Status asthmaticus (SA) is a life-threatening exacerbation of asthma that is refractory to usual therapeutic interventions. The etiologic factors leading to SA and pathophysiologic alterations in airway caliber, respiratory muscle function, and respiratory gas exchange are reviewed. Important parameters in the assessment of patients presenting with SA are highlighted, including ...

1. This study was designed to examine whether normal subjects could differentiate between the 'intensity' of their breathlessness and the amount of 'distress' it evoked, by specific wording of the instructions. 2. A preliminary study showed no significant difference between 'distress' score during exercise measured on two separate occasions (P ...

Although both energy metabolism and ventilation parameters are highly size dependent in adult birds, the usual scaling relationships with mass do not hold in hatchlings or in growing chicks. In Adélie penguins, three distinct behavioral phases during growth and development are reflected in the ontogeny of metabolism and ventilation. Metabolic ...

In order to evaluate the impact of simulation complexity on resuscitation skill performance, 15 pediatric residents were observed in bag-valve-mask ventilation on an infant manikin. Performance was evaluated in a simple exercise in which ventilation was performed as a single isolated task. For each subject, this was compared to performance ...

This study was undertaken to determine if the observed increase in ventilation during passive limb movement was a reflex hyperventilation or a response to an increased metabolic need for oxygen. Experiments on human volunteers were designed to test the hypothesis that the rapid increase of ventilation at the onset of ...

A rating procedure for respiratory disability has been developed; it entails measuring the symptom-limited maximal oxygen uptake or estimating the maximal uptake from the results of a submaximal exercise test and other relevant variables. The derivation assumes a linear scale of disability between the limits 0% and 100% which are ...

This article compares the weaning of challenging patients from mechanical ventilation to an exercise training program experienced by many athletes. Physically, the importance of the correction and maintenance of chronic health issues, nutrition, and hydration are explored. Psychologically, the degree of preparedness by both the patient and the health care ...

The effects of high frequency oscillatory ventilation (HFOV) and conventional mechanical ventilation (CMV) on tracheal secretion were compared in 6 anesthetized dogs. Using a double-balloon endotracheal catheter, 5 ml of saline was instilled into an isolated tracheal segment during HFOV and CMV for 10 min respectively. Two eicosanoids, 15-hydroxyeicosatetraenoic acid ...

Effect of high frequency jet ventilation (HJFV) on tracheobronchial tone was examined in anesthetized dogs. Changes in intraluminal pressure of water-filled endotracheal cuff (Pcuff) were used as an indicator of tracheal smooth muscle tone. Animals were initially ventilated with conventional mechanical ventilation (CMV) to maintain normal Pa(CO)(2). HFJV (2.0 Hz.) ...

The effects of body position and respiratory frequency (f) on regional gas transport during eucapnic conventional ventilation (CV) and high-frequency ventilation (HFV) were assessed from the washout of nitrogen 13 (13NN) using positron-emission tomography. In one protocol, six dogs were ventilated with CV or HFV at f = 6 Hz ...

Several previous studies have shown worsening ventilation-perfusion (VA/Q) relationships in humans during heavy exercise at sea level. However, the mechanism of this deterioration remains unclear because of the correlation with ventilatory and circulatory variables. Our hypothesis was that the decrease in the series dead space-to-tidal volume ratio during exercise might ...

To determine whether the intensity of dyspnea at a given level of respiratory motor output depends on the nature of the stimulus to ventilation, we compared the sensation of difficulty in breathing during progressive hypercapnia (HC) induced by rebreathing, during incremental exercise (E) on a cycle ergometer, and during isocapnic ...

The purpose of the present study was to compare the relative roles of PaCO2 and pulmonary mechanoreceptors in the generation of apnea during high frequency ventilation (HFV) and conventional mechanical ventilation (CMV) in the anesthetized cat. Our hypothesis was that PaCO2 primarily determines the appearance of apnea, while mechanoreceptor input ...

An experimental study to elucidate the physiological changes that occur in respiration during near drowning in the Dead Sea was performed in an experimental model. Findings showed that clinical signs of respiratory failure were due to aspiration rather than ingestion of Dead Sea water and occurred within 10 min of ...

To improve ventilation monitoring during direct laryngoscopy, we have developed a high frequency jet ventilator which allows the aspiration of tracheal gas for carbon dioxide analysis (PtCO2) through the injector after stopping the ventilator. In 41 patients undergoing direct laryngoscopy, PaCO2 and PtCO2 were measured simultaneously during high frequency jet ...

During the course of a critical illness, many patients become ventilator dependent. The standard assessment criteria are not always accurate in predicting potential for extubation. This investigation was designed to analyze whether the work of breathing (WOB) was a more reliable predictor of ventilator dependence. Twenty consecutive ventilator-dependent patients were ...

The relationship between sodium handling and alveolar-arterial oxygen gradient (AaDO2) was studied in 26 preterm babies requiring ventilation from birth. The difference between sodium intake and urinary sodium excretion was determined in sequential, four hourly periods throughout the course of the respiratory illness. Sodium retention changed from positive (mean 1.42 ...

