Articles: respiratory-distress-syndrome.
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The influence of prophylactic ventilator treatment was evaluated in a porcine model of early adult respiratory distress syndrome (ARDS) induced by endotoxaemia. Sixteen animals, controls, under continuous i.v. ketamine anaesthesia were either mechanically ventilated using intermittent positive pressure ventilation (IPPV; n = 6) with air or breathed air spontaneously (n = 10). Twenty animals under continuous i.v. ketamine anaesthesia and spontaneously breathing air were infused i.v. with E. coli endotoxin (10 micrograms X kg-1 X h-1) over 6 h. ⋯ Animals with IPPV also had an improved survival rate. The beneficial effects of mechanical ventilation on pulmonary gas exchange are not due to changes in extravascular lung water, but are caused by its influence in counteracting terminal airway and alveolar closure. These results indicate that mechanical ventilation, when instituted early in the course of human ARDS induced by septicaemia, might be of potential value in the prevention of severe pulmonary failure and death.
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Am. Rev. Respir. Dis. · Jan 1985
Distribution of ventilation and perfusion during positive end-expiratory pressure in the adult respiratory distress syndrome.
The response of respiratory gas exchange to incremental increases in positive end-expiratory pressure (PEEP) was studied in patients with the adult respiratory distress syndrome (ARDS). Fifty total changes in PEEP were studied in 19 PEEP trials performed in 16 patients. The initial patterns of ventilation-perfusion distribution as measured by the multiple inert gas elimination technique showed a large shunt flow (32 +/- 14% of total cardiac output), which was accompanied in half of the patients by perfusion to a region of low ventilation-perfusion ratio (VA/Q ratio less than 0.1). ⋯ In the increments where no increase was observed in PaO2, this reduction in blood flow to shunt or low VA/Q regions did not occur. In some instances, there was an increase in ventilation to unperfused alveoli and evidence of high ventilation-perfusion ratio (VA/Q greater than 10) as the level of PEEP increased. Because patients had an adequate pulmonary artery wedge pressure at the start of the PEEP trial (mean wedge pressure, 12.8 +/- 1.5 mmHg) improvements in oxygenation could usually be attained with only mild decreases in cardiac output.