American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Mar 1995
Comparative StudyDistribution of regional density and vascular permeability in the adult respiratory distress syndrome.
Although recent X-ray computed tomography (CT) data show that ventral-dorsal gradients in density are common in the adult respiratory distress syndrome (ARDS), we hypothesized that the ventral-dorsal gradient of pulmonary vascular permeability would be evenly distributed in patients with ARDS. We tested this hypothesis by analyzing previously reported data (Am Rev Respir Dis 1991; 143:150-154) obtained by the nuclear medicine imaging technique of positron emission tomography (PET). Measurements of regional lung density (LD), extravascular density (EVD), and the pulmonary transcapillary escape rate (PTCER; an index of vascular permeability) were obtained in eight patients with ARDS and in 10 normal subjects. ⋯ A significantly negative slope of PTCER versus bin was detected in five cases and a positive slope in 3, so that the group value was not significant. These data confirm that ventral-dorsal gradients in LD and EVD exist in patients with ARDS. In contrast, no consistent ventral-dorsal distribution of increased pulmonary vascular permeability is present.
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Am. J. Respir. Crit. Care Med. · Mar 1995
Comparative StudyCardiorespiratory effects of volume- and pressure-controlled ventilation at various I/E ratios in an acute lung injury model.
Numerous approaches to the provision of mechanical ventilation during acute lung injury are currently available. Of these, pressure control inverse ratio ventilation has been considered superior to volume control ventilation with PEEP with respect to improving gas exchange and minimizing cardiovascular compromise. However, no study systematically compares volume-controlled (VC) and pressure-controlled (PC) ventilation while maintaining mean airway pressure (MAP) constant at varying I/E ratios. ⋯ MAP was kept constant throughout the study at 25 +/- 2 cm H2O while ventilating all animals with a VT of 10 ml/kg and a rate of 20/min by randomized application of VC and PC with I/E ratios of 1:2, 2:1, and 4:1. Despite liberal fluid administration, all ventilatory modes depressed cardiac output compared with preinjury values. However, gas exchange and hemodynamics did not differ among ventilation modes or I/E ratios.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Mar 1995
Effect of synchronized, systolic, lower body, positive pressure on hemodynamics in human septic shock. A pilot study.
The pathophysiologic disturbance observed in volume-resuscitated patients with septic shock is primarily that of hyperdynamic circulation with a markedly reduced systemic vascular resistance. We hypothesized that external, mechanically applied, phasic lower body positive pressure could increase systemic vascular resistance and, thus, blood pressure in patients with refractory septic shock. A total of nine studies were performed on seven patients with septic shock refractory to volume resuscitation and vasopressors. ⋯ Heart rate, central venous pressure, pulmonary capillary wedge pressure, arterial pH, arterial pO2, and mixed venous pO2 were unchanged. Synchronized external systolic compression of the lower extremities increased mean arterial pressure and cardiac output in seven patients with refractory septic shock. This hemodynamic improvement was independent of changes in calculated systemic vascular resistance.
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Am. J. Respir. Crit. Care Med. · Mar 1995
Lower airways inflammation during rhinovirus colds in normal and in asthmatic subjects.
Human rhinoviruses (HRV) cause the majority of common colds and are etiologically linked with changes in lower airways physiology and asthma exacerbations. We hypothesized that changes in bronchial mucosal inflammatory cell populations may be responsible for HRV-induced changes in airway reactivity. We examined bronchial mucosal biopsies during experimental infections with HRV serotype 16 and measured changes in histamine reactivity. ⋯ There was an increase in epithelial eosinophils with the cold (p = 0.042), and in asthmatics this appeared to persist into convalescence. A peripheral blood lymphopenia correlated with increased responsiveness (r = 0.062, p = 0.014). Rhinoviral colds are associated with a bronchial mucosal lymphocytic and eosinophilic infiltrate that may be related to changes in airway responsiveness and asthma exacerbations.
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Am. J. Respir. Crit. Care Med. · Mar 1995
Tissue factor pathway inhibitor and von Willebrand factor antigen levels in adult respiratory distress syndrome and in a primate model of sepsis.
Tissue factor pathway inhibitor (TFPI) is an anticoagulant protein primarily synthesized by the endothelium. A major fraction (approximately 85%) of TFPI remains associated with the endothelium, whereas a small fraction (approximately 15%) is secreted into the blood. In our attempts to search for a marker(s) of endothelial injury in the setting of adult respiratory distress syndrome (ARDS), we retrospectively measured plasma TFPI levels in patients at risk for and with ARDS caused by several etiologic factors. ⋯ The vWF-Ag levels were elevated approximately 5-fold after infusion of LD100 concentrations of E. coli at 6 h and 4-fold after infusion of sublethal concentrations of E. coli at 24 h. Autopsies on animals in the LD100 group revealed pulmonary congestion, leukocyte infiltration, edema, and hemorrhage, all suggestive of acute lung injury. Thus, in the setting of acute lung injury plasma vWF-Ag appears to be considerably increased prior to significant damage to the endothelium, whereas increased plasma TFPI occurs only after severe injury.(ABSTRACT TRUNCATED AT 400 WORDS)