American journal of respiratory and critical care medicine
-
Am. J. Respir. Crit. Care Med. · May 1994
Should inverse ratio ventilation be used in adult respiratory distress syndrome?
IRV-induced increases in MAP are clearly associated with shunt reduction, but we find no studies that show shunt reduction without increased end-expiratory alveolar pressure. On the other hand, various studies in humans with ARDS and hyaline membrane disease and animal models of acute lung injury indicate that shunt reduction does not occur with IRV if there is no increase in end-expiratory alveolar pressure (21), that shunt reduction is the same with IRV as with conventional ventilation with PEEP when there are comparable levels of end-expiratory volume or alveolar pressure (16, 32), and that shunt reduction is greater when MAP is raised with PEEP than with IRV (27). Improved ventilation-perfusion matching with IRV is theoretically unlikely and, given the high FIO2 used in ARDS, improvements in oxygenation from more even ventilation would not be great. ⋯ However, these potentially salutary effects of IRV are unproven. On the other hand, there are potential deleterious effects of IRV, including increased risk of volotrauma and the requirements for heavy sedation and neuromuscular blockage. IRV remains of unproven value in the management of ARDS.
-
Am. J. Respir. Crit. Care Med. · May 1994
Tidal ventilation at low airway pressures can augment lung injury.
Intermittent positive pressure ventilation with large tidal volumes and high peak airway pressures can result in pulmonary barotrauma. In the present study, we examined the hypothesis that ventilation at very low lung volumes can also worsen lung injury by repeated opening and closing of airway and alveolar duct units as ventilation occurs from below to above the infection point (Pinf) as determined from the inspiratory pressure-volume curve. We ventilated isolated, nonperfused, lavaged rat lungs with physiologic tidal volumes (5 to 6 ml/kg) at different end-expiratory pressures (above and below Pinf) and studied the effect on compliance and lung injury. ⋯ The group ventilated without PEEP had significantly greater respiratory and membranous injury to bronchioles, while the group ventilated with PEEP of 4 cm H2O had significantly greater alveolar duct injury. In conclusion, ventilation at lung volumes below those found at Pinf caused a significant decrease in lung compliance and progression of lung injury. Therefore, in addition to high airway pressures, end-expiratory lung volume is an important determinant of the degree and site of lung injury during positive-pressure ventilation.
-
Am. J. Respir. Crit. Care Med. · Mar 1994
ReviewThe American-European Consensus Conference on ARDS. Definitions, mechanisms, relevant outcomes, and clinical trial coordination.
The acute respiratory distress syndrome (ARDS), a process of nonhydrostatic pulmonary edema and hypoxemia associated with a variety of etiologies, carries a high morbidity, mortality (10 to 90%), and financial cost. The reported annual incidence in the United States is 150,000 cases, but this figure has been challenged, and it may be different in Europe. ⋯ The American-European Consensus Committee on ARDS was formed to focus on these issues and on the pathophysiologic mechanisms of the process. It was felt that international coordination between North America and Europe in clinical studies of ARDS was becoming increasingly important in order to address the recent plethora of potential therapeutic agents for the prevention and treatment of ARDS.