American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Dec 1996
Randomized Controlled Trial Clinical TrialCisapride improves gastric emptying in mechanically ventilated, critically ill patients. A randomized, double-blind trial.
We conducted a randomized, double-blind, placebo-controlled trial in mechanically ventilated intensive care unit (ICU) patients to evaluate the effect of cisapride on gastric emptying using an acetaminophen absorption model. We enrolled 72 patients expected to remain in the ICU for more than 48 h; 39% were female; the average age was 54.0 +/- 19.1 yr; 47% were postoperative, 83% were receiving narcotics, and the mean simplified acute physiology score (SAPS) was 9.5 +/- 3.0. Within 72 h of admission to ICU, 1.6 g of acetaminophen suspension was administered via a nasogastric tube into the stomach (Day 1). ⋯ The difference in area under the time-acetaminophen concentration curve was also greater in the patients receiving cisapride (5,534 versus 2,832, p = 0.09). We conclude that cisapride enhances gastric emptying in critically ill patients. Studies to examine the effect of cisapride on tolerance to enteral nutrition, infectious morbidity, and other clinically important outcomes are warranted.
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Am. J. Respir. Crit. Care Med. · Dec 1996
Randomized Controlled Trial Clinical TrialAntioxidant kinetics in lung lavage fluid following exposure of humans to nitrogen dioxide.
To determine if nitrogen dioxide (NO2), a gaseous free radical, modifies the protective antioxidant pool present in respiratory tract lining fluids, a random, double-blind study utilizing flexible fiberoptic bronchoscopy with bronchial and bronchoalveolar lavage was performed. Healthy, nonsmoking, asymptomatic subjects were exposed to filtered air and 2 ppm NO2 for 4 h on separate occasions. To examine the kinetics of the NO2-induced antioxidant reactions, 44 subjects were randomly assigned to one of three groups. ⋯ In marked contrast, significant increases in GSH concentration were seen at 1.5 and 6 h in bronchial lavage fluid after exposure to NO2, which subsequently returned to control levels by 24 h. No change in bronchoalveolar lavage fluid GSH concentration or malondialdehyde content was seen after NO2 exposure. These data support the view that antioxidants present in lung fluids react with, and hence modulate the impact of, NO2 on the lung.
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Am. J. Respir. Crit. Care Med. · Dec 1996
Influence of gender and endotracheal tube size on preextubation breathing pattern.
An imbalance between work of breathing and respiratory muscle capacity often results in rapid, shallow breathing (increased respiratory rate/tidal volume [f/VT]). Because this imbalance commonly causes unsuccessful weaning from mechanical ventilation, it is not surprising that an elevated f/VT accurately predicts weaning failure. However, while studying extubation outcome, we observed that women and patients with narrow endotracheal tubes are often successfully extubated with an elevated f/VT. ⋯ Although the overall incidence of extubation failure was similar (11/82 [women] versus 23/136 [men], p = NS), among patients with f/VT > or = 100, men were more likely to require reintubation (3/19 [women] versus 5/10 [men], p = 0.08). We conclude that women, especially when breathing through small endotracheal tubes, have a higher f/VT (including likelihood of f/VT > or = 100) than men, independent of extubation outcome. Consideration of factors that elevate the f/VT, unrelated to physiologic work of breathing and respiratory muscle capacity, should improve application of this index to extubation decision making.
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Am. J. Respir. Crit. Care Med. · Dec 1996
Role of chemosensitivity in intrathoracic pressure changes during obstructive sleep apnea.
We tested the hypothesis that the awake ventilatory response to hypoxia and hypercapnia may contribute to the variability of respiratory effort developed in response to upper airway obstruction in obstructive sleep apnea syndrome. The polygraphic recordings of 38 patients diagnosed as having obstructive sleep apnea on the basis of an apnea+hypopnea index greater than 10 were examined. All subjects received hypoxic and hypercapnic ventilatory tests the day before the nocturnal polysomnography. ⋯ No correlation was found between the indices of respiratory effort and body mass index, age, pulmonary function tests, awake blood gases, apnea duration, and apnea desaturation. In rapid eye movement sleep, none of the considered variables predicted the degree of respiratory effort. In conclusion, our results suggest that the degree of ventilatory response to upper airway occlusion in obstructive sleep apnea may be influenced by the sensitivity of central neural drive to chemical stimuli.
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Am. J. Respir. Crit. Care Med. · Nov 1996
Randomized Controlled Trial Comparative Study Clinical TrialPartitioning of inspiratory muscle workload and pressure assistance in ventilator-dependent COPD patients.
To investigate the mechanisms underlying ventilator-dependence in patients with chronic obstructive pulmonary disease (COPD), and to assess the effects of the combination of positive end-expiratory pressure (PEEP) and pressure-support ventilation (PSV) on inspiratory muscle effort, we investigated respiratory mechanics in eight ventilator-dependent COPD patients. The patients' breathing pattern, lung mechanics, diaphragmatic effort (PTPdi), diaphragmatic tension-time index (TTdi), and arterial blood gases were measured during both spontaneous breathing (SB) and ventilatory assistance consisting of PSV alone (15, 20, and 25 cm H2O) and PSV combined with a PEEP of 5 cm H2O (reducing PSV to 10, 15, and 20 cm H2O, respectively, to maintain equivalent inspiratory pressure). The different levels of ventilatory support were delivered in a randomized sequence. ⋯ Application of PEEP during PSV improved ventilatory assistance by further reducing the inspiratory effort (by 17% on average) and by ameliorating patient-ventilator interaction. We conclude that the excessive mechanical load, and in particular the high PEEPi, is the major determinant of ventilator-dependence in COPD patients. Application of PEEP improves the efficiency of PSV in unloading these patients' inspiratory muscles, and can sometimes improve patient-ventilator interaction.