive (IFR) loads, we applied moderate and severe IFR loads in chronically instrumented and awake sheep. We measured inspired minute ventilation (VI), ventilatory pattern [inspiratory time (TI), expiratory time (TE), respiratory cycle time (TT), tidal volume (VT), mean inspiratory flow (VT/TI), ...

To quantitate the relative contributions of rib cage and abdomen to the hyperinflation of asthma, we examined chest wall movements during histamine-induced bronchospasm in 7 male asthmatic subjects. A reduction in FEV1 of 28.1 +/- 4.5% (mean +/- 1 SE) was associated with an increase in functional residual capacity (FRC) ...

In chronic air-flow obstruction (CAO), inspiratory mechanics constitute a potential mechanism of compensation for limitation of expiratory air flow. We sought to determine whether assessment of inspiratory function could improve our ability to predict ventilation at maximal exercise (Ve max) in patients with CAO. Resting inspiratory and expiratory pulmonary function ...

Ventilatory muscle function was examined at rest and during exercise on a cycle ergometer in 8 patients with moderate to severe chronic air-flow limitation (FEV1, 32 +/- 4% predicted) in air and in oxygen. The diaphragmatic electromyogram (EMG) was measured using an esophageal electrode. In addition, measurements of esophageal (Pes), ...

In tetraplegia there is often paradoxical inward motion of the rib cage during inspiration. The volume of this negative contribution is difficult to estimate but can be obtained by optical mapping. The partitioning of ventilation between the rib cage and abdomen in six normal subjects, 10 stable tetraplegic patients, and ...

The antiarrhythmic efficacy of verapamil was determined by serial treadmill testing in 16 patients with reproducible exercise-induced ventricular tachycardia (VT). Twelve of the 16 patients responded to verapamil, 0.2 mg/kg intravenously; in 8 of these 12 responders, an oral verapamil regimen of 160 to 320 mg given every 8 hours ...

Five healthy males exercised progressively with small 2-min increments in work load. We measured inspiratory drive (occlusion pressure, P0.1), pulmonary resistance (RL), dynamic pulmonary compliance (Cdyn), transdiaphragmatic pressure (Pdi), and diaphragmatic electromyogram (EMGdi). Minute ventilation (VE), mean inspiratory flow rate (VT/TI), and P0.1 all increased exponentially with increased work load, ...

We studied diaphragm function in a total of 64 normal subjects, who had no past or present respiratory or neuromuscular impairment. We measured transdiaphragmatic pressure (Pdi) during maximal sniffs and compared these values with Pdi during maximal static inspiratory efforts (PImax.). The range of Pdi during maximal sniffs (82-204 cm ...

It has been suggested that avian intrapulmonary CO2-sensitive receptors (IPC) may be capable of monitoring the rate and extent of CO2 washout from the lung during spontaneous breathing. The purpose of this study was to analyse IPC discharge activity (using computerised bin-averaging and counting techniques) in spontaneously breathing domestic fowl ...