Surfactant protein-A (SP-A) was measured in bronchoalveolar lavage (BAL) samples from ventilated neonates in order to study the concentration of SP-A with regard to: 1) high-frequency oscillatory ventilation (HFOV) vs. conventional mechanical ventilation (CMV); 2) the postnatal course and ontogeny of SP-A; and 3) the correlation with measurements of pulmonary ...

Although impaired respiratory muscle performance that persists up to 5 min after exercise is stopped has been demonstrated during exhaustive exercise in normal young men, it is not known whether impaired respiratory muscle function follows endurance exercise to exhaustion in highly trained athletes. To study the effects of exercise on ...

Using the multiple inert gas elimination technique, we studied ventilation-perfusion (VA/Q) relationships in eight patients with chronic obstructive pulmonary disease (COPD) during mechanical ventilation (MV) and again during weaning (spontaneous ventilation [SV] through an endotracheal tube) from MV needed for acute respiratory failure. The patients, seven men and one woman ...

Patients with asthma frequently show a bimodal distribution of ventilation-perfusion (VA/Q) ratios. One mode is centered on a VA/Q ratio of near normal value, whereas the other has a very low VA/Q ratio. There is usually almost no perfusion of unventilated units. We have suggested that this bimodal pattern is ...

Eight malnourished patients with emphysema (EMPH) and eight malnourished patients without evidence of lung disease (MLAN) received an infusion of 5% dextrose plus electrolytes (D5W) for 48 h and were then randomly assigned to a hypercaloric diet with either 53% of the calories as carbohydrate (CB) or with 55% as ...

T'ai Chi Chuan (TCC) is a widely practiced Chinese martial art said to physically develop balance and coordination as well as enhance emotional and mental health. TCC consists of a series of postures combined into a sequential movement providing a smooth, continuous, low-intensity activity. The purpose of this study was ...

Ventilation and respiratory timing during rest and exercise were measured in normal volunteers by pneumotachograph and by respiratory inductive plethysmography (RIP) to determine if RIP is accurate and to determine if the usual methods of ventilation measurement during respirator research lead to artifacts. Data were collected with a mouthpiece, a ...

Some "old" chest physiotherapy techniques, such as postural drainage of bronchial secretions, breathing control, relaxation, pre- and post-surgical treatments and exercise training have survived until today because of their unquestionable and persistent validity. This does not mean that in this field of rehabilitation medicine nothing new exists. Chest physiotherapy has ...

The efficacy of constant-flow ventilation (CFV) was investigated in eight mongrel dogs before (control-phase) and after development of papain-induced panlobular emphysema (PLE-phase). For CFV, heated, humidified and oxygen-enriched air was continuously delivered via two catheters positioned within each mainstem bronchus at flow rates (V) of 0.33, 0.5 and 0.66 l/s. ...

Arterial plasma potassium concentration ([ K+]a) is increased during exercise. This change is sufficient to excite arterial chemoreceptors and stimulate ventilation (VE) in the anaesthetized cat. Moreover, changes in [K+]a and VE are highly correlated during exercise, however the contribution that [K+]a makes to the control of breathing in man ...

We examined mitochondrial oxidative function 5 minutes and 2 hours after a gradual asphyxial insult in newborn lambs. We subjected 16 ventilated newborn lambs to 75-90 minutes of hypoxia and hypercarbia that resulted in bradycardia and systemic hypotension over the final 15 minutes of the insult. At the end of ...

Suppression of ventilation by tasks such as talking may produce breathlessness in normal individuals under conditions when a strong respiratory drive exists, e.g., during exercise, and in patients with severe lung disease. To investigate the nature of breathlessness produced by a dissociation between ventilation and chemical drive, we studied ten ...

To assess the effect of the normal respiratory resistive load on ventilation (VE) and respiratory motor output during exercise, we studied the effect of flow-proportional pressure assist (PA) (2.2 cmH2O.l-1.s) on various ventilatory parameters during progressive exercise to maximum in six healthy young men. We also measured dynamic lung compliance ...

With positron emission tomography, quantitative measurements of regional alveolar and mixed venous concentrations of positron-emitting radioisotopes can be made within a transaxial section through the thorax. This allows the calculation of regional ventilation-to-perfusion (V/Q) ratios by use of established tracer dilution theory and the constant intravenous infusion of 13N. This ...

Ethane quantitated in the expired alveolar gas is a noninvasive measure of free radical activity. This method has been criticized for lack of control of minute ventilation (VE) in spontaneously breathing animals, although ethane, which is poorly soluble in tissues, should not be affected by changes in VE. We measured ...

The ratio of alveolar ventilations of He and SF6 (VA,He/VA,SF6) was determined in 7 healthy male subjects at rest and at three different levels of exercise on a bicycle ergometer (75, 150 and 225 W). This ratio was calculated from the ratio of the specific ventilations for these gases which ...

