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)] ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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) ...

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 ...

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 ...

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 ...

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. ...

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, ...

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 +/- ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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) ...

To describe the physiologic effects of surfactant treatment on gas exchange in human premature infants with hyaline membrane disease, functional residual capacity (FRC), tidal volume (VT), the alveolar portion of tidal volume (VA), alveolar ventilation (VA), nitrogen clearance index, effective breath fraction calculated as VA/VT, compliance of the respiratory system, ...

Effects of inspiratory tracheal occlusion (TO) on respiratory duration (inspiratory and expiratory duration), ventilation, and the peak integrated diaphragm electromyographic (integral of EMGdi) response were tested in 16 anesthetized cats before and after decerebellation with and without vagal input. The same protocols were repeated in the decerebrate preparation. Decerebellation did ...

1. To study the action of the intermediate area (IA), coextensive with the rostral ventrolateral medulla, on the neurophysiological mechanisms involved in the regulation of respiration, in terms of inspiratory drive and respiratory timing, cats were submitted to topical application of sodium pentobarbital (30 mg/ml), leptazol (200 mg/ml), glutamate (50 ...

We studied whether inspiratory muscle training (IMT) changed respiratory sensation during exercise in 12 healthy women; IMT was performed twice daily, for 15 minutes, using a pressure threshold device and continued for 4 weeks. The inspiratory threshold was set to 30 percent of each individual's maximal inspiratory pressure (Pimax). Breathing ...

Term human newborns were challenged with a 2-3% CO2 gas mixture during quiet sleep. A common ventilatory response, consisting of increased tidal volume with no change in respiratory frequency or timing, was observed in all eight subjects. Minute ventilation and mean inspiratory and expiratory flow rates were elevated in all ...

This study, aimed at investigating some aspects of breathing control at work, was conducted on 8 heart and lung transplant recipients (HLTR) (age 33 +/- 13 years, mean +/- SD; 10 +/- 6 months post-transplantation) and on two control groups, i.e. 11 heart transplant recipients (HTR) and 11 healthy untrained ...

Many daily activities, from basic grooming to employment tasks, require adequate unsupported arm endurance (UAE). We developed an electromechanical device to measure UAE endurance. The purpose of this study was to standardize the instrument for two rates of arm motion, moderate and slow, in 18 normal adult subjects (FEVI = ...

A new design of flowmeter is described and used in a comprehensive study of the respiratory and cardiovascular adjustments that occur during a standardised exercise test in Thoroughbred horses. The flowmeter system and associated lightweight, fibreglass mask (total mass, 0.7 kg) have a maximum dead space of 500 ml and ...

Spontaneous augmented breaths (active sighs) reduced the tidal volume and inspiratory time of succeeding breaths; manual lung inflations (passive sighs) reduced the tidal volume but had little effect on inspiratory time. Sighs in air, whether active or passive, reduced tidal volume more than sighs in hyperoxia (100% oxygen or 33% ...

To investigate the impact of expiratory flow limitation (FL) on breathing pattern and end-expiratory lung volume (EELV), we imposed a small expiratory threshold load for a few breaths during exercise in nine volunteers (29-62 yr): six were healthy and three had mild-to-moderate airflow obstruction (67-71% predicted forced expiratory volume in ...

There is presently no precise way to determine ventilatory capacity for a given individual during exercise; however, this information would be helpful in evaluating ventilatory reserve during exercise. Using schematic representations of maximal expiratory flow-volume curves and individual maximal expiratory flow-volume curves from four subjects, we describe a technique for ...

Previous work has suggested that diaphragm EMGs recorded from the lower thoracic wall yield spuriously low centroid frequencies (Fc). For this reason we compared EMGs recorded from two anterolateral thoracic wall locations with EMGs recorded simultaneously from a bipolar esophageal electrode in 11 stable quadriplegic patients. Their maximal inspiratory pressures ...

We examined diaphragmatic mechanics in awake sheep during quiet breathing (QB) and the randomized application of 5, 10, and 15 cmH2O continuous positive airway pressure (CPAP), inspiratory pressure support (IPS), and equal combinations of IPS and CPAP (IPS/CPAP). We measured esophageal, gastric, and transdiaphragmatic (Pdi) pressures and regional length, shortening, ...

BACKGROUND: Upper abdominal surgery (UAS) induces diaphragmatic dysfunction. Thoracic extradural block (TEB) using 0.5% bupivacaine improves some pressure and motion indices of diaphragmatic function. However, no direct information on diaphragmatic activity is available after UAS. The aim of this study was to assess diaphragmatic electrical activity (Edi) after UAS before ...

The breathing pattern and respiratory muscle function were investigated in ten trained and ten untrained adolescents (aged 15-16 years) while undergoing an incremental intensity exercise test on a cycle ergometer up to 80% maximal oxygen consumption (VO2max), maintained to exhaustion. Before and after exercise, maximal inspiratory (PImax) and expiratory (PEmax) ...

The objective of this study was to compare prospectively the efficacy of fixed burst pacing with that of decremental burst pacing in terminating VT. Forty-four patients with inducible sustained monomorphic VT were studied. The efficacy of fixed burst and decremental burst pacing for terminating 57 distinct types of VT were ...

More rapid and more shallow breathing (RSB) than usual, manifested by a lower tidal volume and greater breathing frequency at a given level of ventilation, may be caused by inspiratory muscle fatigue and pulmonary congestion. It has been observed during recovery in young trained adults after very high exercise levels ...

Patients with quadriplegia have a limited capacity to recruit expiratory muscles and are deprived of respiratory-related feedback from the rib cage and abdominal wall. We wished to evaluate the compensatory strategies available to such patients during expiratory resistive loading (ERL) and to compare their responses with those of normal healthy ...

When breathing room air at sea level the expired gas temperature (TE) increases in proportion to the inspired one (TI). Previous studies conducted under hyperbaric conditions have assumed that the TE vs TI relationship was the same when humans breathed room air at atmospheric pressure or helium-oxygen mixture under hyperbaric ...

This study examines the efficacy of verapamil and diltiazem in the suppression of idiopathic ventricular tachycardia (VT). Eight patients (mean age 29.8 +/- 12.3 years, two males and six females) with VT, without any underlying cardiac abnormality on clinical examination and noninvasive investigation, were studied. The inducibility of the clinical ...

Combination antiarrhythmic drug therapy may be more effective than treatment with a single agent for control of refractory cases of sustained ventricular tachycardia (VT). In a prospective randomized crossover study of 20 patients with impaired left ventricular function (ejection fraction of 28% +/- 8%) and recurrent VT in spite of ...