The American review of respiratory disease
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Am. Rev. Respir. Dis. · Jan 1993
Diaphragmatic dysfunction in neuralgic amyotrophy: an electrophysiologic evaluation of 16 patients presenting with dyspnea.
We report 16 adult men (age, 41 to 75 yr) with neuralgic amyotrophy (NA) who presented with dyspnea due to involvement of the diaphragm. All patients developed breathlessness after a prodrome of acute severe neck and shoulder pain. Bilateral diaphragm paralysis (BDP) was confirmed in 12 patients and unilateral diaphragm paralysis (UDP) in four by the absence of electrical and mechanical responses to percutaneous phrenic nerve stimulation. ⋯ Follow-up muscle studies in five BDP and four UDP patients between 2 and 4 yr after initial referral showed complete recovery of diaphragmatic function in only two UDP patients, one of whom relapsed a year later. We postulate that NA may be an important but underrecognized cause of diaphragmatic paralysis in otherwise normal patients. Diaphragmatic strength returns very slowly, if at all.
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Am. Rev. Respir. Dis. · Dec 1992
Mucus hypersecretion in bronchiectasis. The role of neutrophil proteases.
To investigate the role of neutrophil proteases in the pathogenesis of mucus hypersecretion in bronchiectasis, we collected sputum samples from seven patients with bronchiectasis and measured their secretagogue activity by examining secretion of radiolabeled macromolecules by bovine airway submucosal gland cells incubated with sputum supernatants. There was marked secretagogue activity in bronchiectasis sputum, reaching a maximum of 1,963 +/- 292% (mean +/- SEM) above baseline at 1:15 dilution. ⋯ The combination of aprotinin, an inhibitor of cathepsin G, and ICI 200,355 caused significantly more reduction in the secretory response than ICI 200,355 alone (89.12 +/- 3.8 versus 72.53 +/- 5.89% reduction, p < 0.05). We conclude that bronchiectasis sputum causes a large secretory response from tracheal submucosal glands due mostly to neutrophil proteases.
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Breathlessness induced by hypercapnia may be related to the sensation of respiratory effort or to the central or peripheral effects of CO2. To examine the relationship among breathlessness, respiratory effort, and hypercapnia, we studied eight normal naive subjects. By using a visual feedback system, subjects maintained a constant ventilation of 50-60 L/min. ⋯ Hypercapnia was associated with a significant reduction in effort ratings (-7.3 +/- 6.4, mean +/- SD, p < 0.05) and a concomitant increase in dyspnea (+6.6 +/- 6.0, p < 0.05). We conclude that dyspnea associated with hypercapnia is dissociated from changes in respiratory effort, and that CO2 has a direct central effect that leads to breathlessness. Our data also suggest that the sense of effort at a given level of ventilation is less when the ventilation is the result of "reflex" stimuli to breathe rather than "voluntary" signals to the respiratory muscles.
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Am. Rev. Respir. Dis. · Nov 1992
Clinical TrialEffect of tidal volume on gas exchange and oxygen transport in the adult respiratory distress syndrome.
The effect of tidal volume (VT) on gas exchange and oxygen delivery (DO2) was studied in nine patients with adult respiratory distress syndrome (ARDS) and in 10 postoperative open-heart surgery patients (CABG). During controlled mechanical ventilation, VT was initially 10 to 12 ml/kg, followed by an increase and reduction of 25% (1.25 VT and 0.75 VT, respectively). In both groups of patients, dead space (VD) correlated strongly with VT (p < 0.001), while the VD/VT ratio was independent of VT. ⋯ Venous admixture (QS/QT) decreased with 1.25 VT and increased with 0.75 VT (p < 0.001). A relatively larger increase in cardiac output compensated for the increased QS/QT and the reduced SaO2, resulting in significantly higher DO2 with 0.75 VT (p < 0.01). A lower VT resulted in improved balance between pulmonary gas exchange and whole body oxygen supply.
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Am. Rev. Respir. Dis. · Oct 1992
Lung mechanics and gas exchange during pressure-control ventilation in dogs. Augmentation of CO2 elimination by an intratracheal catheter.
Increased awareness of pressure-related injury to the alveolar-capillary interface has renewed interest in modes of ventilation that limit alveolar distention such as pressure-controlled ventilation (PCV). We examined respiratory system mechanics and gas exchange during PCV in six dogs. Our data conformed to the predictions of our single-compartment mathematical model of respiratory dynamics during PCV (J Appl Physiol 1989; 67:1081-92). ⋯ We conclude that during PCV at a fixed Pset and Tl/Ttot increasing frequency caused VT to fall and VE to reach a plateau. Declining VT was associated with a rise in PaCO2 because of a subsequent fall in alveolar ventilation. Insufflating fresh gas by an intratracheal catheter increased alveolar ventilation and improved CO2 elimination by washing out the anatomic dead space.(ABSTRACT TRUNCATED AT 250 WORDS)