We used inspiratory resistive training (IRT) in an effort to improve the respiratory muscle endurance of 27 patients with respiratory failure who had failed repeated weaning attempts using standard techniques. Seven patients had primary neuromuscular diseases; the other 20 had primary lung diseases. All patients had stable respiratory failure, without ...

We examined the contribution of the neural elements near the ventral medullary surface (VMS) to the respiratory response caused by 2,4-dinitrophenol (DNP). Two series of experiments were performed on 12 vagotomized and sinoaortic denervated cats. The first series examined the effect of focal cooling of the VMS on the respiratory ...

The purpose of this study was to determine the role of lactic acidosis in the ventilatory response to heavy exercise above anaerobic threshold. Seven subjects ingested either NaHCO3 or CaCO3 at a dose of 300 mg/kg body weight and ran on a motor-driven treadmill at a work load corresponding to ...

This study evaluates the direct effect of acetate upon ventilation during acetate-haemodialysis. Eight patients with end-stage renal failure who were receiving chronic haemodialysis treatment underwent acetate infusion for 1 h on a day outside a haemodialysis session. Ventilation was continuously measured using respiratory inductance plethysmography, starting 20 min before the ...

We hypothesized that during high-frequency oscillatory ventilation (HFOV) of a central bronchopleural fistula (BPF), gas flow through the fistula (Vleak) should vary with ventilatory frequency. In six pentobarbital-anesthetized, open-chested dogs, we inserted a cannula into the left lower lobe bronchus. After 30 min of HFOV at 5 Hz (fistula closed), ...

The purpose of this study was to examine the effects of duration and the concomitant ventilatory drift of heavy exercise on the changes in ventilation following the cessation of exercise. Seven male subjects ran on a motor-driven treadmill at a constant work-rate of 90% of VO2max for either 5 min ...

The frequency-domain analysis of respiration is used to put in evidence the respiratory reflexes, mainly the acoustical respiratory reflex. Based on the envelope of the spectrum, numerical parameters of the respiration are introduced and applied to determine respiratory patterns. The use of respirograms is also suggested.

The purpose of this study was to determine the effect of altered metabolic acid-base status on the changes in ventilation in the transition from heavy exercise above anaerobic threshold to rest. Seven subjects ingested, in a randomized and blind manner, either NaHCO3 or CaCO3 (placebo) at a dose of 300 ...

The effect of pleural effusion on lung function and gas exchange has not been adequately defined. We used the multiple "inert" gas technique to study gas exchange and ventilation-perfusion relationships in both the left and the right lateral decubitus positions in a patient with a moderate unilateral (left) pleural effusion. ...

Continuous monitoring of important respiratory indices has the potential for predicting catastrophes and providing an opportunity for the timely institution of lifesaving measures. Arterial oxygenation can be monitored noninvasively using oximetry or transcutaneous oxygen electrodes, while mixed venous oxygenation can be recorded continuously with modified pulmonary artery catheters. A satisfactory ...

We studied six patients with isolated bilateral paralysis or severe weakness of the diaphragm, present for 2 to 60 months (mean = 25), to document the clinical and respiratory sequelae of the condition. Severe diaphragm dysfunction was confirmed by the demonstration of the very low maximal transdiaphragmatic pressure (Pdi) generated ...

The infusion of the hypertonic 7.5% NaCl solution stimulates the afferent vagal innervation of the lungs. In order to verify if this reflex elicits any respiratory mechanical alterations, normovolemic (n = 18) and hypovolemic (n = 18) (20 ml of shed blood/kg) guinea pigs were studied. The animals were assigned ...

The authors recently developed an ambulatory system, in which a self-contained respiratory inductive plethysmograph (RIP) was used, to measure noninvasively the volume and time components of breathing. Since it does not use nasal or oral devices, such a system is particularly suitable for use in studying the effects of respiratory ...

Weaning patients with chronic obstructive pulmonary disease from mechanical ventilators is occasionally a long and difficult process complicated by the patient's fear of losing his or her breath during the weaning procedure. A case is presented of an anxious 58-year-old man who was taught to relax using biofeedback and progressive ...

We tested the hypothesis that postnatal resetting of the carotid chemoreceptors is initiated by, and is dependent on, the rise in arterial PO2 (PaO2) which normally occurs after birth as air breathing is established. Previous studies had indicated that this resetting takes at least 24 h. We applied a technique ...

Four patients were evaluated for persistent dyspnea eight months to four years after inferior vena caval interruption for treatment of pulmonary emboli. Maximal exercise testing with gas-exchange analysis was performed. All patients attained less than 64 percent of predicted maximal oxygen uptake. Peak exercise heart rates were 85 percent or ...

The use of high frequency jet ventilation compared to conventional mechanical ventilation during general anesthesia for extracorporeal shock wave lithotripsy of renal or ureteral calculi can reduce stone movement. This decrease in stone movement theoretically lessens the total shock and energy requirements for stone fragmentation and perirenal tissue damage. To ...