The American review of respiratory disease
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Am. Rev. Respir. Dis. · Mar 1989
The effects of positive expiratory pressure on isovolume flow and dynamic hyperinflation in patients receiving mechanical ventilation.
The use of continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) has been advocated by some to assist in the weaning process of patients receiving mechanical ventilation for respiratory failure. The efficacy of this technique and its effect on respiratory system mechanics are not well understood. The theoretical advantage of CPAP or PEEP during the weaning process can be obliterated if excessive dynamic hyperinflation is induced. ⋯ All patients demonstrated dynamic hyperinflation during controlled ventilation as evident by the existence of intrinsic PEEP. The nominal value of applied PEEP that caused a reduction in isovolume expiratory flow was unrelated to the initial level of intrinsic PEEP. The clinical implications of these findings with respect to CPAP therapy during weaning from mechanical ventilation are discussed.
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Am. Rev. Respir. Dis. · Feb 1989
Comparative StudyInspiratory pressure support prevents diaphragmatic fatigue during weaning from mechanical ventilation.
Persistent inability to tolerate discontinuation from mechanical ventilation is frequently encountered in patients recovering from acute respiratory failure. We studied the ability of inspiratory pressure support, a new mode of ventilatory assistance, to promote a nonfatiguing respiratory muscle activity in eight patients unsuccessful at weaning from mechanical ventilation. During spontaneous breathing, seven of the eight patients demonstrated electromyographic signs of incipient diaphragmatic fatigue. ⋯ Above this level, diaphragmatic activity was further reduced and untoward effects such as hyperinflation and apnea occurred. When electrical diaphragmatic fatigue occurred, the activity of the sternocleidomastoid muscle was markedly increased, whereas it was minimal when the optimal level was reached. We conclude that in patients demonstrating difficulties in weaning from the ventilator: (1) pressure support ventilation can assist spontaneous breathing and avoid diaphragmatic fatigue (pressure support allows adjustment of the work of each breath to provide an optimal muscle load); (2) clinical monitoring of sternocleidomastoid muscle activity allows the required level of pressure support to be determined to prevent fatigue.
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Am. Rev. Respir. Dis. · Jan 1989
Randomized Controlled Trial Clinical TrialCan mild bronchospasm reduce gastroesophageal reflux?
During attacks of asthma, changes in the transdiaphragmatic pressure gradient may impair the antireflux barrier and provoke gastroesophageal reflux (GER). If GER triggers asthma and asthma causes GER, a vicious circle could arise with an increase in the severity of asthma symptoms. The aim of this investigation was to determine whether postprandial reflux in asthmatics with GER disease is increased during histamine-induced bronchospasm and also if theophylline increases GER during provoked episodes of bronchospasm. ⋯ GER was not more pronounced during the provoked bronchospasm period irrespective of theophylline treatment or not. It seems unlikely that mild bronchospasm provokes reflux in patients with asthma and GER. It would appear that mild bronchospasm is rather protective against gastroesophageal reflux.
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Am. Rev. Respir. Dis. · Jan 1989
Long-term follow-up of symptoms, pulmonary function, respiratory muscle strength, and exercise performance after botulism.
Respiratory muscle weakness occurs commonly at presentation in patients with botulism. Although clinical improvement occurs over several months, symptoms such as fatigue and dyspnea persist in many patients in the long term. To determine whether continued respiratory muscle weakness might contribute to these symptoms, we compared lung function tests, respiratory muscle strength, and exercise performance in 13 patients 2 years after type B botulism. ⋯ During exercise, botulism patients had a more rapid and shallow breathing pattern and a higher dyspnea score at a given minute ventilation in comparison to control subjects. Reasons for premature exercise termination in botulism patients were multifactorial. Although respiratory muscle weakness may have been contributory in some patients, most appeared to be limited by reduced cardiovascular fitness, leg fatigue, or reduced motivation.
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Am. Rev. Respir. Dis. · Jan 1989
Case ReportsDyspnea on immersion: mechanisms in patients with bilateral diaphragm paralysis.
Patients with bilateral diaphragm paralysis are able to inflate their lungs by two mechanisms: relaxing the abdominal wall or expanding the rib cage. Each maneuver promotes lung expansion by shifting support of the abdominal contents from the abdominal wall to the diaphragm. We describe a patient with bilateral diaphragm paralysis who experienced acute dyspnea when immersed in water to the level of the abdomen and discuss the precipitation of dyspnea in the context of the strategies available to these patients for lung inflation.