American journal of respiratory and critical care medicine
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Previous studies of grain elevator workers have shown exposure-related increased rates for respiratory symptoms and reduced levels of lung function compared with those of other employed populations. However, some reports have suggested that this effect may be reversible after cessation of exposure. To investigate this, we conducted a respiratory health survey among 75 retired grain elevator workers and 37 retired civic workers. ⋯ Grain elevator retirees reported more dyspnea (44 versus 11%, p < 0.01) and had significantly lower levels for both FEV1 (78.6 versus 88.2% pred) and FVC (90.0 versus 97.7% pred) (both p < 0.05). Compared with civic retirees, grain retirees reported the same average level of breathlessness after the 6-min walk test, but they walked a significantly shorter distance (p < 0.01); they also scored higher on the impairment of activities scale and had a greater proportion of persons reporting impairment of daily activities caused by breathing trouble (p < 0.05). Comparison of the changes in lung function from 1975 to the present study (i.e., from active employment to retirement) showed that grain workers had consistently lower levels of lung function than did civic workers while still employed, with no reversibility after retirement.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Jul 1994
Evolution of bronchoalveolar cell populations in the adult respiratory distress syndrome.
To characterize the evolution of inflammation in the adult respiratory distress syndrome (ARDS) and test the hypothesis that sustained alveolar inflammation is associated with a poor outcome in patients with ARDS, we performed fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) in 125 patients and compared BAL cells and protein concentrations in survivors and nonsurvivors. ARDS followed sepsis syndrome in 35 patients, major trauma in 41, and other causes in 49. When possible, BAL was performed on Days 3, 7, and 14 after the onset of ARDS. ⋯ In patients with ARDS following trauma and other risks, however, BAL PMN measures did not distinguish survivors from patients who died. Analysis of serial data from the patients with more than one BAL showed that alveolar macrophages (AM) increased in survivors of ARDS, both in absolute numbers and as a percentage of total cells; this pattern was most pronounced in the sepsis patients. The cross-sectional data analysis suggests that sustained alveolar inflammation occurs frequently in patients with ARDS following sepsis and is associated with a high mortality.
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Am. J. Respir. Crit. Care Med. · Jul 1994
Comparative StudyEffects of dobutamine on oxygen consumption in septic patients. Direct versus indirect determinations.
Dobutamine has been proposed as a means of disclosing a pathologic oxygen supply (DO2) dependency in critically ill patients. Like other catecholamines, however, dobutamine might increase cellular metabolism, so that oxygen consumption (VO2) would increase regardless of the presence or absence of a supply dependency. This study investigated the effects of graded doses of dobutamine on VO2 in stable, septic patients. ⋯ All of the measured parameters were similar at baseline and after discontinuation of the dobutamine infusion. Dobutamine induced a dose-related increase in the cardiac index (from 3.84 +/- 0.97 to 6.19 +/- 1.56 L/min/m2, p < 0.01) and DO2 (from 501 +/- 123 to 801 +/- 219 ml/min/m2, p < 0.01). Both VO2DIR and VO2INDIR increased, from 161 +/- 37 to 183 +/- 40 ml/min/m2 and from 140 +/- 29 to 168 +/- 42 ml/min/m2, respectively (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Jul 1994
Ventilation-perfusion distributions during mechanical ventilation with superimposed spontaneous breathing in canine lung injury.
Biphasic positive airway pressure (BIPAP) allows unrestricted spontaneous breathing throughout mechanical ventilation. Effects of spontaneous breathing during BIPAP on pulmonary gas exchange were studied on a randomized basis in 12 dogs with oleic acid-induced lung injury using the multiple inert gas elimination technique. ⋯ Improved pulmonary gas exchange caused by better ventilation/perfusion (VA/Q) matching was indicated by a 17 +/- 3% decrease (p < 0.01) in blood flow to shunt units (VA/Q < 0.005), a 15 +/- 3% increase (p < 0.05) in perfusion of normal VA/Q units (0.1 < VA/Q < 10), and a 6 +/- 3% reduction in ventilation of dead space (VA/Q > 100) areas (p < 0.05). Spontaneous breaths superimposed on mechanical ventilation may convert shunt VA/Q units to normal by increased ventilation of poorly or nonventilated units and/or increase blood flow to previously minimal or nonperfused areas.
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Am. J. Respir. Crit. Care Med. · Jul 1994
Mechanism by which the prone position improves oxygenation in acute lung injury.
The mechanism by which oxygenation improves when patients with ARDS are turned from supine to prone position is not known. From results of our previous studies we reasoned that (1) when supine, in the setting of lung injury, transpulmonary pressure will be less than airway opening pressure and (2) atelectasis will develop preferentially in dorsal lung areas, and (3) both ventilation and ventilation/perfusion ratios would improve in these regions on turning prone. ⋯ After oleic acid, the prone position improved (1) oxygenation (mean +/- SD PaO2 = 140 +/- 112 versus 453 +/- 54 mm Hg), (2) median ventilation/perfusion ratios (0.77 versus 0.95), (3) ventilation/perfusion heterogeneity (coefficient of variation 86 +/- 15 versus 61 +/- 6), and (4) the gravitational ventilation/perfusion gradient (dependent to non-dependent slopes of 0.22 versus -0.02, all p < 0.05). The prone position generates a transpulmonary pressure sufficient to exceed airway opening pressure in dorsal lung regions, i.e., in regions where atelectasis, shunt, and ventilation/perfusion heterogeneity are most severe, without adversely affecting ventral lung regions.