The American review of respiratory disease
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Am. Rev. Respir. Dis. · Sep 1991
Effects of positive end-expiratory pressure, lung volume, and inspiratory flow on interrupter resistance in patients with adult respiratory distress syndrome.
Although it has been shown in normal subjects that airway resistance changes significantly with changes in lung volume and inspiratory flow, no studies have as yet examined these phenomena in patients with adult respiratory distress syndrome (ARDS). The effect of positive end-expiratory pressure (PEEP) on airway resistance in ARDS also is unknown. ⋯ This procedure was carried out at four levels of PEEP (0, 5, 10, and 15 cm H2O). We found that (1) at constant inflation volume, Rint,rs did not change significantly with increasing flow; (2) at constant inflation flow, Rint,rs showed an initial decrease followed by a distinct rise with increasing lung volume; (3) on average, PEEP did not significantly change Rint,rs measured during baseline ventilation; and (4) this latter finding occurred because patients behaved differently with application of PEEP, depending on their degree of lung inflation: Rint,rs measured close to full inflation almost invariably exhibited a rise, but values obtained at lower volumes exhibited the characteristic decrease of Rint,rs with increasing inflation volume.
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Am. Rev. Respir. Dis. · Sep 1991
Comparative StudyHuman neutrophil elastase and elastase/alpha 1-antiprotease complex in cystic fibrosis. Comparison with interstitial lung disease and evaluation of the effect of intravenously administered antibiotic therapy.
In cystic fibrosis (CF), extracellular lung matrix is progressively damaged, neutrophils invade the air spaces, and activated neutrophils may release large amounts of neutrophil elastase (NE). Although alpha 1-antiprotease (alpha 1-AP) binds and inactivates NE and is the major antielastase of the lower respiratory tract, antielastase defenses may be overwhelmed in CF, leading to progressive lung damage. To determine whether the ability of alpha 1-AP to neutralize NE is impaired in CF, we compared NE activity in bronchoalveolar lavage (BAL) fluid and human neutrophil elastase/alpha 1-antiprotease (NE/alpha 1-AP) complex in both BAL fluid and peripheral blood serum from patients with CF, normal volunteers, and patients with interstitial lung disease. ⋯ Although in interstitial lung disease there was a significant correlation between increased NE/alpha 1-AP complex in BAL or peripheral blood and the degree of neutrophil influx, NE/alpha 1-AP complex was disproportionately low in CF BAL compared with significantly elevated values in serum. These data suggest that in CF, alpha 1-AP-mediated defense against free NE in the lower respiratory tract is significantly impaired, and high levels of uncomplexed, enzymatically active, NE are present in CF respiratory secretions. To determine whether intravenously administered antipseudomonal antibiotic therapy for exacerbations of CF lung disease diminished the amount of free NE in respiratory secretions, we used BAL to investigate the effect of such therapy on neutrophils and NE in patients with CF colonized with pseudomonads.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Sep 1991
Effect of weight loss on upper airway collapsibility in obstructive sleep apnea.
Previous investigators have demonstrated in patients with obstructive sleep apnea that weight reduction results in a decrease in apnea severity. Although the mechanism for this decrease is not clear, we hypothesize that decreases in upper airway collapsibility account for decreases in apnea severity with weight loss. To determine whether weight loss causes decreases in collapsibility, we measured the upper airway critical pressure (Pcrit) before and after a 17.4 +/- 3.4% (mean +/- SD) reduction in body mass index in 13 patients with obstructive sleep apnea. ⋯ Moreover, decreases in Pcrit were associated with nearly complete elimination of apnea in each patient whose Pcrit fell below -4 cm H2O. In contrast, no significant change in DBR and a minimal reduction in Pcrit from 5.2 +/- 2.3 to 4.2 +/- 1.8 cm H2O (p = 0.031) was observed in the "usual care" group. We conclude that (1) weight loss is associated with decreases in upper airway collapsibility in obstructive sleep apnea, and that (2) the resolution of sleep apnea depends on the absolute level to which Pcrit falls.
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Am. Rev. Respir. Dis. · Aug 1991
Randomized Controlled Trial Comparative Study Clinical TrialAzathioprine combined with prednisone in the treatment of idiopathic pulmonary fibrosis: a prospective double-blind, randomized, placebo-controlled clinical trial.
Twenty-seven newly diagnosed patients with idiopathic pulmonary fibrosis (IPF) who were previously untreated for IPF were enrolled in a prospective, double-blind, randomized, placebo-controlled study to compare the therapeutic effect of combined prednisone/azathioprine (n = 14) with prednisone plus placebo (n = 13). Prednisone was started at 1.5 mg/kg/day (not to exceed 100 mg/day) for the first 2 wk followed by a biweekly taper to a maintenance dose of 20 mg/day. Azathioprine was administered at a daily dose of 3 mg/kg (not to exceed 200 mg/day). ⋯ A Cox model survival analysis shows a nonsignificant but potentially large survival advantage for azathioprine/prednisone (hazard ratio 0.48, with 95% confidence interval increasing from 0.17 to 1.38). When adjusted for age, the survival advantage of azathioprine/prednisone becomes marginally significant (hazard ratio 0.26, with 95% confidence interval increasing from 0.08 to 0.88; p = 0.02 by large sample approximation, p = 0.05 by randomization test). We conclude that combined prednisone and azathioprine is a safe and possibly effective regimen for the treatment of IPF.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Aug 1991
Randomized Controlled Trial Clinical TrialOral mucosal stimulation modulates intensity of breathlessness induced in normal subjects.
Patients with chronic obstructive pulmonary disease (COPD) often report an increase in breathlessness when they breathe through a mouthpiece. We hypothesized that stimulation of receptors in the oral mucosa modulates the sensation of breathlessness. We studied 10 normal naive volunteers in whom breathlessness was induced by having them breathe for 4 min with an inspiratory resistive load (18 cm H2O/L/s) while breathing was stimulated by CO2 inhalation (end-tidal PCO2 maintained at 55 mm Hg). ⋯ Six subjects repeated the protocol on 2 additional days: 1 day with inhalation of warm (34 degrees C), humidified air and 1 day after topical application of 4% lidocaine to the oral mucosa. Both these interventions abolished the differences in breathlessness between mask and mouthpiece and mask alone. We conclude that afferent information from oral mucosal stimulation influences the intensity of breathlessness.