American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Jan 1994
Comparative StudyIntratracheal interferon-gamma augments pulmonary defenses in experimental legionellosis.
To study the effects of recombinant interferon-gamma (IFN-gamma) on pulmonary defenses in vivo, we measured Ia antigen expression by alveolar macrophages and whole-lung clearance of inhaled Legionella pneumophila in normal and corticosteroid-treated rats. We found that Ia antigen was expressed by 7, 29, 50, and 65% of alveolar macrophages harvested from normal rats 24 h after intratracheal administration of 0, 10(3), 10(4), or 10(5) U of IFN-gamma, respectively, and by 76% of alveolar macrophages harvested from corticosteroid-treated rats given 10(5) U of IFN-gamma. ⋯ Intraperitoneally administered IFN-gamma had no effect on Ia expression by alveolar macrophages or on bacterial clearance. IFN-gamma may be useful in the treatment of intracellular infections when targeted to the site of infection in immunosuppressed hosts.
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Am. J. Respir. Crit. Care Med. · Jan 1994
Comparative StudyAcoustic method to estimate the longitudinal area profile of endotracheal tubes.
A problem in mechanical ventilation is the accumulation of mucus secretions in the endotracheal tube (ETT), which tends to reduce the patent cross-sectional area. Here we characterized the extent and locus of the ETT obstruction using an acoustic reflection method recently modified to be applied at bedside. Experiments were conducted both in vivo in 10 intubated patients and in vitro in ETT with or without known constrictions of 1 to 3 mm over 5 cm, located at various distances from the ETT entry: 5, 10, 15, and 20 cm. ⋯ Statistical analysis of the differences between acoustic reflection data and hydraulic data showed that the two methods did not differ significantly. In vitro acoustic results obtained in constricted ETT showed a highly significant correlation with the actual area (r = 0.97, p = 0.0001). Thus, reductions in ETT area may be detected, quantified, and located by the present acoustic reflection method, which therefore provides a means to avoid emergency extubation because of ETT obstruction.
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Am. J. Respir. Crit. Care Med. · Jan 1994
Comparative StudyVolume-pressure curve of the respiratory system predicts effects of PEEP in ARDS: "occlusion" versus "constant flow" technique.
The effects of positive end-expiratory pressure (PEEP) on static ("rapid airway occlusion" technique) and dynamic ("constant flow" technique) volume-pressure (V-P) curves were studied in 19 patients with adult respiratory distress syndrome (ARDS). To describe the shape of both curves, the nonlinear coefficient of a second-order polynomial equation fitted to the static (static nonlinear coefficient) and dynamic (dynamic nonlinear coefficient) V-P curves on zero end-expiratory pressure (ZEEP) was used. Two distinct patterns were observed: (1) in ten patients, the static and dynamic V-P curves on ZEEP exhibited a convex shape with a progressive decrease in slope with increasing inflation volume (nonlinear coefficients: negative). ⋯ A correlation (p < 0.0001) between static and dynamic nonlinear coefficients was found at all levels of PEEP. Both static and dynamic nonlinear coefficients on ZEEP were correlated (p < 0.0001) with the amount of lung volume recruited with PEEP, and the variations of cardiac index (CI), O2 delivery (DO2), right-to-left venous admixture (Qs/Qt), and PaO2 with PEEP. Besides, the effects of PEEP on Cl, DO2, Qs/Qt, and PaO2 were less pronounced (p < 0.001) in patients with convex V-P curves than in patients with concave V-P curves.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Jan 1994
Aerosol deposition in mechanically ventilated patients. Optimizing nebulizer delivery.
Previous studies have suggested that nebulizers are inefficient in delivering aerosolized medication to the lung in patients supported by mechanical ventilation. In a recent bench study, we characterized factors that may affect aerosol delivery, i.e., nebulizer type, ventilator settings (duty cycle), volume fill, and humidification as well as technical factors affecting measurement of deposition (e.g., radiolabeled compounds). Utilizing the predictions from our bench data, the present study was designed to assess nebulized aerosol delivery to ventilated patients under optimal conditions. ⋯ Measured radioactivity at each site was expressed as a percentage of nebulizer charge (i.e., the quantity of radioactivity originally placed in the nebulizer). On average, 30.6 +/- 6.3% (SD) of the charge was inhaled by the ventilated patients. Mean deposition in the TT during inspiration was 2.6 +/- 0.5%.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Jan 1994
Vertical gradient of regional lung inflation in adult respiratory distress syndrome.
We obtained chest computed tomography (CT) sections in 12 normal subjects (controls) and 17 patients with the adult respiratory distress syndrome (ARDS) to investigate regional lung inflation. A basal CT section (just above the diaphragm) was obtained in the supine position at zero cm H2O end-expiratory pressure. In each CT section the distance from ventral to dorsal surface (hT) was divided into 10 equal intervals, and 10 lung levels from ventral (no. 1) to dorsal (no. 10) were defined. ⋯ The tissue volume, however, was 16.7 +/- 0.8 ml x m-2 in control subjects and 31.6 +/- 1.7 ml x m-2 in patients with ARDS (p < 0.01). The g/t ratio in level 1 averaged 4.7 +/- 0.5 in control subjects and 1.2 +/- 0.2 in patients with ARDS (p < 0.01), and this ratio decreased exponentially from level 1 to level 10, both in controls and patients with ARDS. The Kd constant of the exponential decrease was 13.9 +/- 1.3 cm in control subjects and 7.8 +/- 0.8 cm in patients with ARDS (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)